Software Vault: The Gold Collection/Software Vault - The Gold Collection (American Databankers) (1993).ISO/cdr36/ecg621.zip/BBSGLOSS.TXT

Text File | 1993-04-20 | 2MB | 55,569 lines

  (c) The Computer Language Company Inc. 1981-1993
  All rights reserved. Ver. 6.21, 2nd Quarter 1993


             REMEMBER... USE ACRONYMS!
        If you can't find a term, look up
        its acronym.  Try ISO, rather than
        International Standards Organization.







            BE SURE TO LOOK UP LESSONS!
 ╔════════════════════════════════════════════════╗
 ║     THIS VERSION OF THE GLOSSARY HAS BEEN      ║
 ║           DESIGNED FOR USE ON A BBS            ║
 ╚════════════════════════════════════════════════╝


┌────────── Beginning of Glossary Text ───────────┐



A/D converter
(Analog to Digital Converter)  Device that converts
continuously varying analog signals from
instruments that monitor such conditions as
movement, temperature, sound, etc., into binary
code for the computer.  It may be contained on a
single chip or can be one circuit within a chip.
See modem and codec.  Contrast with D/A converter.


A/UX
Apple's version of UNIX for the Macintosh.  It is
based on AT&T's UNIX System V with Berkeley
extensions.


A20
PC address line that points beyond one megabyte.
For downward compatibility with 8086/8088s, this
line is gated in 286s and up and is controlled by
circuitry on the motherboard.  When disabled, it
keeps the machine in Real Mode (under 1MB).  When
enabled, the CPU can address beyond 1MB (Protected
Mode).

   The HMA (high memory area) can also be accessed
in Real Mode when this line is turned on.  There
are 32 address lines on a 386DX (A0-A31), 24 on a
386SX and 286 (A0-A23).


A:
Designation for the first floppy disk drive in a
PC.


ABC
(Atanasoff-Berry Computer)  First electronic
digital computer.  Completed in 1942 by Iowa State
Professor John Atanasoff and graduate student
Clifford Berry, it embodied the input, memory and
arithmetic unit of future computers.

   John Mauchly, cobuilder of the ENIAC, visited
Atanasoff in 1940 and corresponded with him.
Although Eckert and Mauchly are considered the
creators of the first electronic digital computer,
Atanasoff and Berry are acknowledged contributors.

   In 1990, nearly 50 years after his invention,
87-year-old Atanasoff was awarded the National
Medal of Technology.


abend
(ABnormal END)  Also called a crash or bomb, occurs
when the computer is presented with instructions or
data it cannot recognize or the program is reaching
beyond its protective boundary.  It is the result
of erroneous software logic or hardware failure.

   When the abend occurs, if the program is running
in a personal computer under a single-task (one
program at a time) operating system, such as DOS,
the computer locks up and has to be rebooted.
Multitasking operating systems with memory
protection halt the offending program allowing
remaining programs to continue.

   If you consider what goes on inside a computer,
you might wonder why it doesn't crash more often.
A mainframe's memory can easily contain over 300
million storage cells (bits).  Within every second,
millions of these cells change their state from
uncharged to charged to uncharged.  If only one
cell fails, the computer can abend.


ABI
(Application Binary Interface)  Specification for a
particular hardware platform and operating system.
It details the machine language of the CPU family
as well as the calls between the application and
the operating system.


abort
(1) To exit a function or application without
saving any data that has been changed.

(2) To stop a transmission.


About the Glossary
In 1981, "The Computer Glossary" started out as a
330-term compendium to Alan Freedman's computer
literacy seminars.  By 1989, the 4th edition
contained 3,500 terms and 400 illustrations and won
the "Best Reference Book of the Year" award from
Computer Book Review.  The 5th edition was
introduced in both print and electronic form.  The
6th edition contains over 5,400 terms.

   This disk version has more than 6,000 terms and
is updated quarterly.  To upgrade, look up "Order
Form."


                 USE ACRONYMS!
To save index space, most terms in this Glossary
are entered by their acronyms.  Look up ZBR, not
zone bit recording.


            A Note from the Author
My goal is to keep the Glossary informative,
interesting, accurate and timely.  I invite your
suggestions on new and existing terms.  Please
write or fax me.

                  Alan Freedman
          THE COMPUTER LANGUAGE COMPANY
              5521 State Park Road
          Point Pleasant, PA 18950-0265
                FAX [phone]


above the line
See "IBM COBOLs" in COBOL.


ABR
(AutoBaud Rate detect)  Analysis of the first
characters of a message to determine its
transmission speed and number of start and stop
bits.


absolute
In programming, a mathematical function that always
returns a positive number.  For example, ABS(25-
100) yields 75, not -75.


absolute address
Explicit identification of a memory location,
peripheral device, or location within a device.
For example, memory byte 107,443, disk drive 2 and
sector 238 are absolute addresses.  The computer
uses absolute addresses to reference memory and
peripherals.  See base address and relative
address.


absolute vector
In computer graphics, a vector with end points
designated in absolute coordinates.  Contrast with
relative vector.


absolute zero
Theoretical temperature at which molecular activity
ceases (-273.15° C, -459.67 F).


abstract data type
User-defined data type in object-oriented
programming.  See object-oriented programming.


AC
(Alternating Current)  Common form of electricity
from power plant to home/office.  Its direction is
reversed 60 times per second in the U.S.; 50 times
in Europe.  Contrast with DC.


accelerator
Key combination used to activate a task.  See
accelerator board.


accelerator board
Add-in board that replaces the existing CPU with a
higher performance CPU.  See graphics accelerator.


acceptance test
Test performed by the end user to determine if the
system is working according to the specifications
in the contract.


access
To store data on and retrieve data from a disk or
other peripheral device.   See access arm and
access method.


access arm
Mechanical arm that moves the read/write head
across the surface of a disk similar to a tone arm
on a phonograph.  The access arm is directed by
instructions in the operating system to move the
read/write head to a specific track on the disk.
The rotation of the disk positions the read/write
head over the required sector.


access charge
Charge imposed by a communications service or
telephone company for the use of its network.


access code
(1) Identification number and/or password used to
gain access into a computer system.

(2) Number used as a prefix to a calling number in
order to gain access to a particular telephone
service.


access line
Line from a customer site to a telephone company's
central office.


access method
Software routine that is part of the operating
system or network control program which performs
the storing/retrieving or transmitting/receiving of
data.  It is also responsible for detecting a bad
transfer of data caused by hardware or network
malfunction and correcting it if possible.


                Tape Access Methods
With tapes, the sequential access method is always
used for storing data, which places the next block
of data after the previous one.


                Disk Access Methods
For disks, indexed access methods are widely used
to keep track of records and files.  The index is a
table of contents for each file or each record
within the file.  The sequential method is also
used when retrieval of individual records is not
required.  The indexed sequential method, or ISAM,
combines both methods by providing an index that is
kept in sequential order.  For fastest retrieval,
the direct access method uses a formula to convert
the record's identifying field, such as account
number, into a physical storage address.


           Communications Access Methods
Communications access methods, such as IBM's TCAM
and VTAM, transfer data between a host computer and
remote terminals.  These routines prepare the data
for transmission by placing the data into frames
with appropriate control codes.  These methods
reference layers 3, 4 and 5 of the OSI model.

   LAN access methods, such as CSMA/CD (Ethernet)
and token passing (Token Ring), transfer data to
and from connected computers on the network.  These
methods reference layers 1 and 2 of the OSI model.


access time
(1) Memory access time is how long it takes for a
character in memory to be transferred to or from
the CPU.  In a personal computer, fast RAM chips
have an access time of 70 nanoseconds or less.

(2) Disk access time is an average of the time it
takes to position the read/write head over the
requested track.  Fast personal computer hard disks
have access times of 18 milliseconds or less.
Mainframe disks can be less than one millisecond.
This is a common speed measurement, but disk
performance is influenced by channel speed
(transfer rate), interleaving and caching.


account number
Number assigned to an employee, customer, vendor or
product for identification.  Although it may
contain only numeric digits, it is often stored as
a character field, so that parts of the account
number can be searched independently.  For example,
the number could contain a territory code, and
records could be selected by state or region.


accounting machine
Early office machine used to compute and prepare
invoices and payroll, etc., using magnetic stripe
ledger cards or punched cards.


accumulator
Hardware register used to hold the results or
partial results of arithmetic and logical
operations.


ACD
(Automatic Call Distribution)  Routing of an
incoming telephone call to the next available
operator.


ACE
(Advanced Computing Environment)  Open standard
(announced 1991) based on Intel 386 and MIPS
R3000/R4000 hardware and Windows NT and ACE UNIX
operating systems.  ACE was conceived to allow
users to migrate from Intel-based PCs to MIPS RISC
architecture, which is licensed to several
manufacturers.  For information, contact ACE
Program Manager at MIPS, 408/524-7000.


ACF
(Advanced Communications Function)  Official
product line name for IBM SNA programs, such as
VTAM (ACF/VTAM), NCP (ACF/NCP), etc.


ACK
(ACKnowledgment code)  Communications code sent
from a receiving station to a transmitting station
to indicate that it is ready to accept data.  It is
also used to acknowlege the error-free receipt of
transmitted data.  Contrast with NAK.


ACM
(Association for Computing Machinery)  Membership
organization founded in 1947 dedicated to advancing
the arts and sciences of information processing.
In addition to awards and publications, ACM also
maintains special interest groups (SIGs) in the
computer field.  Address: 1515 Broadway, New York,
NY 10036, 212/869-7440.


acoustic coupler
Device that connects a terminal or computer to the
handset of a telephone.  It contains a shaped foam
bed that the handset is placed in, and it may also
contain the modem.


ACS
(Asynchronous Communications Server)
Communications server that manages a pool of
modems.  It directs outgoing messages to the next
available modem and directs incoming messages to
the appropriate workstation.


active addressing
LCD technology that improves passive matrix screen
contrast.  See LCD.


active matrix
LCD technology used in color screens for laptops.
See LCD.


active star
Network topology that provides regeneration of
signals in the central hub.  Contrast with passive
star.  See hub.


ACTOR
Object-oriented programming language for PCs from
The Whitewater Group Inc., Evanston, IL.  It runs
under Windows and has a Pascal-like syntax to ease
the transition to object-oriented languages.


actuator
Mechanism that causes a device to be turned on or
off, adjusted or moved.  The component that moves
the head assembly on a disk drive or an arm of a
robot is called an actuator.


AD/Cycle
(Application Development/Cycle)  SAA-compliant
software from IBM that provides a system for
managing systems development.  It provides a
structure for storing information about all phases
of an information system including systems analysis
and design, database design and programming.


ad hoc query
Non-standardized inquiry.  A query composed to
answer a question as the need arises.


Ada
High-level programming language developed by the
U.S. Department of Defense along with the European
Economic Community and many other organizations.
It was designed for embedded applications and
process control but is also used for logistics
applications.  Ada is a Pascal-based language that
is very comprehensive.

   Ada was named after Augusta Ada Byron (1815-
1852), Countess of Lovelace and daughter of Lord
Byron.  She was a mathematician and colleague of
Charles Babbage, who was developing his Analytical
Engine.  Some of her programming notes for the
machine have survived, giving her the distinction
of being the first documented programmer in the
world.

   The following Ada program converts Fahrenheit to
Celsius:

with Text_IO;
procedure Convert is
 package Int_IO is new Text_IO.Integer_IO(Integer);
 Fahrenheit : Integer;
begin
 Text_IO.Put_Line("Enter Fahrenheit");
 Int_IO.Get(Fahrenheit);
 Text_IO.Put("Celsius is ");
 Int_IO.Put((Fahrenheit-32) * 5 / 9);
 Text_IO.New_Line;
end Convert;


ADABAS
DBMS from Software AG, Reston, VA, for IBM
mainframes, VAXes, various UNIX platforms and OS/2
PCs.  It is an inverted list DBMS with relational
capabilities.  A 4GL called NATURAL, text
retrieval, GIS processing, SQL and distributed
database functions are also available.  Introduced
in 1969, it was one of the first DBMSs.


ADAPSO
See ITAA.


adapter
Device that allows one system to connect to and
work with another.  Display adapters and network
adapters are really controllers, not adapters.  See
host adapter and expansion bus.


adaptive compression
Data compression technique that dynamically adjusts
the algorithm used based on the content of the data
being compressed.


adaptive equalization
Transmission technique that dynamically adjusts its
modulation method based on the quality of the line.


adaptive routing
Ability to select a new communications path to get
around heavy traffic or a node or circuit failure.


ADB
(Apple Desktop Bus)  Macintosh communications port
for keyboards, mice, trackballs, graphics tablets
and other input devices.


ADC
See A/D converter.


ADCCP
(Advanced Data Communications Control Procedure)
ANSI communications protocol that is similar to the
SDLC and HDLC protocols.


add-in, add-on
Refers to hardware modules, such as printed circuit
boards, that are designed to be plugged into a
socket within the computer.


adder
Elementary electronic circuit that adds the bits of
two numbers together.


address
(1) Number of a particular memory or peripheral
storage location.  Like post office boxes, each
byte of memory and each disk sector has its own
unique address.  Programs are compiled into machine
language, which references actual addresses in the
computer.

(2) As a verb, to manage or work with.  For
example, "the computer can address 2MB of memory."


address bus
Internal channel from the CPU to memory across
which the addresses of data (not the data) are
transmitted.  The number of lines (wires) in the
address bus determines the amount of memory that
can be directly addressed as each line carries one
bit of the address.  For example, the 8088 CPU has
20 address lines and can address 1,048,576 bytes.
The 68020 has 32 address lines and can address four
gigabytes.

   Various swapping and switching techniques can be
added to the hardware that allow a computer to use
more memory than is directly addressable by its
address bus.  See EMS.


     ┌──────────┐           ┌──────────┐
     │          ├─────1─────┤          │
     │   CPU    ├─────2─────┤   RAM    │
     │          ├─────4─────┤          │
     │          ├─────8─────┤          │
     │          ├────16─────┤          │
     │          ├────32─────┤          │
     │          ├────64─────┤          │
     │          ├───128─────┤          │

                 Address Bus



address mode
Method by which an instruction references memory.
An indexed address is modified by the contents of
an index register before execution.  An indirect
address points to another address.  Ultimately, in
order to do any actual processing, the instruction
must derive real, or absolute addresses, where the
required data is located.


address register
High-speed circuit that holds the addresses of data
to be processed or of the next instruction to be
executed.


address space
Total amount of memory that can be used by a
program.  It may also refer to virtual memory,
which includes memory and disk.  For example, the
386 can address 4GB of physical memory and 64TB of
virtual memory.


address translation
Transforming one address into another.  For
example, assemblers and compilers translate
symbolic addresses into machine addresses.  Virtual
memory systems translate a virtual address into a
real address.


addressable cursor
Screen cursor that can be programmed to move to any
row or column on the screen.


ADE
(Application Development Environment)  IBM approach
for developing applications that will run in all
SAA environments.  The development software is
client/server based; the main functions reside in
the host.


ADF
(Application Development Facility)  IBM programmer-
oriented mainframe application generator that runs
under IMS.


ADMD
(ADministrative Management Domain)  Public e-mail
service.  See X.400.


Adobe fonts
See PostScript.


Adobe Type Manager
PostScript font utility for the Macintosh and
Windows from Adobe Systems.  It scales Type 1 fonts
into screen fonts and prints them on non-PostScript
dot matrix and HP laser printers.  Rather than
downloading the font to the printer, it sends a
bitmap of the entire page of text to the printer.

   ATM technology is built into OS/2 and NeXTstep,
and was originally developed to provide WYSIWYG
screen fonts for the Mac.  See PostScript.


ADP
(1) (Automatic Data Processing)  Synonymous with
data processing (DP), electronic data processing
(EDP) and information processing.

(2) ADP, Inc.  Nationwide computer services
organization that also provides international
communications services.


ADP system
(Automatic Data Processing system)  Same as
computer system.


ADPCM
(Adaptive Differential PCM)  Advanced PCM technique
that converts speech to 32 or 16 Kbits/sec.
Instead of coding an absolute measurement at each
sample point, it codes the difference between
samples and can dynamically switch the coding scale
to compensate for variations in amplitude and
frequency.


ADRS
(A Departmental Reporting System)  IBM mainframe
report writer.


ADS
(AutoCAD Development System)  Allows C routines to
be run from within AutoCAD.


ADT
(Asynchronous Data Transfer)  Transmission
technique used in ISDN PBXs that dynamically
allocates bandwidth.  See also abstract data type.


AdvanceNet
Network strategy from HP that incorporates OSI and
SNA network architectures.  In 1983, HP was the
first major vendor to make a commitment to OSI.
AdvanceNet also supports MAP, Starlan 10, Ethernet
and X.25 packet switching networks.


AFE
(Apple File Exchange)  Macintosh utility that
converts data files between Mac and PC formats.  It
also includes a file translator between IBM's DCA
format and MacWrite; however, MacLink Plus
Translators can be used for additional capability.


AFIPS
(American Federation of Information Processing
Societies Inc.)  Organization founded in 1961
dedicated to advancing information processing in
the U.S.  It was the U.S. representative of IFIP
and umbrella for 11 membership societies.
Dissolved in 1990 and superseded by FOCUS.


AFP
(AppleTalk Filing Protocol)  Client/server protocol
used in AppleTalk communications networks.  In
order for non-Apple networks to access data in an
AppleShare server, their protocols must translate
into the AFT language.


AFS
Distributed file system for large, widely-dispersed
UNIX networks from Transarc Corp., Pittsburgh, PA.
It is noted for its ease of administration and
expandability and stems from Carnegie-Mellon's
Andrew File System.


agent
Software routine that waits in the background and
performs an action when a specified event occurs.
For example, agents could transmit a summary file
on the first day of the month or monitor incoming
data and alert the user when a certain transaction
has arrived.  See workflow automation.


AI
(1) (Artificial Intelligence)  Devices and
applications that exhibit human intelligence and
behavior including robots, expert systems, voice
recognition, natural and foreign language
processing.  It also implies the ability to learn
or adapt through experience.

   In the future, everything we now know and think
about a computer will change.  By the turn of the
century, you should be able to converse with the
average computer.  Future systems will ask you what
help you need and automatically call in the
appropriate applications to aid you in solving your
problem.

   In the 1990s, the AI buzzword will be abused to
the hilt as it will refer to any and all
advancements.  However, the acid test of AI was
defined in the 1940s by the English scientist, Alan
Turing, who said, "A machine has artificial
intelligence when there is no discernible
difference between the conversation generated by
the machine and that of an intelligent person."

   Note: The term intelligence refers to processing
capability; therefore, every computer is
intelligent.  But, artificial intelligence implies
human-like intelligence.  An ironic twist in
terminology.

(2) (Application Interface)  Programming interface
for IBM's 8514/A.


AIIM
(Assn. for Information and Image Management)
Membership organization that promotes and advances
the development of systems that store, retrieve,
integrate and manage images of documents.  Founded
in 1943, it provides periodicals, industry studies,
educational programs and expositions.  Address:
1100 Wayne Ave., Suite 1100, Silver Spring, MD
20910, 301/587-8202.


AIX
(Advanced Interactive eXecutive)  IBM's version of
UNIX for 386-based PS/2s, RTs and mainframes.  It
is based on AT&T's UNIX System V with Berkeley
extensions.


ALC
(Assembly Language Coding)  Generic term for IBM
mainframe assembly languages.


Aldus Persuasion
Desktop presentation program for the Mac from Aldus
Corp., Seattle, WA.  It is used to create output
for overheads, handouts, speaker notes and film
recorders and provides sophisticated transition
features (fades, gravel, swipes, etc.).


algebraic expression
One or more characters or symbols associated with
algebra; for example, A+B=C or A/B.


ALGOL
(ALGOrithmic Language)  High-level compiler
language that was developed as an international
language for the expression of algorithms between
people and between people and machines.  ALGOL-60
(1960) was simple and widely used in Europe.
ALGOL-68 (1968) was more complicated and scarcely
used, but was the inspiration for Pascal.

   The following example changes Fahrenheit to
Celsius:

 fahrenheit
 begin
   real fahr;
   print ("Enter Fahrenheit ");
   read (fahr);
   print ("Celsius is ", (fahr-32.0) * 5.0/9.0);
 end
 finish


algorithm
Set of ordered steps for solving a problem, such as
a mathematical formula or the instructions in a
program.


alias
(1) Alternate name used for identification, such as
for naming a field or a file.

(2) Phony signal created under certain conditions
when digitizing voice.


aliasing
In computer graphics, the stair-stepped appearance
of diagonal lines.  See anti-aliasing.


All-In-1
Office systems software from Digital for the VAX
series.  It provides a menu to all of Digital's
office systems programs, including word processing,
appointment calendars and e-mail systems.


allocate
To reserve a resource such as memory or disk.  See
memory allocation.


Alpha
Family of advanced RISC-based, 64-bit CPUs from
Digital.  First model introduced early 1992 is the
150MHz 21064-AA, considered equivalent to a Cray-1
on a single chip.  Alpha AXP computer systems use
the Alpha CPU and run under Windows NT, OpenVMS and
OpenOSF operating systems.


alpha channel
High-order eight bits in a 32-bit graphics pixel
used as a separate layer to mask an area for
editing or creating special effects (textures,
montages, etc.).


alpha test
First test of newly developed hardware or software
in a laboratory setting.  The next step is beta
testing with actual users.


alphageometric
See alphamosaic.


alphamosaic
Very-low-resolution display technique that uses
elementary graphics characters as part of its
character set.


alphanumeric
Use of alphabetic letters mixed with numbers and
special characters as in name, address, city and
state.  The text you're reading is alphanumeric.


Altair 8800
Microcomputer kit introduced in 1974 from Micro
Instrumentation and Telemetry Systems.  It sold for
$400 and used an 8080 microprocessor.  In 1975, it
was packaged with Microsoft's MBASIC.  Although
computer kits were advertised earlier by others, an
estimated 10,000 Altairs were sold, making it the
first commercially successful microcomputer.


alternate routing
Ability to use another transmission line if the
regular line is busy.


AlterNet
See UUNET.


Alto
Xerox personal computer that pioneered the
mouse/icon environment.  Developed at PARC, it was
the progenitor of Xerox's Star and Apple's Lisa and
Mac.  Designed in 1973 with 128K RAM, 608x808
screen, 2.5MB removable hard disk and built-in
Ethernet.  About 1,000 Altos were in use by 1979.


ALU
(Arithmetic Logic Unit)  High-speed CPU circuit
that does calculating and comparing.  Numbers are
transferred from memory into the ALU for
calculation, and the results are sent back into
memory.  Alphanumeric data is sent from memory into
the ALU for comparing.  The results are tested by
GOTOs; for example, IF ITEMA EQUALS ITEMB GOTO
UPDATE ROUTINE.


AM
(Amplitude Modulation)  Transmission technique that
blends the data signal into a carrier by varying
(modulating) the amplitude of the carrier.  See
modulate.


AM386
Low-power, 386-compatible chips from Advanced Micro
Devices.  AM386DXL chips are Intel 386DX
compatible, and AM386SXL chips are Intel 386SX
compatible.


ambient
Surrounding.  For example, ambient temperature and
humidity are atmospheric conditions that exist at
the moment.


Amdahl
(Amdahl Corp., Sunnyvale, CA)  Computer
manufacturer founded in 1970 by Gene Amdahl, chief
architect of the IBM System/360.  In 1975, Amdahl
installed its first IBM-compatible mainframe, the
470/V6.  Although not the first to make IBM-
compatible mainframes, it succeeded where others
failed.  Today, Amdahl offers a full range of
mainframe products.

   Dr. Amdahl left the company to form Trilogy in
1979 and now heads Andor Corp., a manufacturer of
products for large IBM mainframe installations.


American Bell
AT&T trade name used after divestiture.  Federal
court order later prohibited its use.


AMI BIOS
Popular PC-compatible ROM BIOS from American
Megatrends, Inc., Norcross, GA.


Ami Pro
Windows word processing program from Lotus that
includes desktop publishing features.  It allows
for the creation of presentation-quality charts and
graphs.  Ami was one of the first full-featured
word processors for Windows and was originally
developed by Samna Corp.


Amiga
Personal computer series from Commodore that runs
under the AmigaDOS operating system, uses the 68000
CPU family and features the Workbench window-
oriented user interface.

   The Amiga 500 is geared for home use and
includes built-in speech synthesis, stereo sound
and color graphics.  The Amiga 2000 is designed for
office applications, including CAD and desktop
publishing.  It has optional PC compatibility and
NTSC video processing.  The Amiga 3000 (68030)
provides enhanced graphics and Workbench interface.


amp
(AMPere)  Unit of electrical current in a circuit.
Volts measure the force or pressure behind the
current.  Watts are a total measurement of power
derived from multiplying amps times volts.


amplitude
Strength or volume of a signal, usually measured in
decibels.


amplitude modulation
See AM.


analog
Representation of an object that resembles the
original.  Analog devices monitor conditions, such
as movement, temperature and sound, and convert
them into analogous electronic or mechanical
patterns.  For example, an analog watch represents
the planet's rotation with the rotating hands on
the watch face.  Telephones turn voice vibrations
into electrical vibrations of the same shape.
Analog implies continuous operation in contrast
with digital, which is broken up into numbers.


           Advantages and Disadvantages
               Of Analog Techniques
Traditionally, audio and video recording has been
analog.  Sound, which is continuously varying air
vibrations, is converted into analogous electrical
vibrations.  Video cameras scan their viewing area
a line at a time and convert the infinitely varying
intensities of light into analogous electrical
signals.

   The ability to capture the subtle nature of the
real world is the single advantage of analog
techniques.  However, once captured, modern
electronic equipment, no matter how advanced,
cannot copy analog signals perfectly.  Third and
fourth generations of audio and video recordings
show marked deterioration.

   By converting analog signals into digital, the
original audio or video data can be preserved
indefinitely and copied over and over without
deterioration.  Once continuously varying analog
signals are measured and converted into digital
form, they can be stored and transmitted without
loss of integrity due to the accuracy of digital
methods.

   The key to conversion is the amount of digital
data that is created from the analog signal.  The
shorter the time interval between samples and the
more data recorded from that sample, the more the
digital encoding reflects the original signal.


analog channel
In communications, a channel that carries voice or
video in analog form as a varying range of
electrical frequencies.  Contrast with digital
channel.


analog computer
Device that processes infinitely varying signals,
such as voltage or frequencies.  A thermometer is a
simple analog computer.  As the temperature varies,
the mercury moves correspondingly.  Although
special-purpose, complex analog computers are
built, almost all computers are digital.  Digital
methods provide programming flexibility.


analog monitor
Video monitor that accepts analog signals from the
computer (digital to analog conversion is performed
in the video display board).  It may accept only a
narrow range of display resolutions; for example,
only VGA or VGA and Super VGA, or it may accept a
wide range of signals including TV.  See multisync
monitor and RGB monitor.  Contrast with digital
monitor.


analysis
See systems analysis & design.


analyst
See systems analyst.


Analytical Engine
Programmable calculator designed by British
scientist, Charles Babbage (mid 1830s).  Although
never completed due to lack of funds and constant
redesign, it was a major advance and contained the
principles of the stored program computer.

   Babbage's colleague, Augusta Ada Byron, daughter
of the poet Lord Byron, explained the machine's
concepts to the public.  See Ada.


AND, OR & NOT
Fundamental operations of Boolean logic.  AND is
true if both inputs are true, OR is true if any
input is true, and NOT is an inverter; the output
is always the opposite.  See Boolean search, chip
and gate.

       AND              OR              NOT
  Inputs  Output   Inputs  Output   Input  Output
 ┌───────┬─────┐  ┌───────┬─────┐  ┌─────┬─────┐
 │ 0   0 │  0  │  │ 0   0 │  0  │  │  0  │  1  │
 │ 0   1 │  0  │  │ 0   1 │  1  │  │  1  │  0  │
 │ 1   0 │  0  │  │ 1   0 │  1  │  └─────┴─────┘
 │ 1   1 │  1  │  │ 1   1 │  1  │
 └───────┴─────┘  └───────┴─────┘



ANDF
(Architecture Neutral Distributed Format)  See OSF.


angstrom
Unit of measurement equal to approximately 1/250
millionth of an inch (.1 nanometer).  It is used to
measure the elements in a chip.


ANI
(Automatic Number Identification)  Telephone
service that provides the telephone number of the
incoming call.


animated graphics
Moving diagrams or cartoons.  Often found in
computer-based courseware, animated graphics take
up far less disk space than video images.


anisotropic
Refers to properties, such as transmission speed,
that vary depending on the direction of
measurement.  Contrast with isotropic.


anode
In electronics, positively charged receiver of
electrons that flow from the negatively charged
cathode.


anomaly
Abnormality or deviation.  It is a favorite word
among computer people when complex systems produce
output that is inexplicable.


ANSI
(American National Standards Institute)  Membership
organization founded in 1918 that coordinates the
development of U.S. voluntary national standards in
both the private and public sectors.  It is the
U.S. member body to ISO and IEC.  Information
technology standards pertain to programming
languages, EDI, telecommunications and physical
properties of diskettes, cartridges and magnetic
tapes.  Address: 11 West 42 St., New York, NY
10036, 212/642-4900.


ANSI character set
ANSI-standard character set that defines 256
characters.  The first 128 are ASCII, and the
second 128 contain math and foreign language
symbols, which are different than those on the PC.
See extended ASCII.


ANSI terminal
Display terminal that follows commands in the ANSI
standard terminal language.  Uses escape sequences
to control the cursor, clear the screen and set
colors, for example.  Communications programs often
support the ANSI terminal.


ANSI.SYS
See DOS ANSI.SYS.


answer only modem
Modem capable of answering a call, but not
initiating one.


anti-aliasing
In computer graphics, a category of techniques that
is used to smooth the jagged appearance of diagonal
lines.  For example, the pixels that surround the
edges of the line are filled in with varying shades
of gray or color in order to blend the sharp edge
into the background.  See dithering.


Antifuse
PLD technology from Actel Corp. that works the
opposite of typical programmable chip methods.
Instead of creating open circuits (blowing the
fuse), connections are made between elements.


antivirus
Program that detects and removes a virus.


ANVIL
Family of CADD/CAM software packages from
Manufacturing and Consulting Services Inc.,
Scottsdale, AZ.  ANVIL products include 2 1/2-D and
3-D mechanical engineering systems for PCs,
workstations, minis and mainframes.


APA
(All Points Addressable)  Refers to an array
(bitmapped screen, matrix, etc.) in which all bits
or cells can be individually manipulated.


APCUG
(Assn. of Personal Computer User Groups) Non-profit
organization dedicated to fostering communication
among and between user groups and between user
groups and vendors.  Address: Suite 700, 1730 M St.
N.W., Washington, DC 20036.


aperture card
Punched card that holds a frame of microfilm.


API
(Application Program Interface)  Language and
message format used by a program to activate and
interact with functions in another program or in
the hardware.  See interface.


APL
(A Programming Language)  High-level, interactive
scientific language noted for its brevity and
matrix generation capabilities.  Developed by
Kenneth Iverson in the mid 1960s, it runs on micros
to mainframes and is often used to develop
mathematical models.  It is primarily an
interpreted language, but compilers are available.

   APL uses unique character symbols and requires
special software or ROM chips to enable the
computer to display and print them.  APL is popular
in Europe.


APM
(Advanced Power Management)  API from Intel and
Microsoft for battery-powered computers that lets
programs communicate power requirements to slow
down and speed up components.  The 386SL takes full
advantage of APM.


Apollo
(Apollo Systems Div. of HP)  Formerly Apollo
Computer, Inc., this maker of high-performance
workstations became a division of HP in 1989.
Founded in 1980, it pioneered networked
workstations.


app
See application.


app code
(APPlication code)  Instructions in a program that
actually process data.


APPC
(Advanced Program-to-Program Communications)  High-
level communications protocol from IBM that allows
a program to interact with another program.  It
supports client/server and distributed computing by
providing a common programming interface across all
IBM platforms for communications over a variety of
transport protocols.  It provides commands for
managing a session, sending and receiving data and
transaction security and integrity (two-phase
commit).

   APPC software is either part of or optionally
available on all IBM and many non-IBM operating
systems.  Since APPC has only supported SNA,
utilizing SNA's LU 6.2 protocol for session
establishment, APPC and LU 6.2 have been considered
synonymous.  In time, APPC will support other
industry protocols, such as TCP/IP and OSI.

   APPC commands have differed across platforms.
Under SAA, the CPI-C interface defines a standard
set of APPC verbs.


append
To add to the end of an existing structure.

Apple
(Apple Computer, Inc., Cupertino, CA)  Manufacturer
of personal computers and the industry's most
fabled story.  Founded in a garage by Steve Wozniak
and Steve Jobs and guided by Mike Markkula, Apple
blazed the trails for the personal computer
industry.  Today, Apple makes more personal
computers than any other single company.

   Apple was formed on April Fool's Day in 1976.
After introducing the Apple I at the Palo Alto
Homebrew Computer Club, 10 retail stores were
selling them by the end of the year.

   In 1977, it introduced the Apple II, a fully-
assembled computer with 4K RAM for $1,298.  Its
open architecture encouraged third-party vendors to
build plug-in hardware enhancements.  This, plus
sound and color graphics, caused Apple IIs to
become the most widely used computer in the home
and classroom.  They were also used in business
primarily for the innovative VisiCalc software that
was launched on it.

   In 1983, Apple introduced the Lisa, the
forerunner of the Macintosh.  Lisa was aimed at the
corporate market, but was soon dropped in favor of
the Mac.  As a graphics-based machine, the Mac was
successful as a low-cost desktop publishing system.
Although praised for its ease of use, its slow
speed, small screen and closed architecture didn't
excite corporate buyers.

   Since the advent of the Mac II in 1987, that has
changed.  Macs offer large screens, open
architecture and color.  Numerous entry-level and
high-speed models have been added and widely
accepted.

   In 1991, Apple surprised the industry by
announcing an alliance with IBM to

   (1) fully integrate Macs into IBM enterprise
networks,

   (2) develop the PowerPC with Motorola, a single-
chip version of IBM's RS/6000 architecture,

   (3) develop PowerOpen, an industry standard UNIX
(OSF/1 compliant) that runs AIX and Mac
applications on the PowerPC,

   (4) form Taligent, Inc. to develop and license
an object-oriented operating system for the
PowerPC, Motorola 68xxx and Intel x86 families with
compatibility with AIX, OS/2 2.0 and System 7,

   (5) form Kaleida Labs, Inc. to develop and
license multimedia software, tools and scripting
languages for a diverse variety of computers and
consumer electronic gear.


Apple II
Personal computer family from Apple that pioneered
the microcomputer revolution and has been widely
used in schools and home.  It uses the 8-bit 6502
microprocessor running at 1MHz, an 8-bit bus and
runs under Apple's DOS or ProDOS operating system.
AppleSoft BASIC is built into ROM and always
available.

   With a Z80 microprocessor board plugged in,
Apple IIs can run CP/M programs, such as dBASE II.

   As of the end of 1992, the Apple IIe and a IIe
card for the Mac LC are the only Apple II models
still in the product line.


APPLE II AND II+
Introduced in 1977, the Apple II came with 4K RAM
and hooked up to a TV and cassette tape recorder.
A floppy disk was available in 1978.  In 1979, an
enhanced II+ came with 48K of RAM.  Screen
resolution is 280x192x6.


APPLE IIe AND IIc
In 1983, the "e"nhanced Apple IIe was introduced
with four cursor keys (not two) and 128K of RAM.
In 1984, the IIc portable was launched with a sleek
design, but limited expandability.


APPLE IIGS
Introduced in 1986 and discontinued in 1992, the
IIGS is faster and adds enhanced graphics and sound
(GS).  It runs standard Apple II software, but
requires GS software to use its enhancements.
Specs: 2.8MHz 16-bit 65C816 CPU, 320x200x256
screen, 15 sounds, AppleTalk.


APPLE III
Yes, there was an Apple III in 1980, intended for
business users.  It was not 100% compatible with
the II and never caught on.


Apple key
Original name of the Command key.


Apple menu
Menu at the top left side of a Macintosh screen
that is always available to provide access to desk
accessories.


AppleShare
Software from Apple that turns a Macintosh into a
file server.  It works in conjunction with the Mac
operating system and can coexist with other
Macintosh applications in a non-dedicated mode.


AppleShare PC
Software for PCs from Apple that allows a PC to
connect to an AppleTalk network.  It requires a
LocalTalk PC Card from Apple for ISA PCs, or a
LocalTalk Card from DayStar Communications for
Micro Channel PCs.


AppleSoft BASIC
Apple's version of BASIC that comes with Apple II
models.  It is installed in firmware and is always
available.


applet
Small application, such as a utility program.


AppleTalk
OSI-based LAN from Apple introduced in 1985.  It
supports Apple's proprietary LocalTalk access
method as well as Ethernet and Token Ring.  The
AppleTalk protocol and LocalTalk access method are
built into all Macs, IIGS's and LaserWriters.  With
products from Apple and others, AppleTalk can run
in PCs, VAXs and UNIX workstations.


AppleWorks
Integrated software package for Apple IIs from
Claris Corp.  Introduced in 1983 by Apple, it
combines word processing, file management,
spreadsheet, business graphics and communications.


application
(1) Specific use of the computer, such as payroll,
inventory and billing.

(2) Same as application program and software
package.


application developer
Individual that develops a business application and
usually performs the duties of a systems analyst
and application programmer.


application development language
Same as programming language.


application development system
Programming language and associated utility
programs that allow for the creation, development
and running of application programs.  DBMSs are
often full application development systems, which
include a programming language, query language,
report writer and the capability to interactively
create and manage database files.


application framework
(1) Building blocks of an application.

(2) Class library that provides the foundation for
programming an object-oriented application.


application generator
Software that generates application programs from
descriptions of the problem rather than by
traditional programming.  It is at a higher level
and easier to use than a high-level programming
language.  One statement or descriptive line may
generate a huge routine or an entire program.
However, application generators always have limits
as to what they can be used for.  Generators used
for complex program development allow if-then-else
programming to be expressed along with the simpler
descriptive entries.


application layer
In communications, the interaction at the user or
application program level.  It is the highest layer
within the protocol hierarchy.  See OSI model.


application notes
Instructions and recommendations from the vendor
provided in addition to the normal reference
manuals.


application package
Software package that is created for a specific
purpose or industry.


application processor
Computer that processes data in contrast with one
that performs control functions, such as a front
end processor or database machine.


application program
Any data entry, update, query or report program
that processes data for the user.  Contrast with
system program.


application program interface
See API.


application program library
Application programs used by an organization.


application programmer
Individual who writes application programs in a
user organization.  Most programmers are
application programmers.  Contrast with systems
programmer.


APPN
(Advanced Peer-to-Peer Networking)  Extensions to
IBM's SNA communications that provide necessary
enhancements for distributed computing.  It
provides intermediate node routing (routing a
message from one computer to another), dynamic
network services (automatic reconfiguration of a
network) and improved administration.  It makes use
of LU 6.2 protocols and is implemented in SNA Node
Type 2.1.


APT
(Automatic Programmed Tools)  High-level
programming language used to generate instructions
for numerical control machines.


Arago
dBASE IV-compatible DBMS and compiler (Arago
Quicksilver) originally developed by WordTech
Systems.  In 1992, the technology was acquired by
Borland.


arbitration
Set of rules for allocating machine resources, such
as memory or peripheral devices, to more than one
user or program.


ARC, ARC+Plus
(1) PC compression programs from System Enhancement
Associates, Inc., Clifton, NJ.  ARC was one of the
first compression utilities to become popular in
the early 1980s.  ARC+Plus provides enhanced
features and speed.

(2) ARC extension previously used by PKWARE Inc. in
its PKARC program.

(3) (Advanced RISC Computing)  Open system
specification based on the MIPS R3000 and R4000
CPUs.  It includes EISA and TURBOchannel buses.


architecture
See computer architecture, network architecture and
software architecture.


archive
(1) To copy data onto a different disk or tape for
backup.  Archived files are often compressed to
maximize storage media.

(2) To save data onto the disk.


archive attribute
File classification that indicates whether the file
has been updated since the last backup.


ARCNET
(Attached Resource Computer NETwork)  Local area
network introduced in 1968 by Datapoint Corp.  It
was the first LAN.  It uses a token passing access
method at 2.5 Mbits/sec with a distributed star
topology for up to 255 nodes.  In 1989, 20
Mbits/sec versions were introduced.  It supports
coax, twisted pair or fiber optic cable.  Adapters
allow it to connect to mini and mainframe networks.


Ardis
(Advanced National Radio Data Service)  Joint
venture of IBM and Motorola that provides wireless
data transmission in the 800MHz FM band.  It covers
most U.S. metropolitan areas with over 1,000 base
stations.


areal density
Bits per square inch of disk surface (BPI x TPI).


arg
See argument.


argument
In programming, a value that is passed between
programs, subroutines or functions.  Arguments are
independent items, or variables, that contain data
or codes.  When an argument is used to customize a
program for a user, it is typically called a
parameter.


arithmetic coding
Statistical data compression method that converts
strings of data into single floating point numbers
between 0 and 1.


arithmetic expression
(1) In mathematics, one or more characters or
symbols associated with arithmetic, such as 1+2=3
or 8÷6.

(2) In programming, a non-text expression.


arithmetic logic unit
See ALU.


arithmetic operators
Symbols for arithmetic functions: + add, -
subtract, * multiply, / divide.  See precedence.


arithmetic overflow
Result from an arithmetic calculation that exceeds
the space designated to hold it.


arithmetic underflow
Result from an arithmetic calculation that is too
small to be expressed properly.  For example, in
floating point, a negative exponent can be
generated that is too large (too small a number) to
be stored in its allotted space.


ARP
(Address Resolution Protocol)  TCP/IP protocol used
to obtain a station's physical address from its
logical IP address.  ARP requests are broadcast
onto the network.  Reverse ARP, or RARP, is used by
a diskless workstation to obtain its logical IP
address.  Responding to a RARP broadcast from the
workstation, a RARP server sends back the IP
address.


ARPANET
(Advanced Research Projects Agency NETwork)
Research network funded by DARPA (originally ARPA)
and built by BBN, Inc., in 1969.  It pioneered
packet switching technology and was the original
backbone and testbed for the now-gigantic Internet.
In 1983, the military communications part of it was
split off into MILNET.


ARQ
(Automatic Repeat Request)  Method of handling
communications errors in which the receiving
station requests retransmission if an error occurs.


array
Ordered arrangement of data elements.  A vector is
a one dimensional array, a matrix is a two-
dimensional array.  Most programming languages have
the ability to store and manipulate arrays in one
or more dimensions.  Multi-dimensional arrays are
used extensively in scientific simulation and
mathematical processing; however, an array can be
as simple as a pricing table held in memory for
instant access by an order entry program.  See
subscript.


array element
One item in an array.


array processor
Computer, or extension to its arithmetic unit, that
is capable of performing simultaneous computations
on elements of an array of data in some number of
dimensions.  Common uses include analysis of fluid
dynamics and rotation of 3-D objects, as well as
data retrieval, in which elements in a database are
scanned simultaneously.  See vector processor and
math coprocessor.


artificial intelligence
See AI.


artificial language
Language that has been predefined before it is ever
used.  Contrast with natural language.


AS
(Application System)  IBM mainframe 4GL that runs
under MVS.  It was originally designed for non-
computer people and includes commands for planning,
budgeting and graphics.  However, a programmer can
also produce complex applications.  It also
provides computer conferencing.


AS/400
(Application System/400)  IBM minicomputer series
introduced in 1988 that supersedes the System/36
and System/38.  System/36 programs run in the
AS/400 in System/36 mode after they have been
recompiled.  System/38 programs run intact in
System/38 mode.  After recompilation, System/38
programs will run in native AS/400 mode, which
takes advantage of all system resources.

   The AS/400 serves in a variety of networking
configurations: as a host or intermediate node to
other AS/400s and System/3x machines, as a remote
system to mainframe-controlled networks and as a
network server to PCs.  The AS/400 offered the
widest range of connectivity in an IBM
introduction.


ascender
The part of lowercase b, d, f, h, k, l, and t, that
extends above the body of the letters.


ASCII
(American Standard Code for Information
Interchange)  Pronounced "ask-ee."  A binary code
for data that is used in communications, most
minicomputers and all personal computers.

   ASCII is a 7-bit code providing 128 character
combinations, the first 32 of which are control
characters.  Since the common storage unit is an 8-
bit byte (256 combinations) and ASCII uses only 7
bits, the extra bit is used differently depending
on the computer.

   For example, the PC uses the additional values
for foreign language and graphics symbols (see
ASCII chart below).  In the Macintosh, the
additional values can be user-defined.  In the Mac
version of this Glossary, the PC symbols are
designed into the font used for the definitions.
See ASCII chart and hex chart.


ASCII chart

╔═══════════════════════════════╦═════════════════╗
║         Standard ASCII        ║ Extended ASCII  ║
║  The first 32 characters are  ║    (IBM PC)     ║
║        control codes.         ║                 ║
║                               ║                 ║
║ 0 Null             │33 !│ 81 Q║128 Ç│174 «│220 ▄║
║ 1 Start of heading │34 "│ 82 R║129 ü│175 »│221 ▌║
║ 2 Start of text    │35 #│ 83 S║130 é│176 ░│222 ▐║
║ 3 End of text      │36 $│ 84 T║131 â│177 ▒│223 ▀║
║ 4 End of transmit  │37 %│ 85 U║132 ä│178 ▓│224 α║
║ 5 Enquiry          │38 &│ 86 V║133 à│179 ││225 ß║
║ 6 Acknowledge      │39 '│ 87 W║134 å│180 ┤│226 Γ║
║ 7 Audible bell     │40 (│ 88 X║135 ç│181 ╡│227 π║
║ 8 Backspace        │41 )│ 89 Y║136 ê│182 ╢│228 Σ║
║ 9 Horizontal tab   │42 *│ 90 Z║137 ë│183 ╖│229 σ║
║10 Line feed        │43 +│ 91 [║138 è│184 ╕│230 µ║
║11 Vertical tab     │44 ,│ 92 \║139 ï│185 ╣│231 τ║
║12 Form feed        │45 -│ 93 ]║140 î│186 ║│232 Φ║
║13 Carriage return  │46 .│ 94 ^║141 ì│187 ╗│233 Θ║
║14 Shift out        │47 /│ 95 _║142 Ä│188 ╝│234 Ω║
║15 Shift in         │48 0│ 96 `║143 Å│189 ╜│235 δ║
║16 Data link escape │49 1│ 97 a║144 É│190 ╛│236 ∞║
║17 Device control 1 │50 2│ 98 b║145 æ│191 ┐│237 φ║
║18 Device control 2 │51 3│ 99 c║146 Æ│192 └│238 ε║
║19 Device control 3 │52 4│100 d║147 ô│193 ┴│239 ∩║
║20 Device control 4 │53 5│101 e║148 ö│194 ┬│240 ≡║
║21 Neg. acknowledge │54 6│102 f║149 ò│195 ├│241 ±║
║22 Synchronous idle │55 7│103 g║150 û│196 ─│242 ≥║
║23 End trans. block │56 8│104 h║151 ù│197 ┼│243 ≤║
║24 Cancel           │57 9│105 i║152 ÿ│198 ╞│244 ⌠║
║25 End of medium    │58 :│106 j║153 Ö│199 ╟│245 ⌡║
║26 Substitution     │59 ;│107 k║154 Ü│200 ╚│246 ÷║
║27 Escape           │60 <│108 l║155 ¢│201 ╔│247 ≈║
║28 File separator   │61 =│109 m║156 £│202 ╩│248 °║
║29 Group separator  │62 >│110 n║157 ¥│203 ╦│249 ∙║
║30 Record separator │63 ?│111 o║158 ₧│204 ╠│250 ·║
║31 Unit separator   │64 @│112 p║159 ƒ│205 ═│251 √║
║32 Blank space      │65 A│113 q║160 á│206 ╬│252 ⁿ║
║                    │66 B│114 r║161 í│207 ╧│253 ²║
║                    │67 C│115 s║162 ó│208 ╨│254 ■║
║                    │68 D│116 t║163 ú│209 ╤│255  ║
║                    │69 E│117 u║164 ñ│210 ╥│     ║
║                    │70 F│118 v║165 Ñ│211 ╙│     ║
║                    │71 G│119 w║166 ª│212 ╘│     ║
║                    │72 H│120 x║167 º│213 ╒│     ║
║                    │73 I│121 y║168 ¿│214 ╓│     ║
║                    │74 J│122 z║169 ⌐│215 ╫│     ║
║                    │75 K│123 {║170 ¬│216 ╪│     ║
║                    │76 L│124 |║171 ½│217 ┘│     ║
║                    │77 M│125 }║172 ¼│218 ┌│     ║
║                    │78 N│126 ~║173 ¡│219 █│     ║
║                    │79 O│127 ║     │     │     ║
║                    │80 P│     ║     │     │     ║
╚════════════════════╧════╧═════╩═════╧═════╧═════╝


ASCII file
Data or text file that contains characters coded in
ASCII.  Text files (not created in a word
processor), batch files and source language
programs are ASCII files.  Contrast with binary
file.

          ASCII Files for Data Conversion
Database files and word processing documents
generally contain proprietary codes and binary
numbers, which are not true ASCII characters.
However, most applications can import and export
ASCII files, which provides a common denominator
for converting one format to another.


ASCII protocol
Simple form of transmitting ASCII data which
implies little or no error checking.


ASCII sort
Sequential order of ASCII data.  In ASCII code,
lower case characters follow upper case.  True
ASCII order would put the words DATA, data and
SYSTEM into the following sequence:

           DATA   SYSTEM   data


Ashton-Tate
Software company founded in 1980 by Hal Lashlee and
George Tate to market dBASE II.  Borland acquired
it in 1991.


ASIC
(Application Specific Integrated Circuit)  Custom
chip designed for a specific application.  It is
designed by integrating standard cells from a
library.  ASIC design is faster than designing a
chip from scratch, and design changes can be made
more easily.


askSam
Text management system for PCs from askSam Systems,
Perry FL.  It holds unstructured text as well as
standard data fields.  The product is noted for its
flexible text retrieval and hypertext capabilities.


ASM
(1) (Association for Systems Management)
International membership organization founded in
1947 with over 10,000 administrative executives and
specialists in information systems.  It sponsors
conferences in all phases of administrative systems
and management and serves business, education,
government and the military.  Address: 24587 Bagley
Rd., Cleveland, OH 44138, 216/243-6900.

(2) File extension for assembly language source
programs.


ASN.1
(Abstract Syntax Notation.1)  Rules for defining
data structures transmitted over an OSI network.


aspect ratio
Ratio of width to height of an object.


ASPI
(Advanced SCSI Programming Interface)  SCSI
standard developed by Adaptec.  See SCSI and
CorelSCSI.


assembler
Software that translates assembly language into
machine language.  Contrast with compiler, which is
used to translate a high-level language, such as
COBOL or C, into assembly language first and then
into machine language.


assembly language
Programming language that is one step away from
machine language.  Each assembly language statement
is translated into one machine instruction by the
assembler.  Programmers must be well versed in the
computer's architecture, and, undocumented assembly
language programs are difficult to maintain.  It is
hardware dependent; there is a different assembly
language for each CPU series.

   In the past, control programs (operating
systems, database managers, etc.) were written in
assembly language to maximize the machine's
performance.  Today, C is often used instead.  Like
assembly language, C can manipulate the bits at the
machine level, but it is also portable to different
computer platforms.  There are C compilers for most
computers.

   Although often used synonomously, assembly
language and machine language are not the same.
Assembly language is turned into machine language.
For example, the assembly instruction  COMPARE A,B
is translated into COMPARE contents of memory bytes
2340-2350 with 4567-4577 (where A and B happen to
be located).  The physical binary format of the
machine instruction is specific to the computer
it's running in.

   Assembly languages are quite different between
computers as is evident in the example below, which
takes 16 lines of code for the mini and 82 lines
for the micro.  The example changes Fahrenheit to
Celsius.


             HP 3000

  begin
  intrinsic  read,print,binary,ascii;
  array buffer(0:17);
  array string(0:3);
  byte array b'string(*) = string;
  integer ftemp, ctemp, len;
    move buffer:= "Enter Fahrenheit ";
    print (buffer,-30,%320);
    len:=read (string,-4);
    ftemp:= binary(b'string,len);
    ctemp:= (ftemp-32) * 5 / 9;
    len:= ascii(ctemp,1-,b'string);
    move buffer:= "Celsius is ";
    move buffer(14) := string, (-len);
    print (buffer,-32,%0);
  end


          IBM PC (x86 family)
(Only 15 of the 82 lines are shown here.)

  cseg    segment para public 'CODE'
          assume  cs:cseg,ds:cseg
  start:
          jmp     start1
  msgstr  db      'Enter fahrenheit '
  crlf    db      13,10,'$'
  nine    db      9
  five    db      5
  outstr  db      'Centrigrade is $'
  start1: push    ds
          push    cs
          pop     ds
          mov     dx,offset cseg:msgstr
          mov     ah,9
          int     21h
    (67 more lines are required!)


assignment statement
In programming, a compiler directive that places a
value into a variable.  For example, COUNTER = 0
creates a variable named counter and fills it with
zeros.  The VARIABLE NAME = VALUE syntax is common
among programming languages.


associative storage
Storage accessed by comparing the content of the
data stored in it rather than by addressing
predetermined locations.


ASSP
(Application Specific Standard Part)  ASIC chip
originally designed for one customer and then
released to the general public.


asymmetric modem
Full-duplex modem that transmits data in one
direction at one speed and simultaneously in the
other direction at another speed.  For example,
data flows at high-speed in one direction while
acknowledgement is returned at low speed in the
other.  Contrast with ping pong.


asymmetric multiprocessing
Multiprocessing design in which each CPU is
dedicated to a specific function.  Contrast with
symmetric multiprocessing.


asymmetric system
(1) System in which major components or properties
are different.

(2) In video compression, a system that requires
more equipment to compress the data than to
decompress it.


asynchronous
(1) Unsynchronized events, for example, the time
interval between event A and B is not the same as B
and C.

(2) Able to initiate a transmission at either end.

(3) In SNA, refers to independent events rather
than concurrent events.  For example, if one user
sends mail to a party who is not available, the
ability to forward the mail at a later time is
considered asynchronous.

(4) Starting the next I/O operation before the
current one is completed.

(5) In SCSI, the acknowledgment of each byte of
data transferred.

Contrast with synchronous.


asynchronous protocol
Communications protocol that controls an
asynchronous transmission, for example, ASCII, TTY,
Kermit and Xmodem.  Contrast with synchronous
protocol.


asynchronous transmission
Transmission of data in which each character is a
self-contained unit with its own start and stop
bits.  Intervals between characters may be uneven.
It is the common method of transmission between a
computer and a modem, although the modem may switch
to synchronous transmission to communicate with the
other modem.  Also called start/stop transmission.
Contrast with synchronous transmission.

  asynchronous
  transmission:  a bc   d    efg hi j kl    m

  synchronous
  transmission:  abcedefghijklm



AT
(Advanced Technology)  IBM's first 286-based PC,
introduced in 1984.  It was the most advanced
machine in the PC line and featured a new keyboard,
1.2MB floppy and 16-bit data bus.  AT-class
machines run considerably faster than XTs (8088-
based PCs).  See PC.


AT bus
Refers to the 16-bit bus introduced with the IBM
AT.  See ISA.


AT class
Refers to PCs that use the 286 CPU and the 16-bit
AT (ISA) bus.


AT command set
Series of machine instructions used to activate
features on an intelligent modem.  Developed by
Hayes Microcomputer Products, Inc., and formally
called the Hayes Standard AT Command Set, it is
used entirely or partially by most every modem
manufacturer.  AT is a mnemonic code for ATtention,
which is the prefix that initiates each command to
the modem.  See Hayes Smartmodem.


AT interface
See AT bus.


AT keyboard
84-key keyboard provided with the PC AT.  It
corrected the non-standard placement of the PC's
return and left shift keys.  See PC keyboard and
Enhanced keyboard.


AT&T
(American Telephone & Telegraph Company)  Largest
long distance communications carrier in the U.S.
Once the largest corporation in America, it was
relieved of its operating telephone companies on
1/1/84, by Federal court order.  It has gone
through a major change from the world's largest
monopoly to a competitive enterprise.  Its ventures
into the PC market have been modest, but in 1991,
it acquired NCR, a seasoned computer company.


ATA
Interface specification for IDE drives.  Also used
for PCMCIA solid state disks.


Atari
(Atari Computer, Sunnyvale, CA)  Manufacturer of
personal computers originally founded in 1972 by
Nolan Bushnell and famous for its "Pong" video
games.  In 1976, it was sold to Time Warner, Inc.,
and in 1984 was sold to Jack Tramiel and investors.
Within six months, the 520ST was introduced, the
first personal computer designed for MIDI
applications.  Its product line, aimed at providing
quality computing at affordable prices, includes
the 1040STE, TT030 workstation and Portfolio
palmtop.


ATE
(Automatic Test Equipment)  Machines that test
electronic systems, primarily chips.  See EDA and
DTA.


ATM
(1) (Automatic Teller Machine)  Special-purpose
banking terminal that allows users to make deposits
and withdrawals.  It can be a stand-alone unit or
online to a central computer system.  ATMs are
activated by inserting a magnetic card (cash card
or credit card) in the machine that contains the
user's identification number.

(2) (Asynchronous Transfer Mode)  High-speed packet
switching technique suitable for MANs and broadband
ISDN transmission.  It uses cell relay
transmission.

(3) See Adobe Type Manager.


atom
In list processing languages, a single element in a
list.


atomic
Indivisible.  An atomic operation, or atomicity,
implies an operation that must be performed
entirely or not at all.  For example, if machine
failure prevents a transaction to be processed to
completion, the system will be rolled back to the
start of the transaction.  See two-phase commit.


attached processor
Additional CPU connected to the primary CPU in a
multiprocessing environment.  It operates as an
extension of the primary CPU and shares the system
software and peripheral devices.


attenuation
Loss of signal power in a transmission.


attribute
(1) In relational database management, a field
within a record.

(2) For printers and display screens, a
characteristic that changes a font, for example,
from normal to boldface or underlined, or from
normal to reverse video.

(3) See file attribute.


audio
Range of frequencies within human hearing (approx.
20Hz at the low to a high of 20,000Hz).

   Traditional audio devices are analog, because
they handle sound waves in an analogous form.
Radios maintain the audio signal as rippling waves
from antenna to speaker.  Sound waves are "carved"
into plastic phonograph records, and audio tape
records sound as magnetic waves.

   Audio is processed in a computer by converting
the analog signal into a digital code using various
techniques, such as PCM.


audio board
Same as sound card.


audio response
See voice response.


audiotex
Voice response application that allows users to
enter and retrieve information over the telephone.
In response to a voice menu, users press the keys
or answer questions to select their way down a path
of choices.  It is used for obtaining the latest
financial quotes as well as for ordering products.
It is also built into interactive systems that
allows databases to be changed.  See VIS.


audiovisual
Audio and/or video capability.


audit
Examination of systems, programming and datacenter
procedures in order to determine the efficiency of
computer operations.


audit software
Specialized programs that perform a variety of
audit functions, such as sampling databases and
generating confirmation letters to customers.  It
can highlight exceptions to categories of data and
alert the examiner to possible error.  Audit
software often includes a non-procedural language
that lets the auditor describe the computer and
data environment without detailed programming.


audit trail
Record of transactions in an information system
that provides verification of the activity of the
system.  The simplest audit trail is the
transaction itself.  If a person's salary is
increased, the change transaction includes the
date, amount of raise and name of authorizing
manager.

   A more elaborate audit trail can be created when
the system is being verified for accuracy; for
example, samples of processing results can be
recorded at various stages.  Item counts and hash
totals are used to verify that all input has been
processed through the system.


authoring program
Software that allows for the development of
tutorials and CBT programs.


authorization code
Identification number or password that is used to
gain access to a local or remote computer system.


Authorware
Macintosh authoring program from Authorware, Inc.,
Minneapolis, MN.  Courseware developed on the Mac
can be converted to the PC.


auto
(AUTOmatic)  Refers to a wide variety of devices
that perform unattended operation.


auto answer
Modem feature that accepts a telephone call and
establishes the connection.  See auto dial.


auto attendant
Voice store and forward system that replaces the
human operator and directs callers to the
appropriate extensions or voice mailboxes.


auto bypass
Ability to bypass a terminal or other device in a
network if it fails, allowing the remaining devices
to continue functioning.


auto dial
Modem feature that opens the line and dials the
telephone number of another computer to establish
connection.  See auto answer.


auto line feed
Feature that moves the cursor or print head to the
next line when a CR (carriage return) is sensed.
PCs put a LF (line feed) after the CR and don't use
this feature.  The Mac uses only a CR, thus auto
line feed causes the CR to move the output device
to the next line.


auto logon
Performing the complete log-on sequence necessary
to gain entry into a computer system without user
intervention.


auto resume
Feature that lets you stop working on the computer
and take up where you left off at a later date
without having to reload applications.  Memory
contents are stored on disk or kept active by
battery and/or AC power.


AutoCAD
Full-featured CAD program from AutoDesk Inc.,
Sausalito, CA, that runs on PCs, VAXs, Macs and
UNIX workstations.  Originally developed for CP/M
machines, it was one of the first major CAD
programs for personal computers and became an
industry standard.  Many software packages import
and export graphics files in DXF, AutoCAD's
external file format.


autocoder
IBM assembly language for 1960s-vintage 1400 and
7000 series computers.


AUTODIN
(AUTOmatic DIgital Network)  Worldwide
communications network of the U.S. Defense
Communications System.


AUTOEXEC.BAT
(AUTOmatic EXECute BATch)  DOS batch file that
executes when the computer is started.  The OS/2
counterpart is STARTUP.CMD.  See DOS AUTOEXEC.BAT.


autoflow
Wrapping text around a graphic image or from one
page to the next.


AutoLISP
AutoCAD language used to create customized menus
and routines.


automata theory
Open-ended computer science discipline that
concerns an abstract device called an "automaton,"
which performs a specific computational or
recognition function.  Networks of automata are
designed to mimic human behavior.


automatic data processing
Same as data processing.


automatic feature negotiation
Ability of a modem to determine and adjust to the
speed, error control and data compression method of
the modem at the other end of the line.


automation
Replacement of manual operations by computerized
methods.  Office automation refers to integrating
clerical tasks such as typing, filing and
appointment scheduling.  Factory automation refers
to computer-driven assembly lines.


autosave
Saving data to the disk at periodic intervals
without user intervention.


autosizing
Ability of a monitor to maintain the same
rectangular image size when changing from one
resolution to another.


autostart routine
Instructions built into the computer and activated
when it is turned on.  The routine performs
diagnostic tests, such as checking the computer's
memory, and then loads the operating system and
passes control to it.


autotrace
Routine that locates outlines of raster graphics
images and converts them into vector graphics.


AUX
(AUXiliary)  DOS name for the first connected
serial port.  See DOS device names.  See also A/UX.


auxiliary memory
High-speed memory bank used in mainframes and
supercomputers.  It is not directly addressable by
the CPU, rather it functions like a disk.  Data is
transferred from auxiliary memory to main memory
over a high-bandwidth channel.  See auxiliary
storage.


auxiliary storage
External storage devices, such as disk and tape.


AVC
(Audio Visual Connection)  Multimedia software from
IBM that works in conjunction with IBM's Audio
Capture and Video Capture boards for the PS/2.  It
allows users to integrate sound and pictures into
applications and includes an authoring language.


AVI
(Audio Video Interleaved)  Windows multimedia video
format from Microsoft.  It interleaves standard
waveform audio and digital video frames (bitmaps)
to provide reduced animation at 15 fps at 160x120x8
resolution.  Audio is 11,025Hz, 8-bit samples.


avionics
Electronic instrumentation and control equipment
used in airplanes and space vehicles.


Award BIOS
Widely-used PC-compatible ROM BIOS from Award
Software, Inc., Los Gatos, CA.  By 1991, over 20
million Award BIOS's have been installed.


awk
(Aho Weinberger Kernighan)  UNIX programming
utility developed in 1977 by Aho, Weinberger and
Kernighan.  Due to its unique pattern-matching
syntax, it is often used in data retrieval and data
transformation.  DOS versions are also available.


AXP
Family of computer systems from Digital that use
the Alpha CPU chip.


azimuth
Trajectory of an angle measured in degrees going
clockwise from a base point.  A disk azimuth
alignment test checks for the correct positioning
of the read/write head to the track.



B/ISDN
(Broadband/ISDN)  See ISDN.


B protocol
File transfer protocol from CompuServe.  Quick B is
a faster version only for downloading.  The latest
versions of B will automatically select Quick B.


b-spline
In computer graphics, a curve that is generated
using a mathematical formula which assures
continuity with other b-splines.


B-tree
(Balanced-tree)  Technique for organizing indexes.
In order to keep access time to a minimum, it
stores the data keys in a balanced hierarchy that
continually realigns itself as items are inserted
and deleted.  Thus, all nodes always have a similar
number of keys.

   B+tree is a version of B-tree that maintains a
hierarchy of indexes while also linking the data
sequentially, providing fast direct access and fast
sequential access.  IBM's VSAM uses this.


B1
DOD computer security levels.  See NCSC.


B:
Designation for the second floppy disk drive in a
PC.


back-end CASE
CASE tools that generate program code.  Contrast
with front-end CASE.


back end processor
Same as database machine.


back up
To make a copy of important data onto a different
storage medium for safety.


backbone
In communications, the part of a network that
handles the major traffic.  It may interconnect
multiple locations, and smaller networks may be
attached to it.


backfilling
Assigning EMS memory to conventional memory in XTs
and ATs in order to let DESQview run more programs
concurrently.  Motherboard chips are disabled and
EMS chips are assigned the low memory addresses.


background
(1) Non-interactive processing in the computer.
See foreground/background.

(2) Base, or backdrop, color on screen.  For
example, in the DOS version of this Glossary, the
text color is white on a blue background.


background ink
Highly reflective OCR ink used to print the parts
of the form not recognized by a scanner.


background noise
Extraneous signal that has crept into a line,
channel or circuit.


background processing
Processing in which the program is not visibly
interacting with the user.  Most personal computers
use operating systems that run background tasks
only when foreground tasks are idle, such as
between keystrokes.  Advanced multitasking
operating systems let background programs be given
any priority from low to high.


backing storage
Same as auxiliary storage.


backlit
LCD screen that has its own light source from the
back of the screen, making the background brighter
and characters appear sharper.


backplane
(1) Reverse side of a panel or board that contains
interconnecting wires.

(2) Printed circuit board, or device, containing
slots, or sockets, for plugging in boards or
cables.  See bus.


backslash
See DOS backslash.


backsolver
See solver.


backspace
(1) To move the screen cursor one column to the
left, deleting the character that was in that
position.  A backspace to the printer moves the
print head one column to the left.

(2) To move to the previous block on a magnetic
tape.


backup
Additional resources or duplicate copies of data on
different storage media for emergency purposes.
See backup types.


backup & recovery
Combination of manual and machine procedures that
can restore lost data in the event of hardware or
software failure.  Routine backup of databases and
logs of computer activity are part of a backup &
recovery program.  See checkpoint/restart.


backup copy
Disk, tape or other machine readable copy of a data
or program file.  Making backup copies is a
discipline most computer users learn the hard way--
after a week's work is lost.


backup disk
Disk used to hold duplicate copies of important
files.  Floppy disks and disks cartridges are used
for backup disks.


backup power
Additional power source that can be used in the
event of power failure.  See UPS.


backup tape
See tape backup.


backup types
Selection of files for backup purposes.

   A full backup backs up all selected files.

   A differential backup backs up selected files
that have been changed.  This is used when only the
latest version of a file is required.

   An incremental backup backs up selected files
that have been changed, but if a file has been
changed for the second or subsequent time since the
last full backup, the file doesn't replace the
already-backed-up file, rather it is appended to
the backup medium.  This is used when each revision
of a file must be maintained for backup.


Backus-Naur form
Also known as Backus normal form, it was the first
metalanguage to define programming languages,
developed by John Backus and Peter Naur in 1959.


backward chaining
In AI, a form of reasoning that starts with the
conclusion and works backward.  The goal is broken
into many subgoals or sub-subgoals which can be
solved more easily.  Known as top-down approach.
Contrast with forward chaining.


backward compatible
Same as downward compatible.


bad sector
Segment of disk storage that cannot be read or
written due to a physical problem in the disk.  Bad
sectors on hard disks are marked by the operating
system and bypassed.  If data is recorded in a
sector that becomes bad, file recovery software,
and sometimes special hardware, must be used to
restore it.


BAK file
(BAcKup file)  DOS and OS/2 file extension for
backup files.


BAL
(1) (Basic Assembly Language)  Assembly language
for the IBM 370/3000/4000 mainframe series.

(2) (Branch And Link)  Instruction used to transfer
control to another part of the program.


ballistic gain
Trackball or mouse feature that changes cursor
travel relative to hand speed.  The faster the ball
is moved, the farther the cursor is moved.


baloon help
On-screen help displayed in a cartoon-style
dialogue box that appears when the pointer (cursor)
is placed over the object in question.


balun
(BALanced UNbalanced)  Device that connects a
balanced line to an unbalanced line; for example, a
twisted pair to a coaxial cable.  A balanced line
is one in which both wires are electrically equal.
In an unbalanced line, such as a coax, one line has
different properties than the other.


band
(1) Range of frequencies used for transmitting a
signal.  A band is identified by its lower and
upper limits; for example, a 10MHz band in the 100
to 110MHz range.

(2) Contiguous group of tracks that are treated as
a unit.

(3) Printing element in a band printer.


band pass filter
Electronic device that prohibits all but a specific
range of frequencies to pass through it.


band printer
Line printer that uses a metal band, or loop, of
type characters as its printing mechanism.  The
band spins horizontally around a set of hammers.
When the desired character is in front of the
selected print position, the corresponding hammer
hits the paper into the ribbon and onto the
character in the band.


bandwidth
Transmission capacity of a computer channel,
communications line or bus.  It is expressed in
cycles per second (Hertz), the bandwidth being the
difference between the lowest and highest
frequencies transmitted.  The frequency is equal to
or greater than the bits per second.  Bandwidth is
also often stated in bits or bytes per second.  See
video bandwidth.


bank
Arrangement of identical hardware components.


bank switching
Engaging and disengaging electronic circuits.  Bank
switching is used when the design of a system
prohibits all circuits from being addressed or
activated at the same time, requiring that one unit
be turned on while the others are turned off.


BAPC
(Business Applications Performance Corp.)
Nonprofit organization founded in 1991 that
develops benchmarks for PC software.


bar chart
Graphical representation of information in the form
of bars.  See business graphics.


bar code
Printed code used for recognition by a scanner.
Traditional one-dimensional bar codes use the bar's
width as the code, but encode just an ID or account
number.  Two-dimensional systems, such as PDF 417
from Symbol Technology, hold 1,800 characters in an
area the size of a postage stamp.  See UPC.


barrel distortion
Screen distortion in which the sides bow out.
Contrast with pincushioning.


barrel printer
Same as drum printer.


base
(1) Starting or reference point.

(2) Component in a bipolar transistor that
activates the switch.  Same as gate in a MOS
transistor.

(3) Multiplier in a numbering system.  In a decimal
system, each digit position is worth 10x the
position to its right.  In binary, each digit
position is worth 2x the position to its right.


base address
Starting address (beginning point) of a program or
table.  See base/displacement and relative address.


base alignment
Alignment of a variety of font sizes on a baseline.


base/displacement
Machine architecture that runs programs no matter
where they reside in memory.  Addresses in a
machine language program are displacement
addresses, which are relative to the beginning of
the program.  At runtime, the hardware adds the
address of the current first byte of the program
(base address) to each displacement address and
derives an absolute address for execution.


base font
Default font used for printing if none other is
specified.


baseband
Communications technique in which digital signals
are placed onto the transmission line without
change in modulation.  It is usually limited to a
few miles and does not require the complex modems
used in broadband transmission.  Common baseband
LAN techniques are token passing ring (Token Ring)
and CSMA/CD (Ethernet).

   In baseband, the full bandwidth of the channel
is used, and simultaneous transmission of multiple
sets of data is accomplished by interleaving pulses
using TDM (time division multiplexing).  Contrast
with broadband transmission, which transmits data,
voice and video simultaneously by modulating each
signal onto a different frequency, using FDM
(frequency division multiplexing).

          Baseband (interleaves signals)
     ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀
       data(1)  data(2)  data(3)  data(1)
     ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄


           Broadband (true simultaneous)
     ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀
       data(1)xxxxxxxxxxxxxxxxxxxxxxxxxxx
      ─────────────────────────────────────
       voice(1)xxxxxxxxxxxxxxxxxxxxxxxxxx
      ─────────────────────────────────────
       data(2)xxxxxxxxxxxxxxxxxxxxxxxxxxx
      ─────────────────────────────────────
       data(3)xxxxxxxxxxxxxxxxxxxxxxxxxxx
     ▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄



baseline
Horizontal line to which the bottoms of lowercase
characters (without descenders) are aligned.  See
typeface.


baselining tool
Network monitor that analyzes communications usage
in order to establish routine traffic patterns.


BASIC
(Beginners All purpose Symbolic Instruction Code)
Programming language developed by John Kemeny and
Thomas Kurtz in the mid 1960s at Dartmouth College.
Originally developed as an interactive, mainframe
timesharing language, it has become widely used on
small computers.

   BASIC is available in both compiler and
interpreter form.  As an interpreter, the language
is conversational and can be debugged a line at a
time.  BASIC is also used as a quick calculator.

   BASIC is considered one of the easiest
programming languages to learn.  Simple programs
can be quickly written on the fly.  However, BASIC
is not a structured language, such as Pascal, dBASE
or C, and it's easy to write spaghetti code that's
difficult to decipher later.

   The following BASIC example converts Fahrenheit
to Celsius:

   10 INPUT "Enter Fahrenheit "; FAHR
   20 PRINT "Celsius is ", (FAHR-32) * 5 / 9



BASIC in ROM
BASIC interpreter stored in a read only memory chip
that is available to the user at all times.


BAT file
(BATch file)  File of DOS or OS/2 commands, which
are executed one after the other.  It has a .BAT
extension and is created with a text editor.  See
DOS batch file and DOS AUTOEXEC.BAT.


batch
Group, or collection, of items.


batch data entry
Entering a group of source documents into the
computer.


batch file
(1) File containing data that is processed or
transmitted from beginning to end.

(2) File containing instructions that are executed
one after the other.  See BAT file.


batch file transfer
Consecutive transmission of two or more files.


batch job
Same as batch program.


batch operation
Some action performed on a group of items at one
time.


batch processing
Processing a group of transactions at one time.
Transactions are collected and processed against
the master files (master files updated) at the end
of the day or some other time period.  Contrast
with transaction processing.


         Batch and Transaction Processing
Information systems typically use both batch and
transaction processing methods.  For example, in an
order processing system, transaction processing is
the continuous updating of the customer and
inventory files as orders are entered.

   At the end of the day, batch processing programs
generate picking lists for the warehouse.  At the
end of some period, batch programs print invoices
and management reports.


batch program
Non-interactive (non-conversational) program such
as a report listing or sort.


batch session
Transmitting or updating an entire file.  Implies a
non-interactive or non-interruptible operation from
beginning to end.  Contrast with interactive
session.


batch stream
Collection of batch processing programs that are
scheduled to run in the computer.


batch system
See batch processing.


batch terminal
Terminal set up for transmitting or receiving
blocks of data, such as a card reader or printer.


batch total
Sum of a particular field in a collection of items
used as a control total to ensure that all data has
been entered into the computer.  For example, using
account number as a batch total, all account
numbers would be summed manually before entry into
the computer.  After entry, the total is checked
with the computer's sum of the numbers.  If it does
not match, source documents are manually checked
against the computer's listing.


batteries
See lead acid, NiCad, nickel hydride and zinc air.


baud
(1) Signalling rate of a line.  It's the switching
speed, or number of transitions (voltage or
frequency changes) that are made per second.  Only
at low speeds are bauds equal to bits per second;
for example, 300 baud is equal to 300 bps.
However, one baud can be made to represent more
than one bit per second.  For example, the V.22bis
modem generates 1200 bps at 600 baud.

(2) Commonly (and erroneously) used to specify bits
per second for modem speed; for example, 1200 baud
means 1200 bps.  See previous paragraph.


baud rate
Redundant reference to baud.  Baud is a rate.


baudot code
Pronounced "baw-doh."  One of the first standards
for international telegraphy developed in the late
19th century by Emile Baudot.  It uses five bits
per character.


BBS
(Bulletin Board System)  Computer system used as an
information source and message system for a
particular interest group.  Users dial into the
BBS, review and leave messages for other users as
well as communicate to other users on the system at
the same time.  BBSs are used to distribute
shareware and may provide access (doors) to other
application programs.


              BOARDWATCH MAGAZINE
               NATIONAL LIST OF
  ELECTRONIC BBSs AND ONLINE INFORMATION SERVICES
            (Copied with permission)

              BOARDWATCH MAGAZINE
             5970 S. Vivian Street
              Littleton, CO 80127

           Information 303/973-6038
           Subscriptions 800/933-6038
           By modem (N81) 303/973-4222


65' North (DESQview utilities)         907/452-1460
ADA 9X Project (Ada language)          800/232-9925
ADA Information Clearinghouse          703/614-0215
Advanced Data Services Inc.            301/695-9116
American Cybernetics                   602/968-1082
ANARC (World/Radio/TV handbook)        913/345-1978
APCUG - Assn. of PC User Groups        408/439-9367

Applied Modeling Research (EPA models) 919/541-1325
Aquila (Fidonet/Interlink/Metronet)    708/820-8344
Ashton-Tate Technical Support          408/431-2275
AST Technical Support                  714/727-4723
AT&T Support (PC 6300 & other models)  908/769-6397
ATI Support (modems & video cards)     416/756-4591
Attention to Details (utilities/ASP)   714/681-6221

Audiophile Network (high-end audio)    818/988-0452
Automobile Consumer Services (prices)  513/624-0552
AviTechnic 1:261/662                   301/252-0717
BBS America (DFW online newsletter)    214/680-3406
BBS Press Service (INFOMAT Online)     913/478-9239
Best Friends (multiline social)        714/828-7093
Big Sky Telegraph (educ/econ Montana)  406/683-7680

Bird Info Network (exotic birds)       303/423-9775
BMUG (Mac support)                     415/849-2684
Boardwatch Magazine Online Info        303/973-4222
Boca Research Support BBS              407/241-1601
Book BBS (info on 3000+ computer books)215/657-6130
Borland Download BBS                   408/439-9096
Bruce's Bar & Grill (social)           203/236-3761

Bucks Telematics 273/201               215/493-5242
C.A.R.L. Library Service (Colorado)    303/863-1350
CAD/Engineering Service 1:116/32       615/824-4938
Canada Remote Systems                  416/798-4713
Capital PC User's Group BBS            301/738-9060
Castle Tabby 107/4122 (Apple, MAC)     908/988-0706
Celebration Station (games chat)       207/374-5161

Census Bureau Office Automation        301/763-4576
Census Bureau Personnel Division       301/763-4574
Channel 1 (45-line PC Board sys)       617/354-8873
Chicago SysLink (TRS 80 support)       312/622-4442
chinet (UNIX Systems Internet mail)    312/283-0559
ClassiComputerFieds (classified ads)   317/359-5199
Clean Air (health, smoking topics)     408/298-4277

Cleveland Freenet (city info)          216/368-3888
CocoNet (San Diego entertainment)      619/456-0815
Comm-Post, The   104/666               303/534-4646
Community News Service (entertainment) 719/520-5000
Compact Audio Disk Exchange (buy/sell) 415/824-7603
CompuCom Support (9600 bps - $279 )    415/499-7711
Computer Garden (treasure hunting)     301/546-1508

Computerized BBS (Ward Christensen)    708/849-1132
Computing Canada Online (PC newspaper) 416/497-5263
Corporate Data Exchange (CDX)(PR news) 609/683-4422
CrossTalk Technical Support            404/740-8428
CTC IEEE Employment Database (resumes) 508/263-3857
Cul-de-Sac Bar & Grill (ham radio)     508/429-1784
Dante Project (Divinia Comedia)        603/643-6310

Dark Side of the Moon (DOS & UNIX)     408/245-7726
Data Core (25 line major BBS)          213/842-6880
DataLink RBBS System (NOAA satellite)  214/394-7438
Dawg Byte (ANSI Art Club 1:116/29)     615/385-4268
Denver Exchange 104/909 (gay, lesbian) 303/623-4965
DragonNet 386/451 (major BBS)          409/765-5459
East Bay X-Change  372/888             803/556-7485

Echo (Unix CAUCUS conferencing)        212/989-8411
Economic Bulletin Board (statistics)   202/377-3870
Ed Hopper's BBS (home of uuPCB)        713/997-7575
Electric Ideas Clearinghouse           206/586-6854
Energy Info Admin E-Publications       202/586-8658
eSoft Product Support (Bread Board)    303/699-8222
Event Horizons (graphics image lib.)   503/697-5100

Exchange BBS (gay/bi/lesbian)          713/521-2191
EXEC-PC (largest BBS in US, 100 lines) 414/789-4210
Executive Network (interlink netmail)  914/667-4567
Eye Contact (gay issues, chat)         415/255-5972
Falken Support (software)              703/803-8000
Far West (Western Canada Galacticomm)  604/381-3934
FAX/Satellite (NOAA Weather)           619/224-3853

FCC Public Access Link                 301/725-1072
Federal Job Information Center         313/226-4423
FEDLINK ALIX II (federal libraries)    202/707-4888
Fido Software 1:125/111                415/863-2739
Fido Tech Stand (info for Holland)     31-30-735900
FOG City 125/10 (gay community)        415/863-9697
Fred the Computer (Weirdnet Newswire)  508/872-8461

FreeBoard (desktop pub. 1:264/212)     804/744-0797
FSBBS Prototype System (FSUUCP & FSBBS)805/543-8227
Fun Connection (entertainment, news)   503/753-8431
Gateway Comm. (NetWare, TCP/IP util.)  714/863-7097
GDP Technologies (PC shareware)        303/673-9470
Gilmore Systems (support MAGNUM BBS)   818/706-9805
GLIB (gay/lesbian information)         703/578-4542

Greenpeace Environet (ecological)      415/512-9108
Hayes Microcomputer (modem support)    800/874-2937
Heartland Free-net                     309/674-1100
Herpnet/Satronics (reptile, amphibian) 215/698-1905
HH Info-Net (windows, OS/2)            203/246-3747
HOLLIS (Harvard online library)        617/495-9500
Hysterics (Amiga 1:163/109)            613/231-7144

IBM National Support Center            404/835-5300
Inbound/Outbound/Teleconnect           212/989-4675
Index Systems (Atlanta BBS)            404/924-8414
Infinity World (8-line galacticomm)    606/271-6556
InfoHost Demo BBS                      201/288-7792
Infolink for Upper East Tenn.          615/434-2552
Inns of Court (LAN related files)      214/458-2620

Intel PCEO Support                     503/645-6275
Invention Factory (shareware catalog)  212/431-1194
Investor's Online Data (stocks)        206/285-5359
JAG-NET (Navy Judge Advocate General)  703/325-0748
JDR Microdevices (hardware catalog)    408/559-0253
JEPP/LINK (pilot weather service)      800/767-7000
JOBBS (job listings technical)         404/992-8937

Keith Graham Shareware (utilities)     914/623-0039
KIMBERELY (prime rate, T-bills, etc.)  612/340-2489
King's Market 104/115 (writer's area)  303/665-6091
LANtastic (tech. support)              602/293-8065
Late Night (GENESIS software)          315/592-7300
Late Night Software 125/555 (UFGATE)   415/695-0759
Leading Edge Auto Info Line            508/836-3967

LegalEase (issues/forms)               509/326-3238
MAC-LINK                               514/935-4257
Macalot (support Second Sight for Mac) 412/846-5312
Macinternational (largest MAC BBS)     803/798-3755
Magpie (support)                       212/420-0527
MaxiHost Support (small easy BBS)      209/836-2402
McAfee Associates (virus info)         408/988-4004

METRO Online Entertainment             212/831-9280
Micro Foundry, The (software support)  415/598-0398
Micro Message Service (news magazines) 919/779-6674
Micro Tech (OSIRIS support, mail)      314/334-6359
Microlink B (USA Today, news)          303/972-9600
Microrim Technical Support BBS         206/649-9836
Microsystems Software Inc. (support)   508/875-8009

Midwest MIDI 1:147/1007                405/733-3102
Minnesota Spacenet (NASA news)         612/920-5566
MOG-UR'S EMS (CD-ROMS, 2.8 GB Hub Serv)818/366-1238
Movie BBS )reviews for movie & TV)     718/939-5462
N.A.C.D. (Cave Scuba Divina)           912/246-3280
N8EMR Ham (ham/radio)                  614/895-2553
NAPLPS Graphics (software)             613/727-5272

NARDAC (Zenith support, federal users) 804/445-1627
NASA Headquarters Info Tech            202/453-9008
NASA Spacelink (flight/space history)  205/895-0028
Nashville Exchange (games, software)   615/383-0727
National Agricultural Library          301/344-8510
National Genealogical (family history) 703/528-2612
NAVWESA (naval weapons engineering)    202/433-6639

Netcom Internet Guest System (lodging) 408/241-9760
Network World Bulletin Board (LAN, WAN)508/620-1178
Neuropsychology Bound 157/3 (support)  216/356-1431
NIST ACTS (computer telephone service) 303/494-4775
NIST Computer Security (virus issues)  301/948-5717
Nixpix (adult graphics images)         303/920-1263
NOAA Space Environment Lab             303/497-5042

NoGate Consulting (PAK archive utility)616/530-3392
Numisnet (coin collecting)             301/498-8205
OASIS (Atlanta BBS)                    404/627-2662
Occupational Health/Safety             212/385-2034
Odyssey (adult chat, games, etc.)      818/358-6968
OERI (educational statistics, data)    800/222-4922
Old Colorado City Comm. (political)    719/632-4111

Online Now (new software, CD-ROMS)     807/345-5522
Online With Hayes                      404/446-6336
Oracle PC (South Australian TBBS)     6108 260-6222
Oracomm Support                        619/346-1608
Osprey's Nest (birdwatching, ecology)  301/989-9036
P.D.S.L.O. (national BBS list)         516/938-6722
PacComm (packet radio equipt. supplier)813/874-3078

PC Ohio (shareware)                    216/381-3320
PHYSICS Forum (astronomical sciences)  413/545-1959
Pinecliff 104/28 (shareware)           303/642-7463
PKWare (PKARC and PKZIP Utilities)     414/354-8670
Pleasure Dome (erotic)                 804/490-5878
Practical Peripherals (modem support)  818/706-2467
ProComm Support                        314/875-0503

Promised Land (WINDOWS, chat & more)   715/387-1339
Public Brand Software (commercial)     317/856-2087
Public Data Network ($2.50/hr access)  503/474-6662
QAQPSTTN (air quality planning)        919/541-5742
QMail Deluxe Support                   901/382-5583
Qualitas, Inc. (support)               301/907-8030
Quick BBS Support BBS 363/34           407/896-0494

Random Access Information Services     503/761-8100
Rose Media (Canadian PC board sys.)    416/733-2780
Rusty & Edies (large ML PCBoard)       216/726-0737
Salt Air (PCBOARD BBS software)        801/261-8976
San Diego NeXt User's Group            619/456-2522
Science Resources Studies (fed budget) 202/634-1764
SDN Project 1:141/840                  203/634-0370

SEAboard! (ARC, SEADOG, AXE software)  201/473-1991
Seagate Technical Support              408/438-8771
Searchlight (support)                  516/689-2566
SemWare Support (QEdit, shareware)     404/641-8968
Short Line 104/36 (varied subjects)    303/733-0773
SIGCAT (CD-ROM/Optical Publishing info)703/648-4168
Sistema Professional Info (Mexico)     525 590-5988

Skeleton Closet (geneology programs)   804/671-8547
Society for Technical Comm.            703/522-3299
Sonshine Express (Christian family)    415/651-2440
Sound Advise (20 line PCBoard)         816/436-4516
Source for Source (Clipper/XBase/etc)  516/968-7824
Spare Parts 1:130/38 (Windows)         817/540-3527
Star-Link Network (75,000 programs)    718/972-6099

State and Local Emergency Management   202/646-2887
Stillwaters (Chicagoland, 500 systems) 708/403-2826
Superdemocracy Foundation (political)  305/370-9376
TAXACOM (botany, FLORA ONLINE news)    716/896-7581
TEAMate Unix Bulletin Board            213/318-5302
Telegodzilla (home of ZModem)          503/621-3746
Telepath (Dr. Dobbs magazine online)   415/364-8315

Telix Support                          416/439-8293
That Old Frog's Swamp (Zen Bhuddist)   715/362-3895
The Back Room (largest gay DB)         718/849-1614
The Business BBS                       213/477-0408
The General (file library)             619/281-8616
The Ledge PCBoard (Textview Door)      818/896-4015
The Opowd Crowd (sports)               708/885-8865

The Other BBS 1:1/0 (Fiodnet)          717/657-2223
The Professional System (lawyers EDP)  303/740-2223
The Well (popular - hourly charges)    415/332-7190
Trinity 1 (UK distributor Boardwatch) 44 392 410210
Titan (adult, games, GIF images)       904/476-1270
Town Hall (conservative political)     800/648-6964
Transnet (language translation)        217/384-5101

TurboTax Support (income tax info)     619/453-5232
U.S. ROBOTICS - Sit UBU Sit            708/982-5092
US Naval Observatory (enter @TCO)      202/653-1079
USGS Quick Epicenter Determination     800/358-2663
USNO Time of Day for Clocks            202/653-0351
UT Library Online Catalog              512/471-9420
Ventura Professional Forum             408/227-4818

Ward and Randy's CBBS (oldest BBS)     312/545-8086
WeatherBank (forecast for any city)    800/827-2727
Western Digital Technical Support      714/753-1068
Wildcat HQ 210/12 (support)            805/395-0650
Windows Online Info (3.0 programs)     510/736-8343
Windsor Manor                          203/688-4973
WordPerfect Customer Support           801/225-4444

WWIV Support BBS                       213/208-6689
XTree (support Pro Gold DOS shell)     805/546-9150
XyQuest Tech Support (XyWrite III+)    508/667-5669
Yellow Dream Machine (disability news) 512/451-3222


BCD
(Binary Coded Decimal)  Storage of numbers in which
each decimal digit is converted into binary and is
stored in a single character or byte.  For example,
a 12-digit number would take 12 bytes.  See
numbers.


BCS
(1) (The Boston Computer Society)  Nonprofit
membership organization founded in 1977 by Jonathan
Rotenberg.  With over 28,000 members, it is the
world's largest personal computer association.
Services include user and special interest groups,
a subscription to BCS publications, access to the
Resource Center, public-domain software and
shareware.  Address: 1 Kendall Square, Cambridge,
MA 02139, 617/252-0600.

(2) (Binary Compatibility Standard)  See ABI.

(3) (The British Computer Society)  Address: 13
Mansfield St., London, England W1M 0BP.


BDOS error
See read error and write error.


beaconing
Continuous signalling of error conditions on a LAN.


bead
(1) Small programming subroutine.  A sequence of
beads that are strung together is called a thread.

(2) Insulator surrounding the inner wire of a
coaxial cable.


BEL
See bell character.


Bell 103
AT&T standard for asynchronous 300 bps full-duplex
modems using FSK modulation on dial-up lines.


Bell 113
AT&T standard for asynchronous 300 bps full-duplex
modems using FSK modulation on dial-up lines.  The
113A can originate but not answer calls, while the
113D can answer but not originate.


Bell 201
AT&T standard for synchronous 2400 bps full-duplex
modems using DPSK modulation.  Bell 201B was
originally designed for dial-up lines and later for
leased lines.  Bell 201C was designed for half-
duplex operation over dial-up lines.


Bell 202
AT&T standard for asynchronous 1800 bps full-duplex
modems using DPSK modulation over four-wire leased
lines as well as 1200 bps half-duplex operation
over dial-up lines.


Bell 208
AT&T standard for synchronous 4800 bps modems.
Bell 208A is a full-duplex modem using DPSK
modulation over four-wire leased lines.  Bell 208B
was designed for half-duplex operation over dial-up
lines.


Bell 209
AT&T standard for synchronous 9600 bps full-duplex
modems using QAM modulation over four-wire leased
lines or half-duplex operation over dial-up lines.


Bell 212
AT&T standard for asynchronous 1200 bps full-duplex
modems using DPSK modulation on dial-up lines.


bell character
Control code used to sound an audible bell or tone
in order to alert the user (ASCII 7, EBCDIC 2F).


Bell compatible
Modem that is compatible with modems originally
introduced by the Bell Telephone System.


Bell Labs
Research and development center of the AT&T Company
and one of the most renowned scientific
laboratories in the world.


Bell System
AT&T and the Bell Telephone Companies before
divestiture.  See divestiture and RBOC.


benchmark
Test of performance of a computer or peripheral
device.  The best benchmark is the actual set of
application programs and data files that the
organization will use.  Running benchmarks on a
single user computer is reasonably effective;
however, benchmarking a multiuser system is
complicated.  Unless the user environment can be
duplicated closely, the benchmark may be
inaccurate.  See Linpack, Dhrystones, Whetstones,
Khornerstones and SPECmark.


BER
(1) (Basic Encoding Rules)  One method for encoding
information in the OSI environment.  For example,
it defines how Boolean data is coded.

(2) (Bit Error Rate)  Average number of bits
transmitted in error.


Berkeley extensions
See BSD UNIX.


Bernoulli Box
Removable disk system for personal computers from
Iomega Corp., Roy, UT.  It uses a SCSI interface.
Introduced in 1983, it used a 10MB, 8" floppy disk
cartridge.  In 1987, 20MB 5.25" cartridges were
introduced and later 44MB and 90MB.  The MultiDisk
150 (1992) accepts 35, 65, 90, 105 and 150MB
cartriges.

   The name comes from 18th century Swiss
scientist, Daniel Bernoulli, who demonstrated fluid
dynamics principles.  Unlike a hard disk in which
the read/write head flies over a rigid disk, the
Bernoulli floppy is spun at high speed and bends up
close to the head.  Upon power failure, a hard disk
must retract the head to prevent a crash, whereas
the Bernoulli floppy naturally bends down.


Beta
First home VCR format, now defunct.  Developed by
Sony, it used 1/2" tape cassettes.  Beta Hi-fi
added CD-quality audio, and SuperBeta improved the
image.  Today, VHS is the standard 1/2" VCR format.


beta test
Test of hardware or software that is performed by
users under normal operating conditions.  See alpha
test.


betaware
Software in beta test that has been provided to a
large number of users in advance of the formal
release.


Bezier
In computer graphics, a curve that is generated
using a mathematical formula which assures
continuity with other Bezier curves.  It is
mathematically simpler, but more difficult to blend
than a b-spline curve.  Within CAD and drawing
programs, Bezier curves are typically reshaped by
moving the handles that appear off of the curve.


BFT
(Binary File Transmission)  Standard for
transmitting data between fax boards in less time
than conventional modems.  It does not allow
transfer between fax boards and data modems.


BI bus
Proprietary high-speed bus used in the VAX series.


bi-endian
Ability to switch between big endian and little
endian ordering.


bidirectional
Ability to move, transfer or transmit in both
directions.


bidirectional printer
Printer that prints alternate lines from right to
left.


BIFF
(Binary Interchange File Format)  Spreadsheet file
format that holds data and charts, introduced with
Excel Version 2.2.


bifurcate
To divide into two.


Big Blue
Slang for IBM coined from the blue covers on most
of its earlier mainframes.


big endian
Order of bytes in a word in which the most
significant byte is first.  Little endian reverses
the order.  See bi-endian.

   16 bit number: 5A01h (23,041 decimal)
      Big endian: 5A01  (Motorola 68xxx)
   Little endian: 015A  (Intel x86)


bill of materials
List of components that make up a system.  For
example, a bill of materials for a house would
include the cement block, lumber, shingles, doors,
windows, plumbing, electric, heating and so on.
Each subassembly also contains a bill of materials;
the heating system is made up of the furnace,
ducts, etc.  A bill of materials "implosion" links
component pieces to a major assembly, while a bill
of materials "explosion" breaks apart each assembly
or subassembly into its component parts.

   The first hierarchical databases were developed
for automating bills of materials for manufacturing
organizations in the early 1960s.


billion
One thousand times one million.  See giga and
nanosecond.


bin
(BINary)  Popular directory name for storing
executable programs, device drivers, etc. (binary
files).


binaries
Executable programs in machine language.


binary
Meaning two.  The principle behind digital
computers.  All input to the computer is converted
into binary numbers made up of the two digits 0 and
1 (bits).  For example, when you press the "A" key
on your personal computer, the keyboard generates
and transmits the number 01000001 to the computer's
memory as a series of pulses.  The 1 bits are
transmitted as high voltage; the 0 bits are
transmitted as low.  The bits are stored as charged
and uncharged memory cells in the computer.

   On magnetic disk and tape, the bits are stored
as positively and negatively charged spots.
Display screens and printers convert the binary
numbers into visual characters.

   The electronic circuits that process these
binary numbers are also binary in concept.  They
are made up of on/off switches (transistors) that
are electrically opened and closed.  The current
flowing through one switch turns on (or off)
another switch, and so on.  These switches open and
close in nanoseconds and picoseconds (billionths
and trillionths of a second).

   A computer's capability to do work is based on
its storage capacity (memory and disk) and internal
transmission speed.  Greater storage capacities are
achieved by making the memory cell or magnetic spot
smaller.  Faster transmission rates are achieved by
shortening the time it takes to open and close the
switch.  In order to increase computer performance,
we keep improving binary devices.


              How Binary Numbers Work
Binary numbers are actually simpler than decimal
numbers as they use only the digits 0 and 1 instead
of 0 through 9.

   In decimal, when you add 9 and 1, you get 10.
But, if you break down the steps you find that by
adding 9 and 1, what you get first is a result of 0
and a carry of 1.  The carry of 1 is added to the
digits in the next position on the left.  In the
following example, the carry becomes part of the
answer since there are no other digits in that
position.


    carry--1
            9
         +  1
         ────
           10

The following example adds 1 ten times in
succession.  Note that the binary method has more
carries than the decimal method.  In binary, 1 and
1 are 0 with a carry of 1.

  Binary   Decimal    Binary   Decimal
      0        0        101        5
   +  1     +  1       +  1     +  1
   ────     ────       ────     ────
      1        1        110        6
   +  1     +  1       +  1     +  1
   ────     ────       ────     ────
     10        2        111        7
   +  1     +  1       +  1     +  1
   ────     ────       ────     ────
     11        3       1000        8
   +  1     +  1       +  1     +  1
   ────     ────       ────     ────
    100        4       1001        9
   +  1     +  1       +  1     +  1
   ────     ────       ────     ────
    101        5       1010       10



binary code
Coding system made up of binary digits.  See BCD,
data code and numbers.


binary compatible
Refers to any data, hardware or software structure
(data file, machine code, instruction set, etc.) in
binary form that is 100% identical to another.


binary field
Field that contains binary numbers.  It may refer
to the storage of binary numbers for calculation
purposes, or to a field that is capable of holding
any information, including data, text, graphics
images, voice and video.  See BLOb.


binary file
(1) Executable program in machine language ready to
run.

(2) File that contains binary numbers.


binary format
(1) Numbers stored in pure binary form in contrast
with BCD form.  See binary numbers.

(2) Information stored in a binary coded form, such
as data, text, images, voice and video.  See binary
file, binary field and BLOb.

(3) File transfer mode that transmits any type of
file without loss of data.


binary notation
Use of binary numbers to represent values.


binary numbers
Numbers stored in pure binary form.  Within one
byte (8 bits), the values 0 to 255 can be held.
Two contiguous bytes (16 bits) can hold values from
0 to 65,535.  See numbers and binary values.


binary search
Technique for quickly locating an item in a
sequential list.  The desired key is compared to
the data in the middle of the list.  The half that
contains the data is then compared in the middle,
and so on, either until the key is located or a
small enough group is isolated to be sequentially
searched.


binary synchronous
See bisync.


binary tree
Data structure in which each node contains one
parent and no more than two children.


binary values
The following table shows the maximum number of
numeric combinations in a binary structure with all
bits set to zero equivalent to one combination.
For example, in one bit, which can be 0 or 1, there
are two possible values.

 Bits       Total values
 1                 2
 2                 4
 3                 8
 4                16

 5                32
 6                64
 7               128
 8               256

 9               512
10             1,024   1K
11             2,048   2K
12             4,096   4K

13             8,192   8K
14            16,384  16K
15            32,768  32K
16            65,536  64K

17           131,072 128K
18           262,144 256K
19           524,288 512K
20         1,048,576   1M

21         2,097,152   2M
22         4,194,304   4M
23         8,388,608   8M
24        16,777,216  16M

25        33,554,432  32M
26        67,108,864  64M
27       134,217,728 128M
28       268,435,456 256M

29       536,870,912 512M
30     1,073,741,824   1G
31     2,147,483,648   2G
32     4,294,967,296   4G

33     8,589,934,592   8G
34    17,179,869,184  16G
35    34,359,738,368  32G
36    68,719,476,736  64G

37   137,438,953,472 128G
38   274,877,906,944 256G
39   549,755,813,888 512G
40 1,099,511,627,776   1T



bind
(1) To assign a machine address to a logical or
symbolic reference or address.

(2) To assign a type or value to a variable or
parameter.  See binding time.

(3) To link modules together.  See linkage editor.


binding time
(1) In program compilation, the point in time when
symbolic references to data are converted into
physical machine addresses.

(2) In programming languages, when a variable is
assigned its type (integer, string, etc.).
Traditional compilers and assemblers provide early
binding and assign types at compilation.  Object-
oriented languages provide late binding and assign
types at runtime when the variable receives a value
from the keyboard or other source.


biomechanics
Study of the anatomical principles of movement.
Biomechanical applications on the computer employ
stick modeling to analyze the movement of athletes
as well as racing horses.


bionic
Machine that is patterned after principles found in
humans or nature; for example, robots.  It also
refers to artificial devices implanted into humans
replacing or extending normal human functions.


BIOS
(Basic I/O System)  Detailed instructions that
activate peripheral devices.  See ROM BIOS.


bipolar
Category of high-speed microelectronic circuit
design, which was used to create the first
transistor and the first integrated circuit.  The
most common variety of bipolar chip is TTL
(transistor transistor logic).  Emitter coupled
logic (ECL) and integrated injection logic (I2L)
are also part of the bipolar family.

   Bipolar and MOS are the two major categories of
chip design.


bipolar transmission
Digital transmission technique that alternates
between positive and negative signals.  The 1s and
0s are determined by varying amplitudes at both
polarities while non-data is zero amplitude.


BIPS
(Billion Instructions Per Second)  See MIPS.


biquinary code
Meaning two-five code.  A system for storing
decimal digits in a four-bit binary number.


birefringence
Using a crystal to split light into two frequencies
that travel at different speeds and at right angles
to each other.  It's used to filter out a color in
an LCD display.


bis
Second version.  It means twice in Old Latin, or
encore in French.


BISDN
(Broadband IDSN)  See ISDN.


bison
Free Software Foundation's version of yacc.


bistable circuit
Same as flip-flop.


bisync
(BInary SYNChronous)  Major category of synchronous
communications protocols used in mainframe
networks.  Bisync communications require that both
sending and receiving devices are synchronized
before transmission of data is started.  Contrast
with asynchronous transmission.


bisynchronous
See bisync.


bit
(BInary digiT)  Single digit in a binary number (0
or 1).  Within the computer, a bit is physically a
transistor or capacitor in a memory cell, a
magnetic spot on disk or tape or a high or low
voltage pulsing through a circuit.  A bit is like a
light bulb: on or off.

   Groups of bits make up storage units in the
computer, called characters, bytes, or words, which
are manipulated as a group.  The most common is the
byte, made up of eight bits and equivalent to one
alphanumeric character.  See space/time.


bit cell
Boundary in which a single bit is recorded on a
tape or disk.


bit density
Number of bits that can be stored within a given
physical area.


bit depth
Number of on-screen colors (number of bits used to
represent a pixel).


bit flipping
Same as bit manipulation.


bit level device
Device, such as a disk drive, that inputs and
outputs data bits.  Contrast with pulse level
device.


bit manipulation
Processing individual bits within a byte.  Bit-
level manipulation is very low-level programming,
often done in graphics and systems programming.


bit map
See bitmap.


bit-oriented protocol
Communications protocol that uses individual bits
within the byte as control codes, such as IBM's
SDLC.  Contrast with byte-oriented protocol.


bit parallel
Transmission of several bits at the same time, each
bit travelling over a different wire in the cable.


bit pattern
Specific layout of binary digits.


bit plane
Segment of memory used to control an object, such
as a color, cursor or sprite.  Bit planes may be
reserved parts of a common memory or independent
memory banks each designed for one purpose.


bit rate
Transmission speed of binary coded data.  Same as
data rate.


bit serial
Transmission of one bit after the other on a single
line or wire.


bit slice processor
Logic chip that is used as an elementary building
block for the computer designer.  Bit slice
processors usually come in 4-bit increments and are
strung together to make larger processors (8 bit,
12 bit, etc.).


bit specifications
(1) Size of the computer's internal word, or
registers, which is the amount of data the CPU can
compute at the same time.  If the clock rates
(16MHz, 20MHz, etc.) and basic architecture are
equal, a 32-bit computer works twice as fast
internally as a 16-bit computer.

(2) Size of the computer's data bus, which is the
pathway over which data is transferred between
memory and the CPU and between memory and the
peripheral devices.  If the bus clock rates are
equal, a 16-bit bus transfers data twice as fast as
an 8-bit bus.

(3) Size of the address bus, which determines how
much memory the CPU can address directly.  Each bit
doubles the number, for example, 20-bits addresses
1,048,576 bytes; 24-bits addresses 16,772,216
bytes.

(4) Number of colors that can be displayed at one
time.  Unless some of the memory is used for cursor
or sprite movement, an 8-bit graphics adapter
generates 256 colors; 16-bit, 64K colors; 24-bit,
16.8 million colors.  See alpha channel.

(5)  See binary values.


bit stream
Transmission of binary signals.


bit stuffing
Adding bits to a transmitted message in order to
round out a fixed frame or to break up a pattern of
data bits that could be misconstrued for control
codes.


bit twiddler
Same as hacker.


bitblit
See bitblt.


bitblt
(BIT BLock Transfer)  In computer graphics, a
hardware feature that moves a rectangular block of
bits from main memory into display memory.  It
speeds the display of moving objects (animation,
scrolling) on screen.

   A hardware bitblt provides fastest speed, but
bitblts are also implemented in software even in
non-graphics systems.  For example, text scrolls
faster when it is copied as a contiguous block
(bitblt) to the next part of the window rather than
processing every character on every line.


bite
See byte.


bitmap
(1) In computer graphics, an area in memory that
represents the video image.  For monochrome
screens, one bit in the bitmap represents one pixel
on screen.  For gray scale or color, several bits
in the bitmap represent one pixel or group of
pixels on screen.

(2) Binary representation in which each bit or set
of bits corresponds to some object (image, font,
etc.) or condition.


bitmapped font
Set of dot patterns for each letter and digit in a
particular typeface (Times Roman, Helvetica, etc.)
for a specified type size (10 points, 12 points,
etc.).  Bitmapped typefaces are either purchased in
groups of pre-generated point sizes, or, for a wide
supply of fonts, font generators allow the user to
create a variety of point sizes.  Bitmapped fonts
take up disk space for each point size.  Contrast
with scalable font.  See font and font generator.


bitmapped graphics
Raster graphics method for generating images.
Contrast with vector graphics and character
graphics.


BITNET
Popular network of university computers funded by
the National Science Foundation and run by the Zero
One Corp.


BIX
(Byte Information eXchange)  Online database of
computer knowledge from BYTE magazine, designed to
help users fix problems and obtain info on hardware
and software products.  Address: 1030 Mass. Ave.,
Cambridge, MA 02138, 800/695-4775, 617/491-3393.
See online services.


Black Apple
Early Apple II+ with a black case and external
audio controls.  Bell and Howell sold them in a
training kit.


black box
(1) Custom-made electronic device, such as a
protocol converter or encryption system.
Yesterday's black boxes often become today's off-
the-shelf products.

(2) (Black Box Corp., Pittsburgh, PA)  Organization
that specializes in communications and LAN
products.  It offers expert services, custom
solutions and hard-to-find products.


blank character
Space character that takes up one byte in the
computer just like a letter or digit.  When you
press the space bar on a personal computer
keyboard, the ASCII character with a numeric value
of 32 is created.


blank squash
Removal of blanks between items of data.  For
example, in the expression CITY + ", " + STATE, the
data is concatenated with a blank squash resulting
in  AUSTIN, TX  rather than  AUSTIN         TX.


blip
Mark, line or spot on a medium, such as microfilm,
that is optically sensed and used for timing or
counting purposes.


blit
See bitblt.


BLOb
(Binary Large OBject)  Coined by Borland, a
database field that holds any digitized
information.


block
(1) Group of disk or tape records that is stored
and transferred as a single unit.

(2) Group of bits or characters that is transmitted
as a unit.

(3) Group of text characters that has been marked
for moving, copying, saving or other operation.


block device
Peripheral device that transfers a group of bytes
(block, sector, etc.) of data at a time such as a
disk.  Contrast with character device.


block diagram
Chart that contains squares and rectangles
connected with arrows to depict hardware and
software interconnections.  For program flow
charts, information system flow charts, circuit
diagrams and communications networks, more
elaborate graphical representations are usually
used.


block move
Ability to mark a contiguous segment of text or
data and move it.


blocking factor
Number of records in a block.


blow
To write code or data into a PROM chip by blowing
the fuses of the 0 bits.  The 1 bits are left
alone.


blow up
Same as crash, bomb or abend.


BMP
(Bit MaP)  Windows graphics format that may be
device dependent or independent.  Device
independent BMP files (DIB) are coded for
translation to a wide variety of displays and
printers.


BNC
Commonly used connector for coaxial cable.  The
plug looks like a tiny tin can with the lid off and
two short pins sticking out on the upper edge on
opposite sides.  After insertion, the plug is
turned, tightening the pins in the socket.


board
See printed circuit board and BBS.


board level
Electronic components that are mounted on a printed
circuit board instead of in a cabinet or finished
housing.


BOC
(Bell Operating Company)  One of 22 telephone
companies that was formerly part of AT&T and now
part of one of the seven regional Bell telephone
companies.


BOCOEX
(BOston COmputer EXchange)  See computer exchange.


body type
Typeface and size commonly used for text in
paragraph copy.  Typically 10 points.


BOF
(Beginning Of File)  Status of a file when it is
first opened or when an instruction or command has
reset the file pointer.


boilerplate
Common phrase or expression used over and over.
Boilerplate is stored on disk and copied into the
document as needed.


boldface
Characters that are heavier and darker on printed
output and brighter than normal on a display
screen.


boldface attribute
Code that turns normal characters into boldface
characters on a printer or display screen.


boldface font
Set of type characters that are darker and heavier
than normal type.  In a boldface font, all
characters have been designed as bold characters.


bomb
Same as abend and crash.


BOMP
(Bill Of Materials Processor)  One of the first
DBMSs used for bill of materials explosion in the
early 1960s from IBM.  A subsequent version, DBOMP,
was used in manufacturing during the 1970s.


Boolean data
Yes/no or true/false data.


Boolean expression
Statement using Boolean operators that expresses a
condition which is either true or false.


Boolean logic
The "mathematics of logic," developed by English
mathematician George Boole in the mid 19th century.
Its rules govern logical functions (true/false).
As add, subtract, multiply and divide are the
primary operations of arithmetic, AND, OR and NOT
are the primary operations of Boolean logic.


Boolean operator
One of the Boolean logic operators such as AND, OR
and NOT.


Boolean search
Search for specific data.  It implies that any
condition can be searched for using the Boolean
operators AND, OR and NOT.  For example, the
English language request: "Search for all Spanish
and French speaking employees who have MBAs, but
don't work in Sales." is expressed in the following
dBASE command:

 list for degree = "MBA" .and.
   (language = "Spanish" .or. language = "French")
     .and. .not. department = "Sales"



boot
Causing the computer to start executing
instructions.  Personal computers contain built-in
instructions in a ROM chip that are automatically
executed on startup.  These instructions search for
the operating system, load it and pass control to
it.  Starting up a large computer may require more
button pushing and keyboard input.

   The term comes from "bootstrap," since
bootstraps help you get your boots on, booting the
computer helps it get its first instructions.  See
cold boot and warm boot.


boot drive
Disk drive that contains the operating system.


boot failure
Inability to locate and/or read the operating
system from the designated disk.


boot record
See boot sector.


boot ROM
Memory chip that allows a workstation to be booted
from the server or other remote station.


boot sector
Area on disk (usually the first sectors in the
first disk partition) reserved for the operating
system.  On startup, the computer looks in the boot
sectors for the operating system, which must be
loaded first.


boot virus
Virus written into the boot sectors of a floppy
disk.  If the floppy is booted, it infects the
system.  For example, the Michelangelo virus, which
destroys data on March 6th, Michelangelo's
birthday, infects a computer if the virus diskette
is left in the drive and booted inadvertently when
the computer is turned back on.


bootable disk
Disk that contains the operating system in a form
ready to load into the computer.  It often refers
to a floppy disk that contains the operating system
in its boot sectors.  If a hard disk personal
computer does not find a bootable floppy disk in
the primary floppy drive at startup (A: in a PC),
it boots from the hard disk.

   It's a good idea to make a bootable disk for
your personal computer in case the hard disk
doesn't boot some day.  That way, you'll be able to
start the computer and access important data.  See
DOS Sys and DOS Format.


bootstrap
See boot.


Borland
(Borland Int'l., Inc., Scotts Valley, CA)  Leading
PC software company founded in 1983 by Philippe
Kahn.  Its Turbo Pascal moved Pascal out of the
academic halls into a commercial product, and its
Turbo C has become an industry standard.  Borland
C++ and Turbo Pascal for Windows are committed to
Windows and object-oriented programming.

   In 1984, Borland's Sidekick was the first PC
desktop accessory program, which popularized TSRs
for DOS applications.

   With Borland's acquisition of Ansa's Paradox in
1987 and Ashton-Tate's dBASE in 1991, it has become
the leader in PC database software.  Using object-
oriented programming as the paradigm for the 1990s,
Borland plans to unify Paradox, dBASE, its Quattro
Pro spreadsheet and programming languages into an
interoperable family of products.


Borland C++
ANSI C and C++ compiler from Borland for DOS and
Windows applications.  It is Turbo C-compatible and
its debugger supports Windows programs written in
Microsoft C.  It includes application frameworks
for Windows (ObjectWindows) and DOS (Turbo Vision).
Borland C++ for OS/2 is also available.


Bourne shell
See UNIX.


bpi
(Bits Per Inch)  Used to measure the number of bits
stored in a linear inch of a track on a recording
surface, such as on a disk or tape.


bps
(Bits Per Second)  Used to measure the speed of
data transfer in a communications system.


branch
(1) Same as GOTO.

(2) Connection between two blocks in a flowchart or
two nodes in a network.


breadboard
Thin plastic board full of holes used to hold
components (transistors, chips, etc.) that are
wired together.  It is used to develop electronic
prototypes or one-of-a-kind systems.


break
To temporarily or permanently stop executing,
printing or transmitting.


break key
Key that is pressed to stop the execution of the
current program or transmission.


breakout box
Device inserted into a multiple-line cable for
testing purposes that provides an external
connecting point to each wire.  A small LED may be
attached to each line, which glows when a signal is
present.


BRI
See ISDN.


bridge
(1) To cross from one circuit, channel or element
over to another.

(2) Computer system that connects two similar LANs
together.  Some bridges provide conversion between
dissimilar LANs, such as Ethernet and Token Ring.
Bridges are inserted into a LAN to improve
performance by keeping traffic contained within
smaller segments.  Bridges work at the data link
level (OSI layer 2).  See transparent bridge,
repeater, router, gateway and hub.


bridgeware
Hardware or software that converts data or
translates programs from one format into another.


Brief
Text editor for PC programming from Borland.  It
provides automatic indentation and the ability to
edit different parts of a source program at the
same time.


brightness
Light level on a display screen.  Contrast with
contrast.


British Telecom
Division of the British Post Office that manages
telecommunications throughout Great Britain and
Northern Ireland.


broadband
Technique for transmitting large amounts of data,
voice and video over long distances.  Using high
frequency transmission over coaxial cable or
optical fibers, broadband transmission requires
modems for connecting terminals and computers to
the network.  Using the same FDM (frequency
division multiplexing) technique as cable TV,
several streams of data can be transmitted
simultaneously.  Contrast with baseband.


broadcast
To disseminate information to several recipients
simultaneously.


Brooklyn Bridge
PC file transfer program from Fifth Generation
Systems, Baton Rouge, LA, that transfers data
between laptops and desktop computers.


brouter
(Bridging ROUTER)  Communications device that is
part bridge and router.  Like a bridge, it
functions at the data link level (OSI layer 2) and
remains independent of higher protocols.  Like a
router, it manages multiple lines and routes
messages.  See router, gateway and hub.


browse
(1) To view and possibly edit a file of data on
screen similar to handling text in a word
processing document.  The user can scroll the data
horizontally and vertically.

(2) To view and edit the class hierarchy of the
objects in an object-oriented programming language.


BSC
(Binary Synchronous Communications)  See bisync.


BSD UNIX
(Berkeley Software Distribution UNIX)  Version of
UNIX developed at Univ. of California at Berkeley.
Extensions include networking, task switching and
larger file names (from 14 to 255 chars.).


BTAM
(Basic Telecommunications Access Method)  IBM
communications program that is used in bisynch,
non-SNA mainframe networks.  Application programs
must interface directly with the BTAM access
method.


BTLZ
(British Telecom Lempel Ziv)  Data compression
algorithm based on the Lempel-Ziv method that can
achieve up to 4x the throughput of 2400 and 9600
bps modems.


BTOS
Burroughs version of CTOS.


Btrieve
Database management system from Novell that
accompanies its NetWare operating systems.


bubble
Bit in bubble memory or a symbol in a bubble chart.


bubble chart
Chart that uses bubble-like symbols often used to
depict data flow diagrams.


Bubble Jet
Canon's ink jet printer technology.


bubble memory
Solid state semiconductor and magnetic storage
device suited for rugged applications.  It is about
as fast as a slow hard disk and holds its content
without power.

   It is conceptually a stationary disk with
spinning bits.  The unit, only a couple of square
inches in size, contains a thin film magnetic
recording layer.  Globular-shaped bubbles (bits)
are electromagnetically generated in circular
strings inside this layer.  In order to read or
write the bubbles, they are rotated past the
equivalent of a read/write head.


bubble sort
Multiple-pass sorting technique that starts by
sequencing the first two items, then the second
with the third, then the third with the fourth and
so on until the end of the set has been reached.
The process is repeated until all items are in the
correct sequence.


bucket
Another term for a variable.  It's just a place to
store something.


buckyballs
Type of carbon, identified in 1985, that has
potential as a superconductor.  It is one of a
group of "buckminsterfullerenes," named after R.
Buckminster Fuller, because of its molecular
similarity to his geodesic domes.


buffer
Reserved segment of memory used to hold data while
it is being processed.  In a program, buffers are
created to hold some amount of data from each of
the files that will be read or written.  A buffer
may also be a small memory bank used for special
purposes.


buffer flush
Transfer of data from memory to disk.


buffer pool
Area of memory reserved for buffers.


bug
Persistent error in software or hardware.  If the
bug is in software, it can be corrected by changing
the program.  If the bug is in hardware, new
circuits have to be designed.  The term was coined
in the 1940s when a moth was found squashed between
the points of an electromechanical relay in the
Mark I.  Contrast with glitch.

              A Note from the Author
On October 19, 1992, I found my first "real bug."
When I fired up my laser printer, it printed
blotchy pages.  Upon inspection, I found a bug
lying belly up in the trough below the corona wire.
The printer worked fine after removing it!


bug compatible
Hardware device that contains the same design flaws
as the original.


bulk storage
Storage that is not used for high-speed execution.
May refer to auxiliary memory, tape or disk.


Bull HN
(Bull HN Information Systems Inc., Billerica, MA)
Computer manufacturer that was formerly Honeywell
Bull Inc.

  In 1927, two temperature control companies,
founded by Alfred Butz in 1885 and Mark Honeywell
in 1906, merged to become the Minneapolis Honeywell
Regulator Company.

   In 1957, Honeywell entered the computer business
with Ratheon when it launched the Datamatic 1000, a
monstrous, tube-driven machine.  Later, it
introduced advanced second-generation computers,
the Models 800 and 400.  In 1963, it introduced its
successful 200 series.  In 1970, it acquired GE's
computer business and its computer division was
named Honeywell Information Systems.

   Through Honeywell's alliance with Bull in Europe
and Bull's association with NEC in Japan, products
were jointly developed starting in the 1970s.  In
1987, Honeywell, Bull and NEC merged to become
Honeywell Bull, Inc.  In 1989, it became Bull HN to
reflect Bull's majority ownership.


bulletin board
See BBS.


bump mapping
In computer graphics, a technique for simulating
rough textures by creating irregularities in
shading.


BUNCH
(Burroughs, Univac, NCR, Control Data and
Honeywell)  IBM's competitors after RCA and GE got
out of the computer business.


bundle
To sell hardware and software as a single product
or to combine several software packages for sale as
a single unit.  Contrast with unbundle.


bunny suit
Protective clothing worn by an individual in a
clean room that keeps human bacteria from infecting
the chip-making process.  The outfit makes people
look like oversized rabbits.


burn in
To test a new electronic system by running it for
some length of time.  Weak components often fail
within the first few hours of use.


burst mode
High-speed transmission mode in a communications or
computer channel.  Under certain conditions, the
system sends a burst of data at higher speed.  For
example, a multiplexor channel may suspend
transmitting several streams of data and send one
high-speed transmission using the entire bandwidth.


burster
Mechanical device that separates continuous paper
forms into cut sheets.  A burster can be attached
to the end of a collator, which separates multipart
forms into single parts.


bus
Common pathway between hardware devices.  A
computer bus connects the CPU to its main memory
and the memory banks that reside on the control
units of the peripheral devices.  It is made up of
two parts.  Addresses are sent over the address bus
to signal a memory location, and the data is
transferred over the data bus to that location.
Widely-used computer buses are ISA, EISA, NuBus,
Micro Channel, TURBOchannel, VMEbus, MULTIBUS and
STD bus.

   A network bus is a common cable that connects
all devices in the network; for example, Ethernet
uses a bus architecture.  A signal is broadcast to
all nodes at the same time, and the requested
station responds.


         Computer Bus            Local Area Network
 ┌──────────┐     ┌──────────┐         ┌─────────┐
 │   CPU    ├─────┤   Main   │     ┌───┤  Work-  │
 │          ├─┐ ┌─┤  Memory  │     │ ┌─┤ Station │
 └──────────┘ │ │ └──────────┘     │ │ └─────────┘
 ┌──────────┐ │B│ ┌──────────┐     │B│ ┌─────────┐
 │   Disk   ├─┘U└─┤  Video   │     │U└─┤  Work-  │
 │Controller├─┐S┌─┤Controller│     │S┌─┤ Station │
 └──────────┘ │ │ └──────────┘     │ │ └─────────┘
 ┌──────────┐ │ │ ┌──────────┐     │ │ ┌─────────┐
 │Parallel  ├─┘ └─┤Serial    │     │ └─┤ Server  │
 │Port or   ├─────┤Port or   │     │ ┌─┤         │
 │Printer   │     │Communications  │ │ └─────────┘
 │Controller│     │Controller│     │ │ ┌─────────┐
 └──────────┘     └──────────┘     │ └─┤  Work-  │
                                   └───┤ Station │
                                       └─────────┘


bus bridge
Device that connects two similar or dissimilar
busses together, such as two VMEbuses or a VMEbus
and a Futurebus.  This is not the same as a
communications bridge, which connects networks
together.  See bridge.


bus card
Expansion board (card) that plugs into the
computer's expansion bus.


bus extender
(1) Board that pushes a printed circuit board out
of the way of surrounding boards for testing
purposes.  It plugs into an expansion slot, and the
expansion board plugs into the bus extender.

(2) Device that extends the physical distance of a
bus.  See repeater.

(3) Device that increases the number of expansion
slots.  It is either an expansion board containing
multiple expansion slots, or an expansion board
that cables to a separate housing that contains the
slots and its own power supply.


bus mastering
Bus design that allows add-in boards to process
independently of the CPU and to be able to access
the computer's memory and peripherals on their own.


bus mouse
Mouse that plugs into an expansion board.  It takes
up an expansion slot whereas a serial mouse takes
up a serial port.  The choice depends on how many
devices must be connected to each type of socket.


business analyst
Individual who analyzes the operations of a
department or functional unit with the purpose of
developing a general systems solution to the
problem that may or may not require automation.
The business analyst can provide insights into an
operation for an information systems analyst.


business graphics
Numeric data represented in graphic form.  While
line graphs, bar charts and pie charts are the
common forms of business graphics, there are many
others.  People think in pictures.  By transforming
numerical data into graphic form, patterns of
business activity can be recognized more easily.


business machine
Any office machine, such as a typewriter or
calculator, that is used in clerical and accounting
functions.  The term has traditionally excluded
computers and terminals.


Butterfly Switch
Parallel processing topology from BBN Advanced
Computers Inc., Cambridge, MA, that mimics a
crossbar and provides high-speed switching of data
between nodes.  It can also be used to create a
hypercube topology.


button
Physical button on a device, such as a mouse, or a
simulated button on screen that is "pushed" by
moving the cursor onto it and clicking the mouse.


buy and sell
See computer exchange.


bypass
In communications, to avoid the local telephone
company by using satellites and microwave systems.


byte
Common unit of computer storage (micro to
mainframe).  It is made up of eight binary digits
(bits).  A ninth bit may be added as a parity bit
for error checking.

    A byte holds the equivalent of a single
character, such as the letter A, a dollar sign or
decimal point.  For numbers, a byte can hold a
single decimal digit (0 to 9), two numeric digits
(packed decimal) or a number from 0 to 255 (binary
numbers).

                Byte Specifications
The primary specifications of hardware are rated in
bytes; for example, a 40-megabyte (40M or 40MB)
disk holds 40 million characters of instructions
and data.  A one-megabyte (1M or 1MB) memory allows
one million characters of instructions and data to
be stored internally for processing.

   With database files and word processing
documents, the file size is slightly larger than
the number of data characters stored in it.  Word
processing files contain embedded codes for layout
settings (margins, tabs, boldface); therefore, a
100,000-byte document implies slightly less than
100,000 characters of text (approx. 30 pages).
Database files contain codes that describe the
structure of the records, thus, a 100,000-byte
database file holds somewhat less than 100,000
characters of data.

   Unlike data and text, a 100,000-byte graphics
file is not indicative of the size of the image
contained in it.  There are many graphics
standards, and the higher the image quality, the
more bytes are needed to represent it.  A low-
resolution graphics file can take as little as
8,000 bytes, while high-resolution files can take
100,000 or more bytes per picture.


byte addressable
Computer that can address each byte of memory
independently of the others.  Contrast with word
addressable.


byte ordering
See big endian.


byte-oriented protocol
Communications protocol that uses control codes
made up of full bytes.  The bisynchronous protocols
used by IBM and other vendors are examples.
Contrast with bit-oriented protocol.



C
High-level programming language developed at Bell
Labs that is able to manipulate the computer at a
low level like assembly language.  During the last
half of the 1980s, C has become the language of
choice for developing commercial software.

   C can be compiled into machine languages for
almost all computers.  For example, UNIX is written
in C and runs in a wide variety of micros, minis
and mainframes.

   C is programmed as a series of functions that
call each other for processing.  Even the body of
the program is a function named "main."  Functions
are very flexible, allowing programmers to choose
from the standard library that comes with the
compiler, to use third party functions from other C
suppliers, or to develop their own.

   Compared to other high-level programming
languages, C appears complicated.  Its intricate
appearance is due to its extreme flexibility.  C
was standardized by ANSI (X3J11 committee) and ISO
in 1989.

   The following C example converts fahrenheit to
centigrade:

     main()   {
     float fahr;
     printf("Enter Fahrenheit ");
     scanf("%f", &fahr);
     printf("Celsius is %f\n", (fahr-32)*5/9);
              }


C shell
See UNIX.


C++
Object-oriented version of C created by Bjarne
Stroustrup.  C++ has become popular because it
combines traditional C programming with OOP
capability.  Smalltalk and other original OOP
languages did not provide the familiar structures
of conventional languages such as C and Pascal.


C2
Minimum security level defined by the National
Computer Security Center.  See NCSC.


C:
Designation for the primary hard disk in a PC.


CA
See Computer Associates.


cable
Flexible metal or glass wire or group of wires.
All cables used in electronics are insulated with a
material such as plastic or rubber.


cable matcher
Same as gender changer.


cabletext
Videotex service that uses coaxial cable.  See
videotex.


cache
Pronounced "cash."  A reserved section of memory
used to improve performance.

   A disk cache is a reserved section of normal
memory or additional memory on the disk controller
board.  When the disk is read, a large block of
data is copied into the cache.  If subsequent
requests for data can be satisfied in the cache, a
slower disk access is not required.  If the cache
is used for writing, data is queued up in memory
and written to the disk in larger blocks.

   A memory cache is a high-speed memory bank
between memory and the CPU.  Blocks of instructions
and data are copied into the cache and instruction
execution and data updating are performed in the
higher-speed memory.


       ████ disk       ┌───────┐     ┌───────┐
 ▀▀▀▀▀▀████▀▀▀▀▀▀ ───│  RAM  │───│  CPU  │
 ▀▀▀▀▀▀████▀▀▀▀▀▀      │ Cache │     └───────┘
       ▀▀▀▀            └───────┘

                      Disk cache

 ┌───────────┐     ┌───────────┐     ┌───────┐
 │    RAM    │───│High-speed │───│  CPU  │
 └───────────┘     │Memory bank│     └───────┘
                   └───────────┘

                    Memory cache


caching controller
Disk controller with a built-in cache.  See cache.


CAD
(Computer-Aided Design)  Using computers to design
products.  CAD systems are high-speed workstations
or personal computers using CAD software and input
devices such as graphic tablets and scanners.  CAD
output is a printed design or electronic input to
CAM systems (see CAD/CAM).

   CAD software is available for generic design or
specialized uses, such as architectural, electrical
and mechanical design.  CAD software may also be
highly specialized for creating products such as
printed circuits and integrated circuits.

   CAD systems are often turnkey systems which are
put together by vendors that may develop or
integrate software into standard or optimized
hardware.  Except in a few cases, CAD systems rely
extensively on graphics.  See graphics, CADD, and
CAE.


CAD/CAM
(Computer-Aided Design/Computer-Aided
Manufacturing)  Integration of CAD and CAM.
Products designed by CAD are direct input into the
CAM system.  For example, a device is designed and
its electronic image is translated into a numerical
control programming language, which generates the
instructions for the machine that makes it.


CADAM
Full-featured IBM mainframe CAD application, which
includes 3-D capability, solid modeling and
numerical control.  Originally developed by
Lockheed for internal use, it was distributed by
IBM starting in the late 1970s.  In 1989, IBM
purchased the Lockheed subsidiary, CADAM, Inc.


CADD
(Computer-Aided Design and Drafting)  CAD systems
with additional features for drafting, such as
dimensioning and text entry.


CADKEY
Integrated 2-D drafting and 3-D design system for
PCs from CADKEY, Inc., Manchester, CT.  It offers a
total design solution with solids creation and
built-in DXF and IGES translators.  Over 200
manufacturing systems link to CADKEY through its
CADL programming language.


CAE
(1) (Computer-Aided Engineering)  Software that
analyzes designs which have been created in the
computer or that have been created elsewhere and
entered into the computer.  Different kinds of
engineering analyses can be performed, such as
structural analysis and electronic circuit
analysis.

(2) (Common Application Environment)  Software
development platform that is specified by X/Open.


CAI
(1) (Computer-Assisted Instruction)  Same as CBT.

(2) See Computer Associates.


Cairo
Code name for an object-oriented version of Windows
NT to be released after Windows NT is established.


CAL
(1) (Computer-Assisted Learning)  Same as CBT.

(2) (Conversational Algebraic Language)
Timesharing language from Univ. of California.


calculated field
Numeric or date field that derives its data from
the calculation of other fields.  Data is not
entered into a calculated field by the user.


calculator
Machine that provides arithmetic capabilities.  It
accepts keypad input and displays results on a
readout and/or paper tape.  Unlike a computer, it
cannot handle alphabetic data.


call
(1) In programming, a statement that references an
independent subroutine or program.  The call is
turned into a branch instruction by the assembler,
compiler or interpreter.  The routine that is
called is responsible for returning to the calling
program after it has finished processing.

(2) In communications, the action taken by the
transmitting station to establish a connection with
the receiving station in a dial-up network.


call by reference
In programming, a call to a subroutine that passes
addresses of the parameters used in the subroutine.


call by value
In programming, a call to a subroutine that passes
the actual data of the parameters used in the
subroutine.


call distributor
PBX feature that routes incoming calls to the next
available agent or operator.


called routine
In programming, a program subroutine that performs
a task and is accessed by a call or branch
instruction in the program.


calling program
In programming, a program that initiates a call to
another program.


calling routine
In programming, a program subroutine that initiates
a call to another program routine.


CALS
(Computer-Aided Acquisition and Logistics Support)
DOD initiative for electronically capturing
military documentation and linking related
information.


CAM
(1) (Computer-Aided Manufacturing)  Automated
manufacturing systems and techniques, including
numerical control, process control, robotics and
materials requirements planning (MRP).  See
CAD/CAM.

(2) (Common Access Method)  ANSI standard for SCSI
host adapters that supports simultaneous operations
on multiple SCSI devices (multitasking I/O).  This
standard, traditionally unsupported in the PC
world, is gradually being implemented in the PC's
ROM BIOS under interrupt 4F.  See SCSI.

(3) (Content Addressable Memory)  Same as
associative storage.


candela
Unit of measurement of the intensity of light.  An
ordinary wax candle generates one candela.  See
lumen.


canned program
Software package that provides a fixed solution to
a problem.  Canned business applications should be
analyzed carefully as they usually cannot be
changed much, if at all.


canned routine
Program subroutine that performs a specific
processing task.


canonical synthesis
Process of designing a model of a database without
redundant data items.  A canonical model, or
schema, is independent of the hardware and software
that will process the data.


capacitor
Electronic component that holds a charge.  It comes
in varying sizes for use in power supplies to the
tiny cells in dynamic RAM chips.


capstan
On magnetic tape drives, a motorized cylinder that
traps the tape against a free-wheeling roller and
moves it at a regulated speed.


CAR
(Computer-Assisted Retrieval)  Systems that use the
computer to keep track of text documents or records
stored on paper or on microform.  The computer is
used to derive the location of a requested item,
which must be manually retrieved from a shelf, bin,
or microform.


card
See printed circuit board, magnetic stripe, punched
card and HyperCard.


card cage
Cabinet or metal frame that holds printed circuit
cards.


card column
Vertical column that is used to represent a single
character of data by its pattern of punched holes.
The common IBM card contains 80 card columns.


card image
Representation of punched cards in which each hole
in the card is represented by a bit on tape or
disk.


card punch
(1) Early peripheral device that punches holes into
cards at 100 to 300 cards per minute.

(2) Same as keypunch machine.


card reader
(1) Peripheral device that reads magnetic stripes
on the back of a credit card.

(2) Early peripheral device that reads punched
cards at 500 to 2,000 cards/minute.  The code is
detected by light patterns created by the holes in
the card.


cardinal number
Number that states how much or how many.  In
"record 43 has 7 fields," the 7 is cardinal.
Contrast with ordinal number.


caret
Up-arrow (^) symbol used to represent a decimal
point or the control key.  For example, ^Y means
Ctrl-Y.  It is the shift-6 key on the keyboard.


carpal tunnel syndrome
Compression of the main nerve to the hand due to
scarring or swelling of the surrounding soft tissue
in the wrist (area formed by carpal bones on top
and muscle tendons below).  Caused by trauma,
arthritis and improper positioning of the wrist, it
can result in severe damage to the hands.  See RSI
and Wrist Pro.


carriage
Printer or typewriter mechanism that holds the
platen and controls paper feeding and movement.


carriage return
See return key.


carrier
Alternating current that vibrates at a fixed
frequency, used to establish a boundary, or
envelope, in which a signal is transmitted.
Carriers are commonly used in radio transmission
(AM, FM, TV, microwave, satellite, etc.) in order
to differentiate transmitting stations.  For
example, an FM station's channel number is actually
its carrier frequency.  The FM station merges
(modulates) its audio broadcast (data signal) onto
its carrier and transmits the combined signal over
the airwaves.  At the receiving end, the FM tuner
latches onto the carrier frequency, filters out the
audio signal, amplifies it and sends it to the
speaker.

   Carriers can be used to transmit several signals
simultaneously.  For example, multiple voice, data
and/or video signals can travel over the same line
with each residing in its own carrier vibrating at
a different frequency.


carrier based
Transmission system that generates a fixed
frequency (carrier) to contain the data being
transmitted.


carrier frequency
Unique frequency used to "carry" data within its
boundaries.  It is measured in cycles per second,
or Hertz.  See FDM.


Carterfone decision
FCC decree (1968) that permitted users to connect
their own telephone equipment to the public
telephone system.


cartridge
Self-contained, removable storage module that
contains disks, magnetic tape or memory chips.
Cartridges are inserted into slots in the drive,
printer or computer.  See font cartridge.


CAS
(Communications Application Specification)  Intel
fax/modem protocol that allows personal computers
to exchange data with fax machines.  Introduced in
1988, Intel provides both the boards and the chips.


cascade
Connected series of chips or other devices.


CASE
(Computer Aided Software Engineering or Computer
Aided Systems Engineering)  Software that is used
in any and all phases of developing an information
system, including analysis, design and programming.
For example, data dictionaries and diagramming
tools aid in the analysis and design phases, while
application generators speed up the programming
phase.

   CASE tools provide automated methods for
designing and documenting traditional structured
programming techniques.  The ultimate goal of CASE
is to provide a language for describing the overall
system that is sufficient to generate all the
necessary programs.


case-based reasoning
AI problem solving technique that catalogs
experience into "cases" and matches the current
problem to the experience.  Such systems are easier
to maintain than rule-based expert systems, because
changes require adding new cases without the
complexity of adding new rules.  It is used in many
areas including pattern recognition, diagnosis,
troubleshooting and planning.


case sensitive
Distinguishing lower case from upper case.  In a
case sensitive language, "abc" is considered
different data than "ABC."


case statement
In programming, a variation of the if-then-else
statement that is used when several ifs are
required in a row.  The following C example tests
the variable KEY1 and performs functions based on
the results.

  switch (key1)   {
    case '+':  add();  break;
    case '-':  subtract();  break;
    case '*':  multiply();  break;
    case '/':  divide();  break;
                   }



cash memory
See cache.


cassette
Removable storage module that contains a supply
reel of magnetic tape and a takeup reel.  Data
cassettes look like audio cassettes, but are made
to higher tolerances.


casting
In programming, the conversion of one data type
into another.


cat
(conCATenate)  UNIX command that displays the
contents of a file.


catalog
Directory of disk files or files used in an
application.  Also any map, list or directory of
storage space used by the computer.


cathode
In electronics, a device that emits electrons,
which flow from the negatively charged cathode to
the positively charged anode.


cathode ray tube
See CRT.


CATV
(Community Antenna TV)  Original name for cable TV,
which used a single antenna at the highest location
in the community.  Now refers to cable TV.


CAU
(Controlled Access Unit)  Intelligent hub from IBM
for Token Ring networks.  Failed nodes are
identified by the hub and reported via IBM's LAN
Network Manager software.


CAV
(Constant Angular Velocity)  Disk technique that
spins the disk at a constant speed.  The number of
bits in each track is the same, but their density
varies because the inner tracks have smaller
circumferences than the outer tracks.  Contrast
with CLV.


CB
(Citizen's Band)  Frequency band for public radio
transmission in the 27 MHz range.


CB simulator
See teleconferencing (3).


CBEMA
(Computer and Business Equipment Manufacturers
Assn.)  Membership organization founded in 1916
composed of over 25 manufacturers and suppliers.
It is concerned with the development of standards
for data processing and business equipment in the
U.S. and abroad.  Address: 311 First St., N.W.,
Washington, DC 20001, 202/737-8888.


CBR
(1) (Computer-Based Reference)  Reference materials
accessible by computer in order to help people do
their jobs quicker.  For example, this Glossary on
disk!

(2) See case-based reasoning.


CBT
(Computer-Based Training)  Using the computer for
training and instruction.  CBT programs are called
courseware and provide interactive training
sessions for all disciplines.  It uses graphics
extensively, as well as CD ROM and videodisc.

   CBT courseware is developed with authoring
languages, such as Adroit, PILOT and Demo II, which
allow for the creation of interactive sessions.


CBX
(Computerized Branch eXchange)  Same as PBX.


cc:Mail
VIM-compliant e-mail system from Lotus.  Lotus
acquired cc:Mail, a Mountain View, CA, software
developer.


CCA
(1) (Common Cryptographic Architecture)  IBM
encryption software for MVS and DOS applications.

(2) (Compatible Communications Architecture)
Network Equipment Technology protocol for
transmitting asynchronous data over X.25 networks.

(3) (Communications Control Architecture)  U.S.
Navy network that includes an ISDN backbone called
BITS (Base Info. Transfer System).


CCD
(Charge Coupled Device)  Electronic memory made of
a special type of MOS transistor that can store
patterns of charges in a sequential fashion.  CCDs
are used in TV and scanning devices since they can
be charged by light as well as by electricity.


CCFL
(Cold Cathode Flurorescent Lamp)  Same as CCFT.


CCFT
(Cold Cathode Fluorescent Tube)  Type of light
source for a backlit screen.  It weighs more and
uses more power than other backlights.


CCIA
(Computer and Communications Industry Assn.)
Membership organization composed of over 60
hardware and software vendors, service bureaus,
leasing and repair companies.  It represents their
interests in domestic and foreign trade, and,
working with the NIST, keeps members advised of
regulatory policy.  Address: 666 11th St., N.W.,
Washington, DC 20001, 202/783-0070.


CCIS
(Common Channel Interoffice Signaling)  Telephone
communications technique that transmits voice and
control signals over separate channels.  Control
signals are transmitted over a packet-switched
digital network, providing faster connects and
disconnects and allowing data, such as calling
number, to be included.  See CCS (2).


CCITT
(Consultative Committee for International Telephony
and Telegraphy)  International organization for
communications standards.  It is one of four organs
of the International Telecommunications Union,
founded in 1865, headquartered in Geneva and
comprised of over 150 member countries.


CCP
(Certificate in Computer Programming)  Award for
successful completion of an examination in computer
programming offered by ICCP.


CCS
(1) (Common Communications Support)  SAA
specifications for communications, which includes
data streams (DCA, 3270), application services
(DIA, DDM), session services (LU 6.2) and data
links (X.25, Token Ring).

(2) (Common Channel Signaling)  Integral part of
ISDN known as "Signaling System 7," which advances
the CCIS method for transmitting control signals.
It allows call forwarding, call waiting, etc., to
be provided anywhere in the network.

(3) (Common Command Set)  De facto instruction set
between a SCSI-1 adapter and a hard disk.

(4) (Continuous Composite Servo)  Magneto-optic
format that places the signal track between two
alignment tracks.

(5) (100 Call Seconds)  Unit of measurement equal
to 100 seconds of conversation.  One hour = 36 CCS.


CD
(Compact Disc)  Audio disc that contains up to 72
minutes of hi-fi stereo sound.  The disc is 4.75"
in diameter, recorded on one side, and individual
selections can be played back in any sequence.
Unlike phonograph records in which the platter
contains "carved sound waves," CDs are recorded in
digital form as microscopic pits (binary code)
covered by a clear, protective plastic layer.
Instead of a needle vibrating in the groove, a
laser shines onto the pits and the reflections are
decoded.

   Sound is converted into digital code by sampling
the sound waves 44,056 times per second and
converting each sample into a 16-bit number.  It
requires about 1.5 million bits of storage for each
second of stereo hi-fi sound.  Digital sound is so
clear because the numbers are turned into sound
electronically.  There's no tape hiss or needle
pops and clicks.  In addition, the CD can handle a
wider range of volume (dynamic range), providing
more realism.  A soft whisper can be interrupted by
a loud cannon blast.  If a phonograph were pushed
that far, the needle would jump out of the groove.

   Other forms of CDs (CD ROM, CD ROM XA, CD-I and
DVI) all stem from the audio CD.  Introduced in the
U.S. in 1983, sales of CDs and CD players exceeded
sales of LPs and turntables in 1986.


CD audio
Same as CD and DAD.


CD caddy
Plastic container that holds a CD ROM disc.  The
caddy is inserted into the disc drive.


CD-I
(Compact Disc-Interactive)  Compact disc format
developed by Philips and Sony that holds data,
audio, still video and animated graphics.  It
provides up to 144 minutes of CD-quality stereo,
9.5 hours of AM-radio-quality stereo or 19 hours of
monophonic audio.

   CD-I includes an operating system standard as
well as proprietary hardware methods for
compressing the data further in order to display
video images.  CD-I discs require a CD-I player and
will not play in a CD ROM player.  See CD, CD ROM,
DVI.


CD ROM
(Compact Disc Read Only Memory)  Compact disc
format used to hold text, graphics and hi-fi stereo
sound.  It's like a music CD, but uses a different
track format for data.  The music CD player cannot
play CD ROMs, but CD ROM players usually play music
CDs and have output jacks for a headphone or
amplified speakers.  A CD ROM player connects to a
controller card, which is plugged into one of the
computer's expansion slots.

   CD ROMs hold in excess of 600MB of data, which
is equivalent to about 250,000 pages of text or
20,000 medium-resolution images.

   Audio and data reside on separate tracks and
cannot be heard and viewed together.
See CD ROM XA, CD-I and DVI.


CD ROM Extensions
Software required to use a CD ROM player on a PC
running DOS.  It usually comes with the player and
includes a driver specialized for the player as
well as Microsoft's MSCDEX.EXE driver.


CD ROM XA
(CD ROM eXtended Architecture)  CD ROM enhancement
introduced in 1988 by Philips, Sony and Microsoft
that lets text and pictures be narrated by allowing
concurrent audio and video.  It provides up to 9.5
hours of AM-quality stereo or 19 hours of
monophonic audio.  It also functions as a bridge
between CD ROM and CD-I, since CD ROM XA discs will
play on a CD-I player.  CD ROM XA uses a standard
CD ROM player, but requires a CD ROM XA controller
card in the computer.  See CD-I and DVI.


CD+Graphics
CD format that adds video.  You can listen to the
opera and read the text on screen.


CDA
(Compound Document Architecture)  Compound document
format from Digital that creates hot links between
documents.


CDC
See Control Data.


CDDI
(Copper Distributed Data Interface)  Version of
FDDI that uses twisted pair rather than optical
fiber.


cdev
(Control Panel DEVice)  Customizable settings in
the Macintosh Control Panel that pertain to a
particular program or device.  Cdevs for the mouse,
keyboard and startup disk, among others, come with
the Mac.  Others are provided with software
packages and utilities.


CDIF
(CASE Data Interchange Format)  EIA standard for
exchanging data between CASE tools.  See PCTE.


CDIP
(Sidebrazed Ceramic DIP)  High-qualty ceramic DIP
that typically uses gold-plated leads attached by
brazing.


CDMA
(Code Division Multiple Access)  Spread spectrum
technique that converts analog signals into digital
for transmission over the cellular network.  It
provides 10 to 20 times the capacity of the analog
network.  Qualcomm, Inc., San Diego, CA, has
several patents on products using its CDMA
implementation.


CDP
(Certificate in Data Processing)  Award for the
successful completion of an examination in
hardware, software, systems analysis, programming,
management and accounting, offered by ICCP.


CDPD
(Cellular Digital Packet Data)  Transmission of
digital data over the cellular network.  Based on
IBM's CelluPlan II, it moves data over unused voice
channels at 19.2Kbps.


CDTV
(Commodore Dynamic Total Vision)  CD system from
Commodore that combines audio, graphics and text.
Introduced in 1991, it is an interactive multimedia
system for the home.  The player connects to a TV
and also plays music CDs, including CD+Graphics and
CD+MIDI.


CEbus
(Consumer Electronics bus)  EIA standard for a
control network.


Ceefax
Teletext service of the British Broadcasting
Corporation.


CEG
(Continous Edge Graphics)  VGA RAMDAC chip from
Edsun Labs that adds anti-aliasing on the fly.  It
can also calculate intermediate shades, thus
providing thousands of colors on an 8-bit board
that normally generates only 256 colors.


cell
(1) Elementary unit of storage for data (bit) or
power (battery).

(2) In a spreadsheet, the intersection of a row and
column.


cell relay
Transmission technology that uses small fixed-
length packets (cells) that can be switched at high
speed.  Good for multimedia transmission.  See ATM.


centering cone
Short plastic or metal cone used to align a 5.25"
floppy disk to the drive spindle.  It is inserted
into the diskette's center hole when the drive door
is closed.


centimeter
Unit of measurement that is 1/100th of a meter or
approximately 4/10ths of an inch (0.39 inch).


central office
Telephone switching facility that interconnects
subscribers' telephone lines to each other and to
intra and intercity trunk lines.


central processing unit
See CPU.


central processor
Same as CPU.


centralized processing
Processing performed in one or more computers in a
single location.  All terminals in the organization
are connected to the central computers.  Contrast
with distributed processing and decentralized
processing.


CENTREX
PBX services provided by a local telephone company.
Switching is done in the telephone company's
central office.  Some services do the switching at
the customer's site, but control it in the central
office.


Centronics
Standard 36-pin parallel interface for connecting
printers and other devices to a computer.  It
defines the plug, socket and signals used and
transfers data asynchronously up to 200 Kbytes/sec.

   The plug (1.5" wide, 1/8" thick) has 18 contacts
each on the top and bottom.  The socket contains
one opening with matching contacts.

   This de facto standard was developed by
Centronics Corp., maker of the first successful dot
matrix printers.  The printer was introduced in
1970, and the company was bought by Genicom Corp.
in 1987.  See printer cable.


CEO
(Comprehensive Electronic Office)  Office software
from Data General introduced in 1981.  It includes
word processing, e-mail, spreadsheets, business
graphics and desktop accessories.


CERDIP
(CERamic DIP)  Type of DIP that uses two ceramic
layers epoxied together.


CGA
(Color/Graphics Adapter)  IBM video display
standard that provides low-resolution text and
graphics.  It was the first graphics standard for
the IBM PC and has been superseded by EGA and VGA.
CGA requires a digital RGB Color Display monitor.
See PC display modes.


CGI
(Computer Graphics Interface)  Device independent
graphics language for display screens, printers and
plotters that stemmed from GKS.


CGM
(Computer Graphics Metafile)  Standard format for
interchanging graphics images.  CGM stores images
primarily in vector graphics, but also provides a
raster format.  Earlier GDM and VDM formats have
been merged into the CGM standard.


chad
Piece of paper that is punched out on a punched
card, paper tape or on the borders of continuous
forms.  A chadded form is when the holes are cut
completely through.  A chadless form is when the
chads are still attached to one edge of the hole.


chain printer
Line printer that uses character typefaces linked
together in a chain as its printing mechanism.  The
chain spins horizontally around a set of hammers.
When the desired character is in front of the
selected print position, the corresponding hammer
hits the paper into the ribbon and onto the
character in the chain.


chained list
Group of items in which each item contains the
location of the next item in sequence.


chaining
Linking items or records to form a chain.  Each
link in the chain points to the next item.


change file
Transaction file used to update a master file.


channel
(1) High-speed metal or optical fiber pathway
between the computer and the control units of the
peripheral devices.  Channels imply independent
transmission paths in which multiple channels can
transfer data concurrently with each other and with
other processing.  In a personal computer, the bus
serves as a common, shared channel.

(2) In communications, any pathway between two
computers or terminals.  It may refer to the
physical medium, such as coaxial cable, or to a
specific carrier frequency (subchannel) within a
larger channel or wireless medium.


channel bank
Multiplexor that merges several low-speed voice or
data lines into one high-speed (typically T1) line
and vice versa.


channel program
Instructions executed by a peripheral channel.  The
channel executes the channel program independently
of the CPU, allowing concurrent operations to take
place in the computer.


chaos
Science that deals with the underlying order of the
seemingly random nature of the universe.  See
fractals.


character
Single alphabetic letter, numeric digit, or special
symbol such as a decimal point or comma.  A
character is equivalent to a byte; for example,
50,000 characters take up 50,000 bytes.


character based
Same as text based.


character cell
Matrix of dots used to form a single character on a
display screen or printer.  For example, an 8x16
cell is made up of 16 rows each containing eight
dots.  Character cells are displayed and printed
contiguously; therefore the design of each letter,
digit or symbol within the cell must include
surrounding blank space.


character code
Same as data code.


character data
Alphanumeric data or text.  Contrast with numeric
data.


character device
Peripheral device that transfers data one byte at a
time at a time, such as a parallel or serial port.
Contrast with block device.


character field
Data field that holds alphanumeric characters.
Contrast with numeric field.


character generator
(1) Circuitry that converts data characters into
dot patterns for a display screen.

(2) Device that creates text characters that are
superimposed onto video frames.


character graphics
Set of special symbols strung together like letters
of the alphabet to create elementary graphics and
forms, as in the following example:

                            ██
 ╒══════╤══════╤═══════╕    ██ ██
 │      │      │       │    ██ ██ ██

             Character Graphics


character mode
Same as text mode.


character-oriented protocol
See byte-oriented protocol.


character pitch
Measurement of the number of characters per inch.
See cpi.


character printer
Printer that prints one character at a time, such
as a daisy wheel or dot matrix printer.  See
printer.


character recognition
Ability of a machine to recognize printed text.
See OCR and MICR.


character set
(1) Group of unique symbols and codes.  For
example, the ASCII character set contains 128
characters numbered 0 to 127.  The English
character set is 26 symbols (A-Z).

(2) See symbol set.


character string
Group of alphanumeric characters.  Contrast with
numeric data.


character terminal
Display screen without graphics capability.


characteristic
In logarithms and floating point, the number that
indicates where the decimal point is placed.


CHARGECARD
Hardware memory manager for 286 PCs from ALL
Computers Inc., Toronto, that turns extended memory
into EMS and uses unused high memory (640-1024K)
for drivers and TSRs.  The 286 chip is removed and
plugged into the CHARGECARD, which is plugged back
into the socket.


chat mode
Communications option that lets users type messages
back and forth to each other.  Each keystroke is
transmitted as it is pressed.


Cheapernet
See Ethernet.


check bits
Calculated number used for error checking.  The
number is derived by some formula from the binary
value of one or more bytes of data.  See parity
checking, checksum and CRC.


check box
Small box that displays an X or checkmark when the
associated option is selected.


check digit
Numeric digit used to ensure that account numbers
are correctly entered into the computer.  Using a
formula, a check digit is calculated for each new
account number, which then becomes part of the
number, often the last digit.

   When an account number is entered, the data
entry program recalculates the check digit and
compares it to the check digit entered.  If the
digits are not equal, the account number is
considered invalid.


check sum
See checksum.


checkpoint/restart
Method of recovering from a system failure.  A
checkpoint is a copy of the computer's memory that
is periodically saved on disk along with the
current register settings (last instruction
executed, etc.).  In the event of any failure, the
last checkpoint serves as a recovery point.

   When the problem has been fixed, the restart
program copies the last checkpoint into memory,
resets all the hardware registers and starts the
computer from that point.  Any transactions in
memory after the last checkpoint was taken until
the failure occurred will be lost.


checksum
Value used to ensure data is transmitted without
error.  It is created by adding the binary value of
each alphanumeric character in a block of data and
sending it with the data.  At the receiving end, a
new checksum is computed and matched against the
transmitted checksum.  A non-match indicates an
error.

   Just as a check digit tests the accuracy of a
single number, a checksum tests a block of data.
Checksums detect single bit errors and some
multiple bit errors, but are not as effective as
the CRC method.


Chicago
Code name for a future 32-bit version (386 and up)
of Windows that runs under DOS.  May be released as
Windows 4.0 and DOS 7.


chicklet keyboard
Keyboard with small, square keys not suitable for
touch typing.


child
In database management, the data that is dependent
on its parent.  See parent-child.


child program
Secondary or subprogram called for and loaded into
memory by the main program.  See parent program.


chip
Integrated circuit.  Chips are squares or
rectangles that measure approximately from 1/16th
to 5/8th of an inch on a side.  They are about
1/30th of an inch thick, although only the top
1/1000th of an inch holds the actual circuits.
Chips contain from a few dozen to several million
electronic components (transistors, resistors,
etc.).  The terms chip, integrated circuit and
microelectronic are synonymous.


            TYPES OF CHIPS BY FUNCTION


                    Logic Chip
A single chip can perform some or all of the
functions of a processor.  A microprocessor is an
entire processor on a single chip.  Desktop and
portable computers use one or more microprocessors
while larger computers may employ several types of
microprocessors as well as hundreds or thousands of
specialized logic chips.


                    Memory Chip
Random access memory (RAM) chips contain from a
couple of hundred thousand to several million
storage cells (bits).  They are the computer's
working storage and require constant power to keep
their bits charged.  Firmware chips, such as ROMs,
PROMs, EPROMs, and EEPROMs are permanent memory
chips that hold their content without power.


                Computer on a Chip
A single chip can contain the processor, RAM, ROM,
I/O control unit, and a timing clock.  It is used
in myriads of consumer and industrial products.


             Analog/Digital Converter
A single chip can perform the conversion between
analog and digital signals, for example, a codec in
a telephone.


               Special Purpose Chip
Chips used in low-cost consumer items (watches,
calculators, etc.) as well as higher-cost products
(video games, automobile control, etc.) may be
designed from scratch to obtain economical and
effective performance.  Today's ASIC chips can be
quickly created for any special purpose.


            Logic Array and Gate Array
These chips contain logic gates which have not been
tied together.  A final set of steps applies the
top metal layer onto the chip stringing the logic
gates together into the pattern required by the
customer.  This method eliminates much of the
design and fabrication time for producing a chip.


                Bit Slice Processor
Bit slice chips contain elementary electronic
circuits that serve as building blocks for the
computer architect.  They are used to custom-build
a processor for specialized purposes.



              HOW THE CHIP CAME ABOUT


                    Revolution
In late 1947, the semiconductor industry was born
at AT&T's Bell Labs with the invention of the
transistor by John Bardeen, Walter Brattain and
William Shockley.  The transistor, fabricated from
solid materials that could change their electrical
conductivity, would eventually replace all the
bulky, hot, glass vacuum tubes used as electronic
amplifiers in radio and TV and as on/off switches
in computers.  By the late 1950s, the giant first-
generation computers were giving way to smaller,
faster and more reliable transistorized machines.


                     Evolution
The original transistors were discrete components;
each one was soldered onto a circuit board to
connect to other individual transistors, resistors
and diodes.  Since hundreds of transistors were
made on one round silicon wafer and cut apart only
to be reconnected again, the idea of building them
in the required pattern to begin with was obvious.
In the late 1950s, Jack Kilby of TI and Robert
Noyce of Fairchild Semiconductor created the
integrated circuit, a set of interconnected
transistors and resistors on a single chip.

   Since then, the number of transistors that have
been put onto a single chip has increased
exponentially, from a handful in the early 1960s to
millions by the late 1980s.  Today, a million
transistors take up no more space than the first
transistor.

   A byproduct of miniaturization is speed.  The
shorter the distance a pulse travels, the faster it
gets there.  The smaller the components making up
the transistor, the faster the transistor switches.
Switch times of transistors are measured in
billionths and trillionths of a second.  In fact, a
Josephson junction transistor has been able to
switch in 50 quadrillionths of a second.


                 Logic and Memory
In first- and second-generation computers, internal
main memory was made of such materials as tubes
filled with liquid mercury, magnetic drums and
magnetic cores.  As integrated circuits began to
flourish in the 1960s, design breakthroughs allowed
memories to also be made of semiconductor
materials.  Thus, logic circuits, the "brains" of
the computer, and memory circuits, its internal
workspace, were moving along the same
miniaturization path.

   By the end of the 1970s, it was possible to put
a processor, working memory (RAM), permanent memory
(ROM), a control unit for handling input and output
and a timing clock on the same chip.

   Within 25 years, the transistor on a chip grew
into the computer on a chip.  When the awesome
UNIVAC I, which you could literally walk into, was
introduced in 1951, who would have believed that
the equivalent electronics would later be built
into a child's stuffed bear.


                  More Evolution
Just as integrated circuits eliminated cutting
apart the transistors only to be reconnected again,
eventually wafer scale integration will eliminate
cutting apart whole chips only to be reconnected
again.  In time, instead of adding more circuits
across the surface, the circuits will be built in
overlapping layers.  Within the next 10 to 15
years, it is conceivable that the electronics in
today's multi-million-dollar supercomputer can be
built within a cube one inch square!



               THE MAKING OF A CHIP

Computer circuits are pathways carrying electrical
pulses from one point to another.  The pulses flow
through on/off switches, called transistors, which
open or close when electrically activated.  The
current flowing through one switch effects the
opening or closing of another and so on.  Small
clusters of transistors form logic gates, which are
the building blocks behind all this magic, and a
specific combination of logic gates make up a
circuit.


              From Logic to Plumbing
Today, the majority of circuits being used have
already been designed and reside in circuit
libraries in a computer.  A computer designer
merely has to pick and choose ready-made modules
(standard cells) from a menu.  But they all had to
be invented at one point, and new circuits still
have to go through an elaborate process to convert
logical patterns on paper into an equivalent maze
of plumbing on the chip.

   Computers help make computers.  The logical
design is entered into the computer and converted
into transistors, diodes and resistors.  Then the
combination of electronic components is turned into
a plumber's nightmare that is displayed for human
inspection.  After corrections have been made, the
completed circuits are transferred to specialized
machinery that create lithographic plates made out
of glass, called photomasks.  The photomasks are
the actual size of the wafer and contain as many
copies of the design of the chip as will fit on the
wafer.  The transistors are built by creating
subterranean layers in the silicon, and a different
photomask is created to isolate each layer to be
worked on.  With each layer, the same part of every
transistor on every chip is constructed at the same
time.


               Chips Are Just Rocks
The base material of a chip is usually silicon,
although materials such as sapphire and gallium
arsenide are also used.  Silicon is found in quartz
rocks and is purified in a molten state.  It is
then chemically combined (doped) with other
materials to alter its electrical properties.  The
result is a silicon crystal ingot from three to
five inches in diameter that is either positively
(p-type) or negatively charged (n-type).  Wafers,
about 1/30th of an inch thick, are cut from this
"crystal salami."


                Building the Layers
Circuit building starts out by adhering a layer of
silicon dioxide insulation on the wafer's surface.
The insulation is coated with film and exposed to
light through the first photomask, hardening the
film and insulation below it.  The unhardened areas
are etched away exposing the silicon base below.
By shooting a gas under heat and pressure into the
exposed silicon (diffusion), a sublayer with
different electrical properties is created beneath
the surface.

   Through multiple stages of masking, etching, and
diffusion, the sublayers on the chip are created.
The final stage lays the top metal layer (usually
aluminum), which interconnects the transistors to
each other and to the outside world.

   Each chip is tested on the wafer, and bad chips
are marked for elimination.  The chips are sliced
out of the wafer, and the good ones are placed into
packages (DIPs, SIMMs, SIPs, etc.).  The chip is
connected to the package with tiny wires, then
sealed and tested as a complete unit.

   Chip making is extremely precise.  Operations
are performed in a "clean room," since air
particles can mix with the microscopic mixtures and
easily render a chip worthless.  Depending on the
design complexity, more chips can fail than
succeed.


                    The Future
In order to miniaturize elements of a transistor
even further, the photomasks have to be made with
x-rays or other beams which are narrower than
light.  Eventually, circuit patterns will be etched
directly onto the chip, eliminating the entire
photographic masking process.

   During the 1990s, multi-million-transistor chips
will be commonplace.  However, when wafer scale
integration becomes a reality, one wafer could hold
100 megabytes of memory along with a quantum
reduction in cost.  If superconductor transistors
take hold, there will be a gigantic leap in
performance.  Should both technologies arise at the
same time, hold on to your hats!


chip card
See smart card and memory card.


chip carrier
(1) Package that a chip is mounted in.

(2) Chip package with connectors on all sides.  See
leaded chip carrier and leadless chip carrier.


chip set
Group of chips designed to work together to perform
a function.


Chkdsk
See DOS Chkdsk.


CHMOS
(High-density CMOS)  Chip with a high density of
CMOS transistors.


Chooser
Macintosh desk accessory that allows the user to
select a printer, file server or network device,
such as a network modem.


CICS
(Customer Information Control System)  TP monitor
from IBM that provides transaction processing for
IBM mainframes.  It controls the interaction
between applications and users and lets programmers
develop screen displays without detailed knowledge
of the terminals used.  It provides terminal
routing, password security, transaction logging for
error recovery and activity journals for
performance analysis.

   CICS commands are written into assembly
language, COBOL, PL/I and RPG programs.  It
implements SNA layers 4, 5 and 6.


CID
(Configuration, Installation and Distribution)  IBM
software for controlling software distribution
throughout a network from a central source.


CIF
(Common Intermediate Format)  Video format that
transmits 36.45 Mbits/sec at 30 frames/sec.  See
QCIF and H.261.


CIM
(1) (Computer-Integrated Manufacturing)
Integrating office/accounting functions with
automated factory systems.  Point of sale, billing,
machine tool scheduling and supply ordering are
part of CIM.

(2) (CompuServe Information Manager)  See
CompuServe.


cine-oriented
Film-image orientation like that of movie film,
which runs parallel to the outer edge of the
medium.  Contrast with comic-strip oriented.


CIO
(Chief Information Officer)  Executive officer in
charge of all information processing in an
organization.


ciphertext
Data that has been coded (enciphered, encrypted,
encoded) for security purposes.


CIR
(Committed Information Rate)  In a frame relay
network, the minimum speed maintained between
nodes.


circuit
(1) Set of electronic components that perform a
particular function in an electronic system.

(2) Same as communications channel.


circuit analyzer
(1) Device that tests the validity of an electronic
circuit.

(2) In communications, same as data line monitor.


circuit board
Same as printed circuit board.


circuit breaker
Protective device that opens a circuit upon sensing
a current overload.  Unlike a fuse, it can be
reset.


circuit card
Same as printed circuit board.


circuit cellular
Transmission of data over the cellular network
using a voice channel and modem similar to using
land-based modems.  Contrast with packet cellular.
See wireless.


circuit switching
Temporary connection of two or more communications
channels.  Users have full use of the circuit until
the connection is terminated.  Contrast with
message switching, which stores messages and
forwards them later, and contrast with packet
switching, which breaks up a message into packets
and routes each packet through the most expedient
path at that moment.


CIS
(CompuServe Information Service)  See CompuServe.


CISC
(Complex Instruction Set Computer)  Pronounced
"sisk."  Traditional computer architecture that
uses microcode to execute very comprehensive
instructions.  Instructions may be variable in
length and use all addressing modes, requiring
complex circuitry to decode them.  Contrast with
RISC.


CL/1
(Connectivity Language/1)  Database language from
Apple that lets a Macintosh access an SQL-based
database in another computer.  CL/1 applications
communicate with the CL/1 client program in the
Mac, and the client program communicates with the
CL/1 server program in the host computer.


cladding
Plastic or glass sheath that is fused to and
surrounds the core of an optical fiber.  It keeps
the light waves inside the core and adds strength
to it.  The cladding is covered with a protective
outer jacket.


clamping ring
The part of a 5.25" floppy disk drive that presses
the disk onto the spindle.  It is usually part of
the centering cone.


Clarion
PC application development programs from Clarion
Software Corp., Pompano Beach, FL.  Professional
Developer includes a Pascal-like programming
language, DBMS and prototyping generator.  Personal
Developer is for non-programmers.


Claris
(Claris Corp., Santa Clara, CA)  Software
subsidiary of Apple that was separated from the
corporation (although mostly owned by it) in 1988
and then bought back in 1990.


Claris CAD
Full-featured 2-D CAD program for the Macintosh
from Claris Corp. that is noted for its ease of
use.  It provides an easy-to-learn path into CAD,
while offering most features found in CAD programs.


class
In object-oriented programming, a user-defined data
type that defines a collection of objects that
share the same characteristics.  A class member
(object) is an "instance" of the class.  Concrete
classes are designed to be "instantiated."
Abstract classes are designed to pass on
characteristics through inheritance.


Class A, B
See FCC Class.


class library
Object-oriented programming classes suplied by
third parties; for example, a GUI library.


Classic
See Macintosh.


CLCC
(Ceramic LCC)  See LCC.


clean room
Room in which the air is highly filtered in order
to keep out impurities.


clear memory
To reset all RAM and hardware registers to a zero
or blank condition.  Rebooting the computer may or
may not clear memory, but turning the computer off
and on again guarantees that memory is cleared.


click
To select an object by pressing the mouse button
when the cursor is pointing to the required menu
option or icon.


client
(1) Workstation or personal computer in a
client/server environment.  See client/server.

(2) One end of the spectrum in a request/supply
relationship between programs.  See X Window and
OLE.


client application
Application running in a network workstation.  See
also OLE.


client/server
Architecture in which the client (personal computer
or workstation) is the requesting machine and the
server is the supplying machine (LAN file server,
mini or mainframe).  The client provides the user
interface and performs some or most of the
application processing.  The server maintains the
databases and processes requests from the client to
extract data from or update the database.  The
server also controls the application's integrity
and security.  Contrast with centralized
processing, in which dumb (non-processing)
terminals are connected to a mini or mainframe.

   Client/server implies software that is designed
for multiple users.  For example, if two users are
attempting to update the same database record at
the same time, the update must be reflected
instantly on the other user's screen.  Simply
downloading files from the server to the client is
not true client/server architecture.


client/server protocol
Communications protocol that provides a structure
for requests between client and server in a
network.  It refers to OSI layer 7.


clip art
Set of canned images used to illustrate word
processing and desktop publishing documents.


clipboard
Reserved memory used to hold data that has been
copied from one application in order to be inserted
into another.


Clipper
(1) Application development system from Computer
Associates.  Originally a dBASE compiler, it has
become a complete stand-alone development
environment with many unique features.  Clipper was
developed by Nantucket Corp., which was acquired by
CA in 1992.

(2) Family of 32-bit RISC microprocessors from
Intergraph Corp., Huntsville, AL.


clipping
Cutting off outer edges or boundaries of a word,
signal or image.  See scissoring.


clipping level
Disk's ability to maintain its magnetic properties
and hold its content.  A high-quality level range
is 65-70%; low quality is below 55%.


clock
Internal timing device.  The different varieties of
clocks are:

                     CPU Clock
Uses a quartz crystal to generate a uniform
electrical frequency from which digital pulses are
created and used.  See clock speed.


                  Realtime Clock
Time-of-day clock that keeps track of hours,
minutes and seconds and makes this data available
to the programs.


                 Timesharing Clock
A timer set to interrupt the CPU at regular
intervals in order to provide equal time to all the
users of the computer.


               Communications Clock
In a synchronous communications device, the clock
maintains the uniform transmission of data between
the sending and receiving terminals and computers.


clock/calendar
Internal time clock and month/year calendar that is
kept active with a battery.  Its output allows
software to remind users of appointments, to
determine the age of a transaction and to activate
tasks at specified times.


clock doubling
Doubling the internal processing speed of a CPU
while maintaining the original clock speed for I/O
(transfers in/out of the chip).  Intel popularized
the technique with its Speed Doubler chips.  See
486 and clock tripling.


clock pulse
Signal used to synchronize the operations of an
electronic system.  Clock pulses are continuous,
precisely spaced changes in voltage.  See clock
speed.


clock speed
Internal heartbeat of a computer.   The clock
circuit uses fixed vibrations generated from a
quartz crystal to deliver a steady stream of pulses
to the CPU.

   A faster clock will speed up internal processing
provided the computer's circuits can handle the
increased speed.  For example, the same processor
running at 20MHz is twice as fast internally as one
running at 10MHz.


clock tripling
Tripling the internal processing speed of a CPU
while maintaining the original clock speed for I/O.


clone
Device that works like the original, but does not
necessarily look like it.  It implies 100%
functional compatibility.


closed
With regard to a switch, closed is "on."  Open is
"off."


closed architecture
System whose technical specifications are not made
public.  Contrast with open architecture.


closed shop
Environment in which only data processing staff is
allowed access to the computer.  Contrast with open
shop.


closed system
System in which specficiations are kept proprietary
to prevent third-party hardware or software from
being used.  Contrast with open system.


cluster
Some number of disk sectors (typically two to 16)
treated as a unit.  The entire disk is divided into
clusters, each one a minimum unit of storage.
Thus, a 30-byte file may use up 2,048 bytes on disk
if the disk cluster is four 512-byte sectors.  See
lost cluster.


cluster controller
Control unit that manages several peripheral
devices, such as terminals or disk drives.

                         ┌───terminal
                         │ ┌────terminal
   ┌────────┐   ┌────────┴─┼──terminal
   │Computer│   │ Cluster  ├────terminal
   │or FEP  ├───┤Controller├───────terminal
   └────────┘   └──────────┘



CLUT
(Color Look Up Table)  Hardware or software table
that contains color mixing information (intensity
of red, green and blue) for each color in a palette
or series of palettes.


CLV
(Constant Linear Velocity)  Disk technique that
spins a disk at different speeds.  By varying the
speed depending on which track is being accessed,
the physical density of bits in each track can be
the same, thus allowing the outer tracks to hold
more data than the inner tracks.

   CLV mechanisms are used in CD ROM players in
order to store larger amounts of data.  Contrast
with CAV.  See ZBR.


CMI
(Computer-Managed Instruction)  Using computers to
organize and manage an instructional program for
students.  It helps create test materials, tracks
the results and monitors student progress.


CMIP
(Common Management Information Protocol)
Pronounced "C-mip."  OSI protocol that defines the
format for network monitoring and control
information.


CMIS
(Common Management Information Services)
Pronounced "C-miss."  OSI standard that defines the
functions for network monitoring and control.


CMOS
(Complementary MOS)  Pronounced "C moss."  Type of
integrated circuit widely used for processors and
memories.  It uses PMOS and NMOS transistors in a
complementary fashion that results in less power to
operate.


CMOS RAM
(1) Memory made of CMOS chips.  Due to their low
power requirement, they are increasingly being used
for main memory in portable computers.

(2) Small, battery-backed memory bank in a personal
computer that is used to hold time, date and system
information such as drive types.


CMOT
(CMIP Over TCP/IP)  Abbreviated version of the CMIP
protocol for TCP/IP networks.


CMS
(1) (Conversational Monitor System)  Software that
provides interactive communications for IBM's VM
operating system.  It allows a user or programmer
to launch an application from a terminal and
interactively work with it.  The CMS counterpart in
MVS is called TSO.  Contrast with RSCS, which
provides batch communications for VM.

(2) (Call Management System)  AT&T call accounting
package for its PBXs.


CMYK
(Cyan Magenta Yellow blacK)  Color model used for
printing.  In theory, cyan, magenta and yellow
(CMY) can print all colors, but inks are not pure
and black comes out muddy.  Black ink is required
for quality printing.  See colors and RGB.


CNC
(Computerized Numerical Control)  See numerical
control.


CNE
See NetWare.


CNI
See NetWare.


CO
(Central Office)  Local telephone company switching
station that covers a geographic area such as a
town or part of a city.


co-resident
Program or module that resides in memory along with
other programs.


coaxial cable
High-capacity cable used in communications and
video, commonly called co-ax.  It contains an
insulated solid or stranded wire surrounded by a
solid or braided metallic shield, wrapped in a
plastic cover.  Fire-safe teflon coating is
optional.

   Although similar in appearance, there are
several types of coaxial cable, each designed with
a different width and impedance for a particular
purpose (TV, baseband, broadband).  Coax provides a
higher bandwidth than twisted wire pair.


COBOL
(COmmon Business Oriented Language)  High-level
business programming language that has been the
primary business application language on mainframes
and minis.  It is a compiled language and was one
of the first high-level languages developed.
Formally adopted in 1960, it stemmed from a
language called Flowmatic in the mid 1950s.

   COBOL requires more writing than other
languages, but winds up more readable as a result.
For example, multiply hourly-rate by hours-worked
giving gross-pay is self-explanatory.  COBOL is
structured into the following divisions:

Division name    Contains
IDENTIFICATION   Program identification.
ENVIRONMENT      Types of computers used.
DATA             Buffers, constants and work areas.
PROCEDURE        The processing (program logic).

The following COBOL example converts a Fahrenheit
number to Celsius.  To keep the example simple, it
performs the operation on the operator's terminal
rather than a user terminal.

  IDENTIFICATION DIVISION.
  PROGRAM-ID.  EXAMPLE.

  ENVIRONMENT DIVISION.
  CONFIGURATION SECTION.
  SOURCE-COMPUTER.   IBM-370.
  OBJECT-COMPUTER.   IBM-370.

  DATA DIVISION.
  WORKING-STORAGE SECTION.
  77 FAHR  PICTURE 999.
  77 CENT  PICTURE 999.

  PROCEDURE DIVISION.
  DISPLAY 'Enter Fahrenheit ' UPON CONSOLE.
  ACCEPT FAHR FROM CONSOLE.
  COMPUTE CENT = (FAHR- 32) * 5 / 9.
  DISPLAY 'Celsius is ' CENT UPON CONSOLE.
  GOBACK.


                    IBM COBOLs
In 1994, IBM will drop support of OS/VS COBOL,
which conforms to ANSI 68 and ANSI 74 standards and
limits a program's address space to 16 bits.  IBM's
VS COBOL II (1984) and COBOL/370 (1991) conform to
ANSI 85 standards and provide 31-bit addressing,
which allows programs to run "above the line."

   COBOL/370 is more compliant with AD/Cycle, has
more string, math and date functions, including
four-digit years, allows development through a PC
window and provides enhanced runtime facilities.


CODASYL
(COnference on DAta SYstems Languages)
Organization devoted to the development of computer
languages.  Founded in 1959, it is made up of
individuals and institutions that contribute their
own time and effort.  COBOL is a product of
CODASYL.  For information, contact Jan Prokop, 29
Hartwell Avenue, Lexington, MA 02173, 617/863-5100.


code
(1) Set of machine symbols that represents data or
instructions.  See data code and machine language.

(2) Any representation of one set of data for
another.  For example, a parts code is an
abbreviated name of a product, product type or
category.  A discount code is a percentage.

(3) To write a program.  See source code and line
of code.

(4) To encode for security purposes.  See
encryption.


code generator
See application generator and macro recorder.


code page
In DOS 3.3 and higher, a table that sets up the
keyboard and display characters for various foreign
languages.


codec
(COder-DECoder)  Electronic circuit that converts
voice or video into digital code (and vice versa)
using techniques such as pulse code modulation and
delta modulation.  A codec is an A/D and D/A
converter.


coder
(1) Junior, or trainee, programmer who writes
simple programs or writes the code for a larger
program that has been designed by someone else.

(2) Person who assigns special codes to data.


CodeView
Microsoft debugger for programs written with
Microsoft C and CodeView-compatible compilers.
Like other modern debuggers, it links source and
object program letting the programmer step through
the source code as the program is executed.


COFF
(Common Object File Format)  UNIX System V machine
language format.


COGO
(COordinate GeOmetry)  Programming language used
for solving civil engineering problems.


Coherent
Version of UNIX for 386s and up from Mark Williams
Co., Northbrook, IL, that supports a variety of
office applications off the shelf.  It includes a C
compiler, over 200 utilities and the Bourne and
Korn shells.  It uses minimal system resources.


cold boot
Starting the computer by turning power on.  Turning
power off and then back on again clears memory and
many internal settings.  Some program failures will
lock up the computer and require a cold boot to use
the computer again.  In other cases, only a warm
boot is required.  See warm boot and boot.


cold start
Same as cold boot.


collating sequence
Sequence, or order, of the character set built into
a computer.  See ASCII chart and EBCDIC chart.


collator
(1) Punched card machine that merges two decks of
cards into one or more stacks.

(2) Utility program that merges records from two or
more files into one file.


collector
Output side of a bipolar transistor.  Same as drain
in a MOS transistor.


collision detection
See CSMA/CD.


color bits
Number of bits associated with each pixel that
represent its color.  For 16 colors, four bits are
used; for 256 colors, eight bits.


color cycling
In computer graphics, a technique that simulates
animation by continuously changing colors rather
than moving the objects.  Also called color lookup
table animation.


color graphics
Ability to display graphic images in colors.


color keying
Technique for superimposing a video image onto
another.  For example, to float a car on the ocean,
the car image is placed onto a blue background.
The car and ocean images are scanned together.  The
ocean is made to appear in the resulting image
wherever background (blue) exists in the car image.
The ocean is cancelled wherever the car appears (no
background).


color map
See CLUT.


color monitor
See monitor.


color printer
Printer that prints in color using dot matrix,
electrophotographic, Cycolor, electrostatic, ink
jet or thermal-transfer techniques.  See printer.


color separation
Separating a picture by colors in order to make
negatives and plates for color printing.  Full
color requires four separations: cyan, magenta,
yellow and black (CMYK).


colors
Perception of the different wavelengths of light.
It is possible to create almost all visible colors
using two systems of primary colors.  Transmitted
colors use red, green and blue (RGB), and reflected
colors use cyan (light blue), magenta (purplish-
red), yellow and black (CMYK).  Color displays use
RGB (colors are added to create white) and color
printing uses CMYK (colors are subtracted to create
white).


column
Vertical set of data or components.  Contrast with
row.


column move
Relocating a rectangular block of characters within
a text document or a column in a spreadsheet.


COM
(Computer Output Microfilm)  Creating microfilm or
microfiche from computer output.  A COM machine can
be online or stand-alone (transfer via tape/disk).
It receives print-image output from the computer
and creates a film image of each page.  Additional
graphics (lines, logos, etc.) may be added.


COM file
(1) (COMmand file)  Executable DOS or OS/2 program
that takes up less than 64K and fits within one
segment.  It is an exact replica of how it looks in
memory.  See EXE file.

(2) VMS file containing commands to be excecuted.


COM port
Serial communications port on a PC.  See COM1 and
serial port.


COM1
Logical name assigned to serial port #1 in DOS and
OS/2.  COM ports are usually connected to a modem
or mouse and sometimes to a printer.  DOS versions
up to 3.2 support COM1 and COM2.  Version 3.3
supports up to COM4, and OS/2 supports eight COM
ports.  Contrast with LPT1.


COMDEX
(COMputer Dealers EXposition)  Trade show intended
for PC manufacturers, developers, dealers and
distributors.  Sponsored by The Interface Group,
Needham, MA, 617/449-6600, COMDEX/Fall is the
largest U.S. computer show.

   In 1979, less than 4,000 attended COMDEX/Fall
with 157 exhibitors.  In 1992, 2,000 exhibitors
drew 145,000 attendees.

                   COMDEX Events
 COMDEX/Spring, Atlanta
  May 24-27, 1993
  May 23-26, 1994
  May 22-25, 1995

 COMDEX/Fall, Las Vegas
  Nov. 15-19, 1993
  Nov. 14-18, 1994
  Nov. 13-17, 1995

 COMDEX/Canada, Toronto
  July 13-15, 1993
  June 14-16, 1994
  June 13-15, 1995

 COMDEX/South America, Sao Paulo
  Aug. 23-27, 1993
  Aug. 1994
  Sept. 1995


comic-strip oriented
Film-image orientation like a comic strip, which
runs perpendicular to the outer edge of the film.
Contrast with cine-oriented.


comm port
May refer to any serial communications port or
specifically to the serial ports on a PC.  See
COM1.


comma delimited
Record layout that separates data fields with a
comma and usually surrounds character data with
quotes, for example:

"Pat Smith","5 Main St.","New Hope","PA","18950"
"K. Jones","34 E. 88 Ave.","Syosset","NY","10024"



command
Instruction for the computer.  See command-driven,
menu-driven and function.


command-driven
Program that accepts commands as typed-in phrases.
It is usually harder to learn, but may offer more
flexibility than a menu-driven program.  Once
learned, command-driven programs may be faster to
use, because the user can state a request
succinctly.  Contrast with menu-driven.


command interpreter
Same as command processor.


Command key
On Apple keyboards, a key with the outline of an
Apple, a propeller, or both.  It is pressed along
with another key to command the computer.


command language
Special-purpose language that accepts a limited
number of commands, such as a query language, job
control language (JCL) or command processor.
Contrast with programming language, which is a
general purpose language.


command line
In a command-driven system, the area on screen that
accepts typed-in commands.


command mode
Operating mode that causes the computer or modem to
accept commands for execution.


command processor
System program that accepts a limited number of
user commands and converts them into the machine
commands required by the operating system or some
other control program or application.


command queuing
Ability to store multiple commands and execute them
one at a time.


command set
Same as instruction set.


command shell
Same as command processor.


COMMAND.COM
Command processor for DOS and OS/2 in Real Mode.
See DOS COMMAND.COM.


comment
Descriptive statement in a source language program
that is used for documentation.


comment out
To disable lines of code in a program by
surrounding them with comment-start and comment-
stop characters.


commercial software
Software that is designed and developed for sale to
the general public.


Commodore
(Commodore Business Machines, Inc., West Chester,
PA)  In 1977, Commodore introduced the PET computer
and launched the personal computer industry along
with Apple and Radio Shack.  In 1982, it introduced
the Commodore 64 (64K RAM) and later the Commodore
128.  These were popular home computers, and over
10 million have been sold.

   In 1985, the successful Amiga series was
introduced, which features advanced capabilities at
affordable prices.  Also offered are a complete
line of IBM-compatible PCs.


common carrier
Government-regulated organization that provides
telecommunications services for public use, such as
AT&T, the telephone companies, ITT, MCI and Western
Union.


communications
Electronic transfer of information from one
location to another.  Data communications refers to
digital transmission, and telecommunications refers
to analog and digital transmission, including voice
and video.

                   The Protocol
The way communications systems "talk to" each other
is defined in a set of standards called protocols.
Protocols work in a hierarchy starting at the top
with the user's program and ending at the bottom
with the plugs, sockets and electrical signals.
See communications protocol and OSI.


         Personal Computer Communications
Personal computer communications takes several
forms.

(1) Data can be transferred between two distant
personal computers by using modems, a telephone
line and a communications program in each computer.

(2) Data can be transferred between two local
computers by cabling them together with a null
modem cable and a communications program in each
computer.

(3) Personal computers can act like a remote
terminal to a mini or mainframe.  For example,
DCA's IRMAboard plugs into a personal computer and
turns it into an IBM mainframe terminal.

(4) Personal computers can be part of a local area
network (LAN), in which databases and printers can
be shared among users.  If the LAN interconnects
with a mini or mainframe networks, then personal
computers can communicate with larger computers.


            Minicomputer Communications
Minicomputer communications systems control as many
as several hundred terminals connected to a single
computer system.  They support a variety of low-
speed dial-up terminals and high-speed local
terminals.  With larger minicomputers, the
communications processing is handled in separate
machines, called communications controllers.

   Minicomputers are designed with communications
in mind.  The communications programs and operating
systems are often integrated and provide simpler
operation than mainframes.

   Minicomputers can connect to a mainframe by
emulating a mainframe terminal, in which case, the
mainframe thinks it's talking to another user
terminal.  Minicomputers can connect directly to
some LANs, or to all LANs via a gateway, which
converts the protocols.


             Mainframe Communications
Mainframe systems can control several thousand
remote terminals.  They support a variety of low-
speed dial-up terminals and high-speed local
terminals.

   Large mainframes use separate machines, called
communications controllers or front end processors,
to handle the communications processing.  These
machines take the data from the mainframes and
package it for transmission over the network.  They
also strip the communications codes from the
incoming messages and send pure data to the
mainframes for processing.

   Mainframes set the standards for communications.
It's usually up to the mini and micro vendors to
provide compatibility with the mainframe systems.


         Analog vs Digital Communications
The most common form of long-distance
communications has been the telephone system,
which, up until a few years ago, transmitted only
voice frequencies.  This technique, known as analog
communications, has been error prone, because the
electronic frequencies get mixed together with
unwanted signals (noise) that are nearby.

   In analog telephone networks, amplifiers are
placed in the line every few miles to boost the
signal, but they cannot distinguish between signal
and noise.  Thus, the noise is amplified along with
the signal.  By the time the receiving person or
machine gets the signal, it may be impossible to
decipher it.

   In a digital network, only two (binary) distinct
frequencies or voltages are transmitted.  Instead
of amplifiers, repeaters are used, which analyze
the incoming signal and regenerate a new outgoing
signal.  Any noise on the line is filtered out at
the next repeater.  When data is made up of only
two signals (0 and 1), it can be more easily
distinguished from the garble.  Digital is simple!


Communications Act
Establishment of the Federal Communications
Commission (FCC) in 1934, the regulatory body for
interstate and foreign telecommunications.  Its
mission is to provide high-quality services at
reasonable cost to everyone in the U.S. on a
nondiscriminatory basis.


communications channel
Also called a circuit or line, it is a pathway over
which data is transferred between remote devices.
It may refer to the entire physical medium, such as
a telephone line, optical fiber, coaxial cable or
twisted wire pair, or, it may refer to one of
several carrier frequencies transmitted
simultaneously within the line as in broadband
transmission (see broadband).


communications controller
Peripheral control unit that connects several
communications lines to a computer and performs the
actual transmitting and receiving as well as
various message coding and decoding activities.

   Communications controllers are typically
nonprogrammable units designed for specific
protocols and communications tasks.  Contrast with
front end processor, which can be programmed for a
variety of protocols and network conditions.


communications network
(1) Communications channels that interconnect
terminals and computers.

(2) Communications channels, all hardware that
supports the interconnections and all software that
manages the transmission.


communications parameters
Basic settings for modem transmission, which
include bit rate (300, 1200, 2400, etc.), parity
(none, even, odd), number of data bits (7 or 8) and
number of stop bits (typically 1).  See N-8-1.


communications program
Software that manages the transmission of data
between computers and terminals.  In personal
computers, it manages transmission to and from the
computer's serial port.  It includes several
communications protocols and can usually emulate
dumb terminals for hookup to minis and mainframes.

   In a file server, the communications program is
called the network operating system (NetWare,
LANtastic).  In mini and mainframe networks, the
programs that support communications are called
access methods, network control programs and TP
monitors.  See front end processor.


communications protocol
Hardware or software standards that govern
transmission between two stations.  On personal
computers, communications programs offer a variety
of protocols (Kermit, Xmodem, Zmodem, etc.) to
transfer files via modem.  On LANs, protocols are
embodied in Ethernet, Token Ring and other access
methods.  In mainframe networks, there are multiple
levels of protocols, and protocols within
protocols.  It's a complicated business managing
enterprise-wide networks.

   The following conceptual exchange is at the data
link level (Zmodem, Ethernet, etc.), which ensures
that a block of data is transferred between two
nodes without error.

              The Data Link Protocol
Are you there?  Yes, I am.  Are you ready to
receive?  Yes, I am.  Here comes the message--bla,
bla, bla-- did you get it?  Yes, I did.  Here comes
the next part--bla, bla, bla-- did you get it?  No,
I didn't.  Here it comes again-- bla, bla, bla--
did you get it?  Yes, I did.  There is no more.
Goodbye.  Goodbye.


communications satellite
Radio relay station in orbit 22,300 miles above the
equator.  It travels at the same rate of speed as
the earth (geosynchronous), so that it appears
stationary.  It contains many communications
channels that receive analog and digital signals
from earth stations.  All signals are transmitted
within a carrier frequency.

   The signals are amplified and transmitted back
to earth, covering either a small geographical area
(spot beam) or almost a third of the earth's
surface.  In the latter case, private data is often
encrypted.


communications server
Computer in a network that manages access to
external networks.  It may manage a pool of modems
and/or provide gateways to dissimilar networks.


compact disc
See CD.


COMPACT II
High-level numerical control programming language
used to generate instructions for numerical control
(machine tool) devices.


compandor
(COMpressor/exPANDOR)  Device that improves the
signal for AM radio transmission.  On outgoing
transmission, it raises the amplitude of weak
signals and lowers the amplitude of strong signals.
On incoming transmission, it restores the signal to
its original form.


Compaq
(Compaq Computer Corp., Houston, TX)  PC
manufacturer founded in 1982 by Rod Canion, Bill
Murto and Jim Harris.  In 1983, it shipped 53,000
PC-compatible COMPAQ Portables, which resulted in
$111 million in revenues and an American business
record.  The Portable's success was due to its
rugged construction, ability to run all PC software
and its semi-portability (it weighed 30 pounds!).

   In 1984, it introduced its DESKPRO desktop
computers and achieved a computer-industry sales
record in its second year.  In 1986, it was the
first to offer a 386-based machine.

   Compaq is an industry leader known for its
rugged and reliable computers.


comparator
Device that compares two quantities and determines
their equality.


compare
Fundamental computer capability.  By comparing one
set of data with another, the computer can locate,
analyze, select, reorder and make decisions.  After
comparing, the computer can indicate whether the
data were equal or which set was numerically
greater or less than the other.  See ASCII chart
and "The 3 C's" in computer.


compatibility
See standards & compatibility.


compatibility mode
Feature of a computer or operating system that
allows it to run programs written for a different
system.  Programs often run slower in compatiblity
mode.


compilation
Compiling a program.  See compiler.


compile time
Time it takes to translate a program from source
language into machine language.  Link editing time
may also be included in compile time.


compiler
(1) Software that translates a high-level
programming language (COBOL, C, etc.) into machine
language.  A compiler usually generates assembly
language first and then translates the assembly
language into machine language.

   The following example compiles program
statements into machine language:

Source code   Assembly Language  Machine language
IF COUNT=10   Compare A to B     Compare 3477 2883
 GOTO DONE    If equal go to C   If = go to 23883
  ELSE        Go to D            Go to 23343
 GOTO AGAIN
ENDIF
              Actual machine code
            10010101001010001010100
            10101010010101001001010
            10100101010001010010010

(2) Software that converts a high-level language
into a lower-level representation.  For example, a
help compiler converts a text document embedded
with appropriate commands into an online help
system.  A dictionary compiler converts terms and
definitions into a dictionary lookup system.


compiler language
See high-level language and compiler.


complement
Number derived by subtracting a number from a base
number.  For example, the tens complement of 8 is
2.  In set theory, complement refers to all the
objects in one set that are not in another set.

   Complements are used in digital circuits,
because it's faster to subtract by adding
complements than by performing true subtraction.
The binary complement of a number is created by
reversing all bits and adding 1.  The carry from
the high-order position is eliminated.  The
following example subtracts 5 from 8.


   Decimal      Binary       Subtraction by
 Subtraction  Equivalent  Adding the complement
       8         1000          1000
      -5        -0101         +1011
     ───        ─────         ─────
       3         0011          0011


component
One element of a larger system.  A hardware
component can be a device as small as a transistor
or as large as a disk drive as long as it is part
of a larger system.  Software components are
routines or modules within a larger system.


composite video
Video-only (no audio) part of a TV signal.  Used on
early personal computers for TV hookup, it mixes
red, green, blue and sync signals like a standard
TV and is not as crisp as separate red, green and
blue cables (RGB).


compound document
Text file that contains both text and graphics.
Eventually, it will routinely hold voice
annotations and video clips.  See OLE.


compress
To compact data to save space.  See data
compression.


compression
See data compression.


compression ratio
Measurement of compressed data.  For example, a
file compressed into 1/4th of its original size can
be expressed as 4:1, 25%, 75% or 2 bits per byte.


compressor
(1) Device that diminishes the range between the
strongest and weakest transmission signals.  See
compandor.

(2) Routine or program that compresses data.  See
data compression.


Compsurf
Netware utility that performs a high-level hard
disk format.  NetWare servers require their own
proprietary format.


CompuServe
Online information service that provides
conferencing, news, sports, weather, e-mail and
access to a large variety of databases.  CompuServe
Information Manager (CIM) software for the personal
computer makes it easier to navigate through the
system.  See online services.


compute
To perform mathematical operations or general
computer processing.  See computer (The 3 C's).


compute bound
Same as process bound.


computer
General-purpose machine that processes data
according to a set of instructions that are stored
internally either temporarily or permanently.  The
computer and all equipment attached to it are
called hardware.  The instructions that tell it
what to do are called software.  A set of
instructions that perform a particular task is
called a program, or software program.


               WHAT A COMPUTER DOES
The instructions in the program direct the computer
to input, process and output as follows:


                   Input/Output
The computer can selectively retrieve data into its
main memory (RAM) from any peripheral device
(terminal, disk, tape, etc.) connected to it.
After processing the data internally, the computer
can send a copy of the results from its memory out
to any peripheral device.  The more memory it has,
the more programs and data it can work with at the
same time.


                      Storage
By outputting data onto a magnetic disk or tape,
the computer is able to store data permanently and
retrieve it when required.  A system's size is
based on how much disk storage it has.  The more
disk, the more data is immediately available.



                    PROCESSING
                   (The 3 C's*)
Once the data is in the computer's memory, the
computer can process it by calculating, comparing
and copying it.


                     Calculate
The computer can perform any mathematical operation
on data by adding, subtracting, multiplying and
dividing one set with another.


                      Compare
The computer can analyze and evaluate data by
matching it with sets of known data that are
included in the program or called in from storage.


                       Copy
The computer can move data around to create any
kind of report or listing in any order.

   By calculating, comparing and copying, the
computer accomplishes all forms of data processing.
For example, records are sorted into a new order by
comparing two records at a time and copying the
record with the lower value in front of the one
with the higher value.

   The computer finds one customer out of thousands
by comparing the requested account number to each
record in the file.  The dBASE query statement:
SUM SALARY FOR TITLE = "NURSE" causes the computer
to compare the title field in each record for NURSE
and then add (calculate) the salary field for each
match.

   In word processing, inserting and deleting text
is accomplished by copying characters from one
place to another.


                Remember The 3 C's*
If you wonder whether the computer can solve a
problem, identify your data on paper.  If it can be
calculated, compared and copied on paper, it can be
processed in the computer.

*(The 3 C's is a registered service mark of The
Computer Language Company Inc.)


            THE STORED PROGRAM CONCEPT
The computer's ability to call in instructions and
follow them is known as the stored program concept.

   Instructions are copied into memory from a disk,
tape or other source before any data can be
processed.  The computer is directed to start with
the first instruction in the program.  It copies
the instruction from memory into its control unit
circuit and matches it against its built-in set of
instructions.  If the instruction is valid, the
processor carries it out.  If not, the computer
comes to an abnormal end (abend, crash).

   The computer executes instructions sequentially
until it finds a GOTO instruction that tells it to
go to a different place in the program.  It can
execute millions of instructions per second tracing
the logic of the program over and over again on
each new set of data it brings in.

   As computers get faster, operations can be made
to overlap.  While one program is waiting for input
from one user, the operating system (master control
program) directs the computer to process data in
another program.  Large computers are designed to
allow inputs and outputs to occur simultaneously
with processing.  While one user's data is being
processed, data from the next user can be retrieved
into the computer.

   It can take hundreds of thousands of discrete
machine steps to perform very routine tasks.  Your
computer could easily execute a million
instructions to put a requested record on screen
for you.


             GENERATIONS OF COMPUTERS
First-generation computers, starting with the
UNIVAC I in 1951, used vacuum tubes, and their
memories were made of thin tubes of liquid mercury
and magnetic drums.

   Second-generation systems in the late 1950s
replaced tubes with transistors and used magnetic
cores for memories (IBM 1401, Honeywell 800).  Size
was reduced and reliability was significantly
improved.

   Third-generation computers, beginning in the mid
1960s, used the first integrated circuits (IBM 360,
CDC 6400) and the first operating systems and
DBMSs.  Online systems were widely developed,
although most processing was still batch oriented
using punched cards and magnetic tapes.

   Starting in the mid 1970s, the fourth generation
brought us computers made entirely of chips.  It
spawned the microprocessor and personal computer.
It introduced distributed processing and office
automation.  Query languages, report writers and
spreadsheets put large numbers of people in touch
with the computer for the first time.

   The fifth generation ought to become more
visible by the mid 1990s with voice recognition,
natural and foreign language translation, fiber
optics, optical disks and technologies still in the
research labs.  By the 21st century, a computer
should be able to converse somewhat intelligently
with us.


           COMPUTERS COME IN MANY SIZES
Computers are as small as a chip or as large as a
truck.  The difference is in the amount of work
they do within the same time frame.  Its power is
based on many factors, including word size and the
speed of its CPU, memory and peripherals.
Following is a rough guide to system cost:

Computer system type              Approximate price
(Bits show word size)                In 1993 $US
Computer on a chip  (chip only)
 (4, 8, 16-bit)                             $2 - 75
Microprocessor  (chip only)
 (4, 8, 16, 32, 64-bit)                    $5 - 500
Personal computer (8, 16, 32, 64-bit) $500 - 15,000
Minicomputer  (16, 32, 64-bit)    $15,000 - 250,000
Supermini (32, 64-bit)           $200,000 - 750,000
Mini-supercomputer (64-bit)      $100,000 - 750,000
Mainframe  (32, 64-bit)        $150,000 - 3,000,000
Supercomputer (64-bit)      $1,000,000 - 20,000,000


computer architecture
Design of a computer system.  It sets the standard
for all devices that connect to it and all the
software that runs on it.  It is based on the type
of programs that will run (business, scientific)
and the number of them run concurrently.

   It specifies how much memory is needed and how
it is managed (memory protection, virtual memory,
virtual machine).  It specifies register size and
bus width (16-, 32-, 64-bit) and how concurrency is
handled (channels, bus mastering, parallel
processing).

   Its native language instruction set stipulates
what functions the computer performs and how
instructions are written to activate them.  This
determines how programs will communicate with it
forever after.

   The trend toward large, complicated instruction
sets has been reversed with RISC computers, which
use simpler instructions.  The result is a leaner,
faster computer, but requires that the compilers
generate more code for complex functions that used
to be handled in hardware.

   Fault tolerant operation influences every aspect
of computer architecture, and computers designed
for single purposes, such as array processors and
database machines, require special designs.


Computer Associates
(Computer Associates Int'l., Inc., Islindia, NY)
World's largest diversified software vendor
offering over 350 applications from micro to
mainframe.  Founded in 1976 by Charles Wang and
three associates, its first product was CA-SORT, an
IBM mainframe utility.  In personal computers, it
was originally known for SuperCalc, one of the
first spreadsheets.  With 1991 revenues exceeding
1.6 billion, CA is concentrating heavily in the
Windows market.


computer center
Same as datacenter.


computer designer
Person who designs the electronic structure of a
computer.


computer exchange
Commodity exchange through which the public can buy
and sell used computers.  After a match, the buyer
sends a check to the exchange and the seller sends
the equipment to the buyer.  If the buyer accepts
it, the money is sent to the seller less
commission.

  Boston Computer Exchange (BoCoEx)
   617/542-4414   FAX [phone]

  National Computer Exchange (NaComEx)
   212/614-0700   FAX [phone]

  The Newman Group
   313/426-3200   FAX [phone]


computer graphics
See graphics.


computer language
Programming language, machine language or the
language of the computer industry.


Computer Library
Ziff Communications Company division that provides
information services.  See Computer Select.


computer literacy
Understanding computers and related systems.  It
includes a working vocabulary of computer and
information system components, the fundamental
principles of computer processing and a perspective
for how non-technical people interact with
technical people.

   It does not deal with how the computer works
(digital circuits), but does imply knowledge of how
the computer does its work (calculate, compare and
copy).  It requires a conceptual understanding of
systems analysis & design, application programming,
systems programming and datacenter operations.

   To be a computer literate manager, you must be
able to define information requirements effectively
and have an understanding of decision support
tools, such as query languages, report writers,
spreadsheets and financial planning systems.  To be
truly computer literate, you must understand
"standards & compatibility" in this Glossary.  If
you can't sleep at night, it's a guaranteed cure
for insomnia!


computer on a chip
Single chip that contains the processor, RAM, ROM,
clock and I/O control unit.  It is used for myriads
of applications from automobiles to toys.


computer power
Effective performance of a computer.  It can be
expressed in MIPS (millions of instructions per
second), clock speed (10Mhz, 16Mhz) and in word or
bus size, (16-bit, 32-bit).  However, as with
automobile horsepower, valves and cylinders, such
specifications are only guidelines.  Real power is
whether it gets your job done quickly.

   A software package is "powerful" if it has a
large number of features.


Computer Press Assn.
See CPA.  Remember... use the acronym first!


computer readable
Same as machine readable.


computer science
Field of computer hardware and software.  It
includes systems analysis & design, application and
system software design and programming and
datacenter operations.  For young students, the
emphasis in typically on learning a programming
language or running a personal computer with little
attention to information science, the study of
information and its uses.

   If students were introduced to data
administration, DBMS concepts and transaction and
master files, they would have a better grasp of an
organization's typical information requirements.


Computer Security Act
First step in improving the security and privacy of
information contained in federal computer systems.
Signed 1/8/88 by President Reagan, the Act:

   Establishes a central authority for developing
guidelines for protecting unclassified, but
sensitive information stored in government
computers.

   Requires each agency to formulate a computer
security plan, tailored to its own circumstances
and based on the guidelines.

   Mandates that each agency provide training for
its computer employees on the threats and
vulnerabilities of its computer systems.

   Ensures that the National Security Agency and
other defense-related government agencies not
control computer security standards in civilian
agencies of government.


Computer Select
CD ROM service from Computer Library that provides
articles and abstracts from over 140 computer-
related periodicals.  It includes over 67,000
hardware, software and communications products and
11,000 manufacturer's profiles.  Subscribers
receive a CD ROM every month with articles from the
preceding 12 months.


computer services
Data processing (timesharing, batch processing),
software development and consulting services.  See
service bureau.


computer system
Complete computer made up of the CPU, memory and
related electronics (main cabinet), all the
peripheral devices connected to it and its
operating system.  Computer systems fall into
ranges called microcomputers (personal computers),
minicomputers and mainframes, roughly small, medium
and large.

   Computer systems are sized for the total user
workload based on (1) number of terminals required,
(2) type of work performed (interactive processing,
batch processing, CAD, engineering, scientific),
and (3) amount of online data required.

   Following are the components of a computer
system and their significance:

   Component              Significance
Machine language   Compatibility with future
                    hardware/software

Operating system   Performance and future
                    hardware/software compatibility

Clock speed        Performance
  (MIPS rate)

Number  of         Number of concurrent users
  terminals

Memory capacity    Performance

Disk capacity      Amount of available information

Communications     Access to inhouse and external
                    information

Programming        Compatibility with future
  languages         hardware

Fail-safe design   Reliability



COMSAT
(COMmunications SATellite Corp.)  Private
communications satellite company created by
Congress in 1962 that provides communications
capacity to carriers such as AT&T and MCI.  In
1965, it launched Early Bird, the first commercial
satellite to transmit signals from a geosynchronous
orbit.  See INTELSAT and INMARSAT.


Comspec
See DOS Comspec.


CON
(CONsole)  DOS name for the keyboard and screen.
See DOS device names and DOS Copy con.


concatenate
To link structures together.  Concatenating files
appends one file to another.  In speech synthesis,
units of speech called phonemes (k, sh, ch, etc.)
are concatenated to produce meaningful sounds.


concentrator
Device that joins several communications channels
together.  It is similar to a multiplexor except
that it does not spread the signals back out again
on the other end.  The receiving computer performs
that function.


conceptual view
See view.


concurrency control
In a DBMS, managing simultaneous access to a
database.  It prevents two users from editing the
same record at the same time and is also concerned
with serializing transactions for backup and
recovery.


Concurrent DOS
Early multiuser DOS-compatible operating system
from Digital Research.  See Multiuser DOS.


concurrent operation
See multitasking, multiprocessing and parallel
processing.


concurrent processing
See multiprocessing.


conditional branch
In programming, an instruction that directs the
computer to another part of the program based on
the results of a compare.  In the following
(simulated) assembly language example, the second
line is the conditional branch.

       COMPARE FIELDA with FIELDB
       GOTO MATCHROUTINE if EQUAL.

   High-level language statements, such as IF THEN
ELSE and CASE, are used to express the compare and
conditional branch.


conditioning
Extra cost options in a private telephone line that
improve performance by reducing distortion and
amplifying weak signals.


conductor
Material that can carry electrical current.
Contrast with insulator.


CONFIG.SYS
DOS and OS/2 configuration file.  It resides in the
root directory and is used to load drivers and
change settings at startup.  See DOS CONFIG.SYS.


configuration
Makeup of a system.  To "configure" is to choose
options in order to create a custom system.
"Configurability" is a system's ability to be
changed or customized.


configuration file
File that contains information about a specific
user, program, computer or file.


configuration management
System for gathering current configuration
information from all nodes in a LAN.  See version
control.


configure
See configuration.


connect time
Amount of time a user at a terminal is logged on to
a computer system.  See online services and service
bureau.


Connection Machine
Family of parallel processing computers from
Thinking Machines Corp., Cambridge, MA, that
contain from 4K to 64K processors.  They can be set
up as hypercubes or other topologies and require
another computer as a front end.  Used for such
applications as signal processing, simulation and
database retrieval.


connection-oriented
In communications, requiring a direct connection or
established session between two nodes for
transmission.  Contrast with connectionless.


connectionless
In communications, the inclusion of source and
destination addresses within each packet so that a
direct connection or established session between
nodes is not required.  Contrast with connection-
oriented.


connectivity
May refer to communications in general or to
hardware that links networks together, such as
bridges, routers and gateways.


connector
(1) Any plug, socket or wire that links two devices
together.

(2) In database management, a link or pointer
between two data structures.

(3) In flowcharting, a symbol used to break a
sequence and resume the sequence elsewhere.  It is
often a small circle with a number in it.


console
(1) Main operator's terminal on a large computer.

(2) Any display terminal.


constant
In programming, a fixed value in a program.
Minimum and maximum amounts, dates, prices,
headlines and error messages are examples.


constant ratio code
Code that always contains the same ratio of 0s to
1s.


consultant
Independent specialist that may act as an advisor
or perform detailed systems analysis and design.
They often help users create functional
specifications from which hardware or software
vendors can respond.


contact
Metal strip in a switch or socket that touches a
corresponding strip in order to make a connection
for current to pass.  Contacts may be made of
precious metals to avoid corrosion.


contention
Condition that arises when two devices attempt to
use a single resource at the same time.  See
CSMA/CD.


contention resolution
Deciding which device gains access to a resource
first when more than one wants it at the same time.


context sensitive help
Help screens that provide specific information
about the condition or mode the program is in at
the time help is sought.


context switching
Switching between active applications.  It often
refers to a user jumping back and forth between
several programs in contrast with repeated task
switching performed by the operating system.
However, the terms context switching and task
switching are used synonymously.


contextual search
To search for records or documents based upon the
text contained in any part of the file as opposed
to searching on a pre-defined key field.


contiguous
Adjacent or touching.  Contrast with fragmentation.


continuity check
Test of a line, channel or circuit to determine if
the pathway exists from beginning to end and can
transmit signals.


continuous carrier
In communications, a carrier frequency that is
transmitted even when data is not being sent over
the line.


continuous forms
Roll of paper forms with perforations for
separation into individual sheets after printing.
See pin feed and burster.


contrast
Difference between the lightest and darkest areas
on a display screen.  Contrast with brightness.


control ball
Same as trackball.


control block
Segment of disk or memory that contains a group of
codes used for identification and control purposes.


control break
(1) Change of category used to trigger a subtotal.
For example, if data is subtotalled by state, a
control break occurs when NJ changes to NM.

(2) See Ctrl-Break.


control character
See control code.


control code
One or more characters used as a command to control
a device.  The first 32 characters in the ASCII
character set are control codes for communications
and printers.  There are countless codes used to
control electronic devices.  See escape character.


Control Data
(Control Data Systems, Inc., Minneapolis, MN)  One
of the first computer companies.  Founded in 1957,
Bill Norris was its first president and guiding
force.  Its first computer, the 1604, was
introduced in 1957 and delivered to the U.S. Navy
Bureau of Ships.  Since then, it has been heavily
involved with governmental agencies.

   Control Data offers a product line from
workstation to supercomputer and has specialized in
large mainframes used in scientific environments
and large service bureaus.  In 1992, it split into
two independent companies.  Control Data Systems,
Inc. makes computers, and Ceridian Corp. handles
military products and provides a variety of
services.


control field
Same as key field.


control key
Abbreviated "ctrl" or "ctl."  Key that is pressed
with a letter or digit key to command the computer;
for example, holding down control and pressing U,
turns on underline in some word processors.  The
caret (shift-6) symbol represents the control key:
^Y means control-Y.


control network
Network of sensors and actuators used for home
automation and industrial control.


Control Panel
Routine that changes the computer's environment
settings, such as keyboard and mouse sensitivity,
sounds, colors and communications and printer
access.  It is a desk accessory in the Macintosh
and a utility program in Windows.


control parallel
Same as MIMD.


control program
Software that controls the operation of and has
highest priority in a computer.  Operating systems,
network operating systems and network control
programs are examples.  Contrast with application
program.


control total
Same as hash total.


control unit
(1) Within the processor, the circuitry that
locates, analyzes and executes each instruction in
the program.

(2) Within the computer, a control unit, or
controller, is hardware that performs the physical
data transfers between memory and a peripheral
device, such as a disk or screen, or a network.

   Personal computer control units are contained on
a single plug-in expansion board, called a
controller or adapter (disk controller, display
adapter, network adapter).  In large computers,
they may be contained on one or more boards or in a
stand-alone cabinet.

   In single chip computers, a built-in control
unit accepts keyboard input and provides serial
output to a display.


control variable
In programming, a variable that keeps track of the
number of iterations of a process.  Its value is
incremented or decremented with each iteration, and
it is compared to a constant or other variable to
test the end of the process or loop.


controller
See control unit (2).


conventional memory
In a PC, the first 640K of memory.  The next 384K
is called the UMA (upper memory area).  The term
also often refers to the entire first megabyte
(1024K) of RAM, which is the memory that DOS can
directly manage without the use of additional
memory managers.  See DOS memory manager.


conventional programming
Using a procedural language.


convergence
Intersection of red, green and blue electron beams
on one CRT pixel.  Poor convergence decreases
resolution and muddies white pixels.


conversational
Interactive dialogue between the user and the
computer.


conversion
(1) Data conversion is changing data from one file
or database format to another.  It may also require
code conversion between ASCII and EBCDIC.

(2) Media conversion is changing storage media such
as from tape to disk.

(3) Program conversion is changing the programming
source language from one dialect to another, or
changing application programs to link to a new
operating system or DBMS.

(4) Computer system conversion is changing the
computer model and peripheral devices.

(5) Information system conversion requires data
conversion and either program conversion or the
installation of newly purchased or created
application programs.


converter
(1) Device that changes one set of codes, modes,
sequences or frequencies to a different set.  See
A/D converter.

(2) Device that changes current from 60Hz to 50Hz,
and vice versa.


cooperative processing
Sharing a job among two or more computers such as a
mainframe and a personal computer.  It implies
splitting the workload for the most efficiency.


coordinate
Belonging to a system of indexing by two or more
terms.  For example, points on a plane, cells in a
spreadsheet and bits in dynamic RAM chips are
identified by a pair of coordinates.  Points in
space are identified by sets of three coordinates.


coprocessor
Secondary processor used to speed up operations by
handling some of the workload of the main CPU.  See
math coprocessor.


copy
To make a duplicate of the original.  In digital
electronics, all copies are identical.

   The text in this Glossary takes up about 1.7
megabytes.  During the course of writing and
updating it, the text has been copied hundreds of
times, causing billions of bits to be transmitted
between disk and memory.  Just to show that things
aren't entirely perfect, a character does get
garbled every once in a while.  We'll have to
settle for 99.9999% instead of 100%!  See DOS Copy.


copy buster
Program that bypasses the copy protection scheme in
a software program and allows normal, unprotected
copies to be made.


copy protection
Resistance to unauthorized copying of software.
Copy protection was never an issue with mainframes
and minicomputers, since vendor support has always
been vital in those environments.

   In the early days of floppy-based personal
computers, many copy protection methods were used.
However, with each scheme introduced, a copy buster
program was developed to get around it.  When hard
disks became the norm, copy protection was
abolished.  In order to manage a hard disk, files
must be easily copied.

   This is a constant dilemma for software vendors.
  Every user has the manufacturing facilities to
produce a perfect copy of the original!  Anyone
figuring out a way to prevent unauthorized copies
without interfering with routine computer
management will become a billionaire overnight!


core
Round magnetic doughnut that represents one bit in
a core storage system.  A computer's main memory
used to be referred to as core.


core storage
Non-volatile memory that holds magnetic charges in
ferrite cores about 1/16th" diameter.  The
direction of the flux determines the 0 or 1.
Developed in the late 1940s by Jay W. Forrester and
Dr. An Wang, it was used extensively in the 1950s
and 1960s.  Since it holds its content without
power, it is still used in specialized applications
in the military and in space vehicles.


Core System
First proposed standard for computer graphics,
developed by the Graphics Standards Planning
Committee of SIGGRAPH and used in the late 1970s
and early 1980s.  Its objectives were portability
of programs between computers and the separation of
modeling graphics from viewing graphics.  Almost
all features of the Core System were incorporated
into the ANSI-endorsed GKS standard.


Corel Draw
Popular windows-based illustration program for 286s
and up from Corel Systems Corp., Ottawa, Ontario.
Introduced in 1989, it includes over 100 fonts and
is known for its speed and ease of use.  It
generates its own CDR vector graphics files, but
can import other graphics formats.


CorelRAID
Software from Corel Systems Corp., Ottawa, Ontario,
that creates RAID arrays on a Novel 3.11 server
using an ASPI-compatible SCSI host adapter and
three or more SCSI disks.


CorelSCSI
SCSI driver from Corel Systems Corp., Ottawa,
Ontario, that supports a wide variety of SCSI
devices, including removable media, juke boxes,
digital cameras and WORM drives and translates them
into the ASPI standard.  See PowerSCSI!.


corona wire
Charged wire in a laser printer that draws the
toner off the drum onto the paper.  It must be
cleaned when the toner cartridge is replaced.


corrupted file
Data or program file that has been altered in some
manner causing the bits to be rearranged and
rendering it unreadable.


corruption
Altering of data or programs due to viruses,
hardware or software failure or power failure.  See
data recovery.


COS
(Corporation for Open Systems Int'l.)  Not for
profit R&D consortium founded in 1986, dedicated to
assuring acceptance of a worldwide open network
architecture.  It is made up of manufacturers and
user organizations that provide development,
service, and support of systems that conform to
international standards, including OSI and ISDN.
Address: 1750 Old Meadow Road, Suite 400, McLean,
VA 22102, 703/883-2700.


cost/benefits analysis
Study that projects the costs and benefits of a new
information system.  Costs include people and
machine resources for development as well as
running the system.

   Tangible benefits are derived by estimating the
cost savings of both human and machine resources to
run the new system versus the old one.  Intangible
benefits, such as improved customer service and
employee relations, may ultimately provide the
largest payback, but are harder to quantify.


counter
(1) In programming, a variable that is used to keep
track of anything that must be counted.  The
programming language determines the number of
counters (variables) that are available to a
programmer.

(2) In electronics, a circuit that counts pulses
and generates an output at a specified time.


Courier
Monospaced typeface originating from the
typewriter.


courseware
Educational software.  See CBT.


covert channel
Transfer of information that violates a computer's
built-in security systems.  A covert storage
channel refers to depositing information in a
memory or storage location that can be accessed by
different security clearances.  A covert timing
channel is the manipulation of a system resource in
such a way that it can be detected by another
process.


CP
(1) (Copy Protected)  See copy protection.

(2) (Central Processor)  See processor and CPU.

(3) See control program.


CP/M
(Control Program for Microprocessors)  Single user
operating system for the 8080 and Z80
microprocessors from Digital Research.  Created by
Gary Kildall, CP/M had its heyday in the early
1980s.

   CP/M was an unsophisticated program that didn't
instill confidence in users, yet it was a major
contributor to the personal computer revolution.
Because the industry never standardized on a CP/M
disk or video format, software publishers had to
support dozens of screen displays and floppy disk
formats.  This chaos helped IBM set the standard
with its PC.

   Although IBM asked Kildall to provide the
operating system for its new PC, he didn't agree to
certain demands.  IBM went to Microsoft, which
purchased an operating system from another company
and turned it into DOS.  DOS was modeled after
CP/M.


CPA
(Computer Press Assn.)  Organization founded in
1983 that promotes excellence in computer
journalism.  Comprised of approximately 300 members
(1992), its annual awards honor outstanding
journalism in print, broadcast and electronic
media.  Address is 529 18th Ave., San Francisco, CA
94121, 415/750-9281.


CPE
(Customer Premises Equipment)  Communications
equipment that resides on the customer's premises.


CPF
(Control Program Facility)  IBM System/38 operating
system that includes an integrated relational DBMS.


CPGA
(Ceramic PGA)  See PGA.


cpi
(1) (Characters Per Inch)  Measures the density of
characters per inch on tape or paper.  A printer's
CPI button switches character pitch.

(2) (Counts Per Inch)  Measures the resolution of a
mouse/trackball as flywheel notches per inch
(horizontal and vertical flywheels rotate as the
ball is moved).  Notches are converted to cursor
movement.

(3) (CPI) (Common Programming Interface)  See SAA
and CPI-C.


CPI-C
(Common Programming Interface for Communications)
General-purpose communications interface under
IBM's SAA.  Using APPC verbs as its foundation, it
provides a common programming interface across IBM
platforms.  See APPC.


CPM
(Critical Path Method)  Project management planning
and control technique implemented on computers.
The critical path is the series of activities and
tasks in the project that have no built-in slack
time.  Any task in the critical path that takes
longer than expected will lengthen the total time
of the project.


cps
(Characters Per Second)  Measures the speed of a
serial printer or the speed of a data transfer
between hardware devices or over a communications
channel.  CPS is equivalent to bytes per second.


CPU
(Central Processing Unit)  Computing part of the
computer.  Also called the processor, it is made up
of the control unit and ALU.

   A personal computer CPU is a single
microprocessor chip.  A minicomputer CPU is
contained on one or more printed circuit boards.  A
mainframe CPU is made up of several boards.

   The CPU, clock and main memory make up a
computer.  A complete computer system requires the
addition of control units, input, output and
storage devices and an operating system.


CPU bound
Same as process bound.


CPU chip
Same as microprocessor.


CPU time
Amount of time it takes for the CPU to execute a
set of instructions and explicitly excludes the
waiting time for input and output.


CR
(Carriage Return)  Return key or the actual code
that is generated when the key is pressed (decimal
13, hex 0D).  See return key.


CR/LF
(Carriage Return/Line Feed)  End of line characters
used in standard PC text files (ASCII 13 10).  In
the Mac, only the CR is used; in UNIX, the LF.


CRAM
(Card RAM)  Magnetic card mass storage device made
by NCR in the 1960s.  In order to read or write
data, a card was pulled out of the cartridge and
wrapped around a rotating drum.


crash
See abend and head crash.


Cray
(Cray Research, Inc., Eagan, MN)  Supercomputer
manufacturer founded in 1972 by Seymour Cray, a
leading designer of large-scale computers at
Control Data.  In 1976, it shipped its first
computer to Los Alamos National Lab.  The CRAY-1
was a 75MHz, 64-bit machine with a peak speed of
160 megaflops, making it the world's fastest vector
processor.

   Large-scale Cray computers are multi-million-
dollar machines that use multiple processors,
liquid-cooled circuits, have gigabytes of main
memory and calculate well into the gigaflop range.

   In 1989, Cray left Cray Research and founded
Cray Computer Corp.


CRC
(Cyclical Redundancy Checking)  Error checking
technique used to ensure the accuracy of
transmitting digital data.  The transmitted
messages are divided into predetermined lengths
which, used as dividends, are divided by a fixed
divisor.  The remainder of the calculation is
appended onto and sent with the message.  At the
receiving end, the computer recalculates the
remainder.  If it does not match the transmitted
remainder, an error is detected.


Cricket Presents
Desktop presentation program for the Macintosh from
Computer Associates.  It provides the ability to
create output for overheads, handouts, speaker
notes and film recorders.


crippleware
Demonstration software with built-in limitations;
for example, a database package that lets only 50
records be entered.


Cristina Foundation
See NCF.


criteria range
Conditions for selecting records; for example,
"Illinois customers with balances over $10,000."


crop marks
Printed lines on paper used to cut the form into
its intended size.


cross assembler
Assembler that generates machine language for a
foreign computer.  It is used to develop programs
for computers on a chip or microprocessors used in
specialized applications, which are either too
small or are incapable of handling the development
software.


cross compiler
Compiler that generates machine language for a
foreign computer.  See cross assembler.


cross tabulate
To analyze and summarize data.  For example, cross
tabulation is used to summarize the details in a
database file into totals in a spreadsheet.


crossfoot
Numerical error checking technique that compares
the sum of the columns with the sum of the rows.


crosshatch
Criss-crossed pattern used to fill in sections of a
drawing to distinguish them from each other.


crossover cable
Same as null modem cable.


crosstalk
(1) In communications, interference from an
adjacent channel.

(2) (Crosstalk)  Family of PC communications
programs from DCA, Inc., Alpharetta, GA.  Crosstalk
products were originally developed by Microstuf,
Inc. (later merged with DCA).

   Crosstalk XVI (1983) is the PC version of the
original Crosstalk developed for CP/M computers.
It included a script language.  Crosstalk Mk.4
(1987) supports a variety of protocols and
terminals, allows concurrent sessions and provides
user-definable menus and a revised language called
CASL (Crosstalk Application Script Language).
Crosstalk for Windows (1989) provides additional
commands.


CRT
(Cathode Ray Tube)  Vacuum tube used as a display
screen in a video terminal or TV.  The term often
refers to the entire terminal.


crunch
(1) To process data.  See number crunching.

(2) To compress data.  See data compression.


cryogenics
Using materials that operate at very cold
temperatures.  See superconductor.


cryptography
Conversion of data into a secret code for security
purposes.  Same as encryption.


crystal
Solid material containing a uniform arrangement of
molecules.  See quartz crystal.


crystalline
Solid state of a crystal.  Contrast with nematic.


CSA
(1) (Canadian Standards Assn.)  Canadian
counterpart of U.S. Underwriters Laboratory.

(2) (Client Server Architecture)  See
client/server.

(3) (CallPath Services Architecture)  IBM standard
that integrates applications with the telephone
system, designed for use with AT&T, Northern
Telecom and other PBX vendors.


CSIC
(Customer Specific Integrated Circuit)  Pronounced
"C-sick."  Custom-developed chips from Motorola.


CSMA/CD
(Carrier Sense Multiple Access/Collision Detection)
Baseband communications access method.  When a
device wants to gain access to the network, it
checks to see if the network is free.  If it is
not, it waits a random amount of time before
retrying.  If the network is free and two devices
attempt access at exactly the same time, they both
back off to avoid a collision and each wait a
random amount of time before retrying.


CSP
(1) (Cross System Product)  IBM application
generator that runs in all SAA environments.
CSP/AD (CSP/Application Development) programs
provide the interactive development environment and
generate a pseudo code that is interpreted by
CSP/AE (CSP/Application Execution) software in the
running computer.  For AS/400 applications, CSP/AD
generates compiled code.  For the PS/2, EZ-PREP and
EZ-RUN are the CSP/AD and CSP/AE counterparts.

(2) (Certified Systems Professional)  Award for
successful completion of an ICCP examination in
systems development.


CSU
See DSU/CSU.


CSV
(Comma Separated Value)  Same as comma delimited.


CTI
(Computer Telephone Integration)  Joining data and
voice systems to enhance telephone services.  For
example, automatic number identification (ANI)
allows a caller's records to be retrieved from the
database while the call is routed to the
appropriate party.  Automatic telephone dialing
from an address list is an outbound example.


Ctl
See control key.


CTO
(Chief Technical Officer)  Executive responsible
for the technical direction of an organization.


CTOS
Operating system that runs on the Intel-based
Unisys B-series, originally developed by Convergent
Technologies (now part of Unisys).  Designed for
network use, its message-based approach allows
program requests to be directed to any station in
the network.


Ctrl
See control key.


Ctrl-Alt-Del
In a PC, holding down the CTRL and ALT keys and
pressing the DEL key reboots the system.


Ctrl-Break
In a PC, holding down the CTRL key and pressing the
BREAK key cancels the running program or batch
file.  Same as Ctrl-C.  See DOS Break.


Ctrl-C
In a PC, holding down the CTRL key and pressing the
C key cancels the running program or batch file.
Same as Ctrl-Break.  See DOS Break.


Ctrl-S
In a PC, holding down the CTRL key and pressing the
S key pauses and continues the running program.


CTS
(1) (Clear To Send)  RS-232 signal sent from the
receiving station to the transmitting station that
indicates it is ready to accept data.  Contrast
with RTS.

(2) See carpal tunnel syndrome.


CUA
(Common User Access)  SAA specifications for user
interfaces, which includes OS/2 PM and character-
based formats of 3270 terminals.  It is intended to
provide a consistent look and feel across platforms
and between applications.


CUI
(Character-based User Interface)  User interface
that uses the character, or text, mode of the
computer and typically refers to typing in
commands.  Contrast with GUI.


Curie point
Temperature (150° C) at which certain elements are
susceptible to magnetism.  See magneto-optic.


current
(1) Present activities or the latest version or
model.

(2) Flow of electrons within a wire or circuit,
measured in amps.

(3) (Current)  Windows PIM from IBM that includes a
calendar, address book, phone dialer, outliner,
word processor and Gantt charts for keeping track
of projects.


current directory
Disk directory the system is presently working in.
Unless otherwise specified, commands that deal with
disk files imply the current directory.


current loop
Serial transmission method originating with
teletype machines that transmits 20 milliAmperes of
current for a 1 bit and no current for a 0 bit.
Today's circuit boards can't handle 20mA current
and use optical isolators at the receiving end to
detect lower current.  Contrast with RS-232.


cursor
(1) Movable symbol on screen that is the contact
point between the user and the data.  In text
systems, it is a blinking rectangle or underline.
On graphic systems, it is also called a pointer,
and it usually changes shape (arrow, square,
paintbrush, etc.) when it moves into a different
part of the screen.

(2) Pen-like or puck-like device used with a
digitizer tablet.  As the tablet cursor is moved
across the tablet, the screen cursor moves
correspondingly.  See digitizer tablet.


cursor keys
Keys that move the cursor on screen, which include
the up, down, left and right arrow, home, end, PgUp
and PgDn keys.  In addition to cursor keys, a mouse
or tablet cursor also moves the cursor.


customized software
Software designed for an individual customer.


cut & paste
To move a block of text from one part of a document
to another or from one file to another.


CUT mode
(Control Unit Terminal mode)  Mode that allows a
3270 terminal to have a single session with the
mainframe.  Micro to mainframe software emulates
this mode to communicate with the mainframe.
Contrast with DFT mode.


CVF
(Compressed Volume File)  See DOS DoubleSpace.


CYBER
Trade name for Control Data computers that includes
models from high-speed workstations to
supercomputers.


cybernetics
Comparative study of human and machine processes in
order to understand their similarities and
differences.  It often refers to machines that
imitate human behavior.  See AI and robot.


cyberpunk
Relating to futuristic delinquency: hackers
breaking into computer banks, survival based on
high-tech wits.  Stems from science fiction novels
such as "Neuromancer" and "Shockwave Rider."


cyberspace
Term coined by William Gibson in his novel
"Neuromancer," to refer to a futuristic computer
network that people use by plugging their brains
into it!  See virtual reality.


cycle
(1) Single event that is repeated.  For example, in
a carrier frequency, one cycle is one complete
wave.

(2) Set of events that is repeated.  For example,
in a polling system, all of the attached terminals
are tested in one cycle.  See machine cycle and
memory cycle.


cycle stealing
CPU design technique that periodically "grabs"
machine cycles from the main processor usually by
some peripheral control unit, such as a DMA (direct
memory access) device.  In this way, processing and
peripheral operations can be performed concurrently
or with some degree of overlap.


cycle time
Time interval between the start of one cycle and
the start of the next cycle.


cycles per second
Number of times an event or set of events is
repeated in a second.  See Hertz.


Cycolor
Printing process from Mead Imaging that prints full
tonal images like photographs.  It uses a special
film coated with light-sensitive microcapsules,
called cyliths, that contain leuco dyes.  The film
is exposed to the color image that is being
printed, resulting in a latent image of hard and
soft cyliths.  The latent image donor film is
transferred onto a special Cycolor paper by being
squeezed together through pressure rollers, thus
releasing the dyes from the film onto the paper.
The paper is then briefly heated, and the result is
a full-color image that resembles a photograph.


cylinder
Aggregate of all tracks that reside in the same
location on every disk surface.  On multiple-
platter disks, the cylinder is the sum total of
every track with the same track number on every
surface.  On a floppy disk, a cylinder comprises
the top and corresponding bottom track.

   When storing data, the operating system fills an
entire cylinder before moving to the next one.  The
access arm remains stationary until all the tracks
in the cylinder have been read or written.


cylinder skew
Offset distance from the start of the last track of
the previous cylinder so that the head has time to
seek from cylinder to cylinder and be at the start
of the first track of the new cylinder.  See head
skew.



D/A converter
(Digital to Analog Converter)  Device that converts
digital pulses into analog signals.  See A/D
converter.


D/CAS
(Working Group for Data/CASsette Drive
Compatibility)  Organization standardizing audio
technology for tape backup.  With high-density
recording, an upgraded version of the common audio
tape cassette holds 600MB of data.


D/DAT
See DATA/DAT.


D-RAM
See dynamic RAM.


D&B Software
(Dun & Bradstreet Software, Atlanta; The Dun &
Bradstreet Corp.)  Software and consulting
organization formed in 1990 as a merger of
Management Science America (MSA) and McCormack &
Dodge.  It is one of the largest software companies
in the world.

   MSA was originally founded in 1963 to provide
textile consulting services.  Under the leadership
of John Imlay, who rejoined the company in 1970 as
Chairman and CEO, MSA grew rapidly in business
applications software and was the first to enter
the international marketplace in 1979.

   McCormack & Dodge began as a packaged financial
software firm in 1969 and later introduced the
first integrated environment for mainframe business
applications.  In 1983, it was acquired by The Dun
& Bradstreet Corp.

   Imlay directed the merger and has headed the new
company in the development of client-server
versions of its mainframe software.


D4
Framing format for T1 transmission that places 12
T1 frames into a superframe.  See ESF.


DA
See desk accessory and data administrator.


DAC
See D/A converter.


DAD
(1) (Database Action Diagram)  Documentation that
describes the processing performed on data in a
database.

(2) (Digital Audio Disc)  Same as CD.


daemon
Pronounced "demon."  Program that waits in the
background ready to perform some action when a
certain event occurs.  From Greek mythology meaning
"guardian spirit."  Same as agent.


daisy chain
Connected in series, one after the other.
Transmitted signals go to the first device, then to
the second and so on.

           ┌──────┐┌──────┐┌──────┐
         █████  ██████  ██████  █████

                 Daisy chain


daisy wheel
Print mechanism that uses a plastic or metal hub
with spokes like an old-fashioned wagon wheel minus
the outer rim.  At the end of each spoke is the
carved image of a type character.

   When the required character spins around to the
print hammer, the image is banged into a ribbon and
onto paper.  The mechanism is then moved to the
next location.  Daisy wheel printers print
typewriter-like quality from 10 to 75 cps and have
been superseded by dot matrix and laser printers.


DAL
(Data Access Language)  Database interface from
Apple that allows the Mac to access DAL-supported
databases on Macs or non-Apple computers.  It is a
superset of SQL.  Database vendors license the
specs and translate DAL calls to their database
engines.


damping
Technique for stabilizing an electronic or
mechanical device by eliminating unwanted or
excessive oscillations.


Darlington circuit
Amplification circuit that uses two transistors
coupled together.


DARPA
(Defense Advanced Research Projects Agency)  See
ARPANET.


DASD
(Direct Access Storage Device)  Pronounced
"dazdee."  Peripheral device that is directly
addressable, such as a disk or drum.


DAT
(1) (Digital Audio Tape)  CD-quality, digital
recording technology for magnetic tape.  A 4mm,
helical-scan DAT drive holds several gigabytes with
extended-length tapes when adapted for data storage
use.  See tape backup.

(2) (Dynamic Address Translator)  Hardware circuit
that converts a virtual memory address into a real
address.


data
(1) Technically, raw facts and figures, such as
orders and payments, which are processed into
information, such as balance due and quantity on
hand.  However, in common usage, the terms data and
information are used synonymously.

   The amount of data versus information kept in
the computer is a tradeoff.  Data can be processed
into different forms of information, but it takes
time to sort and sum transactions.  Up-to-date
information can provide instant answers.

   A common misconception is that software is also
data.  Software is executed, or run, by the
computer.  Data is "processed."  Software is "run."

(2) Any form of information whether in paper or
electronic form.  In electronic form, data refers
to files and databases, text documents, images and
digitally-encoded voice and video.

(3) Plural form of datum.


data abstraction
In object-oriented programming, creating user-
defined data types that contain their own data and
processing.  These data structures, or objects, are
unaware of each other's physical details and know
only what services each other performs.  This is
the basis for polymorphism and information hiding.


data acquisition
(1) Automatic collection of data from sensors and
readers in a factory, laboratory, medical or
scientific environment.

(2) Gathering of source data for data entry into
the computer.


data administration
Analysis, classification and maintenance of an
organization's data and data relationships.  It
includes the development of data models and data
dictionaries, which, combined with transaction
volume, are the raw materials for database design.

   Database administration often falls within the
jurisdiction of data administration; however, data
administration functions provide the overall
management of data as an organizational resource.
Database administration is the technical design and
management of the database.


                  Data Is Complex
The flow of data/information within a company is
complex since the same data is viewed differently
as it moves from one department to the other.

   For example: When a customer places an order,
the order becomes a commission for sales, a
statistic for marketing, an order to keep track of
in order processing, an effect on cash flow for
financial officers, picking schedules for the
warehouse, and production scheduling for
manufacturing.

   Users have different requirements for
interrogating and updating data.  Operations people
need detail, management needs summaries.  Database
design must take this into consideration.


data administrator
Person who coordinates activities within the data
administration department.  Contrast with database
administrator.


data bank
Any electronic depository of data.


data base
Data base is one word (database) in this Glossary.


data bus
Internal pathway across which data is transferred
to and from the processor.  The expansion slots in
personal computers are connected to the data bus.


data carrier
(1) Any medium such as a disk or tape that can hold
machine readable data.

(2) Carrier frequency into which data is modulated
for transmission in a network.


data cartridge
Removable magnetic tape module driven by a wheel
inside the drive that presses against a passive
roller in the cartridge.  A tension belt is
attached to the roller that presses against the
supply and takeup reel.  See QIC.


data cassette
Audio cassette made to higher tolerances for data
storage.


Data Cell
IBM mass storage device (1960s) that used tape
strips selected out of a cartridge and wrapped
around a rotating drum for reading.  See RACE and
CRAM.


data code
(1) Digital coding system for data in a computer.
See ASCII and EBCDIC.

(2) Coding system used to abbreviate data; for
example, codes for regions, classes, products and
status.


data collection
Acquiring source documents for the data entry
department.  It comes under the jurisdiction of the
data control or data entry department.  See data
acquisition.


data communications
Same as communications.


data compression
Encoding data to take up less storage space.  For
example, short names in fixed length fields waste a
lot of space.  A simple method called run length
encoding converts the spaces into a code that
indicates how many blanks follow.

   There are two major methods used for data
compression: statistical and dictionary, and two
widely-used examples of each: Huffman coding and
LZW (Lempel-Ziv-Welch).

   Text files can be compressed the most; for
example, the text you're reading can be compressed
from 50 to 70% depending on method used.  Dense
machine language files compress about a third to a
half.  Some graphics files leave little room for
compaction, others compress well.


data control department
Function responsible for collecting data for input
into a computer's batch processing operations as
well as the dissemination of the finished reports.
The data entry department may be under the
jursidiction of the data control department or vice
versa.


DATA/DAT
(DATA/Digital Audio Tape)  DAT format for data
backup that can be divided into as many as 254
partitions allowing for updating in place.  See
tape backup.


data declaration
Same as data definition (1).


data definition
(1) In a source language program, the definitions
of data structures (variables, arrays, fields,
records, etc.).

(2) Description of the record layout in a file
system or DBMS.


data dictionary
Database about data and databases.  It holds the
name, type, range of values, source, and
authorization for access for each data element in
the organization's files and databases.  It also
indicates which application programs use that data
so that when a change in a data structure is
contemplated, a list of affected programs can be
generated.

   The data dictionary may be a stand-alone system
or an integral part of, and used to control, the
DBMS.  Data integrity and accuracy is better
ensured in the latter case.


data dipper
Software in a personal computer that queries a
mainframe database.


data division
The part of a COBOL program that defines the data
files and record layouts.


data element
Fundamental data structure in a data processing
system.  Any unit of data defined for processing is
a data element; for example, ACCOUNT NUMBER, NAME,
ADDRESS and CITY.  A data element is defined by
size (in characters) and type (alphanumeric,
numeric only, true/false, date, etc.).  A specific
set of values or range of values may also be part
of the definition.

   Technically, a data element is a logical
definition of data, whereas a field is the physical
unit of storage in a record.  For example, the data
element ACCOUNT NUMBER, which exists only once, is
stored in the ACCOUNT NUMBER field in the customer
record and in the ACCOUNT NUMBER field in the order
records.

   Data element, data item, field and variable all
describe the same unit of data and are used
interchangeably.


data encryption
See encryption and DES.


data entry
Entering data into the computer, which includes
keyboard entry, scanning and voice recognition.
When transactions are entered after the fact (batch
data entry), they are just stacks of source
documents to the keyboard operator.  Deciphering
poor handwriting from a source document is a
judgment call that is often error prone.  In online
data entry operations, in which the operator takes
information in person or by phone, there's
interaction and involvement with the transaction
and less chance for error.


data entry department
The part of the datacenter where the data entry
terminals and operators are located.


data entry operator
Person who enters data into the computer via
keyboard or other reading or scanning device.


data entry program
Application program that accepts data from the
keyboard or other input device and stores it in the
computer.  It may be part of an application that
also provides updating, querying and reporting.

   The data entry program establishes the data in
the database and should test for all possible input
errors.  See validity checking, table lookup, check
digit and intelligent database.


data file
Collection of data records.  Contrast with word
processing file and graphics file.


data flow
(1) In computers, the path of data from source
document to data entry to processing to final
reports.  Data changes format and sequence (within
a file) as it moves from program to program.

(2) In communications, the path taken by a message
from origination to destination and includes all
nodes through which the data travels.


data flow diagram
Description of data and the manual and machine
processing performed on the data.


data fork
The part of a Macintosh file that contains data.
For example, in a HyperCard stack, text, graphics
and HyperTalk scripts reside in the data fork,
while fonts, sounds, control information and
external functions reside in the resource fork.


data format
Same as file format.


Data General
(Data General Corp., Westboro, MA)  Computer
manufacturer founded in 1968 by Edson de Castro.
In 1969, it introduced the Nova, the first 16-bit
mini with four accumulators, a leading technology
at the time.  During its early years, the company
was successful in the scientific, academic and OEM
markets.  With its Comprehensive Electronic Office
(CEO) software in the early 1980s, it gained entry
into the commercial marketplace.  Computer
offerings include the 32-bit ECLIPSE family and
UNIX-based systems using Motorola 88000 CPUs.


data glove
Glove used to report the position of a user's hand
and fingers to a computer.  See virtual reality.


data independence
DBMS technique that separates data from the
processing and allows the database to be
structurally changed without affecting most
existing programs.  Programs access data in a DBMS
by field and are concerned with only the data
fields they use, not the format of the complete
record.  Thus, when the record layout is updated
(fields added, deleted or changed in size), the
only programs that must be changed are those that
use those new fields.


data integrity
Process of preventing accidental erasure or
adulteration in a database.


data item
Unit of data stored in a field.  See field.


data library
Section of the datacenter that houses offline disks
and tapes.  Data library personnel are responsible
for cataloging and maintaining the media.


data line
Individual circuit, or line, that carries data
within a computer or communications channel.


data line monitor
In communications, a test instrument that analyzes
the signals and timing of a communications line.
It either visually displays the patterns or stores
the activity for further analysis.


data link
In communications, the physical interconnection
between two points (OSI layers 1 and 2).  It may
also refer to the modems, protocols and all
required hardware and software to perform the
transmission.


data link escape
Communications control character which indicates
that the following character is not data, but a
control code.


data link protocol
In communications, the transmission of a unit of
data from one node to another (OSI layer 2).  It is
responsible for ensuring that the bits received are
the same as the bits sent.  Following are the major
categories:

             Asynchronous Transmission
Originating from mechanical teletype machines,
asynchronous transmission treats each character as
a unit with start and stop bits appended to it.  It
is the common form of transmission between the
serial port of a personal computer or terminal and
a modem.  ASCII, or teletype, protocols provide
little or no error checking.  Xmodem, Ymodem and
Kermit are typical error checking protocols.


             Synchronous Transmission
Developed for mainframe networks using higher
speeds than teletype terminals, synchronous
transmission sends contiguous blocks of data, with
both sending and receiving stations synchronized to
each other.  Synchronous protocols include error
checking.  Examples are IBM's SDLC, Digital's
DDCMP, and the international HDLC.


                       LANs
Developed for medium to high transmission speeds
between stations, LANs typically use collision
detection (CSMA/CD) or token passing methods for
transmitting data between nodes.  Examples are
IBM's Token Ring, Datapoint's ARCNET, Xerox's
Ethernet and AT&T's Starlan.

   The IEEE 802 specification for LANs breaks the
data link layer into two sublayers: the LLC
(Logical Link Control) and MAC (Media Access
Control).  The LLC provides a common interface
point to the MAC layers, which specify the access
method used.  The following compares the data link
layer in LANs to IBM's SNA and ISO's OSI model.


      │ Path       │
      │ Control │  │ Network │
 ──── ├─────────┤  ├─────────┤  ┌────────────────┐
 Data │         │  │         │  │      LLC       │
 Link │  SDLC   │  │  HDLC   │  ├────────────────┤
 Layer│         │  │         │  │ MAC (CSMA/CD,  │
 ──── ├─────────┤  ├─────────┤  ├────┐ Token Bus,│
      │         │  │         │  │    │ Token Ring│
      │         │  │         │  │    └───────────┤
      │ Physical│  │ Physical│  │    Physical    │
      └─────────┘  └─────────┘  └────────────────┘
          SNA          OSI           IEEE 802



data management
Refers to several levels of managing data.  From
bottom to top, they are:

(1) The part of the operating system that manages
the physical storage and retrieval of data on a
disk or other device.  See access method.

(2) Software that allows for the creation, storage,
retrieval and manipulation of files interactively
at a terminal or personal computer.  See file
manager and DBMS.

(3) Function that manages data as an organizational
resource.  See data administration.

(4) Management of all data/information in an
organization.  It includes data administration, the
standards for defining data and the way in which
people perceive and use it.


data management system
See DBMS.


data manipulation
Processing data.


data manipulation language
Language that requests data from a DBMS.  It is
coded within the application program such as COBOL
or C.


data model
Description of the principles of organization of a
database.


data modeling
Identification of the design principles for a data
model.


data module
Sealed, removable storage module containing
magnetic disks and their associated access arms and
read/write heads.


data name
Name assigned to a field or variable.


data network
Communications network that transmits data.  See
communications.


data parallel
Same as SIMD.


data processing
Capturing, storing, updating and retrieving data
and information.  It may refer to the industry or
to data processing tasks in contrast with other
operations, such as word processing.


data processor
(1) Person who works in data processing.

(2) Computer that is processing data, in contrast
with a computer performing another task, such as
controlling a network.


data projector
Video machine that projects output from a computer
onto a remote screen.  It is bulkier than a flat
LCD panel, but is faster for displaying high-speed
animation.


Data Propagator
IBM query language that maintains consistency
between DB2 and IMS/ESA DB databases.  When data is
changed in the IMS database, it is automatically
changed in the DB2 database.


data rate
(1) Data transfer speed within the computer or
between a peripheral and computer.

(2) Data transmission speed in a network.


data recovery
Restoring data that has been physically damaged or
corrupted on a disk or tape.  Disks and tapes can
become corrupted due to viruses, bad software,
hardware failure as well as from power failures
that occur while the magnetic media is being
written.  See DOS data recovery.


data representation
How data types are structured; for example, how
signs are represented in numerical values or how
strings are formatted (enclosed in quotes,
terminated with a null, etc.).


data resource management
Same as data administration.


data set
(1) Data file or collection of interrelated data.

(2) AT&T name for modem.


data signal
Physical data as it travels over a line or channel
(pulses or vibrations of electricity or light).


data sink
Device or part of the computer that receives data.


data source
Device or part of the computer in which data is
originated.


data stream
Continuous flow of data from one place to another.


data striping
See disk striping.


data structure
Physical layout of data.  Data fields, memo fields,
fixed length fields, variable length fields,
records, word processing documents, spreadsheets,
data files, database files and indexes are all
examples of data structures.


data switch
Switch box that routes one line to another; for
example, to connect two computers to one printer.
Manual switches have dials or buttons.  Automatic
switches test for signals and provide first-come,
first-served switching.


data system
Same as information system.


data tablet
Same as digitizer tablet.


data transfer
Movement of data within the computer system.
Typically, data is said to be transferred within
the computer, but it is "transmitted" over a
communications network.  A transfer is actually a
copy function since the data is not automatically
erased at the source.


data transfer rate
Same as data rate.


data transmission
Sending data over a communications network.


data transparency
Ability to easily access and work with data no
matter where it is located or what application
created it.


data type
Category of data.  Typical data types are numeric,
alphanumeric (character), dates and logical
(true/false).  Programming languages allow for the
creation of different data types.

   When data is assigned a type, it cannot be
treated like another type.  For example,
alphanumeric data cannot be calculated, and digits
within numeric data cannot be isolated.  Date types
can only contain valid dates.


database
(1) Set of interrelated files that is created and
managed by a DBMS.

(2) Any electronically-stored collection of data.


Database 2
See DB2.


database administrator
Person responsible for the physical design and
management of the database and for the evaluation,
selection and implementation of the DBMS.

   In small organizations, the database
administrator and data administrator are one in the
same; however, when the two responsibilities are
managed separately, the database administrator's
function is more technical.


database analyst
See data administrator and database administrator.


database designer
See data administrator and database administrator.


database driver
Software routine that accesses a database.  It
allows an application or compiler to access a
particular database format.


database engine
Same as database manager.


database machine
Specially-designed computer for database access
that is coupled to the main computer via high-speed
channel.  It uses multiple processors to perform
fast disk searches.

   Contrast with database server, which is used in
a LAN.  The database machine is tightly coupled to
the main CPU; the database server is loosely
coupled in the network.


database management system
See DBMS.


database manager
(1) With personal computers, software that allows a
user to manage multiple data files (same as DBMS).
Contrast with file manager, which works with one
file at a time.

(2) Software that provides database management
capability for traditional programming languages,
such as COBOL, BASIC and C, but without the
interactive capabilities.

(3) The part of the DBMS that stores and retrieves
the data.


database publishing
Using desktop publishing to produce reports of
database contents.


database server
Computer in a LAN dedicated to database storage and
retrieval.  Contrast with file server, which stores
many kinds of files and programs for shared use.


datacenter
Department that houses the computer systems and
related equipment, including the data library.
Data entry and systems programming may also come
under its jurisdiction.  A control section is
usually provided that accepts work from and
releases output to user departments.


datacom
(DATA COMmunications)  See communications.


DataEase
Relational DBMS for PCs from DataEase Int'l., Inc.,
Trumbull, CT.  It provides a menu-driven interface
for developing applications without programming and
is noted for its ease of use.


datagram
TCP/IP message unit that contains internet source
and destination addresses and data.


DataPhone
AT&T trade name for equipment and services.  See
DDS.


date math
Calculations made upon dates.  For example, March
30 + 5 yields April 4.


datum
Singular form of data; for example, one datum.  It
is rarely used, and data, its plural form, is
commonly used for both singular and plural.


daughter board
Small printed circuit board that is attached to or
plugs into a removable printed circuit board.


dazdee
See DASD.


DB
See database and decibel.


DB-9, DB-15, DB-25..
(DB-9, DB-15, DB-25, DB-37, DB-50)  Category of
plugs and sockets with 9, 15, 25, 37 and 50 pins
respectively, used to hook up communications and
computer devices.  The DB refers to the physical
structure of the connector, not the purpose of each
line.

   DB-9 and DB-25 connectors are commonly used for
RS-232 interfaces.  The DB-25 is also used on the
computer end of the parallel printer cable for PCs
(the printer end is a Centronics 36-pin connector).

   A high-density DB-15 connector is used for the
VGA port on a PC, which has 15 pins in the same
shell as the DB-9 connector.


DB/DC
(DataBase/Data Communications)  Refers to software
that performs database and data communications
functions.


DB2
(DataBase 2)  Relational DBMS from IBM that runs on
large mainframes.  It is a full-featured DBMS that
has become IBM's major database product.  It uses
the SQL language interface.


DBA
See database administrator.


dBASE
Relational DBMS for PCs from Borland.  It was the
first comprehensive DBMS for personal computers.
Originally named Vulcan, dBASE was created by Wayne
Ratliff to manage a company football pool.  It was
modeled after JPLDIS, the DBMS at Jet Propulsion
Labs in Los Angeles.

   Renamed dBASE II when Hal Lashlee and George
Tate formed Ashton-Tate to market it (Ashton-Tate
was acquired by Borland in 1991), dBASE became a
huge success within a couple of years.  It is the
most widely used PC database system, and its file
formats have become de facto standards.

   dBASE provides a Pascal-like, interpreted
programming language and fourth-generation commands
for interactive use.

   The following programming language example
converts Fahrenheit to Celsius:

    INPUT "Enter Fahrenheit  " TO FAHR
    ? "Celsius is ", (FAHR - 32) * 5 / 9


The following fourth-generation language example
opens the product file and displays green items:

    use products
    list for color ='GREEN'



                     dBASE II
Introduced in 1981, it was the original command-
driven dBASE for CP/M machines and later for PCs.
dBASE II data formats and programs must be
converted to run under dBASE III.


               dBASE III & III PLUS
Introduced in 1984, dBASE III was a major upgrade
of dBASE II for PCs only.  It handles larger
databases, has more programming commands and
includes a memo field and menus.  In 1986, dBASE
III PLUS introduced redesigned menus and added new
features including the ability to store queries and
relational views.


                     dBASE IV
Introduced in 1988, it is a major upgrade of dBASE
III PLUS with redesigned menus and report and forms
generation screens.  It adds a QBE method for
asking questions as well as an SQL language
interface.  Many new programming commands and
features are added, including arrays and windows.

   Versions of dBASE IV are also available for UNIX
on 386s, Sun workstations and VAXs under VMS, and a
runtime version is available for the Macintosh.


dBASE compiler
Software that converts dBASE source language into
machine language.  The resulting programs execute
on their own like COBOL or C programs and do not
run under dBASE.  See Clipper, Force and
Quicksilver.


dBASE Mac
Macintosh DBMS from Ashton-Tate that never caught
on because it was incompatible with dBASE.


DBF file
dBASE data file extension.  dBASE II and dBASE III
files both use DBF, but are not compatible.


DBMS
(DataBase Management System)  Software that
controls the organization, storage, retrieval,
security and integrity of data in a database.  It
accepts requests from the application and instructs
the operating system to transfer the appropriate
data.

   DBMSs may work with traditional programming
languages (COBOL, C, etc.) or they may include
their own programming language for application
development.

   DBMSs let information systems be changed more
easily as the organization's requirements change.
New categories of data can be added to the database
without disruption to the existing system.


             MAJOR FEATURES OF A DBMS

                   Data Security
The DBMS can prevent unauthorized users from
viewing or updating the database.  Using passwords,
users are allowed access to the entire database or
subsets of it called subschemas.  For example, in
an employee database, some users may be able to
view salaries while others may view only work
history and medical data.

                  Data Integrity
The DBMS can ensure that no more than one user can
update the same record at the same time.  It can
keep duplicate records out of the database; for
example, no two customers with the same customer
number can be entered.

                 Interactive Query
Most DBMSs provide query languages and report
writers that let users interactively interrogate
the database and analyze its data.  This important
feature gives users access to all management
information as needed.

        Interactive Data Entry and Updating
Many DBMSs provide a way to interactively enter and
edit data, allowing you to manage your own files
and databases.  However, interactive operation does
not leave an audit trail and does not provide the
controls necessary in a large organization.  These
controls must be programmed into the data entry and
update programs of the application.

   This is a common misconception about personal
computer DBMSs.  Complex business systems can be
developed in dBASE and Paradox, etc., but not
without programming.  This is not the same as
creating lists of data for your own record keeping.

                 Data Independence
With DBMSs, the details of the data structure are
not stated in each application program.  The
program asks the DBMS for data by field name; for
example, a coded equivalent of "give me customer
name and balance due" would be sent to the DBMS.
Without a DBMS, the programmer must reserve space
for the full structure of the record in the
program.  Any change in data structure requires
changing all application programs.


                  DATABASE DESIGN
A business information system is made up of
subjects (customers, employees, vendors, etc.) and
activities (orders, payments, purchases, etc.).
Database design is the process of organizing this
data into related record types.  The DBMS that is
chosen is the one that can support the
organization's data structure while efficiently
processing the transaction volume.

   Organizations may use one kind of DBMS for daily
transaction processing and then move the detail to
another DBMS better suited for random inquiries and
analysis.

   Overall systems design decisions are performed
by data administrators and systems analysts.
Detailed database design is performed by database
administrators.


  HIERARCHICAL, NETWORK AND RELATIONAL DATABASES
Information systems are made up of related files:
customers and orders, vendors and purchases, etc.
A key DBMS feature is its ability to manage these
relationships.

   Hierarchical databases link records like an
organization chart.  A record type can be owned by
only one owner.  In the following example, orders
are owned by only one customer.  Hierarchical
structures were widely used with early mainframe
systems; however, they are often restrictive in
linking real-world structures.

     ┌──────────────┐
     │   Customer   │
     └───────────┬──┘
                 │
               ┌─┴───────────┐
               │    Order    │
               └─────────────┘


In network databases, a record type can have
multiple owners.  In the example below, orders are
owned by both customers and products, reflecting
their natural relationship in business.

     ┌──────────────┐   ┌─────────────┐
     │   Customer   │   │   Product   │
     └───────────┬──┘   └──┬──────────┘
                 │         │
               ┌─┴─────────┴─┐
               │    Order    │
               └─────────────┘


Relational databases do not link records together
physically, but the design of the records must
provide a common field, such as account number, to
allow for matching.  Often, the fields used for
matching are indexed in order to speed up the
process.

   In the following example, customers, orders and
products are linked by comparing data fields and/or
indexes when information from more than one record
type is needed.  This method is more flexible for
ad hoc inquiries.  Many hierarchical and network
DBMSs also provide this capability.

┌────────────┐  ┌─────────────┐  ┌─────────────┐
│  Customer  │  │    Order    │  │   Product   │
└────────────┘  └─────────────┘  └─────────────┘


               INTELLIGENT DATABASES
All DBMSs provide some data validation; for
example, they can reject invalid dates or
alphabetic data entered into money fields.  But
most validation is left up to the application
programs.

   Intelligent databases provide more validation;
for example, table lookups can reject bad spelling
or coding of items.  Common algorithms can also be
used such as one that computes sales tax for an
order based on zip code.

   When validation is left up to each application
program, one program could allow an item to be
entered while another program rejects it.  Data
integrity is better served when data validation is
done in only one place.  Mainframe DBMSs are
increasingly becoming intelligent.  Eventually all
DBMS will follow suit.


                 FUTURE DATABASES
The world of information is made up of data, text,
pictures and voice.  Many DBMSs manage text as well
as data, but very few manage both with equal
proficiency.  Throughout the 1990s, DBMSs will
begin to integrate all forms of information.
Eventually, it will be common for a database to
handle data, text, graphics, voice and video with
the same ease as today's systems handle data.  When
this happens, the office of the future will have
finally arrived!


╔══█═ to/from terminals ═════════════(RAM)══════╗
║┌─▀───────┐   ┌────────────────────────────┐   ║
║│ Comm.   ■■■■■   TP Monitor (Multiuser)   │   ║
║│ Access  │   └─▄───────▄─────────────▄────┘   ║
║│ Methods │     █ ┌─────▀─────┐ ┌─────▀──────┐ ║
║├─────────┤     █ │Application│ │Application │ ║
║│         │     █ │in COBOL or│ │in DBMS's   │ ║
║│         │     █ │other lang.│ │own language│ ║
║│         │     █ └──────────▄┘ └─────▄──────┘ ║
║│   OS    │.....█............█........█ .......║
║│         │.┌───▀──────────┐ █  ┌─────▀─────┐ .║
║│         │.│Interactive:  │ █  │Interpreter│ .║
║│         │.│enter, edit,  │ █  └─────▄─────┘ .║
║│         │.│query, reports│ █        █       .║
║├─────────┤.└─────▄────────┘ █        █       .║
║│ Disk    │.  ┌───▀──────────▀────────▀──────┐.║
║│ Access  ■■■■■       Database manager       │.║
║│ Methods │.  └──────────────────────────────┘.║
║└─▄───────┘...............DBMS ................║
╚══█═ to/from disk ═════════════════════════════╝

                    DBMS


DBOMP
(DataBase Organization and Maintenance Processor)
Early DBMS that was derived from BOMP.


DBS
(Direct Broadcast Satellite)  One-way broadcast
service direct from a satellite to a user's dish
(antenna).  They are used to deliver private
information and TV services.


dBXL
dBASE III PLUS-compatible DBMS from WordTech
Systems, Inc., Orinda, CA, that features a menu-
driven option for interactive use.  See Arago.


DC
(1) (Direct Current)  Electrical current that
travels in one direction and used within the
computer's electronic circuits.  Contrast with AC.

(2) (Data Communications)  See DB/DC.


DCA
(1) (Document Content Architecture)  IBM file
formats for text documents.  DCA/RFT (Revisable-
Form Text) is the primary format and can be edited.
DCA/FFT (Final-Form Text) has been formatted for a
particular output device and cannot be changed.
For example, page numbers, headers and footers are
placed on every page.

(2) (Distributed Communications Architecture)
Network architecture from Unisys.

(3) (Digital Communications Associates, Inc.,
Alpharetta, GA)  Communications products
manufacturer.  See IRMAboard.


DCC
(Digital Compact Cassette)  Digital tape format
that uses a variation of the common audio cassette.
Also plays analog audio cassettes.


DCE
(1) (Data Communications Equipment or Data Circuit-
terminating Equipment)  Device that establishes,
maintains and terminates a session on a network.
It may also convert signals for transmission.  It
is typically the modem.  Contrast with DTE.

(2) (Distributed Computing Environment)  See OSF.


DCS
(1) (Distributed Communications System)  Telephone
system that puts small switches close to
subscribers making local loops shorter and
maximizing long lines to the central office.

(2) (Distributed Control System)  Process control
system that uses disbursed computers throughout the
manufacturing line for control.

(3) (Digital Cross-connect System)  High-speed data
channel switch that accepts separate instructions
for switching independently of the data travelling
through it.

(4) (Document Control Software)  Menu-driven query
system from Workgroup Technologies for Oracle
databases on PCs and Sun stations.

(5) (Desktop Color Separation)  Quark format for
defining color separated output from a personal
computer.


DCT
See discrete cosine transform.


DD
(Double Density)  Designation for low-density
diskettes, typically the 5.25" 360K and 3.5" 720K
floppies.  See double density.  Contrast with HD.


DDBMS
(Distributed Database Management System)  See
distributed database.


DDCMP
(Digital Data Communications Message Protocol)
Digital's proprietary, synchronous data link
protocol used in DECnet.


DDE
(Dynamic Data Exchange)  Message protocol in
Windows that allows application programs to request
and exchange data automatically.  A program in one
window can query a program in another window.


DDL
(1) (Data Description Language)  Language used to
define data and their relationships to other data.
It is used to create files, databases and data
dictionaries.

(2) (Document Description Language)  Printer
control language from Imagen that runs on the HP
LaserJet series.

(3) (Direct Data Link)  Ability of a supplier to
directly interrogate a customer's inventory
database in order to manage scheduling and shipping
more efficiently.  Pioneered by Ford Motor Co. in
1988, Ford lets suppliers check stock levels in
assembly plants throughout North America.


DDM
(Distributed Data Management)  Software in an IBM
SNA environment that allows users to access data in
remote data files within the network.  DDM works
with IBM's LU 6.2 session to provide peer-to-peer
communications and file sharing.


DDP
(Distributed Data Processing)  See distributed
processing.


DDS
(1) (Dataphone Digital Service)  AT&T private line
digital service with data rates from 2400 bps to
56Kbps.  Private analog lines can be connected to
DDS lines.

(2) (Digital Data Service)  Private line digital
services from non-AT&T carriers.

(3) (Digital Data Storage)  DAT format for data
backup.  It is a sequential recording method; data
must be appended at the end of previous data.  See
tape backup.


de facto standard
Widely-used format or language not endorsed by a
standards organization.


de jure standard
Format or language endorsed by a standards
organization.


deadlock
See deadly embrace.


deadly embrace
Stalemate that occurs when two elements in a
process are each waiting for the other to respond.
For example, in a network, if one user is working
on file A and needs file B to continue, but another
user is working on file B and needs file A to
continue, each one waits for the other.  Both are
temporarily locked out.  The software must be able
to deal with this.


deallocate
To release a computer resource that is currently
assigned to a program or user, such as memory or a
peripheral device.


deblock
To separate records from a block.


debug
To correct a problem in hardware or software.
Debugging software is finding the errors in the
program logic.  Debugging hardware is finding the
errors in circuit design.


debugger
Software that helps a programmer debug a program by
stopping at certain breakpoints and displaying
various programming elements.  The programmer can
step through source code statements one at a time
while the corresponding machine instructions are
being executed.


DEC
(Digital Equipment Corp.)  Trade name for products
(DECmate, DECnet, etc.).  Many refer to the company
as DEC.


decay
Reduction of strength of a signal or charge.


decentralized processing
Computer systems in different locations.  Although
data may be transmitted between the computers
periodically, it implies limited daily
communications.  Contrast with distributed
processing and centralized processing.


decibel
(dB)  Unit that measures loudness or strength of a
signal.  dBs are a relative measurement derived
from an initial reference level and a final
observed level.  A whisper is about 10 dB, a noisy
factory 90 dB, loud thunder 110 dB.  120 dB is
painful.


decimal
Meaning 10.  Universal numbering system that uses
10 digits.  Computers use binary numbers because it
is easier to design electronic systems that can
maintain two states rather than 10.


decision box
Diamond-shaped symbol that is used to document a
decision point in a flowchart.  The decision is
written in the decision box, and the results of the
decision branch off from the points in the box.


decision instruction
In programming, an instruction that compares one
set of data with another and branches to a
different part of the program depending on the
results.


decision making
Making choices.  The proper balance of human and
machine decision making is an important part of a
system's design.

   It is easy to think of automating tasks
traditionally performed by people, but it is not
that easy to analyze how decisions are made by an
experienced, intuitive worker.  If an improper
analysis of human decision making is made, the
wrong decision making may be placed into the
machine, which can get buried in documentation that
is rarely reviewed.  This will become an important
issue as AI applications proliferate.

   From a programming point of view, decision
making is performed two ways: algorithmic, a
precise set of rules and conditions that never
change, or heuristic, a set of rules that may
change over time (self-modify) as conditions occur.
Heuristic techniques are employed in AI systems.


decision support system
See DSS and EIS.


decision table
List of decisions and their criteria.  Designed as
a matrix, it lists criteria (inputs) and the
results (outputs) of all possible combinations of
the criteria.  It can be placed into a program to
direct its processing.  By changing the decision
table, the program is changed accordingly.


decision tree
Graphical representation of all alternatives in a
decision making process.


deck
(1) The part of a magnetic tape unit that holds and
moves the tape reels.

(2) Set of punched cards.

(3) See DEC.


declaration
In programming, an instruction or statement that
defines data (fields, variables, arrays, etc.) and
resources, but does not create executable code.


DECmate
Family of computer systems from Digital specialized
for word processing.  Introduced in 1981, DECmates
use the PDP-8 architecture.


DECmcc
(DEC Managment Control Center)  Digital's network
management software for DECnet and TCP/IP.  DECmcc
Management Stations for VMS and ULTRIX support X
Window and provide color-coded alarms.


DECnet
Digital's communications network, which supports
Ethernet-style LANs and baseband and broadband WANs
over private and public lines.  It interconnects
PDPs, VAXs, PCs, Macs and workstations.  In DECnet
philosophy, a node must be an intelligent machine
and not simply a terminal as in other systems.  See
DNA.

   DECnet/DOS allows DOS machines to function as
end nodes in DECnet networks, and DECnet/OSI is the
implementation of DECnet Phase V that supports OSI
and provides compatibility with DECnet Phase IV and
TCP/IP.


decoder
Hardware device or software program that converts a
coded signal back into its original form.


decollator
Device that separates multiple-part paper forms
while removing the carbon paper.


decompiler
Program that converts machine language back into a
high-level source language.  The resulting code may
be very difficult to maintain as variables and
routines are named generically: A0001, A0002, etc.


decompress
To restore compressed data back to its original
size.


decrement
To subtract a number from another number.
Decrementing a counter means to subtract 1 or some
other number from its current value.


DECstation
(1) Series of RISC-based single-user workstations
from Digital, introduced in 1989, that run under
ULTRIX.

(2) PC series from Digital introduced in 1989.

(3) Small computer system from Digital, introduced
in 1978, used primarily for word processing
(DECstation 78).


DECsystem
(1) Series of RISC-based, 32-bit computers from
Digital that run under ULTRIX.  Introduced in 1989,
the 5400 model is a Q-bus system; the 5800 model
uses the XMI bus.

(2) Series of mainframes from Digital that were
introduced from 1974 through 1980 and were the
successor to the 36-bit PDP-10 computers.


DECtalk
Voice synthesizing system from Digital that accepts
serial ASCII text and converts it into audible
speech.  It is used in Touch-tone telephone
response systems as well as for voice-output for
visually handicapped users.


DECwindows
Digital's windowing architecture, based on X
Window, Version 11.  It is compatible with X Window
while adding a variety of enhancements.


dedicated channel
Computer channel or communications line that is
used for one purpose.


dedicated service
Service that is not shared by other users or
organizations.


default
Current setting or action taken by hardware or
software if the user has not specified otherwise.


default directory
Same as current directory.


default drive
Disk drive used if no other drive is specified.


default font
Typeface and type size used if none other is
specified.


defragment
To reorganize the disk by putting files into
contiguous order.  Because the operating system
stores new data in whatever free space is
available, data files become spread out across the
disk if they are updated often.  This causes extra
read/write head movement to read them back.
Periodically, the hard disk should be defragmented
to put files back into order.  See DOS Defrag.


degausser
Device that removes unwanted magnetism from a
monitor or the read/write head in a disk or tape
drive.


DEL key
(DELete key)  Keyboard key used to delete the
character under the screen cursor or some other
block of data.  It is often used in combination
with the shift, control and alt keys to delete
various text segments.


delay line
Communications or electronic circuit that has a
built-in delay.  Acoustic delay lines were used to
create the earliest computer memories.  For
example, the UNIVAC I used tubes of liquid mercury
that would slow down the digital pulses long enough
(a fraction of a second) to serve as storage.


delete
To remove an item of data from a file or to remove
a file from the disk.  See undelete.


delimiter
Character or combination of characters used to
separate one item or set of data from another.  For
example, in comma delimited records, a comma is
used to separate each field of data.


Dell
(Dell Computer Corp., Austin, TX)  PC manufacturer
founded in 1984 by Michael Dell.  Originally
selling PCs under the "PCs Limited" brand, Dell was
the first to legitimize mail-order PCs by providing
quality telephone support.  Dell made the Fortune
500 in 1991, and its fiscal 1993 revenues may
exceed one billion.


delta modulation
Technique that is used to sample voice waves and
convert them into digital code.  Delta modulation
typically samples the wave 32,000 times per second,
but generates only one bit per sample.  See PCM.


DEMA
(Assn. for Input Technology and Management)
Organization devoted to the advancement of managers
in data entry technologies.  Founded in 1976 as the
Data Entry Management Assn., it sponsors
educational courses and conferences.  Address: 101
Merritt 7, Norwalk, CT 06851, 203/846-3777.


demand paging
Copying a program page from disk into memory when
required by the program.


demand processing
Same as transaction processing.


Demo II
Demonstration, authoring and prototyping program
for PCs from Intersolv, Rockville, MD.  It is used
to create courseware and slide shows and simulate
interactive user interfaces for prototyping.
Originally "Dan Bricklin's Demo Program," written
by the author of VisiCalc.


demodulate
To filter out the data signal from the carrier.
See modulate.


demon
See daemon.


demoware
Demonstration software that shows some or all of
the features of a commercial product.  See
crippleware.


demultiplex
To reconvert a transmission that contains several
intermixed signals back into its original separate
signals.


density
See packing density and bit density.


departmental computing
Processing a department's data with its own
computer system.  See distributed processing.


dependent segment
In database management, data that depends on data
in a higher level for its full meaning.


dequeue
Pronounced "d-q."  To remove items from a queue in
order to process or transmit them.


DES
(Data Encryption Standard)  NIST-standard
encryption technique that scrambles data into an
unbreakable code for public transmission.  It uses
a binary number as an encryption key with 72
quadrillion possible combinations.  The key,
randomly chosen for each session, is used to create
the encryption pattern for transmission.  See RSA.


descenders
The parts of the lower case characters g, j, p, q
and y that fall below the line.  Sometimes these
characters are displayed and printed with shortened
descenders in order to fit into a smaller character
cell, making them difficult to read.


descending sort
Arranging data from high to low sequence (Z to A,
9 to 0).


descriptor
(1) Word or phrase that identifies a document in an
indexed information retrieval system.

(2) Category name used to identify data.


deserialize
To convert a serial stream of bits into parallel
streams of bits.


Designer
Popular, full-featured Windows drawing program from
Micrografx, Inc., Richardson, TX.  It was the first
PC program to provide almost all the design tools
found in Macintosh drawing programs.  It creates
its own DRW file format and supports PIC files
compatible with other Micrografx products.


desk accessory
In the Macintosh, a program that is always
available from the Apple menu no matter what
application is running.  With System 7, all
applications can be turned into desk accessories.


desk checking
Manually testing the logic of a program.


DeskJet
Family of popular desktop ink-jet printers for PCs
from HP.  Color models are also available.


DESKPRO
Compaq trade name for its PCs.


desktop
(1) On-screen representation of a desktop.  See
Macintosh user interface and Windows.

(2) Buzzword attached to applications traditionally
performed on more expensive machines that are now
on a personal computer (desktop publishing, desktop
mapping, etc.).


desktop accessory
Software that simulates an object normally found on
an office desktop, such as a calculator, notepad
and appointment calendar.  It is typically RAM
resident.  See TSR.


desktop application
See desktop accessory.


desktop computer
Same as personal computer or microcomputer.


desktop manager
The part of a GUI that displays the desktop and
icons, allows programs to be launched from the icon
and files to be visually dragged & dropped (copied,
deleted, etc.).  The desktop manager combined with
the window manager make up the GUI.  The desktop
manager is included with the Mac and Windows.  In
OSF/Motif and Open Look, products such as IXI's
X.desktop and Visix Software's Looking Glass add
this capability.


desktop mapping
Using a desktop computer to perform digital mapping
functions.


desktop media
Integration of desktop presentations, desktop
publishing and multimedia (coined by Apple).


desktop organizer
See desktop accessory.


desktop presentations
Creation of presentation materials on a personal
computer, which includes charts, graphs and other
graphics-oriented information.  It implies a wide
variety of special effects for both text and
graphics that will produce output for use as
handouts, overheads and slides as well as sequences
that can be viewed on screen.  Advanced systems
generate animation and control multimedia devices.


desktop publishing
Abbreviated "DTP."  Using a personal computer to
produce high-quality printed output or camera-ready
output for commercial printing.  It requires a
desktop publishing program, high-speed personal
computer, large monitor and a laser printer.

   DTP packages provide the ultimate in page layout
capabilities, including magazine style columns,
rules and borders, page, chapter and caption
numbering as well as precise typographic aligment.
A key feature is its ability to manage text and
graphics on screen WYSIWYG style.  The program can
flow text around graphic objects in a variety of
ways.

   Text and graphics may be created in the DTP
program, but few of them have full-featured text
and graphics capability.  Usually, the work is
created in word processing, CAD, drawing and paint
programs and then imported into the publishing
system.

   A laser printer may be used for final text
output, but it cannot print line art and shaded
drawings respectably unless its resolution is 1000
dpi or greater.  Imagesetters, at resolutions of
1270 and 2540 dpi, can accept file formats from
popular DTP packages and generate high-quality
camera ready material.

   Since DTP has dramatically brought down the cost
of high-end page makeup, it is often thought of as
"the" way to produce inhouse newsletters and
brochures.  However, creating quality material
takes experience.  Desktop publishing is no
substitute for a graphics designer who knows which
fonts to use and how to lay out the page
artistically.


DeskWriter
Family of popular desktop ink-jet printers for the
Macintosh from HP.  Color models are also
available.


DESQview
Popular multitasking, windows environment for DOS
from Quarterdeck Office Systems, Santa Monica, CA.
It runs multiple DOS text and graphics programs in
resizable windows.  Calendar, notepad, calculator
and communications utilities are also available.

   DESQview 386 for 386s and up includes the
widely-used QEMM-386 expanded memory manager and
utilizes the virtual machine capability of the 386.


DESQview/X
Version of DESQview that runs DOS, Windows and X
Window applications locally or remotely on other
DESQview/X PCs or X workstations.  QEMM-386 and
Adobe Type Manager are included.  There are several
ways DESQview/X can be implemented.

   It adds X Windows to a PC network, allowing each
DOS machine to run multiple applications on
different PCs in the network.  As an integration
product, it allows DOS and Windows apps to run in
an X Window network under UNIX or any other X-based
environment.  In a stand-alone DOS machine, it adds
a graphical and customizable interface to DESQview.

   Optional DESQview/X Motif and X11 toolkits allow
Motif and X applications to be recompiled to a DOS
machine.


destructive memory
Memory that loses its content when it is read,
requiring that the circuitry regenerate the bits
after the read operation.


detail file
Same as transaction file.


developer's toolkit
Set of software routines used in programming to
link an application program to a particular
operating environment (GUI, OS, DBMS, etc.).


development cycle
See system development cycle.


development system
(1) Programming language and related components.
It includes the compiler, text editor, debugger,
function library and any other supporting programs
that enable a programmer to write a program.

(2) Computer and related software for developing
applications.


development tool
Any hardware or software that assists in the
creation of electronic machines or software
programs.  See developer's toolkit.


device
(1) Electronic or electromechanical machine or
component from a transistor to a disk drive.
Device always refers to hardware.

(2) In semiconductor design, it is an active
component, such as a transistor or diode, in
contrast to a passive component, such as a resistor
or capacitor.


device adapter
Same as interface adapter.


device address
See address.


device control character
Communications code that activates a function on a
terminal.  See ASCII chart (17-20).


device dependent
Refers to programs that address specific hardware
features and work with only one type of peripheral
device.  Contrast with device independent.  See
machine dependent.


device driver
See driver.


device independent
Refers to programs that work with a variety of
peripheral devices.  The hardware-specific
instructions are in some other program (OS, DBMS,
etc.).  Contrast with device dependent.  See
machine independent.


device level
(1) In circuit design, refers to working with
individual transistors rather than complete
circuits.

(2) Refers to communicating directly with the
hardware at a machine language level.


device name
Name assigned to a hardware device that represents
its physical address.  For example, LPT1 is a DOS
device name for the parallel port.


DFT mode
(Distributed Function Terminal mode)  Mode that
allows a 3270 terminal to have five concurrent
sessions with the mainframe.  Contrast with CUT
mode.


DG
See Data General.


DGIS
(Direct Graphics Interface Standard)  Graphics
interface for PC video display boards from Graphic
Software Systems, Beaverton, OR.  It is primarily
used with TI's 340x0 graphics chip and custom
drivers are licensed to video board manufacturers.


Dhrystones
Benchmark program that tests a general mix of
instructions.  The results in Dhrystones per second
are the number of times the program can be executed
in one second.  See Whetstones.


DIA
(Document Interchange Architecture)  IBM SNA format
used to exchange documents from dissimilar machines
within an LU 6.2 session.  It acts as an envelope
to hold the document and does not set any standards
for the content of the document, such as layout
settings or graphics standards.


Diablo emulation
Printer that accepts the same commands as the
Diablo printer.


diacritical
Small mark added to a letter that changes its
pronunciation, such as the French cedilla (Ç).


diagnostic board
Expansion board with built-in diagnostic tests that
reports results via its own readout.  Boards for
PCs, such as Landmark's KickStart and UNICORE's
POSTcard, have their own POST system and can test a
malfunctioning computer that doesn't boot.


diagnostic tracks
Spare tracks on a disk used by the drive or
controller for testing purposes.


diagnostics
(1) Software routines that test hardware components
(memory, keyboard, disks, etc.).  In personal
computers, they are often stored in ROM and
activated on startup.

(2) Error messages in a programmer's source code
that refer to statements or syntax that the
compiler or assembler cannot understand.


dial-up line
Two-wire line as found in the dial-up network.
Contrast with leased line.


dial-up network
Switched telephone network regulated by government
and administered by common carriers.


dial-up services
See online services.


DIALOG
Online information service that contains the
world's largest collection of databases.  Address:
3460 Hillview Ave., Palo Alto CA 94304, 415/858-
2700.  See online services.


dialog box
Small, on-screen window displayed in response to
some request.  It provides the options currently
available to the user.


diazo film
Film used to make microfilm or microfiche copies.
It is exposed to the original film under
ultraviolet light and is developed into identical
copies.  Copy color is typically blue, blue-black
or purple.


DIB
(Device Independent Bit map)  See BMP.


dibit
Any one of four patterns from two consecutive bits:
00, 01, 10 and 11.  Using phase modulation, a dibit
can be modulated onto a carrier as a different
shift in the phase of the wave.


DIBOL
(DIgital coBOL)  Version of COBOL from Digital that
runs on the PDP and VAX series.


dice
See die.


dictionary method
See LZW.


die
Formal term for the square of silicon containing an
integrated circuit.  The popular term is chip.


dielectric
Insulator (glass, rubber, plastic, etc.).
Dielectric materials can be made to hold an
electrostatic charge, but current cannot flow
through them.


DIF
(1) (Data Interchange Format)  Standard file format
for spreadsheet and other data structured in row
and column form.  Originally developed for
VisiCalc, DIF is now under Lotus' jurisdiction.

(2) (Display Information Facility)  IBM System/38
program that lets users build custom programs for
online access to data.

(3) (Document Interchange Format)  File standard
developed by the U.S. Navy in 1982.

(4) (Dual In-line Flatpack)  Type of surface mount
DIP with pins extending horizontally outward.


Difference Engine
Early calculator designed by Charles Babbage
(1820s) and subsidized by the British government.
It used rods and wheels, which was tried before by
other designers.  Never completed, Babbage turned
his attention to the Analytical Engine.


Differential Analyzer
Analog computational device built to solve
differential equations by Vannevar Bush (MIT,
1930s).  Less than a dozen were built, but they
were effective in calculating ballistics tables in
World War II.  The machine took up an entire room
and was programmed by changing camshaft-like gears
with screwdriver and wrench.


differential backup
See backup types.


differential configuration
Use of wire pairs for each electrical signal for
high immunity to noise and crosstalk.  Contrast
with single-ended configuration.


diffusion
Semiconductor manufacturing process that infuses
tiny quantities of impurities into a base material,
such as silicon, to change its electrical
characteristics.


digit
Single character in a numbering system.  In
decimal, digits are 0 through 9.  In binary, digits
are 0 and 1.


digital
(1) Traditionally, the use of numbers and comes
from digit, or finger.  Today, digital is
synonymous with computer.

(2) Digital.  See Digital Equipment.


digital camera
Video camera that records its images in digital
form.  Unlike traditional analog cameras that
convert light intensities into infinitely variable
signals, digital cameras convert light intensities
into discrete numbers.

   It breaks down the picture image into a fixed
number of pixels (dots), tests each pixel for light
intensity and converts the intensity into a number.
In a color digital camera, three numbers are
created, representing the amount of red, green and
blue in each pixel.


digital channel
Communications path that handles only digital
signals.  All voice and video signals have to be
converted from analog to digital in order to be
carried over a digital channel.  Contrast with
analog channel.


digital circuit
Electronic circuit that accepts and processes
binary data (on/off) according to the rules of
Boolean logic.


                 Digital Plumbing!
A digital circuit can be conceptualized as a mass
of plumbing: the circuit paths are the pipes, the
transistors are the valves, and the electricity is
the water.  Imagine opening a valve, and the water
that passes through it and down a pipe will
eventually reach a second valve, causing it to turn
on, allowing water in another pipe to flow through
the second valve, which will reach another valve,
and so on.

   A resistor can be viewed as a large pipe that
narrows into a pipe with a smaller diameter, a
capacitor as a storage tank, and a diode as a one-
way valve, allowing water to flow in only one
direction.


digital computer
Computer that accepts and processes data that has
been converted into binary numbers.  All common
computers are digital.  Contrast with analog
computer.


Digital Darkroom
Macintosh graphics editing program from Silicon
Beach Software, Inc., for enhancing black & white
photographs.  Version 2.0 supports color overlays
for colorizing gray scale images.


digital data
Data in digital form.  All data in the computer is
in digital form.


Digital Equipment
(Digital Equipment Corp., Maynard, MA)  Major
computer manufacturer, commonly known as DEC or
Digital.  Founded in 1957 by Kenneth Olsen, who
headed the company until he retired in 1992,
Digital pioneered the minicomputer industry with
its PDP series.

   Its early success came from the scientific,
process control and academic communities; however,
after the VAX was announced in 1977, Digital gained
a strong foothold in commercial data processing.
The VAX evolved into a complete line from desktop
to mainframe, using the same VMS operating system
in all models and causing Digital to achieve
substantial growth in the 1980s.

     Over the years, Digital has been widely
recognized for its high-quality systems.  Its
strategy for the 1990s and beyond is its powerful,
RISC-based Alpha architecture introduced in 1992,
which will evolve into a complete family of
systems.


digital mapping
Digitizing geographic information for a geographic
information system (GIS).


digital monitor
Video monitor that accepts a digital signal from
the computer and converts it into analog signals to
illuminate the screen.  Common examples are MDA,
CGA and EGA monitors.  Contrast with analog
monitor.


digital PABX
See digital PBX.


Digital Paper
Non-erasable storage material from ICI Electronics
used for tape and disk archival storage.  It uses a
polyester film coated with a reflective layer on
top of which is adhered a dye polymer layer that is
sensitive to infrared light.  A laser burns pits
into the film as close as half a micron apart.
Capacities are about one Gbyte on a 5.25" disk and
600 GBytes on a 2,400 foot tape reel.


digital PBX
(digital Private Branch Exchange)  Modern PBX that
uses digital methods for switching in contrast to
older PBXs that use analog methods.


digital radio
Microwave transmission of digital data via line of
sight transmitters.


digital recording
See magnetic recording.


Digital Research
(Digital Research, Inc., Monterey, CA)  Software
company founded in 1976 by Gary Kildall that
spearheaded the microcomputer revolution with its
CP/M operating system.  DRI's products include the
GEM windows environment, FlexOS realtime operating
system and DR DOS, a DOS-compatible operating
system with advanced features.

   In 1991, it was acquired by Novell, Inc., Provo,
UT, makers of the widely-used NetWare operating
systems.


digital signal processing
Category of techniques that analyze signals from a
wide range of sources, such as voice, weather
satellites, earthquake monitors and nuclear tests.
It converts the signals into digital data and
analyzes it using various algorithms such as Fast
Fourier Transform.

   Once a signal has been reduced to numbers, its
components can be isolated and analyzed more
readily than in analog form.  It is used in such
fields as biomedicine, sonar, radar, seismology,
speech and data communictions.


digital signature
Coded message that can be verified by the receiver
as being sent by an authentic sender.  See RSA and
DSS (2).


digitize
To convert an image or signal into digital code by
scanning, tracing on a graphics tablet or using an
analog to digital conversion device.  3-D objects
can be digitized by a device with a mechanical arm
that is moved onto all the corners.


digitizer tablet
Graphics drawing tablet used for sketching new
images or tracing old ones and for selecting from
menus.  The user makes contact with the tablet with
a pen-like or puck-like device called a cursor
(mistakenly called a mouse), which is connected to
the tablet by a wire.  For sketching, the user
draws with the tablet cursor and the screen cursor
"draws" a corresponding image.  When tracing an
image on the tablet, a series of x-y coordinates
(vector graphics) are created, either as a
continuous stream of coordinates, or as end points.

   Menu selection is accomplished by a tablet
overlay or by a screen display.  The tablet cursor
selects an item by making contact with it on the
overlay, or by controlling the screen cursor.  See
mouse.


dimension
One axis in an array.  In programming, a dimension
statement defines the array and sets up the number
of elements within the dimensions.


dimensioning
In CAD programs, the management and display of the
measurements of an object.  There are various
standards that determine such things as tolerances,
sizes of arrowheads and orientation on the paper.


DIN connector
(Deutsches Institut für Normung - German Standards
Institute)  Plug and socket used to connect a
variety of devices; for example, the PC keyboard
uses a five-pin DIN.  DIN plugs look like an open
metal can about a half inch in diameter with pins
inside in a circular pattern.


dingbats
Group of typesetting and desktop publishing symbols
from International Typeface Corp. that include
arrows, pointing hands, stars and circled numbers.
They are formally called ITC Zapf Dingbats.


diode
Electronic component that acts primarily as a one-
way valve.  As a discrete component or built into a
chip, it is used in a variety of functions.  It is
a key element in changing AC into DC.  They are
used as temperature and light sensors and light
emitters (LEDs).  In communications, they filter
out analog and digital signals from carriers and
modulate signals onto carriers.  In digital logic,
they're used as one-way valves and as switches
similar to transistors.


DIP
(Dual In-line Package)  Common rectangular chip
housing with leads (pins) on both long sides.  Tiny
wires bond the chip to metal leads that wind their
way down into spider-like feet that are inserted
into a socket or are soldered onto the board.


DIP switch
(Dual In-line Package switch)  Set of tiny toggle
switches built into a DIP, which is mounted
directly on a circuit board.  The tip of a pen or
pencil is required to flip the switch on or off.

   Remember!  Open is "off."  Closed is "on."


Dir
(DIRectory)  CP/M, DOS and OS/2 command that lists
the file names on the disk.  See DOS Dir.


direct access
Ability to go directly to a specific storage
location without having to go through what's in
front of it.  Memories (RAMs, ROMs, PROMs, etc.)
and disks are the major direct access devices.


direct access method
Technique for finding data on a disk by deriving
its storage address from an identifying key in the
record, such as account number.  Using a formula,
the account number is converted into a sector
address.  This is faster than comparing entries in
an index, but it only works well when keys are
numerically close: 100, 101, 102.


direct-connect modem
Modem that connects to a telephone line without the
use of an acoustic coupler.


directory
Simulated file drawer on disk.  Programs and data
for each application are typically kept in a
separate directory (spreadsheets, word processing,
etc.).  Directories create the illusion of
compartments, but are actually indexes to the files
which may be scattered all over the disk.


directory management
Maintenance and control of directories on a hard
disk.  Usually refers to menuing software that is
easier to use than entering commands.


directory tree
Graphic representation of a hierarchical directory
as in the following example.  See DOS Tree.

     ├DATABASE┐
     │        ├BUDGETS
     │        ├CLIENTS
     │
     ├STORIES┐
     │       ├SHORT
     │       ├NOVELS



dirty power
Non-uniform AC power (voltage fluctuations, noise
and spikes), which comes from the electric utility
or from electronic equipment in the office.


disable
To turn off a function.  Disabled means turned off,
not broken.  Contrast with enable.


disc
Alternate spelling for disk.  Compact discs and
videodiscs are spelled with the "c."  Most computer
disks are spelled with a "k."


discrete
Component or device that is separate and distinct
and treated as a singular unit.


discrete component
Elementary electronic device constructed as a
single unit.  Before integrated circuits (chips),
all transistors, resistors and diodes were
discrete.  They are widely used in high-power
applications and are still used on circuit boards
intermingled with the chips.


discrete cosine transform
Algorithm, similar to Fast Fourier Transform, that
converts data (pixels, waveforms, etc.) into sets
of frequencies.  The first frequencies in the set
are the most meaningful; the latter, the least.
For compression, latter frequencies are stripped
away based on allowable resolution loss.


discretionary hyphen
User-designated place in a word for hyphenation.
If the word goes over the margin, it will split in
that location.


dish
Saucer-shaped antenna that receives, or transmits
and receives, signals from a satellite.


disk
Direct access storage device.  See floppy disk,
hard disk, magnetic disk, optical disk and
videodisc.


disk array
Two or more disk drives combined in a single unit
for increased capacity, speed and/or fault tolerant
operation.  See RAID.


disk based
(1) Computer system that uses disks as its storage
medium.

(2) Application that retrieves data from the disk
as required.  Contrast with memory based.


disk cache
See cache.


disk cartridge
Removable disk module that contains a single hard
disk platter or a floppy disk.


disk controller
Circuit that controls transmission to and from the
disk drive.  In a personal computer, it is an
expansion board that plugs into an expansion slot
in the bus.  See hard disk.


disk crash
See head crash.


disk drive
Peripheral storage device that holds, spins, reads
and writes magnetic or optical disks.  It may be a
receptacle for disk cartridges, disk packs or
floppy disks, or it may contain non-removable disk
platters like most personal computer hard disks.


disk dump
Printout of disk contents without report
formatting.


disk duplicator
Device that formats and makes identical copies of
floppy disks for software distribution.  Simple
units contain two floppy disks and require manual
loading, elaborate units have automatic loading and
may also attach the labels.


disk emulator
Solid state replication of a disk drive.


disk file
Set of instructions or data that is recorded,
cataloged and treated as a single unit on a disk.
Source language programs, machine language
programs, spreadsheets, data files, text documents,
graphics files and batch files are examples.


disk format
Storage layout of a disk as determined by its
physical medium and as initialized by a format
program.  For example, a 5.25" 360KB floppy vs a
3.5" 1.44MB floppy or a DOS disk vs a Mac disk.
See low-level format, high-level format, DOS format
and file format.


disk management
Maintenance and control of a hard disk.  Refers to
a variety of utilities that provide format, copy,
diagnostic, directory management and defragmenting
functions.


disk memory
Same as disk storage.  In this book, disks and
tapes are called storage devices, not memory
devices.


disk mirroring
Recording of redundant data for fault tolerant
operation.  Data is written on two partitions of
the same disk, on two separate disks within the
same system or on two separate computer systems.


disk operating system
See DOS.


disk optimizer
Utility program that defragments a hard disk.  See
defragment.


disk pack
Removable hard disk module used in minis and
mainframes that contains two or more platters
housed in a dust-free container.  For mounting, the
bottom of the container is removed.  After
insertion, the top is removed.


disk partition
Subdivision of a hard disk.  The maximum size of a
disk partition depends on the operating system
used.  See DOS Fdisk.


disk striping
Spreading data over multiple disk drives to improve
performance.  Data is interleaved by bytes or by
sectors across the drives.  For example, with four
drives and a controller designed to overlap reads
and writes, four sectors could be read in the same
time it normally takes to read one.  Disk striping
does not inherently provide fault tolerance or
error checking.  It is used in conjunction with
various other methods.  See RAID.


Diskcopy
DOS and OS/2 utility used to copy entire floppy
disks track by track.  See DOS Diskcopy.


diskette
Same as floppy disk.


diskless workstation
Workstation without a disk.  Programs and data are
retrieved from the network server.


DISOSS
(DIStributed Office Support System)  IBM mainframe
centralized document distribution and filing
application that runs under MVS.  Its counterpart
under VM is PROFS.  It allows for e-mail and the
exchange of documents between a variety of IBM
office devices, including word processors and PCs.


dispatcher
Same as scheduler.


dispersed intelligence
Same as distributed intelligence.


displacement
Same as offset.  See base/displacement.


display
(1) To show text and graphics on a video or flat
panel screen.

(2) Screen or monitor.


display adapter
Same as video display board.


display attribute
See attribute.


display board
Same as video display board.


display card
Same as video display board.


display cycle
In computer graphics, the series of operations
required to display an image.


display device
See display screen and video display board.


display element
(1) In graphics, a basic graphic arts component,
such as background, foreground, text or graphics
image.

(2) In computer graphics, any component of an
image.


display entity
In computer graphics, a collection of display
elements that can be manipulated as a unit.


display font
Same as screen font.


display frame
In computer graphics, a single frame in a series of
animation frames.


display list
In computer graphics, a collection of vectors that
make up an image stored in vector graphics format.


display list processor
In computer graphics, an engine that generates
graphic geometry (draws lines, circles, etc.)
directly from the display list and independently of
the CPU.


Display PostScript
Screen counterpart of the PostScript printer
language that translates elementary commands in an
application to graphics and text elements on
screen.  It is designed for inclusion in an
operating system to provide a standard, device-
independent display language.


display screen
Surface area upon which text and graphics are
temporarily made to appear for human viewing.  It
is typically a CRT or flat panel technology.


display terminal
See video terminal.


DisplayWrite
Full-featured IBM word processing program for PCs
that stems from the typewriter-oriented
DisplayWriter word processing system first
introduced in 1980.  See XyWrite III Plus.


dissassembler
Software that converts machine language back into
assembly language.  The resulting code is difficult
to maintain as variables and routines are named
generically (A001, A002, etc.).


distributed computing
Same as distributed processing.  See parallel
computing.


distributed data processing
See distributed processing.


distributed database
Database physically stored in two or more computer
systems.  Although geographically dispersed, a
distributed database system manages and controls
the entire database as a single collection of data.
If redundant data is stored in separate databases
due to performance requirements, updates to one set
of data will automatically update the additional
sets in a timely manner.


distributed file system
Software that keeps track of files stored across
multiple networks.  It converts file names into
physical locations.


distributed function
Distribution of processing functions throughout the
organization.


distributed intelligence
Placing processing capability in terminals and
other peripheral devices.  Intelligent terminals
handle screen layouts, data entry validation and
other pre-processing steps.  Intelligence placed
into disk drives and other peripherals relieves the
central computer from routine tasks.


distributed logic
See distributed intelligence.


distributed processing
System of computers connected together by a
communications network.  The term is loosely used
to refer to any computers with communications
between them.  However, in true distributed
processing, each computer system is chosen to
handle its local workload, and the network has been
designed to support the system as a whole.
Contrast with centralized processing and
decentralized processing.


dithering
In computer graphics, the creation of additional
colors and shades from an existing palette.  In
monochrome displays, shades of grays are created by
varying the density and patterns of the dots.  In
color displays, colors and patterns are created by
mixing and varying the dots of existing colors.

   Dithering is used to create a wide variety of
patterns for use as backgrounds, fills and shading,
as well as for creating halftones for printing.  It
is also used in anti-aliasing.


divestiture
Breakup of AT&T.  By federal court order, AT&T
divested itself on 1/1/84 of its 23 operating
companies.  Bell Labs was renamed AT&T Bell Labs,
and its Western Electric manufacturing division
became AT&T Technologies.  See RBOC.


divide overflow
Program error in which a number is accidentally
divided by zero or by a number that creates a
result too large for the computer to handle.


DL/1
(Data Language 1)  Database language in IMS.


DLC
(1) (Data Link Control)  See data link and OSI.

(2) (Data Link Control)  Protocol used in IBM's
Token Ring networks.

(3) (Digital Loop Carrier)  See loop carrier.


DLL
See dynamic link library.


DMA
(Direct Memory Access)  Specialized circuitry or a
dedicated microprocessor that transfers data from
memory to memory without using the CPU.  Although
DMA may periodically steal cycles from the CPU,
data is transferred much faster than using the CPU
for every byte of transfer.


DME
(Distributed Managment Environment)  See OSF.


DMPL
(Digital Microprocessor Plotter Language)  Vector
graphics file format from Houston Instruments that
was developed for plotters.  Most plotters support
the DMPL or HPGL standards.


DNA
(Digital Network Architecture)  Introduced in 1978,
DNA defines Digital's protocols, formats and
control of message exchange over a network.  DECnet
is the implementation of this architecture.


DNS
(Domain Naming System)  E-mail addressing system
used in networks such as Internet and Bitnet.


do loop
High-level programming language structure that
repeats instructions based on the results of a
comparison.  In a DO WHILE loop, the instructions
within the loop are performed if the comparison is
true.  In a DO UNTIL loop, the instructions are
bypassed if the comparison is true.  The following
DO WHILE loop prints 1 through 10 and stops.

   COUNTER = 0
   DO WHILE COUNTER < 10
     COUNTER = COUNTER + 1
     ? COUNTER
   ENDDO



do nothing instruction
Same as no-op.


docking station
Base station for a laptop that includes a power
supply and expansion slots as well as monitor and
keyboard connectors.


docs
Short for documents or documentation.


document
(1) Any paper form that has been filled in.

(2) Word processing text file.

(3) In the Macintosh, any text, data or graphics
file created in the computer.


document handling
Procedure for transporting and handling paper
documents for data entry and scanning.


document imaging
Scanning paper documents into electronic pictures
for online retrieval and processing.  Document
imaging systems are used to replace paper-intensive
operations in large organizations.  They are often
simpler to develop and implement than data
processing systems, because users have been
familiar with the paper documents that appear on
screen.  In addition, documents can be shared by
all users on a network and routing can be
controlled by the computer (workflow automation).

   Document images are created in raster graphics
format, and although a small amount of text (key
words) may be associated with the document in order
to index it, the meaning of the document content is
known only to the human viewer, not the computer.
Like microfilm, signatures and other original
markings remain intact.


document mark
In micrographics, a small optical blip on each
frame on a roll of microfilm that is used to
automatically count the frames.


document processing
Processing text documents, which includes indexing
methods for text retrieval based on content.  See
document imaging.


documentation
Narrative and graphical description of a system.
Documentation for an information system includes:


               Operating Procedures
 1. Instructions for turning the system on and
    getting the programs initiated (loaded).

 2. Instructions for obtaining source documents for
    data entry.

 3. Instructions for entering data at the terminal,
    which includes a picture of each screen layout
    the user will encounter.

 4. A description of error messages that can occur
    and the alternative methods for handling them.

 5. A description of the defaults taken in the
    programs and the instructions for changing
    them.

 6. Instructions for distributing the computer's
    output, which includes sample pages for each
    type of report.


               System Documentation
 1. Data dictionary - Description of the files and
    databases.

 2. System flow chart - Description of the data as
    it flows from source document to report.

 3. Application program documentation - Description
    of the inputs, processing and outputs for each
    data entry, query, update and report program in
    the system.


              Technical Documentation
 1. File structures and access methods

 2. Program flow charts

 3. Program source code listings

 4. Machine procedures (JCL)


docuterm
Word or phrase in a text document that is used to
identify the contents of the document.


domain
(1) In database management, all possible values
contained in a particular field for every record in
the file.

(2) In communications, all resources under control
of a single computer system.

(3) In magnetic storage devices, a group of
molecules that makes up one bit.

(4) In a hierarchy, a named group that has control
over the groups under it, which may be domains
themselves.


dominant carrier
Telecommunications services provider that has
control over a large segment of a particular
market.


dongle
Same as hardware key.


door
(1) In a BBS system, a programming interface that
lets an online user run an application program in
the BBS.

(2) See drive door.


doorway mode
In a communications program, a mode that passes
function, cursor, ctrl and alt keystrokes to the
BBS computer in order to use the remote application
as if it were on the local machine.


dopant
Element diffused into pure silicon in order to
alter its electrical characteristics.


doping
Altering the electrical conductivity of a
semiconductor material, such as silicon, by
chemically combining it with foreign elements.  It
results in an excess of electrons (n-type) or a
lack of electrons (p-type) in the silicon.



DOS
(1) (Disk Operating System)  Pronounced "dahss."
Generic term for operating system.

(2) (Disk Operating System)  Single-user operating
system for the PC, PS/1 and PS/2 series from IBM.
DOS is also called PC-DOS to distinguish it from
MS-DOS, the version for non-IBM PCs.  DOS and MS-
DOS are developed by Microsoft, are almost
identical, and both are referred to as DOS.  IBM
has participated in DOS development in varying
degrees.  See "Operating Environment" in the PC
definition.

   In this Glossary, DOS refers to both PC-DOS and
MS-DOS.  See DOS abc's.


DOS /
Slashes are used to identify switches, or
parameters, in a DOS command.  They precede letters
or numbers and their meaning is pertinent only to
the command they are used with.  There are many
examples of this in the Glossary.  See DOS
backslash (\).


DOS %
Percent signs are used in DOS batch files to define
user input.  The following batch file example would
copy a file and then delete it:

   copy %1 %2
   del %1

   If the above file were named MOVEIT.BAT, the
following example moves file ABC into the \HOLD
directory and then deletes it from the current
directory:

   moveit abc \hold




DOS .
The single dot in a DOS command refers to all files
in the current directory.  For example, del . is
the same as del *.*, which deletes all files.



DOS ..
The double dots refer to the directory one level
above the current directory.  The command cd ..
switches you to the higher directory.  Double
clicking on a [..] in a file menu does the same
thing.



DOS 5
Major DOS upgrade in 1991 that includes an enhanced
DOS shell with task swapping, undelete commands, a
full-screen text editor and online help.  It
includes memory managers that support extended and
expanded memory and allow part of DOS to be loaded
into the high memory area (HMA).  It supports 2GB
hard disks and 2.88MB floppies.

   DOS 5 includes Microsoft's QBasic language,
which supersedes GW-BASIC in the MS-DOS version and
accompanies BASICA in the IBM version.  Major DOS 5
features in this Glossary are:

           DOS Dos
           DOS Doskey
           DOS Editor
           DOS EMM386.EXE
           DOS Loadhigh
           DOS Mirror
           DOS online help
           DOS Setver
           DOS Task Swapper
           DOS Undelete
           DOS Unformat


   An excellent, comprehensive book on DOS 5 that
includes handy utilities on disk, is "DOS 5" by
Alfred Glossbrenner, ISBN 0-679-73925-4.

   For a thorough understanding of DOS memory
management, read "DOS Beyond 640K" by James S.
Forney, ISBN 0-8306-3744-3.



DOS 6
Upgrade introduced in 1993 that includes built-in
realtime compression and new utilities for memory
management, backup, file transfer, disk
optimization, antivirus and for managing multiple
startup configurations.  Following is a list of
major DOS 6 features in this Glossary.  To review
them sequentially, go into Search Definitions and
search on "DOS 6."

           DOS Defrag
           DOS Deltree
           DOS DoubleSpace
           DOS Interlink
           DOS Memmaker
           DOS Move
           DOS MSAV
           DOS MSbackup
           DOS MSD
           DOS startup options



DOS 7
The next version of DOS (code named Chicago) is
expected to be a 32-bit operating system that will
only run in 386s and up.  It should be a
significant change to DOS.



DOS ::
Double colons are used to make a comment in a DOS
batch file.  For example, the following line will
not be processed by DOS or displayed on screen:

  :: sbl.exe is the screen blanker program



DOS abc's
This is an overview of DOS concepts.  For details,
look up each DOS definition.

   To keep your place in the abc's, set a bookmark
by pressing Ctrl-B for the DOS version or clicking
SET BOOKMARK in the Windows version.  Press Ctrl-F
or click FIND BOOKMARK to come back.

   If you'd like hard copy of this tutorial, look
up and print "DOS abc's" and "DOS abc's continued."
Look up the definition, then press Ctrl-P if you're
using the DOS version or select Print from the File
menu if you're using the Windows version.


  ┌────────────────────────────────────────────┐
  │             WHAT THIS COVERS...            │
  │                                            │
  │  1. Examples of DOS commands in this       │
  │     Glossary cover ALL the things users    │
  │     do MOST of the time.  Refer to your    │
  │     DOS manual for more options.           │
  │  2. This is geared to users who have       │
  │     computers with a hard drive and who    │
  │     are using DOS Version 3.0 and higher.  │
  │                                            │
  └────────────────────────────────────────────┘



                   WHAT IS DOS?
DOS (pronounced "dawss") stands for disk operating
system.  It is a master control program that is
automatically run when you start your PC.  DOS
stays in the computer all the time letting you

    run a program   and   manage files.


To use DOS, you must know

    where your program is stored

             and

                how to talk to DOS.



           WHERE YOUR PROGRAM IS STORED
Everything DOS does... absolutely everything...
is based on the "default drive and current
directory."  The default drive is the drive DOS
uses unless you tell it otherwise.  When you start
the computer, the default drive is normally C.

   Floppy drives are named A: and B:.  The hard
drive is named C:.  DOS Versions 2.x and 3.x can
manage disks up to 32MB (megabytes) in size, so in
these versions larger hard disks are broken up into
several "logical" drives (C:, D:, E:, etc.).

   DOS 4.01 manages disks up to 512MB.  Starting
with DOS 5, DOS will manage disks up to 2GB.  Even
though these versions can handle large hard disks,
sometimes users still break them up into several
smaller ones to help organize their data.


                       Hard disks
  Floppy   ┌───DOS versions──────────────────┐
  Disks     2.x, 3.x      4.01       5 & 6
 ┌──────┐ ┌──────────┐  ┌──────┐  ┌──────────┐
 │  A:  │ │ C: (32M) │  │ C:   │  │ C:       │
 └──────┘ ├──────────┤  │      │  │          │
          │ D: (32M) │  │(512M)│  │   (2G)   │
 ┌──────┐ ├──────────┤  │      │  │          │
 │  B:  │ │ E: (32M) │  │      │  │          │
 └──────┘ └──────────┘  └──────┘  └──────────┘


                    Directories
Disks are further divided into simulated file
drawers, called "directories," the size of which is
limited only by the unused space left on the disk.

          ┌───────┐ ┌───────┐ ┌───────┐
          │ Data  │ │ Words │ │Numbers│
          │  ╒═╕  │ │  ╒═╕  │ │  ╒═╕  │
          └───────┘ └───────┘ └───────┘

   Your software package's install program usually
creates the directory for you and copies the
appropriate files into it.  But there are times
when you'll want to create your own directories and
move files among them.  Suppose you'd like to
transfer office work to your home computer.  DOS
lets you copy files into the appropriate
directories on each machine.


                  Root Directory
The current directory is the file drawer you're in
on each disk.  When you start the computer, the
current directory is the "root" directory.  All
other directories stem from the root.

   You can store anything in the root directory,
but typically the hard disk's root directory is
used for utility programs and batch files, not
applications.  Applications are stored in their own
directories, one for database, one for word
processing, etc.:

                 ┌───────┐
                 │ Root  │
                 │  ╒═╕  │
                 └───┬───┘
           ┌─────────┼─────────┐
       ┌───┴───┐ ┌───┴───┐ ┌───┴───┐
       │ Data  │ │ Words │ │Numbers│
       │  ╒═╕  │ │  ╒═╕  │ │  ╒═╕  │
       └───────┘ └───────┘ └───────┘


   When you start DOS, the default drive is C and
the current directory is the root.  When you first
switch to another drive, the current directory is
the root directory of that disk.

   Every disk has a root directory as is noted in
the following illustration (each rectangle
represents a directory or subdirectory).


  Floppy         Hard disk           Hard disk
  Disks      DOS 2.x and 3.x      DOS 4.01 and up
    A:               C:                  C:
 ┌──────┐   ┌─────┬─────┬────┐  ┌─────┬──────┬───┐
 │ root │   │root │     │    │  │root │      │   │
 │      │   ├─────┼───┬─┴──┬─┤  ├─────┼─────┬┴───┤
 └──────┘   └─────┴───┴────┴─┘  ├───┬─┼───┬─┤    │
    B:               D:         │   │ │   │ │    │
 ┌──────┐   ┌────┬─────┬───┬─┐  ├───┼─┴───┼─┴────┤
 │ root │   │root│     │   │ │  │   │     │      │
 │      │   ├────┼─────┼───┴─┤  ├───┴─────┤      │
 └──────┘   └────┴─────┴─────┘  │         │      │
                     E:         └─────────┴──────┘
            ┌─────┬──────┬───┐
            │root │      │   │
            │     │      │   │
            └─────┴──────┴───┘


                       Note!
On a floppy, everything is typically stored in the
root directory, because floppies are usually
dedicated to one purpose.



                     Remember!
DOS's reference point is the default drive and
current directory.  You can think of them as the

        "current" drive and directory, or

        "working" drive and directory, or

        "default" drive and directory.



                HOW TO TALK TO DOS
DOS is command-driven.  You type in a command, and
DOS carries it out.


       Entering a Command at the DOS Prompt
DOS commands are entered when DOS displays its
"prompt" on screen.  The prompt also informs you
which drive and directory you're currently in.  The
following prompt means C drive and root directory:

                   C:\>


   The C: means drive C.  The backslash \ means
root directory.  The > is an end symbol.

   If you switched to the DATA directory, your
prompt would change to:

                C:\DATA>.

              C:    C drive
              \     root directory
              DATA  data directory
              >     end of prompt


                  Are We in Sync?
Does your on-screen prompt look like the examples
above?  If it doesn't, and all you see is C> or D>
no matter which directory you're in, you're missing
an important command in your AUTOEXEC.BAT file.

   For now, type the following command at the DOS
prompt:
                 prompt $p$g


   Later on, you will want to set this prompt
permanently.  See DOS prompt and DOS AUTOEXEC.BAT.


             Can't Get the DOS Prompt?
All DOS commands in this tutorial are run from the
DOS prompt.  If your computer starts up with a menu
of programs to run, you'll have to exit this
menuing system (also called a shell) first.

   Usually there's a "To DOS," "DOS prompt" or
"Command Prompt" option in the menu.  Select it to
get your DOS prompt.



        Pressing Enter Executes the Command
After you type in your command, pressing the Enter
key causes DOS to begin the action.  The following
command renames a file from RED to BLUE.  The
action is taken when you press the Enter key:

             C:\>rename red blue(ENTER)


   You must have a space between the command verb
Rename and the next word.

   In further examples, you won't see the (ENTER)
notation.  It is however always implied.  Nothing
happens until you press Enter!



               Switching Directories
Assume you have the following directories on your
hard disk:

                    C:\>
                 ┌───────┐
                 │ Root  │
                 │  ╒═╕  │
                 └───┬───┘
                     │
          ┌──────────┼───────────┐
      C:\DATA>   C:\WORDS>  C:\NUMBERS>
      ┌───────┐  ┌───────┐  ┌───────┐
      │ Data  │  │ Words │  │Numbers│
      │  ╒═╕  │  │  ╒═╕  │  │  ╒═╕  │
      └───────┘  └───────┘  └───────┘


   If you're in the C:\DATA> directory now, and you
want to go to the C:\NUMBERS> directory, you would
type:

                             Explanation
    C:\DATA>cd \numbers    change to NUMBERS
    C:\NUMBERS>            prompt has changed


               cd \numbers means

CHANGE DIRECTORY TO   ROOT  then  NUMBERS DIRECTORY
           cd           \             numbers


   Switch back to the root directory by typing:

                               Explanation
      C:\NUMBERS>cd \     change to root directory
      C:\>                prompt has changed


         CHANGE DIRECTORY TO   ROOT
                 cd              \



                  Subdirectories
Subdirectories are directories subordinate to your
main directories.  The following example organizes
files separately for two writers:

                      ┌───────┐
    Directory         │ Words │
                      │       │
                      └───┬───┘
                     ┌────┴────┐
                 ┌───┴───┐ ┌───┴───┐
 Subdirectories  │Joseph │ │Helene │
                 │  ╒═╕  │ │  ╒═╕  │
                 └───────┘ └───────┘


   For more on directories and subdirectories, look
up DOS directories.



                 Switching Drives
To switch from one drive to another, type the drive
letter and colon as in the following examples:

                 Explanation
   C:\>d:     change from C to D
   D:\>       prompt has changed to show new drive

   Switch to A:

   D:\>a:     change from D to A
   A:\>       prompt has changed



                     Remember!
Don't forget the colon.  The letter A by itself
would be a file name, not a drive ID.  The a:
identifies the A drive.



DOS abc's (continued)
This is a continuation of DOS abc's above.

To review...

  DOS is a master control program that lets you
  run a program and manage files.



RUNNING A PROGRAM
To run a program, go to the directory the program
is in and type in the program's name.  For example,
to go to the LOTUS directory and run the 123.EXE
program, you would type:

    C:\>cd \lotus    go to directory
    C:\LOTUS>123     run 123.EXE program


   The .EXE is a file extension for a program that
is ready to run (EXEcute).  You'll learn about file
extensions in DOS file names.

   You can usually (but not always) run a program
in a different directory or even a different disk
by naming the path to it.

   Suppose you're in the ANYWHERE directory on
drive C, you could run PARADOX3.EXE in directory
DATA on E by typing:

    C:\ANYWHERE>e:\data\paradox3


   Note: You don't enter the .EXE extension when
naming a program to run.

   Also note:  The "ANYWHERE" above is a prompt
used in examples to indicate that the command will
work no matter which directory you're currently in.


                   Command Sytax
Most programs are run by typing in their name.  For
example, the DOS version of the Glossary is loaded
and run by typing gloss at the DOS prompt.

   Sometimes, additional information can be given
to the program when it is run.  For example, in the
Windows version of this Glossary, adding the word
mono to the program name changes the display for a
laptop; for example:

               wingloss mono


   When managing your files with DOS, the commands
often require additional input; for example, the
Format command must be typed with the name of the
disk you want to format:

                 format a:




                  MANAGING FILES
To learn how to create directories and
subdirectories, copy files back and forth and use
DOS to manage your computer, look up the following
topics in the Glossary.  At this point, the DOS
topics are in alphabetical order, not in lesson
order.

   .............................................
   Why don't you print out the following summary
and keep it handy.  To do this, move the dotted
line to the top of the text window with the Up or
Down Arrow keys.  Be sure your printer is turned
on, and then press Ctrl-P if you're using the DOS
version of the Glossary, or select Print from the
File Menu if you are in the Windows version.


      WHAT YOU NEED TO LEARN


      DOS file names
      Learn about names and extensions.

      DOS wild cards
      Learn how to select groups of files.

      DOS directories
      More examples on switching directories.

      DOS Dozen
      12 commands that do everything.

      DOS batch file
      How to automate procedures.

      DOS AUTOEXEC.BAT
      How to automatically set up your
      computer each time you turn it on.

      DOS CONFIG.SYS
      How to configure the computer.



      ┌──────────────────────────────────┐
      │        End of the ABC's.         │
      │                                  │
      │ The rest of the DOS commands are │
      │ in A-Z order under DOS xxxx.     │
      └──────────────────────────────────┘



DOS Abort, Retry
See DOS error messages.



DOS ANSI.SYS
Driver used for screen control (cursor movement,
screen clearing) and as a keyboard macro processor
to assign commands to a function key or reassign
awkwardly placed keys.  Some applications require
ANSI.SYS.  See DOS CONFIG.SYS.



DOS antivirus
See DOS MSAV.



DOS Append
External command as of DOS 3.3 that lets programs
open data files as if they were in the current
directory.  It is used only with older programs
that cannot access different directories.

   append          display appended paths
   append e:\abc   append E:\ABC
   append;         cancel appends


              Want to Combine Files?
If you want to append one file to another, look up
DOS combining files.



DOS Assign
External command used to reassign drives when
programs work only with specific drives.  In DOS 6,
this command is no longer installed, although it
still resides on the DOS 6 Supplemental Disk.

   The following example allows an install program
that requires the floppy to be in drive A: to run
from drive B:.

              assign a=b

   To cancel assignments, type:

              assign


   If your program is ancient and works only with
drive A:, you can fake it into accessing the hard
disk with:

              assign a=c


                    Important!
Cancel assignments before using Backup, Diskcopy,
Format, Join, Label, Print, Restore or Subst.



DOS Attrib
External command that displays and changes file
attributes, which are settings in every DOS file.

             FILE ATTRIBUTES

             A - Archive
             H - Hidden file
             R - Read only
             S - System file


  To display the current attributes in all files in
the current directory, type:

      attrib *.*     files only
      attrib *.* /s  files & subdirectories
                      (DOS 3.3 and up)

READ ONLY STATUS
When a file is read-only, it can't be changed or
deleted.  To set and reset VITAL.TXT, type:

   attrib vital.txt +r   set to read-only
   attrib vital.txt -r   reset to read/write


ARCHIVE ATTRIBUTE
As of DOS 3.3, all files are set to archive status,
which assists in making backups.  When files are
copied (Xcopy and Backup), the archive status is
turned off and not turned on again until the file
has been modified (changed by some program).  The
following example removes and restores the archive
status in XYZ.TXT.

   attrib xyz.txt -a   turn off
   attrib xyz.txt +a   turn back on


   To back up only modified files (archive status
on), use the /m switch with the Xcopy and Backup
commands.  After copying, the archive status is
turned off (archive bit set to zero).  For example,
to Xcopy only modified files (archive bit on) to
the B drive, type:

          xcopy *.* b: /m


SYSTEM AND HIDDEN ATTRIBUTE (as of DOS 5)
These attributes are assigned to important DOS
files and other files that your applications may
generate.  As a rule, you should not tamper with
them unless you know what you are doing.  Prior to
DOS 5, you needed a third-party utility to do this.
As of DOS 5, you can reset these attributes in
most, but not all files, in which case you may
still need a third-party program.

   attrib xyz +s   make XYZ a system file
   attrib xyz -s   clear system file status

   attrib xyz +h   make XYZ a hidden file
   attrib xyz -h   clear hidden status



DOS AUTOEXEC.BAT
Special DOS batch file that is automatically
executed whenever the computer is started or
restarted.  It must be stored in the root
directory.

   It is used to load TSR (Terminate and Stay
Resident) programs that stay in memory and "pop up"
whenever you call them.  It's also used to start an
application when the computer is turned on, perhaps
a menu program that launches a variety of
applications.

   Two common commands in AUTOEXEC.BAT are:

   PROMPT - Usually prompt $p$g.
   PATH   - The Path line contains the
            directories you want access to
            no matter which directory you're in.

   To load or run a program, enter the program name
on a separate line.  Any DOS commands in
AUTOEXEC.BAT will be executed like a normal DOS
batch file.

   The following example sets the prompt and path,
loads the Doskey program in the DOS directory
switches to the LOTUS directory and runs the 123
program:

         prompt $p$g
         path c:\data;d:\words;e:\budget
         c:\dos\doskey
         cd \lotus
         123

                     Remember!
AUTOEXEC.BAT must be stored in the root directory.


    Your Configuration Files Get Tampered With
Install programs may edit your AUTOEXEC.BAT and
CONFIG.SYS files during installation.  For example,
they may want to add the new directory to the path
or to set an environment variable (see DOS Set).
They made also need to add a new driver.  You are
generally informed that this is being done and
often shown the changes as they are made.  The
original files are usually renamed with a different
extension and left on the disk.

   If you want to delete the application soon after
it was installed, you can rename these files back
to AUTOEXEC.BAT and CONFIG.SYS (after deleting the
current ones).  However, after several software
installations, you may not remember which is which,
and all these previous configuration files may have
little value unless carefully inspected.



DOS backslash (\)
Backslashes are used to represent the root
directory when it precedes the first directory of
file name in a path.  Used elsewhere in the path,
it is a symbol that separates file and directory
names.  See DOS abc's.



DOS Backup/Restore
(For DOS 6 users, see DOS MSbackup.)  Backup and
Restore are external commands that let you back up
your hard disk onto as many floppies as required.

   To back up all the files in directory WORK on
drive C onto floppies in drive A, type:

          backup c:\work a:


BACK UP AND FORMAT
If you don't have a lot of formatted floppies, you
can format them at the same time you're backing up.
In DOS 3.3 and lower, add /f:

          backup c:\work a: /f

   As of DOS 4.01, Backup automatically runs the
Format program if it finds an unformatted disk.


BACK UP ONLY UPDATED FILES
To back up only those files that have been changed
since the last update, add /m (see Archive
Attribute in DOS Attrib):

          backup c:\work a: /m


BACK UP SUBDIRECTORY FILES TOO
To back up the files in WORK as well as all files
in subdirectories attached to WORK, add /s:

          backup c:\work a: /s


ADDING FILES
When running Backup, existing files on the floppies
are erased.  To add to the disks (keep existing
files), use /a:

          backup c:\work a: /a


   You can mix any of the switches (/s, /m, /f,
etc.); such as:

          backup c:\work a: /m /s


CREATE A BACKUP LOG
Starting with DOS 3.3, the /l switch lets you
create a file containing the names of each file
backed up along with its backup disk number.  If
you don't name the file, BACKUP.LOG will be created
in the root directory of the current drive.  If the
log file exists, file names will be added to the
list.  The following example creates MYLOG in MYDIR
on drive E:

   backup c:\work a: /m /s /l:e:\mydir\mylog



RESTORING FILES
To restore files, you must explicitly state which
files.  To restore all files back into the C:\WORK
directory from the A drive, type:

         restore a: c:\work\*.*

   To restore only EXE files, type:

         restore a: c:\work\*.exe

   To restore all files, including the subdirectory
files, add the /s:

         restore a: c:\work\*.* /s



DOS batch file
File of DOS commands for "batch" processing.  Each
line of a batch file is executed by DOS until the
end of the file is reached.

   To create a batch file, use Copy Con, a text
editor such as Edlin or Edit or a word processor.
If using a word processor, save your batch file as
an ASCII text file, not as a standard document.
Name it, and always include the .BAT extension.

   The following batch file switches to the E
drive, goes to the PAT directory and runs the
MYPROG program:

         e:
         cd \pat
         myprog

   If the above file was PAT.BAT in the root
directory, you would execute it by typing:

        C:\>pat

   Since the batch file switches drives and goes to
the required directory, it doesn't matter which
drive or directory you're in when you run it.


                       Tip!
If you use batch files to launch applications, put
the batch files in the root and make sure the root
is in the path.  That way, you can run a batch file
from whichever directory you're in.  Another option
is to create a directory called \BATCH and put
C:\BATCH in the path.


               Stopping a Batch File
To stop a batch file in operation, press Ctrl-C or
Ctrl-Break.


  ┌──────────────────────────────────────────────┐
  │  The following commands are here for quick   │
  │  reference only.  If you are not an          │
  │  experienced batch file programmer, consult  │
  │  a good book on the subject, such as Kris    │
  │  Jamsa's "DOS Batch File Power" published    │
  │  by SAMS.                                    │
  └──────────────────────────────────────────────┘


             Additional Batch Commands
  cls        Clear the screen
  rem        Remarks (documentation)
  ::         Non-displayable remarks (see DOS ::)
  echo off   Turn off display.
  @echo off  Turn off display (3.3 and up).
  echo on    Turn on display.
  echo       Display message; for example,
              echo Press any key to continue.
  call       Call other batch file.
  pause      Stop (wait for keystroke).
  choice     (in DOS 6) more organized method for
              getting user input


             Advanced Batch Commands
  For reference only.  Refer to your DOS manual.
  if not exist filename goto :line
  if not string1==string2 goto :line
  if not errorlevel 0 goto :line
  for %%varname in (files) do command
  %0        - Batch file name.
  %1 - %9   - Input variables.
  %varname% - Variable used with Set.

   Following is an example of the choice batch file
command in DOS 6.  It loads three different
programs depending on receiving A, B or C from the
user.  If A is entered, errorlevel is 1, B is 2 and
C is 3.  IF ERRORLEVEL always tests for >=, which
is why the largest number is tested first.

   choice /c:abc  Run A.  Run B.  Run C.
   if errorlevel 3 goto runC
   if errorlevel 2 goto runB
   :runA
   run program A
   goto end
   :runB
   run program B
   goto end
   :runC
   run program C
   :end



DOS box
DOS compatibility mode.  The "box" is an OS/2 or
Windows window that is running a standard DOS
application.



DOS Break
Ctrl-C and Ctrl-Break are key commands that stop
the current operation; however, certain functions
such as disk I/O cannot normally be halted.  Break
is a CONFIG.SYS setting that tests the keyboard
more frequently for Ctrl-C and Ctrl-Break.  To
extend Ctrl-C checking, add the following to your
CONFIG.SYS file:

          break=on

   Note that applications can be programmed to
ignore Ctrl-C and Ctrl-Break regardless of the
Break setting.



DOS buffers=
See DOS CONFIG.SYS.



DOS cache
See DOS SmartDrive.



DOS Cd
Internal command that changes the current
directory.  Chdir is an alternate form.  To change
to the DATA directory type:

     C:\ANYWHERE>cd \data

         or type:

     C:\ANYWHERE>chdir \data


   See DOS directories and DOS abc's.



DOS changing directories
See DOS Cd and DOS directories.



DOS Chdir
See DOS Cd.



DOS Chkdsk
External command that reports free memory and disk
space.  To display memory and disk status, type:

         chkdsk

   Improperly closed files, caused by rebooting
from a frozen application for example, generate
lost clusters, which are unidentifiable files.
Most of the time, these are temporary files not
worth recovering.  To reclaim these lost clusters,
run Chkdsk with the /f switch.  When you're asked
"Convert lost chains to files?", answering Y for
yes will convert lost clusters to FILE0000.CHK
files, which you can examine.  Answering N will
remove them.  For example:

         chkdsk /f

   To list recovered files, type:

         dir *.chk


                    Important!
Don't go to the DOS prompt (shell out) from within
Windows or any other program and then run the
Chkdsk utility.  You may get invalid results and
possibly destroy data.



DOS CHKSTATE.SYS
Software driver used by Memmaker exclusively during
its optimization process.  The line is placed into
CONFIG.SYS and then removed when Memmaker is
finished.  See DOS SIZER.EXE.



DOS clean boot
See DOS startup options.



DOS Cls
Internal command that clears the screen.  To clear
the screen, type:

           cls



DOS combining files
To combine text files, use the Copy command.  For
example, to combine the files FIRST and SECOND,
creating a new file named COMBINED, type:

         copy first+second combined


   To append SECOND to the end of FIRST, type:

         copy first+second

   After the copy, SECOND still exists as a single
file, and it has also been appended to FIRST.



DOS command history
See DOS Doskey.



DOS COMMAND.COM
Command interpreter that displays the DOS prompt
and accepts and executes your typed-in commands.
If a command interpreter other than COMMAND.COM is
used, it is specified with the Shell command (see
DOS Shell).

   DOS loads COMMAND.COM from the disk at startup.
Part of COMMAND.COM is always resident in memory.
The rest of it, or transient part, may be
overwritten when a program is executed.  When the
program is done, the transient portion is reloaded
into memory.  See DOS Sys.



DOS Comp
External command that compares two files for
identical content and reports up to 10 mismatches.
In DOS 6, this command is no longer installed,
although it still resides on the DOS 6 Supplemental
Disk.  To compare file RED with GREEN, type:

           comp red green


   Mismatches are reported as follows:

     Compare error at OFFSET AA
     File 1 = BB
     File 2 = BB

  AA = location of characters
  BB = characters (in hex)


   As of DOS 5, these optional switches can be
added to the command:

    /a   Show ASCII characters (not hex)
    /l   Display line numbers (not offset)
    /c   Non case-sensitive compare

   See also DOS FC.



DOS comparing files
See DOS FC and DOS Comp.



DOS compressing files
See DOS DoubleSpace.



DOS compression ratios
To see the compression ratios of your DoubleSpace
files, use the /c switch with the Dir command to
list each file's ratio and an average for the
selected group.  The following example displays
ratios for all .EXE files:

             dir *.exe /c



DOS Comspec
DOS environment variable that holds the path to
COMMAND.COM.  See DOS COMMAND.COM and DOS Set.



DOS CONFIG.SYS
Configuration file that DOS looks for in the root
directory upon startup.  It is used to load drivers
and change system settings.  Adding a new type of
peripheral to the computer usually requires
installing the driver program to make it operate.

 Common
 Commands            Purpose
 DEVICE    Names a driver to be loaded.
 FILES     Files open at one time (8-255).  Default
            is 8, but this is often set to 20-40.
            Some apps open a lot of files.
 BUFFERS   528-byte areas of RAM reserved for input
            and output (1-99).  Default is usually
            15, but this is often set to 20 or 30.
            The more buffers, the faster the I/O.
            /x switch in 4.01 puts buffers in EMS.
 LASTDRIVE Last drive letter (see DOS Subst).

   Look up DOS Loadhigh for storing drivers in high
memory in DOS 5 and up.

   Following is an example of the contents of a
CONFIG.SYS file for a 386:

    device=c:\dos\himem.sys
    device=c:\dos\emm386.exe ram
    device=c:\dos\ansi.sys
    device=c:\mouse\mouse.sys
    files=30
    buffers=40
    dos=high,umb


  Common
  Drivers              Purpose
 ansi.sys      Screen and keyboard control.
 display.sys   Supports code-page switching.
 driver.sys    Identifies 3rd & 4th floppy and
                allows copying from/to same drive.
 mouse.sys     Mouse driver.
 printer.sys   Code-page support for printers.
 himem.sys     Extended memory (XMS) manager.
 emm386.exe    386 EMS manager.
 qemm386.sys   Quarterdeck's 386 EMS manager.
 ramdrive.sys  RAM disk (extended or EMS memory).
 smartdrv.sys  Disk cache (extended or EMS memory).



DOS Copy
Internal command for making duplicate disk files.
The command format is:

               COPY  FROM  TO


COPY TO/FROM FLOPPIES
  copy a:*.* b:     all A files to B
  copy b:*.* a:     all B files to A
  copy b:sales a:   SALES file in B to A


COPY FROM FLOPPY TO CURRENT HARD DISK DIRECTORY
  copy a:sales      SALES file on A
  copy a:*.*        all A files


COPY FROM CURRENT HARD DISK DIRECTORY TO FLOPPY
  copy sales b:     SALES file in  to B
  copy *.* b:       all files to B
  copy . b:         shortcut of above


COPY FROM CURRENT DIRECTORY TO ANOTHER DIRECTORY
  copy filex \text copy FILEX to TEXT directory

  copy *.* \text   all files to TEXT directory
  copy . \text     shortcut of above


COPY FROM ANOTHER DIRECTORY INTO CURRENT DIRECTORY
  copy \abc\x.bat   X.BAT from ABC directory

  copy \abc\*.*     all files from ABC
  copy \abc         shortcut of above


COPY AND RENAME AT THE SAME TIME
The following example duplicates and renames a PC
Paintbrush file within the same directory:

      copy logo.pcx logo2.pcx


YOU CAN VERIFY YOUR COPY
To be extra sure that the copy is correct, add the
/v switch to compare the new file with the old
file; for example:

      copy *.* a: /v


                     Remember!
There's less typing if you're in the directory you
want to copy to.  For example, from any directory,
you could issue:

   D:\ANYWHERE>copy a:*.* c:\budgets\1992


   But, if you're already in C:\BUDGETS\1992, the
TO is implicit:

        C:\BUDGETS\1992>copy a:*.*



            LOOK UP THESE COPY COMMANDS
COPY only copies files, but XCOPY copies both files
and subdirectories and creates the directory names
on the target disk.

DISKCOPY makes exact copies of floppy disks and
formats them at the same time.

REPLACE is great for backup and copies only files
that have been changed.


DOS Copy con
Internal command for creating a quick batch file.
For example, to create the WRITE batch file, type:

            copy con write.bat

   After pressing Enter, you'll get a blank line.
Type your text and press Enter to end the line.
When done, press F6 (ctrl-Z), then press Enter.

   Copy Con works a line at a time.  You can't go
back and change lines, but you can use backspace to
delete characters on the same line.


DOS Ctty
Internal command that redirects the keyboard and
screen to the serial port.  This is used to connect
a remote keyboard to a PC.

      ctty aux     change to serial port
      ctty con     restore keyboard and screen



DOS data recovery
See DOS Recover, DOS Unformat, DOS Undelete and
"There's More to Mirror" in DOS Mirror.



DOS Date
See DOS Time/Date.



DOS Debug
External command that performs a variety of machine
language functions.  Debug is used to edit memory,
executable files, input/output ports, assemble
small programs and perform hex arithmetic.  To load
Debug, type:

          C:\>debug      load Debug
          -              Debug prompt (-)

   Some simple Debug commands follow for reference
only.  See your DOS manual for details.

 Commands             Purpose
   ?            Online help (as of DOS 5).
   q            Quit.

   d cs: 100    Display 128 bytes of RAM at 100h in
                 the CS segment (current program).
   d            Display next 128 bytes.

   h xxxx yyyy  Hex math.  X and y are hex numbers.
                 Results are x+y  x-y.
   g=C800:5     Go to address C800:5



DOS Defrag
Starting with DOS 6, Defrag is a utility that
defragments the hard disk.  Some users run a
defragmenter every day, others every couple of
months.  It's up to you.  Defragmenting will
improve the performance of applications in which
you continuously update the data.  If done
routinely, it will help reduce wear and tear on the
hard disk.  Follow this procedure to defragment
your hard disk:

  1. Delete all unnecessary files on the disk.
  2. Quit all running programs, including Windows.
  3. Check for lost clusters by typing chkdsk /f.
     If prompted "Convert lost chains to files?",
       answer Y.
  4. Run Defrag by typing defrag.



DOS Del
Internal command that removes a file from the disk.
To erase a file named OLD.TXT, type:

        del old.txt   or   erase old.txt


   To erase all files in your current directory,
type:

           del *.*   or   erase *.*


   To delete all DOC files, type:

          del *.doc  or   erase *.doc


   Before DOS 5, there was no undelete.  However,
deleted files can be recovered, because deleting
only changes the name entry in the directory.  The
data is still there.

   If you accidentally delete vital data, do this:

   In DOS 3.x and 4.01:

   1. Stop!
   2. Turn the computer off.  If you must save
       what you're working on, save it to a
       different disk drive.
   3. Get a file recovery program and follow its
       instructions.


   In DOS 5 and DOS 6:

   Just type the following and follow the prompts:

                     undelete


   See DOS Undelete.



DOS Deltree
Starting with DOS 6, an external command that
removes directories.  It differs from the Rd
command in that the directories do not have to be
empty.  All files contained in the directory and
all subdirectories attached to that directory as
well as any files contained in them will be
deleted.  Like the Rd command, you must not
currently be in the directory that you want to
delete.  For example, to delete the C:\BUDGETS
directory, you could type:

   C:\>deltree budgets      from the root
   C:\WORK>deltree budgets  from a non-related
                             directory

   If BUDGETS contained subdirectories; for
example, \BUDGETS\1992 and \BUDGETS\1993, those
subdirectories and files will also be deleted.



DOS device names
DOS reserved names for common input and output
devices.  See DOS redirection, DOS Sort and DOS
Dir.

  Reserved name   Device
  AUX             First connected serial port
  PRN             First connected parallel port
  COM1 thru COM4  Serial ports (modem, mouse, etc.)
  LPT1 thru LPT3  Parallel ports (printer)
  CON             Keyboard and screen
  NUL             Dummy (testing purposes)



DOS device=
See DOS CONFIG.SYS.



DOS Devicehigh
See DOS Loadhigh.



DOS Dir
Internal command for displaying the names of files
within a single directory.  To list all file names
in the current directory, type:

                   dir


   To display only files with an .EXE extension,
type:

         dir *.exe  or   dir .exe


   See DOS wild cards for more on selecting file
names.

   A Dir list contains the following information
(see example below):

 Line 1  Drive name.  "Has no label" means
          it hasn't been named.
 Line 2  Drive serial no. (DOS 4.01 and up)
 Line 3  Current directory name.
 Line 4  The "." line represents the entire current
  directory and shows the creation date.  Let it
  remind you of the shortcut for "*.*".
 Line 5  The ".." line means the directory is
  attached to a higher level (they all are except
  for the root).
 Lines 6, 7 & 9  Name, extension, size, creation
  date/time of each file selected.
 Line 8  Name of subdirectory attached to this
  directory.


Volume in drive C has no label         Line 1
Volume Serial Number is NNNNNNNNN      Line 2
Directory of D:\DIRNAME                Line 3

.             <DIR>     MM-DD-YY  H:MM Line 4
..            <DIR>     MM-DD-YY  H:MM Line 5
NAME     EXT     SIZE   MM-DD-YY  H:MM Line 6
NAME     EXT     SIZE   MM-DD-YY  H:MM Line 7
NAME          <DIR>     MM-DD-YY  H:MM Line 8
NAME     EXT     SIZE   MM-DD-YY  H:MM Line 9


              Important Variations

LIST ONLY DIRECTORIES
To display subdirectory names attached to the
directory you're in, type:

                   dir *.


   Starting with DOS 5, use the /ad switch to list
directories.  Only directories will be displayed,
whereas with the DIR *. example above, depending on
DOS version, you may also get file names that do
not have extensions.

                  dir /ad


WIDE DISPLAY
To display names across the full width of the
screen rather than in one column, add /w:

                   dir /w


PRINT THE LIST
To print a Dir list, redirect the output to the
printer.  The following example prints the list
rather than displaying it.  Add the > prn to any of
these examples to print instead of display.

                  dir > prn


ONE SCREENFUL AT A TIME
To display a screenful at a time and pause, add the
/p switch:

                   dir /p


LIST FILES ALPHABETICALLY (Before DOS 5)
To list file names alphabetically no matter what
DOS version is installed in your machine (DOS 2.0
and up), you can pipe the output to the Sort
external command as follows:

              dir *.exe | sort


LIST FILES ALPHABETICALLY (As of DOS 5)
To list file names alphabetically, type:

   dir /o    subdirectories 1st, files 2nd
   dir /on   subdirectories and files mixed


   By extension:

     dir /oe      subdirectories and files mixed
     dir /oe /og  separate


   By file size:

     dir /os       low to high (mixed)
     dir /os /og   separate

     dir /o-s      high to low (mixed)
     dir /o-s /og  separate


   By date:

     dir /od       earliest to latest (mixed)
     dir /od /og   separate

     dir /o-d      latest to earliest (mixed)
     dir /o-d /og  separate



SEARCH FOR DUPLICATE FILE NAMES (As of DOS 5)
You can use Dir to find all files with the same
name in the current directory and its
subdirectories.  For example, to find out where
X.BAT is located, type:

        dir x.bat /s


LOWER CASE OPTION (As of DOS 5)
To display all names in lower case, add /l:

        dir /l


DISPLAY FILE ATTRIBUTES (As of DOS 5)
Use the /a switch to display the various attributes
that can be assigned to a file:

    dir /ar    read only files
    dir /ah    hidden files
    dir /aa    files ready for archiving
    dir /as    system files


CHANGE DIR COMMAND DEFAULTS (As of DOS 5)
Use can change the defaults for the Dir command by
setting the DIRCMD environment variable.  The
following example sets alpha order and a screenful
at a time:

     set dircmd=/o /p    change defaults
     set                 view current settings
     set dircmd=         restore defaults

   Add the Set Dircmd line in your AUTOEXEC.BAT
file to change defaults each time you start.


SHOW COMPRESSION RATIOS (As of DOS 6)
To see how effective your DoubleSpace compression
is, see DOS compression ratios.



DOS Dircmd
Environment variable that lets you set the default
options for the Dir command.  The explanation is at
the end of DOS Dir (Page Up once).



DOS directories
Simulated file drawers on a disk.  To understand
directory basics, look up DOS abc's.


         Directories and Subdirectories
DOS directories are hierarchical in structure.  The
starting point is the root directory.  In fact,
when several people use the same computer, the
"directory tree" looks like an organization chart:

                    root
       ┌───────┬─────┴─────┬───────┐
     karen    sam         pat    robin
       │
   ┌───┴───┐
  budget  text

   A subdirectory is a directory that is
subordinate to (below, or attached to) another
directory like BUDGET and TEXT above.  Since all
directories are below the root directory, all
directories are technically subdirectories.  The
two terms become intertwined.  Don't worry about
this.

   More importantly, don't set up too many levels
in the hierarchy or you'll drive yourself nuts
trying to manage them at the DOS prompt.  However,
if you have a menu system that let's you point to
the directory you want, you can manage several
levels of directories more easily.


                 A Real Bummer
The hardest thing about DOS commands is creating
the proper path name to the files you want to work
with.

   It's tricky because the structure for naming the
path isn't clearcut.  The culprit is the backslash
symbol (\), which means two entirely different
things depending on its position in the path.

   The first time it's used, it stands for root
directory.  The second and subsequent times it's
used, it's a symbol that separates file and
directory names.

   The following commands for creating, removing
and changing directories will show you many ways
path names are used.  There are plenty of examples
that follow:


         Creating a Stand-alone Directory
A stand-alone directory is one attached to the
root.  To create stand-alone directory KAREN, type:

   C:\ANYWHERE>cd \    go to the root
   C:\>md karen        make directory off the root
   C:\>                you're still in the root

   To go to that directory, type:

   C:\>cd karen       change directories
   C:\KAREN>          prompt changed to Karen


                       Note!
Directories are named the same as files, with a
name up to eight characters and an optional
extension of up to three.  See DOS file names.


              Creating a Subdirectory
To create a subdirectory called BUDGET that is
located within the KAREN directory, type:

 *     C:\ANYWHERE>cd \karen    go to KAREN
       C:\KAREN>md budget       make subdirectory
 **    C:\KAREN>cd budget       go to budget
       C:\KAREN\BUDGET>         prompt has changed

   * Going to KAREN requires a backslash in front
of KAREN, because the first backslash means ROOT
directory, and KAREN is off the root.
** Going to BUDGET does not use the backslash,
because BUDGET is off KAREN, not off the root.
More on this in a moment.


                    Also Note!
The above methods were chosen for demonstration,
because the syntax is the same for creating both
stand-alone directories and subdirectories.
However, you should know that you can create both
types of directories no matter which directory
you're in.  For example, from the ANYWHERE
directory, you could have created KAREN by typing
md \karen  being sure you have the backslash in
front of KAREN.  You could then attach the BUDGET
subdirectory to KAREN with md \karen\budget.


               Removing a Directory
First, be sure all files in the directory have been
erased.  Second, move back a level to the directory
before it.

   The following example switches to the KAREN
directory, deletes all files, moves back one level
and removes the KAREN directory:

      C:\>cd karen      go to KAREN
      C:\KAREN>del *.*  delete all files
      C:\KAREN>cd ..    move back one level
      C:\>rd karen      remove KAREN directory


                     Remember!
1. You can't be in the directory you're deleting.
   Go to the level before it.

2. You can't delete a directory that's not empty.



               Switching Directories
The CD (change directory) command means go to
another directory.  What actually changes is the
DOS prompt, which displays the name of the
directory you've switched to.

   Suppose you have three subdirectories under the
PLANS directory:

              C:\PLANS\1991
              C:\PLANS\1992
              C:\PLANS\1993

   If you're in the 1991 directory and you want to
go to the 1992 directory, you have to state the
path starting at the root:

      C:\PLANS\1991>cd \plans\1992
      C:\PLANS\1992>


   Another way is to type:

       C:\PLANS\1991>cd ..    back up one level
**     C:\PLANS>cd 1992       go to 1992
       C:\PLANS\1992>

**Note: When going from PLANS to 1992, you don't
use the backslash (\), because 1992 is subordinate
to PLANS, not the root.


   Let's examine this some more.  In the command:

              cd \plans\1991

   The first \ means ROOT.  The second \ separates
one directory name from another.  Therefore, if
you're in PLANS already, you cannot type:

           C:\PLANS>cd \1991

   You'll get an "Invalid directory" message,
because 1991 is not off the root.

           \1991 means root 1991

   Using the PLANS directories again:

              C:\PLANS\1991
              C:\PLANS\1992
              C:\PLANS\1993

   Only the first example below is correct:

 correct   C:\PLANS>cd 1991   1991 is off PLANS
 no good   C:\>cd 1991        You're in the root
 no good   C:\>cd \1991       1991 is not off root



             Switching Between Drives
When switching between directories on different
drives, you must switch drives first.

   For example, to switch from C:\PLANS\1991> to
D:\BUDGETS>, you would type:

     C:\PLANS\1991>d:   switch drives first
     D:\>cd budgets     then change directories
     D:\BUDGETS>        prompt has changed


   Think of drives as buildings and directories as
floors.  You can't get to the 3rd floor of the
college if you're on the 2nd floor of the high
school by simply switching floors.  You have to
leave the college and go to the high school first.


          Using Paths with Other Commands
Drive letters ARE NOT used with the CD command.

   Drive letters ARE used with all other commands
whenever the drives are not implicit.  For example,
to copy the SALES worksheet from C:\PLANS to
D:\BUDGETS, you would type:

 E:\ANYWHERE>copy c:\plans\sales.wk1 d:\budgets


   Notice that, because you're in drive E, both
FROM and TO drive letters must be used (C: and D:).

   Also notice that the SALES file name is simply
added to the end of the path, separated by a
backslash.

   If you were already in C:\PLANS, you would only
need to reference the file name:

     C:\PLANS>copy sales.wk1 d:\budgets


                     Remember!
Drive letters must be stated whenever a drive is
not implicit.  If you're not sure, state the drive
letters anyway.  Both examples below work:

      C:\PLANS>copy c:\plans\sales.wk1 a:
      C:\PLANS>copy sales.wk1 a:




DOS directory rules


               DIRECTORY RULE #1
When going to a directory on a different drive,
change drives first, then change directories.


               DIRECTORY RULE #2
The backslash represents the root directory.  It is
also used as a separator symbol between directory
and file names.


               DIRECTORY RULE #3
When using the CD command to go to a directory on
the same or previous level, the path name must
begin with the root (\).



DOS disk cache
See DOS SmartDrive.



DOS disk recovery
See DOS Recover, DOS Unformat, DOS Undelete and
"There's More to Mirror" in DOS Mirror.



DOS Diskcomp
External command that compares two floppy disks
track by track and reports the side and track
number if it finds a mismatch.

      diskcomp a: b:   two identical drives
      diskcomp a:      one drive


   On one-drive compares, you'll be prompted to
insert the source and target diskettes a few times.



DOS Diskcopy
External command that makes an exact copy of a
floppy disk.  Disk types MUST BE THE SAME.  You
can't Diskcopy a 720KB disk onto a 1.44MB disk.

   If the target disk is unformatted, Diskcopy will
format it.

      diskcopy a: b:    two identical drives
      diskcopy a: a:    one-drive

   On one-drive copies, you'll be prompted to
insert the source and target diskettes a few times.



DOS Dos
CONFIG.SYS setting as of DOS 5 that allows part of
DOS to be loaded into the HMA area (1024-1088K).
In order to do this, HIMEM.SYS or some other XMS
driver must precede the Dos command in CONFIG.SYS,
for example:

          device=himem.sys
          dos=high


   To allow drivers and programs to be loaded into
unused memory blocks (UMBs) in the UMA area (640-
1024K), use:

          dos=umb

   or activate both with dos=high,umb


   See DOS Loadhigh and DOS HIMEM.SYS.



DOS Doskey
External command starting with DOS 5 that provides
command history and macros (typed-in commands
stored for later use).  The command buffer
(reserved space) is 512 bytes long unless you
specify otherwise.  Three examples for loading
Doskey follow:

    doskey                 512 byte buffer
    doskey /bufsize=1000   1K buffer
    doskey /bufsize=256    minimum size

   Use Up and Down Arrow to move through command
history, and press Page Up and Page Down for the
oldest and most recent command.  Doskey uses these
additional key commands:

       Key       Function
        F7  Display command history
    Alt-F7  Clear command history
   Alt-F10  Clear macros
        F9  Recall command by number
  Ctrl <--  --> Cursor previous/next word
  Home/End  Cursor beginning/end line
       Esc  Clear line
       Ins  Insert mode for this line
F1, F3 and F6 work as usual.  See DOS key commands.


CREATING MACROS
Doskey macros are useful for shortening phrases
that are hard to type; for example, suppose you
often copy the file D:\PKWARE\PKUNZIP.EXE to
different directories or disks.  You could create a
macro named PK as follows:

   doskey pk = copy d:\pkware\pkunzip.exe $1

   The $1 creates a blank field for data entry.
Now that the macro is created, to copy PKUNZIP.EXE
to the B drive, you would type:

            pk b:


   Entering the command above converts the macro
into the following command (the b: replaces the
$1):

    pk = copy d:\pkware\pkunzip.exe  b:


   To see the macros you've created, type:

            doskey /macros


   Doskey macros last for only the current session.
If you save them in a batch file and add the word
DOSKEY in front of each one, you can execute the
batch file and recreate the macros in the next
session.  To store your macros in MYMACRO.BAT,
type:

       doskey /macros > mymacro.bat

   In order to make the resulting file a command
file, you have to type the word DOSKEY at the
beginning of each line.



DOS DoubleSpace
DoubleSpace is a realtime compression capability
built into DOS 6 that increases the disk's storage
capacity as much as twofold.  The actual
compression obtainable depends on the data being
stored.  DOS 6 does not compress your drives
automatically.  You must run the DoubleSpace
program to do it.

   To compress your hard disk, type dblespace.  The
first time you run DoubleSpace, you'll have a
choice of Express or Custom Setup.  To compress
your C: drive including all existing files, select
Express Setup.  To compress another drive or to
compress part of your C: drive leaving your
existing files uncompressed, select Custom Setup.

   The compressed drives that DoubleSpace creates
are actually files with names such as DBLSPACE.000
and DBLSPACE.001 that reside on an uncompressed
drive as hidden "compressed volume files" or CVFs.
The uncompressed drive, known as the host drive, is
either the C: drive if you did not compress all of
it or some other drive that DoubleSpace creates.

   If you're curious, you can view the hidden CVFs
in the uncompressed host drive by typing dir /ah.
However, do not restore them to normal status or
tamper with them in any manner!  When viewing them,
you will notice DBLSPACE.BIN.  This program file is
loaded at startup and gives DOS access to the
compressed DoubleSpace disks.

   To review the status of your compressed drives,
to change them or to make new ones, type dblspace
and select the appropriate menu options.

   You can see how effective the DoubleSpace
compression is on your files by using the Dir
command (see DOS compression ratios).



DOS Dozen
Twelve DOS commands that let you do almost
everything.

           The DOS Dozen (tm)
   format  Initialize a floppy
   dir     List file names
   del     Remove a file
   rename  Change names
   type    Display a text file
   xcopy   Copy files and directories
   copy    Copy files
   md      Make directory
   cd      Go to a directory
   rd      Remove directory
   chkdsk  Test for corrupted files
   cls     Clear screen




DOS drive identification
DOS drives are identified with a letter and colon.

       A: First floppy
       B: Second floppy
       C: Main hard drive
       D: Second hard drive, second partition
           within the main hard disk or some
           other device such as a CD ROM drive.
           Drive letters E: through Z: also used.

   To switch drives, type drive letter and colon;
for example, to go to drive D, type:

            C:\>d:    switch drives
            D:\>      prompt has changed



DOS DRIVER.SYS
Driver used to add newer devices (typically floppy
disks) to older PCs that did not originally support
them.  It's also used to assign a second drive
letter to a single drive to allow you to copy to
and from the same drive.  The following codes are
used to define drives and drive types:


 Drive /d:     Factor /f:      Switches     Default

 0 - First     0 -  360KB   /h: Heads (1-99)    (2)
 1 - Second    1 -  1.2MB   /s: Sectors (1-99)  (9)
 2 - Third     2 -  720KB   /t: Tracks (1-999) (80)
 3 - Fourth    7 - 1.44MB   /c  Change line support
 etc.          9 - 2.88MB   /n  Nonremovable device

   The following lines in CONFIG.SYS add support
for a third floppy disk:

 device=driver.sys /d:2 /f:0 /t:40     360KB
 device=driver.sys /d:2 /f:1 /s:15     1.2MB
 device=driver.sys /d:2 /f:2           720KB
 device=driver.sys /d:2 /f:7 /s:18    1.44MB
 device=driver.sys /d:2 /f:9 /s:36    2.88MB


   The following line creates a second "logical"
drive for a 1.2MB A: drive.  If drive C was the
last drive letter, this CONFIG.SYS line will create
drive D:, which references A:.

  device=driver.sys /d:0 /f:1 s:15


  If you type:

              copy a:*.* d:


   DOS will inform you when to switch disks, and
you can Copy or Diskcopy to and from the same
drive.


                       Note!
DRIVER.SYS differs from Drivparm as it will always
make the device the highest drive letter.  For
example, if a 3.5" drive is added to a PC with an
A: and C: drive, DRIVER.SYS will assign it drive D:
rather than B:.



DOS Drivparm
CONFIG.SYS command that redefines the current
settings for a device and maintains the same drive
letter.  The following codes are used:


 Drive /d:     Factor /f:     Switches

 0 - First    0 -  360KB    /h: Heads (1-99)
 1 - Second   1 -  1.2MB    /s: Sectors (1-99)
 2 - Third    2 -  720KB    /t: Tracks (1-999)
 3 - Fourth   5 - Hard disk /c  Change line support
 etc.         6 - Tape      /n  Nonremovable device
              7 - 1.44MB
              8 - Read/write optical disk
              9 - 2.88MB floppy


   The following line in CONFIG.SYS would define a
tape unit on drive B: that writes 10 tracks with
128 sectors per track:

     drivparm=/d:1 /f:6 /h:1 /s:128 /t:10


                       Note!
To add a device and create a new drive letter, see
DOS DRIVER.SYS.  Also, Drivparm should not be used
experimentally.  Get the right specs before you
proceed.



DOS Editor
Full-screen text editor starting with DOS 5 for
creating ASCII text files (batch files).  To create
or edit a file, type edit followed by the name of
the file.  For example, to edit AUTOEXEC.BAT, type:

             edit autoexec.bat


   DOS Editor is easy to use and help is online.
Use the Arrow keys to move around.  Press Alt-F for
the File menu and select Exit when you're done.


                       Note!
You must have the QBASIC.EXE program in your DOS
directory to run the DOS Editor (EDIT.COM).

   For DOS versions previous to 5, see DOS Edlin.



DOS Edlin
Text editor that comes with every version of DOS.
However, in DOS 6, it is no longer installed, but
still resides on the DOS 6 Supplemental Disk.  It
allows only one line to be edited at a time.
Starting with DOS 5, use the full-screen editor
(see DOS Editor).

   To create or edit a file, type edlin followed by
the name of the file.  For example, to edit
AUTOEXEC.BAT, type:

         edlin autoexec.bat


   The screen will display "End of input file"
followed by the Edlin asterisk prompt ("*").
Press L and Enter to list the file's contents.

TO EDIT A LINE
Type the line number and press Enter.  Press Right
Arrow to bring one character at a time into view,
or press F3 to restore the whole line.  When you're
done editing the line, press Enter for the "*"
prompt.  Press Enter again for the next line.
Ctrl-C cancels changes to the current line.

TO INSERT TEXT
Type i to insert text in front of the current line,
which is marked with an asterisk; for example: 3:*.
To change to a different line, type the line number
and press Enter.  After typing new text, press
Enter to end the line.  Then press Ctrl-C to end
insert mode or keep typing more text.

TO QUIT
At the "*" prompt, press e and Enter.


               Basic Edlin commands
 L   List contents (for specific lines, type:
      start,stop L; for example: 5,25 L).
 i   Insert at current line. │Ctrl-C ends│
 #i  Insert at end of file.  │insert mode│
 n   Line number to edit.
 nd  Delete line (for example, 5d deletes line 5).
 q   Abandon edit.
 e   End Edlin.
 r   Search/replace. (start,stoprsearch<F6>replace)
      For example:  1,20rBlue<F6>Red  changes
      all Blue to Red in lines 1 to 20.
      F6 enters a Ctrl-Z.

Ctrl-V[ Insert an escape character.



DOS EMM386.EXE
Starting with DOS 5 and Windows 3.0, EMM386.EXE is
an expanded memory manager (EMM) for 386s and up,
which is software that converts extended memory
into EMS memory.  It also allows TSRs and drivers
to be stored in the upper memory area (UMA) between
640K and 1M.  It is activated with a statement in
the CONFIG.SYS file.  The HIMEM.SYS driver must
also be activated before EMM386.EXE:

        device=himem.sys
        device=emm386.exe


   To provide access to the UMA, either the RAM or
NOEMS parameters must be added:

      device=emm386.exe ram      UMA and EMS
      device=emm386.exe noems    UMA only


   The default amount of memory used is 256K, but
you can allocate from 16 to 32768K, for example:

     device=emm386.exe 1300 ram


   For DOS 6 Users: The EMM386.EXE that comes with
DOS 6 can dynamically convert extended memory into
EMS memory when an application requires it.  To
free up all of extended memory until some of it is
required for your EMS application, type:

     device=emm386.exe min=0 ram



   EMM386.EXE is an executable program, which can
be run after it has been initialized in order to
change settings.  For example, you can turn off EMS
memory management off by typing:

           emm386 off

           emm386 on      turn it back on



DOS environment
Reserved area in DOS for holding values used by DOS
and other applications.  The values stored in this
area are called "environment variables" and are
created with the Set command (see DOS Set).



DOS Erase
See DOS del.



DOS error messages
There are hundreds of error messages in DOS.
Messages that generally occur more frequently are
explained below:

  Access denied
The file you are deleting is protected.  See DOS
Attrib.


  Bad command or file name
Means that DOS does not understand the command you
entered, or it cannot find the program you asked it
to run.


  Data error reading drive X
Means that an area of the disk is unreadable.
Press R to retry.  Most likely, you'll have to
press A to stop (abort).  If the data or program is
critical and there's no backup, use a utility
program to try to reconstruct the damaged area.
See DOS Recover.


  Duplicate file name or file not found
Means that you are referencing a file that does not
exist or that you are renaming a file to a file
name that already does exist.


  Exception error 12
Means that DOS does not have enough room to handle
hardware interrupts.  Increase the number of stacks
in the STACKS= command in the CONFIG.SYS file (see
DOS Stacks).


  General failure (error) reading drive X
  Abort, Retry, Ignore? (Fail?)
Usually means that an unformatted floppy is being
used.  Press A to Abort, format the floppy and try
again.  You'll also get this if you try to read a
high-density disk in a low-density drive.  High-
density disks require high-density drives.


  Not ready (error) reading drive X
  Abort, Retry, Fail? (Ignore?)
Means the drive door is left open, or the floppy
disk is not in the drive.  Either put the
appropriate floppy disk in the drive or close the
drive door (turn lever) and press R.

   To switch to another drive, press A.  If you get
the message  "Current drive is no longer valid>",
type the drive (c:, d:, etc.) you want to go back
to.  If you get this message again, press F (or I
for DOS 3.3 and earlier).


  Not ready (error) writing device PRN
  Abort, Retry, Ignore? (Fail?)
Means the printer is turned off or unavailable.
Press A to cancel, or turn the printer on and press
R.  You might also check the cable connection to
the printer.


  Non-system disk or disk error
  Replace and press any key when ready
Usually means there's a non-bootable floppy in
drive A.  The computer looks for DOS on a floppy
before it looks for DOS on the hard disk.  If an
ordinary floppy is in drive A at startup, it causes
this error.  Remove the disk and press any key.


  Incorrect DOS Version
Means that the command you are using belongs to
another version of DOS.  Somehow an earlier or
later version of a command is on your hard disk.
Commands from one DOS version often do not work in
other versions.


  Internal Stack Failure
Means that DOS has gotten completely confused.
Turn off the computer and restart.


  Invalid directory
Means that you entered the name of a directory that
does not exist.


  Invalid drive specification
If you get this message on a valid drive such as
C:, it may mean that your hard disk has become
corrupted.  See DOS Mirror.


  Invalid parameter
Means DOS doesn't understand the command line.  It
indicates that a switch is used incorrectly.  If
you're typing path names, be sure to use a
backslash (\), not a forward slash (/).  The
forward slash is used to enter parameters (see DOS
switch and DOS abc's).


  Packed file is corrupt
See DOS Loadfix.


  Path not found
Means that you entered an invalid path name.


  Stack overFlow
Means that DOS does not have enough room to handle
hardware interrupts.  Increase the number of stacks
in the STACKS= command in the CONFIG.SYS file (see
DOS Stacks).


  Write protect error
Means that the floppy disk has been protected and
data cannot be recorded on it.  Either unprotect it
or use another disk.  See file protection.



DOS Exit
Internal command that returns control from DOS to
the previous level.  Many applications can "shell
out" to DOS, letting you run DOS commands and then
return to the application.  Simply type exit to
return.



DOS extender
Software that is combined with a DOS application to
allow it to run in extended memory (beyond 1MB).
Some DOS extenders work with 286s and up, others
require a 386 minimum.  To gain access to extended
memory, it runs the application in Protected Mode.
When the application requests DOS services, the DOS
extender either handles them itself or, with
functions such as disk accesses, resets the machine
to Real Mode, lets DOS service the request and then
switches back into Protected Mode.

   DOS-extended programs can run by themselves in a
DOS machine, but the VCPI specification was
developed to enable them to run cooperatively with
DESQview and other VCPI-compliant applications.
The DPMI spec was developed for compliance with
Windows 3.0.

   If an XMS driver is present, DOS extenders will
use XMS to allocate memory.



DOS extensions
Names used to identify DOS file types.  See
extension and DOS file names.



DOS external command
Separate utility program that comes with DOS, such
as Format, Diskcopy, XCopy, Tree, Backup and
Restore, but is not resident within DOS, such as
Copy and Dir.

   The directory that contains these programs
should be on the path so that you can run them no
matter which directory you're in.  Contrast with
DOS internal command.



DOS Fastopen
External command starting in DOS 3.3 that reopens
hard disk files quickly.  If a drive is specified
with Fastopen, the locations of the files opened
are stored in memory.  When opened again within the
same session, their exact location is known.

   Fastopen is put in the AUTOEXEC.BAT file with
the number of files you want to hold in memory:

 fastopen c:=50        hold 50 file names on C:
 fastopen c:=50 d:=75  50 on C:, 75 on D:


   DOS 4.01 can optionally keep track of all the
file fragments.  This second number is usually four
times greater than the number of names:

            fastopen c:=(50,200)


                     Caution!
Fastopen cannot be used on network drives, and it
can be used only once per computer session.



DOS FAT
(DOS File Allocation Table)  The part of the DOS
and OS/2 file system that keeps track of where data
is stored on disk.  When the disk is high-level
formatted, the FAT is recorded twice and contains a
table with an entry for each disk cluster.

   The directory list, which contains file ID
(name, extension, date of last update...) points to
the FAT entry where the file starts.  If a file is
larger than one cluster, that entry points to
another entry and so on.  If a cluster becomes
damaged, its FAT entry is marked and not used
again.



DOS FC
External command that compares two files for
content.  .EXE, .COM, .SYS, .OBJ, .LIB and .BIN
files are compared byte for byte, otherwise,
comparison is line by line.  To compare text files
FILE1 and FILE2, type:

 fc file1 file2        blank areas must match
                        character for character
 fc file1 file2 /w     blank areas can be of
                        different sizes
 fc file1 file2 /a     show only start and end
                        text on mismatches

   Mismatches in ASCII files show as:

  ***** first file
  start
  ...
  ...
  end
  ***** second file
  start
  ...
  ...
  end
  *****

   To compare program files ABC.EXE and XYZ.EXE,
type:

         fc abc.exe xyz.exe

   Mismatches in binary files show as:

         AAAAAAAA BB BB

 A = Hex location from start of file.
 B = Hex characters in first and second files.



DOS FCB
(DOS File Control Block)  Method of handling files
in DOS 1.0.  Applications still exist that remain
compatible with 1.0 and use this method.  See DOS
Share.



DOS Fdisk
External command used to partition a hard disk,
which is necessary before high-level formatting.
For the procedure, see "How to Format a Hard Disk"
under DOS Format.



DOS file
(1) Any computer file created under DOS.

(2) ASCII text file.  See DOS batch file.



DOS file names
On a disk, every independent collection of
instructions or data is a "file."  Programs,
databases, word procesing documents, spreadsheets
and graphics images are examples of files.

   All files have a file name, and most files have
an extension.  Extensions are attached to the name
with a period (no spaces in between).  For example,
the following files make up the DOS and Windows
versions of this Glossary:

        Name  Extension   Purpose

      WINGLOSS.EXE       Windows Glossary program
      WINGLOSS.HLP       Windows Version help

        GLOSS.EXE        DOS Glossary program
        GLOSS.HLP        DOS Version help

        GLOSS.ABC        Configuration data
        GLOSS.TXT        Text file
        GLOSS.NDX        Index


   The name can be from one to eight characters in
length.  The extension, if used, can be from one to
three characters long.

   All runnable programs in DOS have either a BAT,
COM or EXE extension (look up "extension" for a
list of over 100 common DOS extensions).

   Valid characters in names and extensions are:
A-Z,  a-z,  0-9  ! @ # $ % & ( ) ' ` -  { } ~


                 The Dot is Sacred
If an extension is used, it is added to the file
name with a period, for example, GLOSS.TXT.
As a result, the dot can't be used in a file name.
For example, GL.OSS.TXT isn't valid.


              Your Own Filing System.
Most applications use proprietary extensions for
the data files that they create.  However, several
word processors do not, and if you can organize
your documents with your own filing system.  For
example, the NOV extension could be a novel with
chapters INTRO.NOV, MAIN.NOV and END.NOV.


                       Note!
Directories are named just like files with a name
and optional extension.



DOS files=
See DOS CONFIG.SYS.



DOS filters & pipes
Filters are external commands that change data in
some manner.  The filters are:

   FIND - Searches for text
   SORT - Rearranges data in alpha order
   MORE - Displays data a screenful at a time

   Pipes let you direct the output of one command
as input to another.  The pipe symbol is a vertical
bar (shift backslash key).  Pipes are used with
filters as follows.

   To get a Dir list of all the files that have
"ZIP" somewhere in their names, you would type:

    C:\>dir | find "ZIP"    command
    PKUNZIP   EXE           results displayed
    PKZIP     EXE
    C:\>

   The pipe redirects the Dir list output to the
find command, which looks for ZIP and filters only
lines with "ZIP" in them through to output.  See
DOS Find, DOS Sort and DOS Dir.



DOS Find
External command used to search for a particular
string of text in a text file.  The following
example will display the line numbers of the lines
that contain c: in the RUNJOB.BAT batch file:

           find "c:" runjob.bat

   Find is case sensitive.  "C:" will not find
"c:".  See DOS filters & pipes.



DOS Format
File structure used by DOS to keep track of data on
a disk.  All disks must be formatted (initialized)
before use.  This process creates the sectors on
the disk (low-level format) that are later filled
with data and also generates the tables that DOS
uses (high-level format) to keep track of the data.

   Hard disks are regularly formatted at the
factory, but floppies are usually not.

   The Format external command creates both low-
and high-level format on floppies, but only a high-
level format on hard disks.


              Formatting a Floppy
To format an unformatted floppy fresh from the box,
put it into drive A or B and type:

         format a:   or   format b:

   and answer the prompts.


FLOPPY DISK SIZES
There are five floppy disk capacities:

 Diameter  Capacity    Name
   5.25"     1.2MB   High density
   5.25"     360KB   Low density (Double Density)
    3.5"    2.88MB   Extra high density
    3.5"    1.44MB   High density
    3.5"     720KB   Low density (Double Density)

   Higher-density drives can read and write low-
density disks.  But to format a low-density disk in
a high-density drive, you must modify the command
as follows.


FORMATTING 5.25" DISKS
To format a 360K disk in a 1.2M drive, type:

    format a: /4         All versions
    format a: /f:360     DOS 4.01 and up


                     Caution!
360K disks formatted on very early 1.2MB drives may
cause reading problems.


FORMATTING 3.5" DISKS
To format a 720KB disk in a 1.44MB drive, type:

    format a: /n:9 /t:80  All versions
    format a: /f:720      DOS 4.01 and up


   To format a 1.44M disk in a 2.88M drive, type:

             format a: /f:1.44


REFORMATTING A FLOPPY (As of DOS 5)
The /q switch causes Format to bypass checking for
bad sectors.  To quickly reformat a formatted disk
that you know is OK, type:

             format a: /q


   Previous to DOS 5, the format program completely
formatted a floppy losing all data if previously
formatted.  As of DOS 5, Format creates a "safe
format" by saving additional data on the disk.
This takes a bit longer but allows the disk to be
unformatted.  Since you will not have to unformat
blank disks, you can format "unconditional" and
speed up the format process with the /u switch:

             format a: /u

   Also previous to DOS 5, any bad sector on a
diskette eliminated the entire track.  As of 5,
only that sector is marked as bad.


CREATING A BOOTABLE FLOPPY
To format a floppy and make it "bootable" by
copying DOS from the hard disk onto it, type:

             format a: /s

   The DOS COMMAND.COM file is also necessary on
the bootable floppy.  Starting with DOS 5, the
Format command copies COMMAND.COM to the floppy
automatically.  In DOS 4.01 and earlier, you have
to copy COMMAND.COM manually.


              Formatting a Hard Disk
A hard disk format requires:
     1. Low-level format
     2. Create partitions (Fdisk)
     3. High-level format (Format)

LOW-LEVEL FORMAT
If your hard drive is not already low-level
formatted from the factory (most IDE drives are),
the low-level format is accomplished by running a
utility program that comes from the disk
manufacturer or other software provider.  The
program may also be resident in the BIOS of the
disk controller card.


CREATE PARTITIONS
Fdisk is an external command that creates
partitions and "logical drives" on the hard disk.
To run Fdisk on your C: drive, boot the computer
with a floppy in drive A that contains DOS as well
as the Fdisk program.  If you're adding a second or
subsequent hard drive, load Fdisk from your C:
drive.  Type fdisk to load the program and follow
the menu options.

   DOS 3.3 and under handles disks up to 32MB in
size, therefore after making a primary partition of
up to 32MB, you'll be making an extended partition
if your disk exceeds 32MB.  DOS 4.01 handles disks
up to 512MB, and DOS 5 up to 2GB, in which case you
only need to create the primary partition.

   After making the primary partition, make an
extended partition if you require logical drives
(D:, E:, etc.) either for convenience or because
you want to install two operating systems on your
disk.  After making the extended partition, make
one or more logical drives.

   The active partition (the one to boot from) is
assumed to be the C: drive.  If not, you can change
that from the Fdisk menu.

   Starting with DOS 5, Fdisk only creates DOS
partitions.  If you have to create a partition for
another operating system, refer to that operating
system's manual.


HIGH-LEVEL FORMAT
The final step is to run Format for each logical
drive (C:, D:, etc.).  This step prepares the root
directory, FAT tables and places startup data in
the boot sector.

   To format your C: drive, boot the computer with
a floppy in drive A that contains DOS as well as
the Format program.  Use the /s switch to transfer
DOS at the end of the format.  To format drive C,
type:

                format c: /s


   To format a second or subsequent hard drive,
load Format from your C: drive.



DOS hidden file
DOS file with a status that prevents it from being
altered, erased or normally recognized.  DOS system
files are all hidden files.  See DOS Attrib.



DOS high memory
Area between 640K and 1024K reserved for system
use.  Also may refer to the area between 1024K and
1088K (HMA).  See PC memory map.



DOS HIMEM.SYS
Starting with DOS 5 and Windows 3.0, HIMEM.SYS is
an XMS driver, which is software that manages
extended memory in the PC.  It allows part of DOS
to be loaded into the high memory area (HMA) to
free up more conventional memory.  HIMEM.SYS is
required if you use EMM386.EXE to load TSRs and
drivers in the upper memory area (UMA) or to turn
extended memory into expanded memory.  HIMEM.SYS is
activated in the CONFIG.SYS file and must precede
all drivers that use extended memory; for example:

     device=himem.sys
     device=emm386.exe       EMS memory manager
     device=smartdrv.sys     disk cache
     device=ramdrive.sys /e  RAM disk


   Note: Windows requires extended memory and comes
with its own HIMEM.SYS driver that is automatically
installed.  However, HIMEM.SYS from DOS 5
supersedes the HIMEM.SYS from Windows 3.0.


   Only one program can reside in the HMA at one
time.  In order to reserve it for the largest
program, you can specify the minimum size the
program must be with the HMAMIN switch.  In the
following example, a program must be at least 50K
to use the HMA:

     device=himem.sys /hmamin=50


   See DOS Dos and DOS EMM386.EXE.



DOS history
See DOS Doskey.



DOS installing from drive B:
See DOS Assign.



DOS Interlink
Starting with DOS 6, the Interlink utility lets you
transfer files between two PCs connected via their
serial or parallel ports.  The serial port cable
can be a 3-wire file transfer cable or a 7-wire
null modem cable, and the parallel cable must be a
bidirectional parallel cable.

   The PC with DOS 6 and the INTERLNK.EXE program
is the client PC, and the second machine (DOS 3.0
and up) is the server PC.  The program INTERSVR.EXE
must be transferred to the server PC via floppy or
by remote copy (see below).

   Once the link is established, the disks on the
server become different drive letters on the
client.  For example, if the server has an A:, B:
and C: drive, those drives would be assigned as
follows on the client:

           Client    Server
             A:
             B:
             C:
             D:         A:
             E:         B:
             F:         C:

   You can copy and move files between the client
and server, and you can even delete and run
programs on the server as if they were on the
client by using the new drive letters.

SETTING UP THE CLIENT
Add up the total number of drives on both PCs, add
the following line to the bottom of your CONFIG.SYS
file and reboot the computer.  The following
example assumes five total drives:

   device=c:\dos\interlnk /drives:5


SETTING UP THE SERVER
Transfer the INTERSVR.EXE program from the client
to the server via floppy or use the following
procedure for a remote transfer:

  1. Cable PCs together.
  2. Type interlnk /rcopy on the client.
  3. Follow instructions.


ESTABLISHING THE LINK
  1. Cable PCs together.
  2. Type intersvr on the server.
  3. Type interlnk on the client.

   The server will display a status screen during
the link, but the client will return to the DOS
prompt so you can use the Copy command to transfer
files.  To review the new drive assignments, type
interlnk on the client.

   Note that the INTERLNK.EXE driver loaded by
CONFIG.SYS will take up memory each time you start
up the computer unless you remove that line.



DOS internal command
Command capability within DOS (COMMAND.COM) at all
times, such as Dir, Copy, Del, Ren, Type and Cls.
Contrast with DOS external command.



DOS Join
External command that assigns a drive to a
directory.  For example, if a program accesses
files on C only, but you want it to use files on B,
you can make the B drive appear to be a directory
of C.  Join creates the directory, but it must be
off the root.

    join b: c:\bdrive  join B to C:\BDRIVE
    join b: /d         unjoin B
    join               display join status


   Don't use Join with Assign, Subst, Backup,
Chkdsk, Diskcomp, Diskcopy, Fdisk, Format, Label,
Recover, Restore or Sys commands on a joined drive.



DOS key commands
The following keyboard keys can be used:

Ctrl-Alt-Del  Reset computer
 Ctrl-C or
  Ctrl-Break  Cancel operation
      Ctrl-S  Stop scrolling
      Ctrl-P  Print what's displayed (on/off)
 Shift-PrtSc  Print current screen
   F1 or -->  Redisplay last DOS entry a
               character at a time
          F3  Redisplay last DOS entry
          F6  Enter Ctrl-Z (end-of-file character)
   Alt-Digit  Enter ASCII character by value (use
               numeric keypad)



DOS Label
External command that names a disk (volume label).
The name can be up to 11 characters long, and it
can contain spaces.  To name the disk in A
1992 BUDGET, type:

             label a:1992 budget


                    Important!
Don't use Label on a network drive, or one that has
been ASSIGNed, JOINed or SUBSTituted.



DOS Lastdrive
Used in the CONFIG.SYS file, it specifies the
maximum number of drives that can be accessed.  The
following line in CONFIG.SYS sets the last drive
letter to M:

            lastdrive=m



DOS Loadfix
External command starting with DOS 5 that loads a
program beyond the first 64K of RAM, solving a
problem with some earlier programs.  As of DOS 5,
part of DOS can be loaded into high memory, thus
freeing up more lower memory.  Some programs cannot
run in this lower RAM and generate a "Packed file
corrupt" error.  "Packed" refers to an older method
for compressing EXE files, and this method had a
bug in it that prevents it from running in lower
RAM.

   The following example loads the program ABC
beyond the first 64K:

              loadfix abc



DOS Loadhigh
Internal command starting with DOS 5 that loads a
program into the UMA (upper memory area: 640K-1M)
in 386s and up.  It requires that the HIMEM.SYS and
EMM386.EXE memory managers be loaded and the
dos=umb command be present.

   If you have programs that need expanded memory
(EMS), the following three lines in CONFIG.SYS are
required to use Loadhigh.  The RAM parameter
informs EMM386 to manage both the UMA and expanded
memory:

   device=\dos\himem.sys
   device=\dos\emm386.exe ram
   dos=umb

   The following example uses the NOEMS parameter
to inform EMM386 to manage only the UMA and not
expanded memory:

   device=\dos\himem.sys
   device=\dos\emm386.exe noems
   dos=umb


   If the lines above are in your CONFIG.SYS file,
you can load programs into upper memory.  The
following example, which can be run from the DOS
prompt or in your AUTOEXEC.BAT file, loads POPUP
into the UMA.  If POPUP is too big to fit into an
available, contiguous memory block, it will load
below 640K.

   loadhigh popup  or  lh popup


   To load a device driver into upper memory, use
the Devicehigh command in CONFIG.SYS instead of
Device; for example:

    device=ansi.sys      below 640K
    devicehigh=ansi.sys  above 640K


   See DOS Dos and DOS Mem.



DOS Md
Internal command that makes a new directory.  Mkdir
is an alternate form.  To create the HARRY
directory off the root, type:

        C:\>md harry

           or type:

        C:\>mkdir harry


   See DOS directories and DOS abc's.



DOS Mem
External command starting with DOS 4.01 that
displays the amount of memory currently used and
free.  Type:

                 mem


   Starting with DOS 5, to display the contents of
memory by program name and show the available free
memory blocks (UMBs) in upper memory (UMA), type:

                 mem /c



DOS Memmaker
Starting with DOS 6, Memmaker is a utility that
optimizes memory on 386s and up by determining the
best order to load TSRs and drivers in the upper
memory area (UMA).  Memmaker may change device=
statements to devicehigh= in your CONFIG.SYS file
in order to load drivers in the UMA.  It may add
the loadhigh command to TSRs loaded in your
AUTOEXEC.BAT file to load them "high" as well.  To
run Memmaker, type memmaker.

   Choosing Express Setup will configure your
system automatically.  If certain TSRs and drivers
placed in the upper memory area cause conflicts,
you can exclude them by running Memmaker and
choosing Custom Setup or by adding their names to
the MEMMAKER.INF file.  Use the DOS Editor to open
MEMMAKER.INF and read the instructions.

   Choosing Custom Setup lets you specify further
optimization.  For example, if you use an EGA or
VGA monitor and not Super VGA, answer Yes to "Use
monochrome region for running programs."  If you
run only Windows applications, choose "No" to
"Optimize upper memory under Windows?"  See DOS
CHKSTATE.SYS and DOS SIZER.EXE.



DOS memory manager
Software that expands DOS' ability to manage more
than one megabyte of memory or to manage its first
megabyte more effectively.  Since the early days of
DOS, third party memory managers, such as QEMM and
386MAX, have used every trick in the book to move
TSRs and drivers out of the lower 640K and into the
384K upper memory area (UMA).

   Starting with DOS 5, DOS includes its own memory
managers.  HIMEM.SYS manages extended memory, and
EMM386.EXE manages expanded memory.  See DOS
HIMEM.SYS, DOS EMM386.EXE, DOS Memmaker, memory
allocation, PC memory map, EMS, XMS, VCPI and DPMI.
Also see "Operating Environment" in the PC
definition.

               DOS Memory Areas
   Conventional memory        0-640K
   Upper memory area (UMA)  640-1024K
   High memory area (HMA)  1024-1088K
   Extended memory         1024 and up
   Expanded memory         Bank switched memory



DOS Mirror
External command in DOS 5 that loads the Delete
Tracker memory-resident program (TSR).  It takes 6K
of RAM and monitors the files you delete.  It
doesn't provide a 100% guarantee, but it adds a
level of protection in case you have to undelete a
file later.

   In DOS 6, the Undelete command is used to
activate Delete Tracker.  Also, Delete Sentry is
even better (see DOS Undelete).  In DOS 6, Mirror
is not installed, but still resides on the DOS 6
Supplemental Disk.

   Also note "There's More to Mirror" below.

   Mirror creates and uses a MIRROR.FIL file and
also creates hidden MIRORSAV.FIL and PCTRACKR.DEL
files.  To automatically load it each time you
start up, place the command in your AUTOEXEC.BAT
file.  The following example tracks drives C and D:

          mirror c: d: /tc /td


   If you must unload Delete Tracker from memory,
type:

             mirror /u


   Use the Undelete command to undelete a file.
For example, to undelete SALES.DBF, type:

          undelete sales.dbf


THERE'S MORE TO MIRROR
Mirror is also used to save information about your
hard disk partition, directories and FAT table,
which could get corrupted in the event of a power
failure while writing to the hard disk.  This
command, initiated in DOS 5, has been relegated to
the DOS 6 Supplemental Disk.  Most DOS 6 books
don't even mention it, no doubt because data
recovery is not an exact science.

   One DOS 6 book that does elaborate on Mirror is
"MS-DOS 6, The Ultimate Guide for Experienced DOS
Users" by Minasi, Camarda, Stang and Ashton, ISBN
1-56205-132-6.

   Nevertheless, if you want to provide more
protection, you can run Mirror in both DOS 5 and
DOS 6 as follows.


SNAPSHOT YOUR PARTITION TABLE
To save vital data about your hard disk partition
in a file called PARTNSAV.FIL on a floppy disk,
type:

          mirror /partn


   Put the floppy in a safe place.  If you ever get
an "Invalid drive specification" on your valid
drive, the partition table may be corrupted.  To
restore your partion, find your PARTNSAV.FIL
floppy, and type (see warning below):

          unformat /partn


SNAPSHOT YOUR DRIVES DAILY
Take a snapshot of your hard disk directories and
FAT table every time you start up by placing the
Mirror command in your AUTOEXEC.BAT file.  A
MIRROR.FIL and a hidden MIRORSAV.FIL file will be
created.  For example, to snapshot drives C and D,
type:

             mirror c: d:


   The following procedure is used to restore your
C drive, providing you take daily snapshots that
have not become corrupted (see warning below):

 1. type unformat /partn  to restore partition
 2. insert PARTNSAV.FIL floppy disk
 3. insert bootable floppy to reboot
 4. type unformat c: /j  test outcome of step #5
 5. type unformat c: /u  to restore directories
                          and FAT


                 ! W A R N I N G !

You can try the above procedure if you absolutely
cannot get to your data at all, but there is no
guarantee you will succeed.  The success ratio of
users trying to do their own data recovery on badly
corrupted disks is most likely the reason Microsoft
has all but abandoned Mirror in DOS 6.

   However, if you experience problems, one of the
worst things you can do is to keep rebooting from
your hard drive, providing you can reboot.

   Although Mirror keeps a previous and current
snapshot, rebooting over and over can easily cause
you to take new snapshots of bad disks.  You're
better off rebooting from a bootable floppy.

   You're also far better off getting help from an
experienced data recovery expert, such as the tech
support rep from your hardware supplier or the
software company that you purchased data recovery
utilities from, such as Central Point Software,
Symantec or Fifth Generation.

   BETTER THAN ALL OF THIS IS TO MAKE BACKUPS OF
YOUR DATA REGULARLY.  Your vital data takes up less
room than you think.  Even if you have a 200MB
drive, you may be surprised to find out that most
of it is software, which you can re-install, even
if it takes several hours and is a royal pain.

   You may be able to store all your vital data on
less than a dozen floppies if you compress it with
PKZIP or some other backup or compression utility.
If you have DOS 6, see DOS MSbackup.


                    Important!
Don't run Mirror on any drive that has been
redirected with Join or Subst.  If using the Assign
command, do the Assign before executing Mirror.



DOS Mkdir
See DOS Md.



DOS Mode
External command that allows changes to a variety
of settings.  Following are common examples:


SET THE SERIAL PORT FOR COMMUNICATIONS
To set the first serial port to 2400 baud, No
parity, 8 bits and 1 stop bit, type:

         mode com1:2400,n,8,1


SET THE SERIAL PORT FOR THE PRINTER
To set the first serial port to 4800 baud and even
parity for a printer, type:

         mode com1:4800,e,,,p


REDIRECT THE PRINTER PORT
To redirect printing from the parallel port to
serial port #1, type:

     mode lpt1:=com1:      reroute data
     mode lpt1             cancel rerouting


CHANGE KEYBOARD SPEED
As of DOS 4.01, Mode changes keyboard repeat rate
and amount of delay before repeating.  To change
rate to 20 and delay to .5 sec, type:

        mode con rate=20 delay=2

Rates: 1-32  Delays: 1-4 (.25 .50 .75 1.0 sec.)


LEFT HANGING IN 40-COLUMN MODE?
If a program leaves you in 40-column mode (extra
wide text characters on screen), you can switch
back to 80 column mode with

              mode 80



DOS Move
External command starting with DOS 6 that moves a
file to a new location (it copies first, then
deletes the source file).  The syntax is like the
Copy command; however, you must always enter a
target destination.  That means even though you are
already in the directory you want to move the file
into, you still have to state it.  For example, to
move file ABC from the B: drive into the UTILITY
directory, type:

      C:\UTILITY>move b:abc \utility

   Note: The C: drive is implicit, but the \UTILITY
directory is not and must be explicitly stated even
though you are already in it.



DOS MSAV
(DOS MicroSoft AntiVirus)  Starting with DOS 6,
MSAV is a menu-driven utility that scans memory and
disk for viruses.  To run it, type msav.  To run
the program automatically each time you start the
computer, add one of the following lines in your
AUTOEXEC.BAT file:

     msav /p     scan memory and drives
     msav /p /l  limit scan to local drives
                  if network drives are used

   A memory resident antivirus utility is also
included that will continually check for viruses.
To load it, type vsafe.  To unload it, press Alt-V
and Alt-U.

                 For Windows Users
A Windows version of MSAV.EXE is included with DOS
6 called MWAV.EXE.  This is run from an icon in
Windows, which is installed in the Microsoft Tools
Program Group.



DOS MSbackup
Starting with DOS 6, the MSbackup program provides
a menu-driven backup and restore utility for floppy
disks that contains its own help.  To run it, type
msbackup.  The first time you run it, it will ask
you to perform a compatibility test to adjust to
your computer's hardware configuration.  See backup
types.

                 For Windows Users
A Windows version of MSBACKUP.EXE is included with
DOS 6 called MWBACKUP.EXE.  This is run from an
icon in Windows, which is installed in the
Microsoft Tools Program Group.



DOS MSD
(DOS MicroSoft Diagnostics)  Starting with DOS 6,
MSD is a diagnostic utility that reports the
current hardware and software configuration of your
system.  Type msd to load the program.



DOS multiple startups
See DOS startup options.



DOS online help
Starting with DOS 5, online help is available from
the DOS prompt.  For example, in DOS 5, to see a
summary of syntax and switches for the Xcopy
command, type:

         help xcopy  or  xcopy /?

   To display a list of all DOS commands, type help
by itself.

   Starting with DOS 6, there are two kinds of
help.  Typing help loads a help system with
hypertext links to related commands.  To load the
system and immediately go to a specific command,
type the name of the command; for example, help
xcopy.  Typing xcopy /? will generate a summary
help screen as it does in DOS 5.



DOS optimizing memory
See DOS memory manager and DOS Memmaker.



DOS Path
Internal command that sets up a search path to one
or more directories.  If DOS can't find a program
in the current directory, it looks in the path.

   For example, the DOS directory, which holds
DOS's external commands (Format, Xcopy, etc.) is
always put in the path so you can use the commands
from whichever directory you happen to be in.

   The path command is placed into the AUTOEXEC.BAT
file, which is executed on startup.  The following
example sets up a search path to C:\(root), C:\DOS
and E:\UTILITY.  Directory names are separated with
a semicolon (;):

           path c:\;c:\dos;e:\utility


   To add the C:\123 directory to the example
above, you would add  ;c:\123  to the end of the
line, resulting in:


     path c:\;c:\dos;e:\utility;c:\123


   See DOS AUTOEXEC.BAT.



DOS pipes
See DOS filters & pipes.



DOS Print
External command that prints text files or pre-
formatted word processing files in the background
allowing you to continue work on something else.
To print files ABC and XYZ, type:

                print abc xyz


   To print all files with a .TXT extension, type:

                 print *.txt


   Specified files are placed in a queue and
printed one after the other.  Print queue commands
are:

       print      display status
       print /t   cancel all printing

   To increase the number of files allowable in the
queue from 10 (default) to 20 (max 32), type:

            print *.txt /q:20


                Other Print Options
You can also print text files with DOS's Type
command (see DOS Type).  To display the current
text screen, press Shift-Print Screen.  In
addition, to print directory lists, press Ctrl-P
before typing the Dir command.  The text on screen
will be sent to the printer.  Press Ctrl-P again
when you're done.



DOS prompt
Message DOS displays when ready to accept user
input.  The default prompt (C>, D>...) displays the
current drive and doesn't say which directory
you're in.  Since this can be changed, PCs are
usually configured with the following line in the
AUTOEXEC.BAT file, which creates the prompt used in
our examples:
                  prompt $p$g

 Prompt
  Code      Displays
   $p   Current drive/directory
   $g   >
   $l   <
   $b   |
   $$   $
   $n   Default drive
   $t   Time
   $d   Date
   $v   DOS version
   $_   Go to next line

   The command, prompt XYZ Company$_$d  $p$b
would generate the following DOS prompt:

          XYZ Company
          Tue 04-30-1993  C:\|



DOS RAM disks
RAM disks simulate a disk drive in memory and
provide fast retrieval of programs and data.  If
operations are disk intensive, they can be speeded
up using RAM disks; for example, copying files
within a RAM disk is almost instantaneous.
However, some operations may benefit only slightly.
You'll have to try it to find out.

   RAM disk contents are lost if the power fails or
the computer is turned off, thus, data updated in
RAM disks should be periodically copied to real
disks.  RAM disks take on the next available drive
letter.

   To copy files into RAM disks on startup, put
Copy commands in your AUTOEXEC.BAT file.

   RAM disks are activated by adding a line in
CONFIG.SYS.  The following examples assume that
VDISK.SYS and RAMDRIVE.SYS are in the root
directory.

 Number of directory entries ┐
 Sector size (128-256-512)─┐ │
 RAM disk size (KBytes)┐   │ │       Install
                       │   │ │       RAM disk in
                       │   │ │       this memory:
   DOS 3.x
   device=vdisk.sys  100 512 5       conventional
   device=vdisk.sys 2000 512 150 /e  extEnded
   device=vdisk.sys 1000 512 50 /a   expAnded (EMS)

   DOS 4.01 and up:
device=ramdrive.sys  100 512 5       conventional
device=ramdrive.sys 2000 512 150 /e  extEnded
device=ramdrive.sys 1000 512 50 /a   expAnded (EMS)

   Starting with DOS 5, 4096K is the maximum disk
size for one RAMDRIVE.SYS disk.  For multiple RAM
disks, use multiple DEVICE= lines.

   Use 128 sector size for small files; 512 for
large ones.  The default is 128 in VDISK and 512 in
RAMDRIVE.  If you leave this out, you can't include
a directory entry number.

   Number of directory entries is 2 to 512 for
VDISK; 2 to 1024 for RAMDRIVE.  The default is 64.


                       Note!
In order to use extended or expanded (EMS) memory
for your RAM disk, you must load the extended
memory or EMS driver from CONFIG.SYS before loading
your RAM disk driver.  See DOS HIMEM.SYS and DOS
EMM386.EXE.



DOS RAMDRIVE.SYS
See DOS RAM disks.



DOS Rd
Internal command that removes a directory.  Rmdir
is an alternate form.  Directories must be empty
first, and the command must be entered from the
previous level or from a non-related directory.  To
remove the HARRY directory directly off the root,
type:

       C:\>rd harry

          or type:

       C:\>rmdir harry

   HARRY can also be removed while in another
directory by stating the full path to it; for
example:

       C:\WORK>rd \harry


   For DOS 6 Users: See DOS Deltree to remove
directories that contain files and subdirectories.

   See DOS directories and DOS abc's.



DOS Recover
External command up to but not including DOS 6 that
reads data on disks that are physically damaged.
It reads files a sector at a time recovering
whatever data it can and puts the recovered files
into the root directory.  You can recover an entire
disk by specifying only the drive letter, but
recovered files are renamed starting with
FILE0001.REC, and you won't know which is which.
It is best to recover one file at a time; for
example:

         recover a:sales.dbf



DOS redirection
Redirecting keyboard input and screen output (see
DOS Mode to redirect the printer port).  Normally,
DOS gets input from the keyboard and displays
output on screen.  However, you can redirect input
from the keyboard to another file and redirect
output from the screen to the printer or a disk
file.  The symbols are:

   <   Redirect input
   >   Redirect output to a new file
   >>  Redirect output to an existing file

   For example, to redirect the output of a Dir
list to the printer, type:

                 dir > prn


   PRN is the name of the parallel port (see DOS
device names).

   The following example redirects input to sort a
text file named FIRST into alphabetical order and
display it on screen:

               sort < first


   Using both input and output redirection, the
sorted file can be copied into a new file called
SECOND.  Think of < as "input from," and > as
"output to."

            sort < first > second


   Redirection can be used with the Pipe command,
which funnels output of one command into another.
The following example, using the pipe's vertical
bar symbol, funnels output of the Dir list to the
Sort filter before redirecting it to a disk file
called NEWLIST:

            dir | sort > newlist

   Since the pipe and redirection symbols act as
word separators, you could type the above command
as:

            dir|sort>newlist


   See DOS Sort.



DOS Rem
Remarks statement in DOS batch files and CONFIG.SYS
file.  For example, the following REM line is for
documentation purposes only:

  rem   the following driver activates the mouse
  device=mouse.sys


   You can bypass the command on the line by adding
REM at the beginning.  In the following example,
MOUSE.SYS will not be loaded:


        rem    device=mouse.sys



DOS Rename
Internal command that changes the name of one file
at a time.  To change from ABC.DOC to XYZ.DOC,
type:

          rename file.abc file.xyz  or
             ren file.abc file.xyz

   Put a space between words and names.



DOS Replace
External command (DOS 3.3 and up) that copies files
that have been updated.   The /u checks time and
date and copies only files from the source
directory that are newer than the files in the
target directory.  To update .TXT files on drive B,
type:

           replace *.txt b: /u



DOS restoring disks
See DOS Recover, DOS Unformat, DOS Undelete, DOS
Backup/Restore and "There's More to Mirror" in DOS
Mirror.



DOS Rmdir
See DOS Rd.



DOS root
First directory on a disk.  See DOS abc's and root
directory.



DOS Set
Internal command that sets environment variables,
which are stored values used by DOS as well as many
applications.  PATH, APPEND, COMSPEC and PROMPT are
actually environment variables too.

   An environment variable is often used to
indicate where temporary files are stored, such as
in the following example:

          set temp=c:\dos


   This Glossary softwware also uses an environment
variable.  For example, if the Glossary is shared
on a network server, lookup history will be common.
If you want to review tomorrow what you looked up
today, and not what your neighbor looked up, you
have to create a private file for lookup history
and tell the Glossary software where it is.

   Copy GLOSS.ABC from the network server into your
local machine.  Then add a line in your
AUTOEXEC.BAT file that sets the Glossary
environment variable GLOSSPATH to your local
machine.  For example, if you stored a copy of
GLOSS.ABC in your C:\UTILITY directory, add the
following line in your AUTOEXEC.BAT file:

          set glosspath=c:\utility

   To display the current values for all the
environment variables, type:

                  set


                    Important!
In other DOS commands, spaces after the equals sign
don't matter.  With Set, they do.  The command set
state = IL would make the first character of the
STATE variable a blank (" IL").



DOS Setver
External command starting with DOS 5 that updates a
version table containing names of programs and the
DOS version number they need to run under.
Programs may test version numbers and function
differently as a result (all DOS's are not the
same), but some programs didn't plan on 5 as a
future number.  This command "fakes them out" by
supplying them with the version number they need.

   A list of known programs in the version table is
included, and the DOS install program puts a
device=setver.exe line in the CONFIG.SYS file,
which loads the version table.

   To see the current list, type:

             setver


   You can add and delete programs to the list.  To
set the program OLDPROG.EXE to Version 3.3, type:

          setver oldprog.exe 3.30


   To remove it from the list, type:

          setver oldprog.exe /delete



DOS Share
External command that provides file sharing and
file locking in a network environment.  To load
Share, type:

                 share


Starting with DOS 5, load SHARE.EXE in the
CONFIG.SYS file with the Install command:

           install=\dos\share.exe


           Important for DOS 4.01 Users!
In DOS 4.01, which increased disk handling from
32MB to 512MB, Share lets applications written for
compatibility with DOS 1.0 work properly with disks
over 32MB.  You'll never know if you've got such an
application, so if you're running large disks under
DOS 4.01, be sure to put Share in your
AUTOEXEC.BAT.  Note: Share is not used this way as
of DOS 5.  See DOS AUTOEXEC.BAT and DOS FCBs.



DOS shell
Shells provide the user interface in DOS, or the
way you interact with the system.  COMMAND.COM is
the program that provides the command-driven user
interface described in this tutorial.  Other shells
can be substituted for COMMAND.COM, by adding the
Shell command in the Config.sys file; for example:

            shell=xyzmenu.com


   As of DOS 4.01, an optional user interface
called DOSSHELL is provided that lets you command
DOS with menus.  The 4.01 install program (Select)
creates the DOSSHELL.BAT batch file, which loads
DOSSHELL when executed.  Type:

            dosshell


   As of DOS 5, the menu-driven user interface has
been completely revised, and the DOSSHELL.COM is
used to start it.  Run it by typing:

      dosshell /t    text (character) mode
      dosshell /g    graphics mode
      dosshell /bw   black & white (laptops)



DOS SIZER.EXE
Utility used by Memmaker exclusively during its
optimization process that checks the size of each
program loaded.  The command is placed into
CONFIG.SYS and AUTOEXEC.BAT and then removed when
Memmaker is finished.  See DOS CHKSTATE.SYS.



DOS SmartDrive
Disk cache software included with DOS and Windows
starting with DOS 4.01 and Windows 3.0.  SmartDrive
speeds up hard disk performance by reserving a
block of memory and reading and writing larger
chunks from the disk (see cache).  There are two
versions of SmartDrive depending on DOS and Windows
version.

       File name        DOS     Windows
     SMARTDRV.SYS    4.01, 5      3.0
     SMARTDRV.EXE        6        3.1


           DOS 4.01 & 5 and Windows 3.0
The SMARTDRV.SYS driver is loaded from CONFIG.SYS,
and its default setting uses 256K of extended
memory, for example:

     device=c:\dos\smartdrv.sys


   You can reserve more memory by adding the number
of K's to the line; for example, to reserve two
megabytes, type:

 device=smartdrv.sys 2048     extended memory
 device=smartdrv.sys 2048 /a  expAnded memory


                       Note!
In order to use extended or expanded (EMS) memory
for your disk cache, you must load the extended
memory or EMS driver from CONFIG.SYS before loading
SMARTDRV.SYS.  See DOS HIMEM.SYS, DOS EMM386.EXE
and cache.


               DOS 6 and Windows 3.1
The SMARTDRV.EXE program is loaded from the
AUTOEXEC.BAT file.  If a SCSI drive was detected on
installation, SMARTDRV.EXE is also loaded from
CONFIG.SYS as in the following example:

             No SCSI drive detected
    c:\dos\smartdrv        in AUTOEXEC.BAT

              SCSI drive detected
    c:\dos\smartdrv        in AUTOEXEC.BAT
    CONFIG.SYS:
    device=c:\dos\smartdrv.exe /double_buffer


   To determine if the device= line can be removed
from CONFIG.SYS, type smartdrv (after SMARTDRV has
been loaded in AUTOEXEC.BAT).  If every line under
the column "buffering" reads NO, you can remove the
line.

   SmartDrive's default setting uses 1 to 2MB of
extended memory depending on the amount of RAM
installed.  You can reserve more memory by adding
the number of K's to the line.  The following
AUTOEXEC.BAT example reserves 4MB (4096KB) of
extended memory for DOS applications.  The second
number (2048KB) limits Windows to reducing the
cache size to 2MB.  After Windows is exited, the
cache is restored to 4096K.

        c:\dos\smartdrv 4096 2048


                       Note!
In order to use extended memory for your disk
cache, you must load the extended memory driver
from CONFIG.SYS before loading SMARTDRV.SYS.  See
DOS HIMEM.SYS.



DOS Sort
External command that sorts a text file or Dir list
into alphabetical order.  Lines in the text files
must be uniform and columns (fields) must line up,
such as the text within the BBS definition in this
Glossary.

   The following example sorts the text file ABC
(starting at column 1), creating ABC2.  The < means
"input from," and the > means "output to."

              sort < abc > abc2


   Let's assume that the text in our BBS definition
is stored in a file called BBS.  The following
examples create a new file in telephone number
sequence.  They use the /+ switch to indicate that
the telephone numbers begin in column 40 (character
position 40):

  sort /+40 < bbs > bbs2     a-z order
  sort /+40 /r <bbs> bbs2    z-a order (reverse)


   To sort the file and print it without saving the
results, type:

       sort /+40 < bbs > prn


   To display a sorted Dir list, type:


                dir | sort


   You can sort Dir lists by file characteristics.
Use the /+ switch to begin the sort on other than
column one of the line:

      dir | sort /+10   by extension
      dir | sort /+14   by file size
      dir | sort /+23   by month
      dir | sort /+29   by year


   To write the sorted Dir list to a disk file,
type:

     dir | sort > xyz   create new XYZ file
     dir | sort >> xyz  add to existing XYZ file


   To append the current sorted directory list to
the end of a file called XYZ, type:

              dir | sort >> xyz


                       Note!
As of DOS 5, additional sorting options for Dir are
provided (see DOS Dir).



DOS Stacks
CONFIG.SYS command that reserves memory for
hardware interrupts.  The Stacks command has become
more of an issue with Windows, as mouse interrupts
must be stored until Windows finishes its current
operation and can service them.  The stacks=9,256
line is placed in the CONFIG.SYS file by Windows
3.1's install program.  This allocates nine stacks
of 256 bytes taking up 2,304 bytes of conventional
memory.

   Some computers save memory for this function and
can operate without additional stacks (stacks=0,0);
however, Microsoft recommends that if your PC hangs
up when you move your mouse, try the following
entries in CONFIG.SYS, one at a time:

           stacks=12,128
           stacks=9,256
           stacks=12,256
           stacks=0,0


   The first number in the command allocates the
number of stacks from 8 to 64.  The second number
is the size of the stack in bytes from 32 to 512.
The stacks=0,0 command allocates no stacks.



DOS startup options
Starting with DOS 6, there are multiple startup
options for the CONFIG.SYS and AUTOEXEC.BAT files.
You can bypass them, decide which lines to execute
or set up multiple configurations for selection at
startup.


                    Clean Boot
You can "boot the computer clean" by bypassing the
CONFIG.SYS and AUTOEXEC.BAT files.  This is useful
if you want to test something without any TSRs or
drivers loaded.  In addition, if you changed
CONFIG.SYS or AUTOEXEC.BAT and the computer locks
up, you can still boot from the hard disk rather
than having to boot from a floppy.

   To clean boot, press and release F5 as soon as
the "Starting MS-DOS..." message appears on screen.


             Execute a Line at a Time
If a new driver or TSR causes problems, you have
the option of bypassing it at startup.  This is
helpful for testing purposes until you change the
CONFIG.SYS file permanently.  To select this
option, press and release F8 as soon as the
"Starting MS-DOS..." message appears.  Each line in
CONFIG.SYS will be displayed for confirmation.
Press Y to execute or N to bypass.  After
CONFIG.SYS is read, you will be prompted to run
AUTOEXEC.BAT in its entirety or to bypass it.


              Multiple Configurations
You can create multiple configurations within the
same CONFIG.SYS and AUTOEXEC.BAT files.  If there
isn't enough memory to load the TSRs and drivers
for all the applications in a PC, or if one TSR or
driver conflicts with another, users typically set
up separate CONFIG.SYS and AUTOEXEC.BAT files to
run different sets of software.  In order to
activate them before DOS 6, the current CONFIG.SYS
and AUTOEXEC.BAT are renamed and the required set
is given those names.  DOS 6 lets you place
multiple configurations in CONFIG.SYS and in
AUTOEXEC.BAT and prompts you for your choice at
startup.

   To do this, create a menu in CONFIG.SYS that
defines two or more configuration blocks.  The
following example simulates stand-alone and network
versions of CONFIG.SYS.  The optional text "Select
this for..." next to the MENUITEM= lines is used by
DOS as the menu option at startup.  If no text is
placed to the right of the line, then the name of
the configuration block is used as the menu option.

   The menu and configuration block headers must be
enclosed in left and right brackets ([ ]).

 [menu]
 menuitem=nonet   Select this for no network.
 menuitem=net     Select this for network.
 menudefault=nonet,5  <- default to "nonet" in 5
                         seconds if no choice made

 [nonet]             <- configuration block "nonet"
 device=c:\driver1.sys  <-statements that pertain
 device=c:\driver2.sys  <-to "nonet"

 [net]               <- configuration block "net"
 device=c:\netdrivr.sys

 [common]            <- common configuration block
 files=40               <-statements that pertain
 buffers=20             <-to all configurations
 etc.

   You may use an include= line in a configuration
block that includes all the items in another
configuration block.

   Important!  Be sure to put the [common]
configuration block last as many install programs
add lines to the CONFIG.SYS file.


CONFIGURING AUTOEXEC.BAT
You can create multiple configurations in
AUTOEXEC.BAT, but they must correspond to the
CONFIG.SYS configuration blocks.  To do this, add
the goto %config% line at the end of all common
statements in AUTOEXEC.BAT; for example:

   all common lines in AUTOEXEC.BAT
   goto %config%

   :nonet             <- be sure to use colon
   all statements for "nonet"
   goto end

   :net
   all statements for "net"
   goto end

   :end               <- last line in AUTOEXEC.BAT



DOS Subst
External command that creates a virtual drive and
provides a shortcut for referencing long path
names.  For example, to reference C:\KAREN\BUDGETS
with drive K:, type:

       subst k: c:\karen\budgets


   If you were in the root, you could display
MYFILE by typing:

           C:\>type k:myfile

   instead of

     C:\>type c:\karen\budgets\myfile


   To cancel the K disk, type:

            subst k: /d


                    Important!
The last drive letter is normally E.  See DOS
Lastdrive.  Do not use Assign, Backup, Chkdsk,
Diskcomp, Diskcopy, Fdisk, Format, Join, Label,
Recover, Restore and Sys on a virtual drive.



DOS switch
Code that modifies a command.  DOS switches use a
forward slash (not backslash) followed by some
letter, digit or code.  For example, the /w changes
the Dir command to list "wide" across the screen
instead of in a column:

                 dir /w



DOS switching directories
See DOS Cd and DOS directories.



DOS Sys
External command that transfers hidden DOS system
files.  To make a bootable diskette, copy DOS from
the hard disk to a floppy with the Sys command.
The COMMAND.COM file must also be copied, which,
previous to DOS 5, must be done manually.  Starting
with DOS 5, COMMAND.COM is copied automatically by
the Sys command.

 Previous to DOS 5
  C:\>sys a:               copy system

 Starting with DOS 5
  C:\>sys a:               copy system
  C:\>copy command.com a:  copy COMMAND.COM


   DOS is made up of IBMBIO.COM and IBMDOS.COM or
IO.SYS and MSDOS.SYS hidden system files along with
COMMAND.COM.  Hidden files can be listed with the
Attrib command starting with DOS 5 or a utility
such as Norton's File Attribute program.



DOS Sys files
DOS extension used with driver programs.  See DOS
CONFIG.SYS.



DOS system file
DOS file that contains the fundamental part of DOS
(the kernel).  See DOS Sys.



DOS Task Swapper
Starting with DOS 5, you can run multiple
applications and switch between them.  Do the
following:

  1. Load DOSSHELL.COM by typing dosshell.

  2. To see your active tasks on screen, select
     Program/File Lists from the View menu
     (Alt V F).

  3. Select Enable Task Swapper from the
     Options menu (Alt O E).  Note: This will
     stay in effect for future sessions.

  4. Run the first program either by selecting Run
     from the File menu (Alt F R) and typing in
     the program's name, or by selecting it
     from the directory list on screen (double
     click it or highlight and press Enter).
     After the program is running, press Ctrl-Esc
     to return to the Shell.

     You can alternatively put the program into
     the Active Task List without running it, by
     selecting the program name from the on-screen
     directory list and pressing Shift-Enter.

  5. Repeat step 4 for each program.

  6. To switch between active programs, hold down
     the Alt key and press Tab until you see the
     name of the program you want at the top of
     the screen.  Then release Alt.  To switch
     between the two last programs, press Alt-Tab.

     You can also select a program from the Active
     Task List at the bottom of the Shell screen.

   There are a variety of ways to switch between
active tasks.  Look up Keyboard, Active Task List
Keys from the Shell's Help menu.



DOS text file
Text file that does not contain any proprietary
coding schemes.  Batch files and source language
programs are examples.  It contains only ASCII
characters and has a CR/LF (carriage return/line
feed) code at the end of each line.  Text files are
read by text editors as well as word processors
with "ASCII" or "text" input options.



DOS Time/Date
Internal commands that set the system time and date
and update the internal battery-powered clock.
Versions previous to 3.3 do not set the internal
clock.  A separate setup program is used.

       time           display time
       time 14:30     set to 2:30pm

       date           display date
       date 12-11-92  set to 12-11-92


TO UPDATE A FILE'S TIME AND DATE
To give a file a current time and date without
changing it, use the Copy command.  For example, to
update XYZ.BAT, type:

      copy /b xyz.bat+,,

   Be sure to add the plus, comma, comma after the
file name.  The /b ensures that no change is made
to the file.



DOS Tree
External command that displays a list of the
subdirectories in the current directory.  To
display a directory tree, type:

                tree


   To display files names and subdirectories, type:

                tree /f



DOS tutorial
See DOS abc's.



DOS Type
Internal command that displays the contents of text
files.  To display the contents of XYZ.BAT, type:

                type xyz.bat


   Type lets you view only text files (batch
files).  If garbage appears on screen, the file is
a program or data file, not straight text.

   To print the file, redirect Type's output to the
printer:

                type xyz.bat > prn



DOS Undelete
Prior to DOS 5, bringing a file back that has just
been deleted requires an undelete utility such as
found in Symantec's Norton Utilities, Central
Point's PC Tools or Fifth Generation's Mace
Utilities.

   Starting with DOS 5, an undelete command is
provided.  For example, to restore VITAL.TXT after
having deleted it, type the following and follow
the prompts:

             undelete vital.txt


   If you don't mention a file name, Undelete will
undelete all deleted files, prompting you one at a
time.


DELETE TRACKER
Starting with DOS 5, the Delete Tracker option
provides an extra level of protection in case you
have to undelete a file.  This is activated with
the Mirror command.  If you use DOS 5, see DOS
Mirror.  If you use DOS 6, read the following.

   In DOS 6, Delete Tracker is activated with the
Undelete command.  It's not as much protection as
Delete Sentry (see below), but you would use this
if you have little room left on your hard disk.

   Tracker takes up 13K of RAM and creates hidden
MIRORSAV.FIL and PCTRACKR.DEL files.  To
automatically load Tracker on startup, place the
command in your AUTOEXEC.BAT file.  The following
example tracks drives C and D:

          undelete /tc /td


USE DELETE SENTRY FOR MAXIMUM PROTECTION
In DOS 6, the Delete Sentry intercepts the files
you delete and actually moves them to a hidden
\SENTRY directory, renaming them with coded file
names.  Sentry will purge (really remove) the files
after seven days or when 20% of the hard disk is
used up with deleted files and it needs room for
more newly-deleted files.  Sentry also creates a
hidden CONTROL.FIL file in the \SENTRY directory.

   Like Tracker, Sentry will take up 13K or RAM.
To automatically load Sentry on startup, place the
command in your AUTOEXEC.BAT file.  The following
example activates Sentry for drives C and D:

         undelete /sc /sd


   If you must remove Tracker or Sentry from
memory, type:

         undelete /u


EDITING UNDELETE.INI
The first time Sentry is loaded, it creates an
UNDELETE.INI configuration file in the \DOS
directory that can be edited with a text editor.

   To change the drives Sentry intercepts, you can
add or delete DRIVELETTER= lines.  For example, to
bypass protection on floppy drives, delete the A=
or B= lines.

   To change when Sentry purges deleted files from
seven to four days, change days=7 to days=4.

   To change the maximum amount of space Sentry
uses to hold deleted files from 20% to 10%, change
percentage=20 to percentage=10.

   UNDELETE.INI excludes certain types of files
from being intercepted, such as temporary files.
It also excludes .IMG files.  If you work with .IMG
files and want protection for them, remove -*.IMG,
from the sentry.files= line.  You may wish to
exclude other types of files; for example, .BAK
files.  To exclude .BAK files, add ,-*.BAK to the
end of the sentry-files= line.

   Once UNDELETE.INI is created, you can also load
Sentry with undelete /s or undelete /load.


                 For Windows Users
A Windows version of Undelete is included with DOS
6 called MWUNDEL.EXE.  This is run from an icon in
Windows, which is installed in the Microsoft Tools
Program Group.

   If you're in Windows, use MWUNDEL.EXE first.  It
also lets you undelete directories, which you
cannot do with Undelete for DOS.  However, if you
cannot undelete a file with MWUNDEL.EXE under
Windows, go to the DOS prompt and try to undelete
it with Undelete.



DOS Unformat
External command starting with DOS 5 that restores
a formatted disk to its previous contents,
providing it was formatted under DOS 5 without the
/S switch.  The /S switch bypasses saving unformat
information during the format process (see DOS
Format).

   Unformatting is not guaranteed.  However, you
can find out if you can unformat the disk before
doing it.  For example, to test the disk in drive
A, type:

             unformat a: /test


   To unformat the disk in drive A, type:

               unformat a: /u


   Also see DOS Mirror for additional ways Unformat
is used in data recovery.



DOS upgrading
Starting with DOS 5, Microsoft provides upgrade
packages that make it easy to upgrade a PC that has
a previous version of DOS installed on it.  The
install program records data on "uninstall" disks
during the conversion.  If the new version doesn't
work properly, you can revert to the previous one.
To install the DOS 5 or DOS 6 upgrade:

  1. Start computer as usual.
  2. Have one blank high-density floppy or two
      blank low-density floppies handy (formatted
      or unformatted).
  3. Insert disk 1 into drive A or B.
  4. Type a:setup or b:setup.



DOS upper memory
See UMA and UMB.



DOS/V
Japanese version of DOS that supports two-byte-long
characters for handling the Kanji character set.
It can switch between English and Japanese and is
geared for 286s and up with VGA graphics.  Backed
by IBM Japan and the OADG.  In Japan, NEC is the
major personal computer vendor with its PC-9801
series.



DOS VDISK.SYS
See DOS RAM disks.



DOS Ver
Internal command that displays the DOS version.
Type:

                   ver



DOS Verify
Internal command that tests each write operation by
reading it back.

      verify on     turn on
      verify off    turn off
      verify        display status



DOS versions
Like most software, DOS improves with age:

Version      Major new features
  1.0  1981  8-sector 160KB floppy (SS).
  1.05       Bug fix.
  1.1  1982  8-sector 320KB floppy (DS).
  2.0  1983  10M hard disk, 9-sector 360KB floppy,
              directories, more batch commands.
  2.1  1983  PCjr cartridge support and bug fixes.
  3.0  1984  20MB hard disk, 1.2MB floppy, VDISK,
              PATH, new commands.
  3.1  1985  Network support, bug fixes.
  3.2  1986  720KB floppy, new commands.
  3.3  1987  1.44MB floppy, FDISK partitions.
  4.0  1988  Menu and mouse support (DOS shell),
              improved commands, EMS support,
              512MB hard disks.
  4.01 1988  Bug fix (4.0 rarely used).
  5    1991  Major upgrade: new DOS shell, ability
              to use high memory, task swapping,
              online help, new text editor,
              2GB hard disks, 2.88MB floppies,
              enhanced commands.
  6    1993  Includes built in disk compression
              and various utilities for antivirus,
              backup, undelete and file transfer.



DOS Vol
Internal command that displays the name of the
current drive (volume).  Type:

                   vol



DOS Vsafe
See DOS MSAV.



DOS/VSE
See VSE.



DOS wild cards
Wild cards are symbols that let you reference
groups of related files.  As in card games, wild
cards take on any value.  DOS wild cards are the
"*" and "?."


                 The Asterisk (*)
The asterisk takes the value of any number of
characters; for example, if you typed in:

                  dir gloss*

   GLOSS1, GLOSS10 and GLOSSARY files would be
selected:



   To delete all files with a TXT extension, type:

                  del *.txt


   To delete all the files in the current
directory, type:

                  del *.*



               The Question Mark (?)
The question mark matches any single character.
For example, ?GLOSS would find 1GLOSS, 2GLOSS and
XGLOSS.  Note that *GLOSS is not valid for this.


   To copy CHP files that begin with CO, type:

              copy CO*.CHP a:


   To list files that begin with CO and have an
extension that begins with D, type:

              dir CO*.D*



                       Tip!
The dot is a shortcut for *.*.  The following
commands both copy all files to the B drive:

              copy *.* b:

              copy . b:



DOS Xcopy
External command starting with DOS 3.2 that copies
files and subdirectories.  The following examples
copy from the root directory on C to the D drive:

 C:\>xcopy *.* d:      all files in the root

 C:\>xcopy *.* d: /s   all files and subdirectories
                        that contain files

 C:\>xcopy *.* d: /s /e   all files and all
                           subdirectories (whether
                           empty or not)


   To be prompted each time Xcopy copies a source
file, add /p:

          xcopy *.* d: /s /e /p


   To be extra sure the copy is correct, add the /v
switch, which compares the new file with the old
one; for example:

          xcopy *.* d: /v


   Xcopy can copy files and create a new directory
at the same time.  The following example creates
the NEW directory and copies all the files from the
OLD directory:

       C:\OLD>xcopy *.* \new


   Use Xcopy's /m switch to back up only files that
have been changed since the last time they were
Xcopied.  The following example backs up all files
onto the B disk:


          xcopy *.* b: /m



                       Note!
In versions previous to DOS 5, Xcopy copies hidden
and system files.  Starting with DOS 5, you must
remove the hidden and system attributes with Attrib
first.



DOS \
See DOS backslash.



DOSmark
Unit of performance based on Ziff-Davis' PC Labs
tests.  It rates a PC's ability to run DOS
applications, which is a composite of CPU, memory,
disk and video tests.  See Winmark.


Dosshell
See DOS shell.


dot
(1) Tiny round, rectangular or square spot that is
one element in a matrix, which is used to display
or print a graphics or text image.  See dot matrix.

(2) A period; for example, V dot 22 is the same as
V.22.


dot addressable
Ability to program each individual dot on a video
display, dot matrix printer or laser printer.


dot chart
Same as scatter diagram.


dot gain
Increase in size of each dot of ink when printed
due to temperature, ink and paper type.


dot matrix
Pattern of dots that form character and graphic
images on video screens and printers.  Display
screens use a matrix (rows and columns) of dots
just like TVs.  Serial printers use one or two
columns of dot hammers that are moved across the
paper.  Laser printers "paint" dots of light a line
at a time onto a light-sensitive photographic drum.

   The more dots per square inch, the higher the
resolution of the characters and graphics.


dot matrix printer
Printer that forms images out of dots.  The common
desktop dot matrix printer uses one or two columns
of dot hammers that are moved serially across the
paper.  The more dot hammers used, the higher the
resolution of the printed image.  24-pin dot matrix
printers produce typewriter-like output.


dot pitch
Distance between a red (or green or blue) dot and
the closest red (or green or blue) dot on a color
monitor (typically from .28 to .51mm; large
presentation monitors may go up to 1.0mm).  The
smaller the dot pitch, the crisper the image.  A
.28 dot pitch means dots are 28/100ths of a
millimeter apart.  A dot pitch of .31 or less
provides a sharp image, especially on text.

   Dot pitch measurements between conventional
tubes and Sony's Trinitron tubes are roughly, but
not exactly equivalent.  Sony's CRTs use vertical
stripes, not dots, and its measurement is the
distance between stripes, not the diagonal distance
between dots.


double buffering
Programming technique that uses two buffers to
speed up a computer that can overlap I/O with
processing.  For example, data in one buffer is
being processed while the next set of data is read
into the second buffer.


double click
To press the mouse button twice in rapid
succession.


double density
Twice the capacity of the prior format.
Yesterday's double density can be today's low
density (see DD).


double dots
See DOS ...


double precision
Using two computer words instead of one to hold a
number used for calculations, thus allowing twice
as large a number for more arithmetic precision.
Contrast with single precision.


double scan CGA
Hardware circuit that improves CGA resolution.


double sided disk
Floppy disk that is recorded on both of its sides.


double strike
Printing a character twice in order to darken the
image.


double twist
Same as supertwist.


double word
Twice the length of a single computer word.  A
double word is typically 32 bits long.  See word.


DoubleSpace
Realtime compression technique built into DOS 6.
See DOS DoubleSpace.


down
Refers to a computer that fails to operate due to
hardware or software failure.  A communications
line is down when it is unable to transfer data.


downlink
Communications channel from a satellite to an earth
station.  Contrast with uplink.


download
To transmit a file from one computer to another.
When conducting the session, download means
receive, upload means transmit.  It implies sending
a block of data rather than interacting in a
conversational mode.


downloadable font
Same as soft font.


downsizing
Converting mainframe and mini-based systems to
personal computer LANs.


downtime
Time during which a computer is not functioning due
to hardware or system software failure.  That's
when you truly understand how important it is to
have reliable hardware.


downward compatible
Also called backward compatible.  Refers to
hardware or software that is compatible with
earlier versions.  Contrast with upward compatible.


DP
See data processing and dot pitch.


DPCM
(Differential PCM)  Audio digitization technique
that codes the difference between samples rather
than coding an absolute measurement at each sample
point.  See ADPCM.


dpi
(Dots Per Inch)  Measurement of printer resolution.
A 300 dpi printer means 90,000 dots are printable
in one square inch (300x300).  400 dpi generates
160,000 dots; 500 dpi yields 250,000 dots.


DPMA
(Data Processing Management Assn.)  Membership
organization founded in 1951 with over 40,000
managers of DP installations, programmers, systems
analysts and research specialists.  It founded the
CDP examinations, now administrated by ICCP.
Offers many educational programs and seminars, in
addition to sponsoring student organizations around
the country interested in DP.  Address: 505 Busse
Highway, Park Ridge, IL 60068, 312/825-8124.


DPMI
(DOS Protected Mode Interface)  DOS extender
specification for 286s and up that allows DOS
extended programs to cooperatively run under
Windows 3.x.  Developed by Microsoft, it keeps a
DOS-extended application from crashing the computer
and usurping Windows' control.  It is not
compatible with VCPI, the first DOS extender
standard, but Windows 3.1 is more tolerant of VCPI
applications than Windows 3.0.


DPPX
(Distributed Processing Programming EXecutive)
Operating system for the 8100, now defunct.
DPPX/370 is a version allowing users to migrate to
9370s.


DPS
Minicomputer series from Bull HN.


DPSK
(Differential Phase Shift Keying)  Common form of
phase modulation used in modems.  It does not
require complex demodulation circuitry and is not
susceptible to random phase changes in the
transmitted waveform.  Contrast with FSK.


DR DOS
(Digital Research DOS)  DOS-compatible operating
system from Novell noted for its many features.
Version 5.0 includes built-in help, passwords, disk
cache, file transfer, the ability to store itself
and drivers in high memory and an optional
graphical interface.  Version 6.0 includes file
compression that doubles hard disk space.


Drafix
2-D and 3-D CAD packages for PCs and Atari STs from
Foresight Resources Corp., Kansas City, MO.  It
features professional functions and provides
constant on-screen information during drawing.


draft mode
Highest-speed, lowest-quality printing mode.


drag
To move an object on screen in which its complete
movement is visible from starting location to
destination.  The movement may be activated with a
stylus, mouse or keyboard keys.


drag & drop
Ability to execute a function graphically without
typing in a command.  For example, in the
Macintosh, selecting a floppy disk icon and
dragging it onto the trashcan icon causes the
floppy to be ejected.


drag lock
Ability to lock onto a screen object so that it can
be dragged with the mouse without continuously
holding down the mouse (or trackball) button.


drain
Output (receiving) side of the bridge in a field
effect transistor.  When the gate is charged,
current flows from the source to the drain.  Same
as collector in a bipolar transistor.


DRAM
See dynamic RAM.


DRAW
(Direct Read After Write)  Reading data immediately
after it has been written to check for recording
errors.


drawing program
Graphics software that allows the user to design
and illustrate products and objects.  It maintains
an image in vector graphics format, which allows
all elements of the graphic object to be isolated
and manipulated individually.

   Drawing programs and CAD programs are similar;
however, drawing programs usually provide a large
number of special effects for fancy illustrations,
while CAD programs provide precise dimensioning and
positioning of each graphic element in order that
the objects can be transferred to other systems for
engineering analysis and manufacturing.  Contrast
with paint program.


DRDA
(Distributed Relational Database Architecture)
SAA-compliant enhancement that allows data to be
distributed among DB2 and SQL/DS databases.  Users
or programs can access data from SAA or non-SAA
systems that implement DRDA.


DRDBMS
(Distributed Relational DBMS)  Relational DBMS that
manages distributed databases.  See distributed
database.


DRI
See Digital Research.


dribbleware
Software that is publicly displayed and previewed
well in advance of its actual release.  Dribbleware
is one stage beyond vaporware.


drift
Change in frequency or time synchronization of a
signal that occurs slowly.


drill down
To move from summary information to the detailed
data that created it.


drive
(1) Electromechanical device that spins disks and
tapes at a specified speed.  Also refers to the
entire peripheral unit such as disk drive or tape
drive.

(2) To provide power and signals to a device.  For
example, "this control unit can drive up to 15
terminals."


drive bay
Slot for a disk drive in a computer cabinet.


drive door
Panel, gate or lever used to lock a disk in a disk
drive.  In a 5.25" floppy drive, the drive door is
the lever that is turned down over the slot after
inserting the disk.


drive type
See hard disk.


driver
(1) Also called a device driver, a program routine
that links a peripheral device or internal function
to the operating system.  It contains the precise
machine language necessary to activate all device
functions and includes detailed knowledge of its
characteristics, such as sectors per track or the
number of pixels of screen resolution.

   Basic drivers come with the operating system,
and drivers are added when new peripheral devices
are installed.  For example, if you add a mouse or
CD ROM player to your personal computer, you have
to install the appropriate driver so that the
operating system knows how to handle it.

   In the DOS world, applications provide their own
screen and printer drivers in order to provide
complete control over the display and printing of a
document.

   Memory managers, RAM disks and disk caches are
also activated by drivers.  See DOS CONFIG.SYS.

(2) Device that provides signals or electrical
current to activate a transmission line or display
screen.  See line driver.


drop cap
In typography, a large first letter that drops
below the first line, for example:

         █████ his is an example
           █ of a drop cap in
           █ printing.



drop-down menu
See pull-down menu.


drop in
Extraneous bit on a magnetic medium that was not
intentionally written, due to a surface defect or
recording malfunction.


drop out
(1) On magnetic media, a bit that has lost its
strength due to a surface defect or recording
malfunction.

(2) In data transmission, a momentary loss of
signal that is due to system malfunction or
excessive noise.


droupie
(Data gROUPIE)  Person who likes to spend time in
the company of programmers and data processing
professionals.


drum
See magnetic drum.


drum plotter
Graphics plotter that wraps the paper around a
drum.  The drum turns to produce one direction of
the plot, the pen moves to provide the other.


drum printer
Line printer that uses formed character images
around a cylindrical drum as its printing
mechanism.  There is a band of characters for each
print position.  When the desired character for the
selected print position has rotated around to the
hammer line, the hammer hits the paper from behind
and pushes it into the ribbon and onto the
character.


dry plasma etching
Method for inscribing a pattern on a wafer by
shooting hot ions through a mask to evaporate the
silicon dioxide insulation layer.  Dry plasma
etching replaces the wet processing method that
uses film and acid for developing the pattern.


drystone
See Dhrystone.


DS
(Digital Signal)  Speed measurements:
         DS-0       64Kbps
         DS-1    1.544Mbps  (T1)
         DS-1C   3.152Mbps
         DS-2    6.312Mbps  (T2)
         DS-3   44.736Mpbs  (T3)
         DS-4  274.176Mpbs  (T4)


DS/DD
(Double Sided/Double Density)  Refers to floppy
disks, such as the 5.25" 360KB PC format and 3.5"
720KB PC and 800KB Mac formats.


DS/HD
(Double Sided/High Density)  Refers to floppy
disks, such as the 5.25" 1.2MB PC format and 3.5"
1.44MB PC and Mac formats.


DSA
(1) (Distributed Systems Architecture)   Bull HN
network architecture.

(2) (Directory Systems Agent)  X.500 routine that
looks up the location of a message recipient.  It
accepts requests from the Directory User Agent
counterpart in the workstation.

(3) (Digital Storage Architecture)  Disk controller
standard from Digital.

(4) (Digital Signal Analyzer)  Tektronix
oscilloscope that samples high-frequency signals.


DSP
See digital signal processing.


DSR
(Data Set Ready)  RS-232 signal sent from the modem
to the computer or terminal indicating that it is
able to accept data.  Contrast with DTR.


DSS
(1) (Decision Support System)  Information and
planning system that provides the ability to
interrogate computers on an ad hoc basis, analyze
information and predict the impact of decisions
before they are made.

   DBMSs let you select data and derive information
for reporting and analysis.  Spreadsheets and
modeling programs provide both analysis and "what
if?" planning.  However, any single application
that supports decision making is not a DSS.  A DSS
is a cohesive and integrated set of programs that
share data and information.  A DSS might also
retrieve industry data from external sources that
can be compared and used for historical and
statistical purposes.

   An integrated DSS directly impacts management's
decision-making process and can be a very cost-
beneficial computer application.  See EIS.

(2) (Digital Signature Standard)  National Security
Administration standard for authenticating an
electronic message.  See RSA and digital signature.


DSTN
(Double SuperTwisted Nematic)  LCD display that
uses an extra display layer (compensating layer)
between the main display and the rear polarizer,
resulting in an almost-pure black and white display
with little color tinge.


DSU/CSU
(Data Service Unit/Channel Service Unit)  Pair of
communications devices that connect an inhouse line
to an external digital circuit (T1, DDS, etc.).
The CSU terminates the external line at the
customer's premises and provides signal
regeneration and remote testing.  The DSU provides
buffering and flow control between the customer's
internal line and the CSU.  The DSU/CSU is similar
to a modem, but connects a digital circuit rather
than an analog one.


DTA
(Design and Test Alliance)  Group of ATE, EDA, chip
makers and systems houses dedicated to improving
testing of complicated electronic systems.


DTE
(Data Terminating Equipment)  Communications device
that is the source or destination of signals on a
network.  It is typically a terminal or computer.
Contrast with DCE.


DTP
See desktop publishing.


DTR
(Data Terminal Ready)  RS-232 signal sent from the
computer or terminal to the modem indicating that
it is able to accept data.  Contrast with DSR.


DTS
(1) (Digital Termination Service)  Microwave-based,
line-of-sight communications provided directly to
the end user.

(2) (DeskTop Server)  Motorola 68000-based network
server from Banyan.

(3) (Developer Technical Support)  Tech-support
group for developers at Apple.


DUA
(Directory User Agent)  X.500 routine that sends a
request to the Directory Systems Agent to look up
the location of a user on the network.


dual boot
Computer that can be started with either one of two
different operating systems.


dual in-line package
See DIP.


dumb terminal
Display terminal without processing capability.  It
is entirely dependent on the main computer for
processing.  Contrast with smart terminal and
intelligent terminal.


dump
To print the contents of memory, disk or tape
without any report formatting.  See memory dump.


duplex channel
See full-duplex.


duplexed system
Two systems that are functionally identical.  They
both may perform the same functions, or one may be
standby, ready to take over if the other fails.


duplicate keys
Identical key data in a file.  Primary keys, such
as account number cannot be duplicated, since no
two customers or employees should be assigned the
same number.  Secondary keys, such as date, product
and city, may be duplicated in the file or
database.


DVE
(Digital Video Effects)  Video effects such as
fades, wipes, dissolves, page flips, and iris and
funnel effects performed by computer.


DVI
(Digital Video Interactive)   Intel compression
technique for data, audio and full-motion video.
On a CD ROM, it provides up to 72 minutes of full-
screen video, 2½ hours of half-screen video, 40,000
medium-resolution or 7,000 high-resolution images.
It compresses full-motion video at ratios greater
than 100 to 1 and still images at 10 to 1.

   Split screen capabilities allow still and moving
images side by side.  For example, a training
course could show an operation taking place along
with pictures of the components being used.

   DVI uses standard storage devices, but requires
a DVI controller board in the personal computer.
Developed by RCA's Sarnoff Research labs in
Princeton, Intel acquired it in 1988.

   Software-only versions of DVI are also
forthcoming.  See CD, CD ROM, CD-I.


Dvorak keyboard
Keyboard layout designed in the 1930s by August
Dvorak, Univ. of Washington, and his brother-in-
law, William Dealey.  70% of words are typed on the
home row compared to 32% with qwerty, and, more
words are typed using both hands.  In eight hours,
fingers of a qwerty typist travel 16 miles, but
only one for the Dvorak typist.

              Qwerty

   52%   Q W E R T Y U I O P
   32%    A S D F G H J K L ; '
   16%     Z X C V B N M , . /

              Dvorak

   22%   ' , . P Y F G C R L ?
   70%    A O E U I D H T N S -
    8%     ; Q J K X B M W V Z


DVST
(Direct View Storage Tube)  Early graphics screen
that maintained an image without refreshing.  The
entire screen had to be redrawn for any change.


DX
See 386 and 486.


DX2
See 486.


DXF
AutoCAD 2-D graphics file format.  Many CAD systems
import and export the DXF format for graphics
interchange.


dyadic
Two.  Refers to two components being used.


dye diffusion
See thermal dye diffusion.


dye polymer recording
Optical recording technique that uses dyed plastic
layers as the recording medium.  A single dye
polymer layer is used in some WORM devices.
Erasable optical disks use two dyed plastic layers,
a top retention layer and a bottom expansion layer.
A bit is written by shining a laser through the
retention layer onto the expansion layer, which
heats the area and forms a bump that expands into
the retention layer.  The retention layer bumps are
the actual bits read by the unit.  To erase a bit,
another laser (different wavelength) strikes the
retention layer and the bump subsides.


dynamic
Refers to operations performed while the program is
running.  The expression, "buffers are dynamically
created," means that space was created when
actually needed, not reserved beforehand.


dynamic address translation
In a virtual memory system, the ability to
determine what the real address is at the time of
execution.


dynamic binding
Linking a routine or object at runtime based on the
conditions at that moment.  See polymorphism.


dynamic compression
Ability to compress and decompress data in
realtime; for example, as it's being written to or
read from the disk.


dynamic link
Connection established at runtime from one program
to another.


dynamic link library
Executable routines available to applications at
runtime.  They are typically written in reentrant
code so they can serve more than one application at
the same time.


dynamic network services
Realtime networking capabilities, such as adaptive
routing, automatically reconfiguring the network
when a node is added or deleted and the ability to
locate any user on the network.


dynamic RAM
Most common type of computer memory, also called D-
RAM ("dee-RAM") and DRAM.  It usually uses one
transistor and a capacitor to represent a bit.  The
capacitors must be energized hundreds of times per
second in order to maintain the charges.  Unlike
firmware chips (ROMs, PROMs, etc.) both major
varieties of RAM (dynamic and static) lose their
content when the power is turned off.  Contrast
with static RAM.

   In memory advertising, dynamic RAM is often
erroneously stated as a package type; for example,
"DRAMs, SIMMs and SIPs on sale."  It should be
"DIPs, SIMMs and SIPs," as all three packages
typically hold dynamic RAM chips.


dynamic range
Range of signals from the weakest to the strongest.


dynamic SQL
SQL statements interpreted by the SQL database at
runtime.  Dynamic SQL may be generated by programs
or entered interactively by the user.  Contrast
with embedded SQL.


dynlink
See dynamic link.



E
See exponent.


e-beam
See electron beam.


e-disk
(Emulated-disk)  Same as RAM disk.


e-mail
See electronic mail.


E-time
See execution time.


E1
European counterpart to T1, which transmits at
2.048 Mbits/sec.


EAM
(Electronic Accounting Machine)  Same as tabulating
equipment.


early binding
Assigning types in the compilation phase.  See
binding time.


EAROM
(Electrically Alterable ROM)  Same as EEPROM.


earth station
Transmitting/receiving station for satellite
communications.  It uses a dish-shaped antenna for
microwave transmission.


easy to learn and use
Easy to learn refers to software that is well
designed and capable of being used right away.  If
you make the program work with little problem, it's
easy to learn.

   Easy to learn implies easy to use right away,
but it does not imply easy to use after you're
familiar with it.  The menus that coddled you in
the beginning can become tiresome when used
constantly.  Advanced programs have a macro
recorder that lets you store a series of menu
selections and execute them automatically.


EasyCAD 2
Full-featured PC CAD program from Evolution
Computing, Tempe, AZ, that is known for its ease of
use.  EasyCAD users can migrate to FastCAD, which
looks almost identical on screen, but provides
multiple windows and is designed for high-speed
operations.


EBCDIC
(Extended Binary Coded Decimal Interchange Code)
Pronounced "eb-suh-dick."  IBM data code
originating with System/360, used in its mainframes
and most midrange computers.  It is an 8-bit code
(256 combinations) that stores one alphanumeric
character or two decimal digits in a byte.

   EBCDIC and ASCII are the two codes most widely
used to represent data.


EBCDIC chart

╔════════════════════════════════════════════════╗
║                     EBCDIC                     ║
║ Extended Binary Coded Decimal Interchange Code ║
║                                                ║
║ 00 Null             │ 40 (3) │ 80     │ C0 {   ║
║ 01 Start of heading │ 41 (4) │ 81  a  │ C1 A   ║
║ 02 Start of text    │ 42     │ 82  b  │ C2 B   ║
║ 03 End of text      │ 43     │ 83  c  │ C3 C   ║
║ 04 Select           │ 44     │ 84  d  │ C4 D   ║
║ 05 Horizontal Tab   │ 45     │ 85  e  │ C5 E   ║
║ 06 Required New Line│ 46     │ 86  f  │ C6 F   ║
║ 07 Delete           │ 47     │ 87  g  │ C7 G   ║
║ 08 Graphic Escape   │ 48     │ 88  h  │ C8 H   ║
║ 09 Superscript      │ 49     │ 89  i  │ C9 I   ║
║ 0A Repeat           │ 4A ¢   │ 8A     │ CA (5) ║
║ 0B Vertical Tab     │ 4B .   │ 8B     │ CB     ║
║ 0C Form Feed        │ 4C <   │ 8C     │ CC     ║
║ 0D Carriage return  │ 4D (   │ 8D     │ CD     ║
║ 0E Shift out        │ 4E +   │ 8E     │ CE     ║
║ 0F Shift in         │ 4F │   │ 8F     │ CF     ║
║ 10 Data link escape │ 50 &   │ 90     │ D0 }   ║
║ 11 Device control 1 │ 51     │ 91  j  │ D1 J   ║
║ 12 Device control 2 │ 52     │ 92  k  │ D2 K   ║
║ 13 Device control 3 │ 53     │ 93  l  │ D3 L   ║
║ 14 Rest/Enable Pres │ 54     │ 94  m  │ D4 M   ║
║ 15 New Line         │ 55     │ 95  n  │ D5 N   ║
║ 16 Backspace        │ 56     │ 96  o  │ D6 O   ║
║ 17 Prog/Oper Comm   │ 57     │ 97  p  │ D7 P   ║
║ 18 Cancel           │ 58     │ 98  q  │ D8 Q   ║
║ 19 End of medium    │ 59     │ 99  r  │ D9 R   ║
║ 1A Unit Backspace   │ 5A !   │ 9A     │ DA     ║
║ 1B Customer Use 1   │ 5B $   │ 9B     │ DB     ║
║ 1C File Separator   │ 5C ∙   │ 9C     │ DC     ║
║ 1D Group Separator  │ 5D )   │ 9D     │ DD     ║
║ 1E Record Separator │ 5E ;   │ 9E     │ DE     ║
║ 1F (1)              │ 5F ─┐  │ 9F     │ DF     ║
║ 20 Digit Select     │ 60 -   │ A0     │ E0 \   ║
║ 21 SOS              │ 61 /   │ A1  ~  │ E1 (6) ║
║ 22 Field Separator  │ 62     │ A2  s  │ E2 S   ║
║ 23 Word Underscore  │ 63     │ A3  t  │ E3 T   ║
║ 24 (2)              │ 64     │ A4  u  │ E4 U   ║
║ 25 Line Feed        │ 65     │ A5  v  │ E5 V   ║
║ 26 End Trans Block  │ 66     │ A6  w  │ E6 W   ║
║ 27 Escape           │ 67     │ A7  x  │ E7 X   ║
║ 28 Set Attribute    │ 68     │ A8  y  │ E8 Y   ║
║ 29 Start Field Ext. │ 69     │ A9  z  │ E9 Z   ║
║ 2A Set Mode/Switch  │ 6A |   │ AA     │ EA     ║
║ 2B Ctrl Seq Prefix  │ 6B ,   │ AB     │ EB     ║
║ 2C Modify Field Atr │ 6C %   │ AC     │ EC     ║
║ 2D Enquiry          │ 6D -   │ AD     │ ED     ║
║ 2E Acknowledge      │ 6E >   │ AE     │ EE     ║
║ 2F Bell             │ 6F ?   │ AF     │ EF     ║
║ 30                  │ 70     │ B0     │ F0 0   ║
║ 31                  │ 71     │ B1     │ F1 1   ║
║ 32 Synchronous Idle │ 72     │ B2     │ F2 2   ║
║ 33 Index Return     │ 73     │ B3     │ F3 3   ║
║ 34 Pres Position    │ 74     │ B4     │ F4 4   ║
║ 35 Transparent      │ 75     │ B5     │ F5 5   ║
║ 36 Numeric Backspace│ 76     │ B6     │ F6 6   ║
║ 37 End of Trans     │ 77     │ B7     │ F7 7   ║
║ 38 Subscript        │ 78     │ B8     │ F8 8   ║
║ 39 Indent Tab       │ 79 `   │ B9     │ F9 9   ║
║ 3A Required Frm Feed│ 7A :   │ BA     │ FA     ║
║ 3B Customer Use 3   │ 7B #   │ BB     │ FB     ║
║ 3C Device Ctrl 4    │ 7C @   │ BC     │ FC     ║
║ 3D Negative Ack     │ 7D '   │ BD     │ FD     ║
║ 3E                  │ 7E =   │ BE     │ FE     ║
║ 3F Substitute       │ 7F "   │ BF     │ FF (7) ║
╚═════════════════════╧════════╧════════╧════════╝
  (1) Bypass/Inhibit Presentation
  (2) Intermediate Trans Block/
       Interchange Unit Separator
  (3) Space
  (4) Required Space
  (5) Syllable Hyphen
  (6) Numeric Space
  (7) Eight Ones


EBL
(Extended Batch Language)  Shareware programming
language by Frank Canova that allows for more
complex programming in DOS batch files.


ECF
(Enhanced Connectivity Facilities)  IBM software
that allows DOS PCs to query and download data from
mainframes as well as issue mainframe commands.  It
also allows printer output to be directed from the
PC to the mainframe.  It uses the SRPI interface
and resides in the PC (client) and mainframe
(server).  Applications issue SRPI commands to
request services.


echo
(1) Same as echoplex.

(2) DOS and OS/2 screen command that displays
messages and turns off/on screen responses.  See
DOS batch file.


echo cancellation
High-speed modem technique that isolates and
filters out unwanted signals caused by echoes from
the main transmitted signal.  This permits full-
duplex modems to send and receive on the same
frequency.

   Telephone networks often use echo cancellers in
addition to or in place of echo suppressors.
Network-based echo cancellation can interfere with
modems that do their own, such as V.32, so a method
is provided for those modems to disable network
echo cancellers.


echo check
In communications, an error checking method that
retransmits the data back to the sending device for
comparison with the original.


echo suppressor
Communications technique that turns off reverse
transmission in a telephone line, thus effectively
making the circuit one way.  It is used to reduce
the annoying effects of echoes in telephone
connections, especially in satellite circuits.


echoplex
Communications protocol that transmits the received
data back to the sending station allowing the user
to visually inspect what was received.


ECL
(Emitter-Coupled Logic)  Variety of bipolar
transistor that is noted for its extremely fast
switching speeds.


ECLIPSE
Series of 32-bit minicomputers from Data General.
The development of the initial 32-bit ECLIPSE
MV/Family supermini, the MV/8000, was the subject
of Tracy Kidders' best selling book, "Soul of a New
Machine."


ECMA
(European Computer Manufacturers Assn.)
Organization devoted to international standards.
Address: Rue du Rhone 114, CH-1204 Geneva,
Switzerland.


ED
(1) (Extra High Density)  Refers to 2.88M floppy
disks.

(1) (EDitor)  Early UNIX line editor that contained
functionality later incorporated into vi.


EDA
(1) (Electronic Design Automation)  Using the
computer to design and simulate the performance of
electronic circuits on a chip.  See ATE.

(2) (EDA/SQL) (Enterprise Data Access/SQL)
Software from Information Builders, Inc., New York,
that provides a common interface between a wide
variety of SQL programs and SQL databases.  It also
allows queries on data from different types of
databases at the same time.

(3) (Electronic Document Authorization)
Authorizing certificates used to identify public
keys for encrypting data under the RSA method.


edge connector
Row of etched lines on the edge of a printed
circuit board that is inserted into an expansion
slot.


EDI
(Electronic Data Interchange)  Electronic
communication of transactions between
organizations, such as orders, confirmations and
invoices.  Independent service organizations
provide EDI services that enable users to
interconnect with another organization's network
regardless of type of equipment used.  See X12,
Tradacoms and EDIFACT.


EDIFACT
(Electronic Data Interchange For Administration
Commerce and Transport)  ISO standard for EDI that
is proposed to supersede both X12 and Tradacoms
standards to become the worldwide standard.


edit
To make a change to existing data.  See update.


edit checking
Same as validity checking.


edit instruction
Computer instruction that formats a field for
display or printing.  Using an edit mask, it
inserts decimal points, commas and dollar signs
into the data.


edit key
Key combination or function key that changes the
program into edit mode when pressed.


edit mask
Pattern of characters that represent formatting
codes through which data is filtered for display or
printing.  See picture.


edit mode
Operational state in a program that allows existing
data to be changed.


edit program
(1) Data entry program that validates user input
and stores the newly created records in the file.

(2) Program that allows users to change data that
already exists in a file.  See update.


edit routine
Routine in a program that tests for valid data.
See validity checking.


editable PostScript
File of PostScript commands that can be edited by a
word processor or other program.  This allows
PostScript documents to be changed without
requiring the use of the application that
originally created it.


editor
See text editor and linkage editor.


Edlin
Archaic text editor used in DOS.  The OS/2
counterpart is SSE.  See DOS Edlin.


EDP
(Electronic Data Processing)  First name used for
the computer field.


education
Teaching concepts and perspectives.  Computer
education includes computer systems and information
systems.  Contrast with training.


edutainment
Entertaining educational material.


EE
See Extended Edition.


EEMS
See EMS.


EEPROM
(Electrically Erasable Programmable Read Only
Memory)  Memory chip that holds its content without
power.  It can be erased, either within the
computer or externally and usually requires more
voltage for erasure than the common +5 volts used
in logic circuits.  It functions like non-volatile
RAM, but writing to EEPROM is slower than writing
to RAM.

   EEPROMs are used in devices that must keep data
up-to-date without power.  For example, a price
list could be maintained in EEPROM chips in a point
of sale terminal that is turned off at night.  When
prices change, the EEPROMs can be updated from a
central computer during the day.


eesa
See EISA and ESA/370.


EFF
(Electronic Frontier Foundation)  Organization
founded in 1990 by Mitchell Kapor and John Perry
Barlow dedicated to raising public awareness of the
opportunities and challenges posed by computing and
telecommunications.  Address: 155 Second St.,
Cambridge, MA 02141, 617/864-0665.


EFT
(Electronic Funds Transfer)  Transfer of money from
one account to another by computer.


EGA
(Enhanced Graphics Adapter)  IBM video display
standard that provides medium-resolution text and
graphics.  It supports previous display modes and
requires a digital RGB Enhanced Color Display or
equivalent monitor.  EGA has been superseded by
VGA.  See PC display modes.


EGP
(Exterior Gateway Protocol)  Gateway protocol that
broadcasts TCP/IP IP addresses to the gateway of
another self-contained network.


EIA
(Electronic Industries Assn.)  Membership
organization founded in 1924 as the Radio
Manufacturing Assn.  It sets electronic interface
standards and sponsors shows and seminars.  In
1984, the TIA (Telecommunications Industry Assn.)
became part of EIA.  Address: 2001 Pennsylvania
Ave., N.W., Washington, DC 20006, 202/457-4900.


EIA-232
See RS-232.


EIA-422, 423, 449
See RS-422, 423, 449


EIA-485
See RS-485.


EIA-568
EIA standard for telecommunications wiring in a
commercial building.


EIS
(Executive Information System)  Information system
that consolidates and summarizes ongoing
transactions within the organization.  It should
provide management with all the information it
requires at all times from internal as well as
external sources.  See DSS.


EISA
(Extended ISA)  Pronounced "e-suh."  PC bus
standard that extends the AT bus (ISA bus) to 32
bits and provides bus mastering.  It was announced
in 1988 as a 32-bit alternative to the Micro
Channel that would preserve investment in existing
boards.  PC and AT cards (ISA cards) can plug into
an EISA slot.


EL
See electroluminescent.


electricity
Flow of electrons in a circuit.  The speed of
electricity is the speed of light (approx. 186,000
miles per second).  In a wire, it is slowed due to
the resistance in the material.

   Its pressure, or force, is measured in volts and
its flow, or current, is measured in amperes.  The
amount of work it produces is measured in watts
(amps X volts).


electrode
Device that emits or controls the flow of
electricity.


electroluminescent
Flat panel display that provides a sharp, clear
image and wide viewing angle.  It contains a
powdered or thin film phosphor layer sandwiched
between an x-axis and a y-axis panel.  When an x-y
coordinate is charged, the phosphor in that
vicinity emits visible light.  Phosphors are
typically amber, but green is also used.


electrolyte
In a rechargeable battery, the material that allows
electricity to flow from one plate to another by
conducting ions.


electromagnet
Magnet that is energized by electricity.  A coil of
wire is wrapped around an iron core.  When current
flows in the wire, the core generates an energy
called magnetic flux.


electromagnetic radiation
Energy that exists in all things, including humans,
which incorporates cosmic rays, gamma rays, x-rays,
ultraviolet light, visible light, infrared light
and radar.


electromagnetic spectrum
Range of electromagnetic radiation.


electromechanical
Use of electricity to run moving parts.  Disk
drives, printers and motors are examples.
Electromechanical systems must be designed for the
eventual deterioration of moving parts.


electromotive force
Pressure in an electric circuit measured in volts.


electron
Elementary particle that circles the nucleus of an
atom.  Electrons are considered to be negatively
charged.


electron beam
Stream of electrons, or electricity, that is
directed towards a receiving object.


electron gun
Device which creates a fine beam of electrons that
is focused on a phosphor screen in a CRT.


electron tube
Same as vacuum tube.


electronic
Use of electricity in intelligence-bearing devices,
such as radios, TVs, instruments, computers and
telecommunications.  Electricity used as raw power
for heat, light and motors is considered
electrical, not electronic.

   Although coined earlier, "Electronics" magazine
(1930) popularized the term.  The magazine
subheading read "Electron Tubes - Their Radio,
Audio, Visio and Industrial Applications."  The
term was derived from the electron (vacuum) tube.


electronic circuit
See circuit and digital circuit.


electronic mail
Transmission of memos and messages over a network.
Users can send mail to a single recipient or
broadcast it to multiple users.  Sophisticated
systems prompt recipients for a reply if they
haven't responded within a certain time frame.
With multitasking workstations, mail can be
delivered and announced while the user is working
in an application.  Otherwise, mail is sent to a
simulated postal box in the network server or host
computer, which must be interrogated.

   The fax machine has become the most universal
electronic mail today, showing the power of a
common standard.  However, it isn't called e-mail
as the text cannot be edited at the other end
without scanning and using text recognition
software.  See X.400, X.500 and EDI.


Electronic Mail Assn.
Membership organization founded in 1983 with over
250 vendor and user companies involved in
electronic messaging and information exchange.
Concerns include marketing e-mail within the
corporation, privacy, security, interconnection and
standards.  Address: 1555 Wilson Blvd., Suite 300,
Arlington, VA 22209, 703/875-8620.


Electronic Message Service
See EMS (2).


electronic messaging
Same as electronic mail.


electronic printer
Printer that uses electronics to control the
printing mechanism, such as a laser printer and
certain line printers.


electronic publishing
Providing information in electronic form to readers
or subscribers of the service.  See information
utility and videotex.


electronic switch
On/off switch activated by electrical current.


electronic typewriter
See memory typewriter and word processing.


electrophotographic
Printing technique used in copy machines and laser
printers.  A negative image made of dots of light
is painted onto a photosensitive drum or belt that
has been electrically charged.  The light comes
from a laser, LEDs or liquid crystals that shutter
a light source.

   Wherever light is applied, the drum becomes
uncharged.  A toner (dry ink) is applied and
adheres to the charged areas of the drum.  The drum
transfers the toner to the paper, and pressure and
heat fuse the toner and paper permanently.

   Some electrophotographic systems use a positive
approach in which the toner is attracted to the
laser-produced latent image.


electrosensitive printer
Dot matrix printer that burns away dots on the
outer silver coating of a special black paper.


electrostatic
Stationary electrical charges in which no current
flows.


electrostatic plotter
Plotter that uses a special paper that is charged
as it passes by a line of electrodes.  Toner is
then applied to the charged paper.  Models print in
in black and white or color, and some handle paper
up to six feet wide.


electrostatic printer
Same as electrostatic plotter.


elegant program
Program that is simple in design, uses the least
amount of memory and runs fast.


ELF
(Extemely Low Frequency)  See low radiation.


elite
Typeface that prints 12 cpi.


em
In typography, a unit of measure equal to the width
of the capital letter M in a particular font.


EMA
(1) (Enterprise Management Architecture)  Digital's
stategic plan for integrating network, system and
application management.  It provides the operating
environment for managing a multi-vendor network.

(2) See Electronic Mail Assn.


EMACS
(Editor MACroS)  UNIX text editor developed at MIT
that is used for writing programs.  It provides a
wide variety of editing features including multiple
windows.


embedded command
(1) Command inserted within text or other codes.

(2) In word processing, a command within the text
that directs the printer to change fonts, print
underline, boldface, etc.  The command is inserted
when the user selects a layout change.  Commands
are often invisible on screen, but can be revealed
if required.

   Embedded commands in a document are proprietary
to the word processor used.  When a document is
printed, the text is copied to a temporary file,
and the embedded commands are converted into
printer commands for the printer.  When printing is
finished, the temporary file is erased.  See print
to disk.


embedded SQL
SQL statements written into a high-level language
source program, such as C or Pascal.  In a separate
compiling phase, the SQL may be optimized and
converted into special function calls.  Contrast
with dynamic SQL.


embedded system
Specialized computer used to control a device such
as an automobile, appliance or space vehicle.
Operating system and application functions are
often combined in the same program.


Emerald Bay
PC database engine from Ratliff Software
Productions, Inc., Montrose, CA, that is designed
to interface with different languages.  Introduced
in 1988 and written by Wayne Ratliff (dBASE II), it
provides a binary field that can store any type of
information.


EMI
(ElectroMagnetic Interference)  Electromagnetic
waves that eminate from an electrical device.  It
often refers to both low-frequency waves from
electromechanical devices and high-frequency waves
(RFI) from chips and other electronic devices.
Allowable limits are governed by the FCC.


emitter
Supply of current in a bipolar transistor.  Same as
source in a MOS transistor.


emitter-coupled logic
See ECL.


EMM
(Expanded Memory Manager)  Software that manages
expanded memory (EMS).  In XTs and ATs, expanded
memory boards must also be used.  In 386s and up,
the EMM converts extended memory into EMS.


EMM386
See DOS EMM386.EXE.


emoticon
(EMOTional ICON)  In e-mail, expressing emotion by
typing character combinations.  The following
examples are viewed sideways.

  :)   original smiley face
  :-)  smile
  :-(  frown
  ;-)  wink
  :-D  big smile
  :-O  mouth open in amazement
  :-Q  tounge hanging out in nausea
  :-{) smile (user has moustache)
  :-{)} moustache and beard
  8-)  smile (user wears glasses)
  (-:  smile (user left handed or Australian)
  :*)  red nosed smile, suggesting inebriation
  *<|:{)}  Santa Claus!
  @:{)===  sikh with turban and long beard


EMS
(1) (Expanded Memory Specification)  Technique for
increasing memory in DOS PCs.  EMS Version 4.0
allows DOS to work with up to 32MB of extra memory
by bank switching 16K segments of EMS memory, known
as the "page frame," into conventional memory.

   In XTs and ATs, EMS is installed by plugging in
an EMS memory board and adding an EMS driver.  In
386s and up, EMS is created by expanded memory
manager (EMM) software that turns extended memory
into EMS.

   In order to use EMS, the application is either
written to use it directly (Lotus 1-2-3 Ver. 2.x,
AutoCAD, etc.) or the application is run in an
environment that uses it, such as DESQview.

   In 1984, Lotus, Intel and Microsoft introduced
EMS (LIM EMS), which allowed up to 8MB of EMS
memory.  By Version 3.2, it was widely-supported,
but limited to one 64K page frame (four 16K pages)
only in the UMA (640K-1M region).

   AST, Quadram and Ashton-Tate later introduced
Enhanced EMS (EEMS), letting the page frame take
the full 1M address space (64 16K pages), allowing
programs such as DESQview to multitask large
applications within conventional memory.

   In 1987, Lotus, Intel and Microsoft introduced
Version 4.0, increasing memory to 32MB and
incorporating the EEMS standard.


        │ Extended
        │ Memory     │
        │            │
  -----├────1M──────┤
    │   │ UMA        │   ┌───────────────┐
    │   │            │   │               │
  Range │▒▒▒▒▒▒▒▒▒▒▒▒──┐ │   EMS memory  │
   of   │ page frame │ │ │               │
   DOS  │            │ └───▒▒▒▒▒▒▒▒▒▒▒▒ │
    │   │            │   │               │
    │   ├───640K─────┤   │ Circuits on   │
    │   │            │   │ the EMS board │
    │   │ User       │   │ remap the     │
  Conv. │ Memory     │   │ requested EMS │
 Memory │            │   │ area into the │
    │   │            │   │ page frame,   │
    │   │            │   │ which DOS     │
    │   │            │   │ can address.  │
    │   │            │   └───────────────┘
  -----└────0K──────┘


             Expanded versus Extended
Expanded memory (EMS) and extended memory are not
the same.  EMS can be installed in XT-class
machines and up, whereas extended memory requires
at least a 286.  EMS broke the 1MB memory barrier
in the early days, however, now that 286s are the
low-end CPU, extended memory is finally being
utilized due to the widespread use of Windows 3.x
and DOS-extended applications.  See "Operating
Environment" in the PC definition.

   For an excellent, detailed book on EMS, extended
memory and more, read "DOS Beyond 640K," 2nd Ed.,
by James Forney, ISBN 0-8306-3744-3.

(2) (Electronic Message Service)  Part of the radio
spectrum assigned to electronic messaging over
digital satellite circuits.


EMS emulator
Before the 386, it referred to a driver for
8086/88s and 286s that simulated EMS memory in
extended memory or disk.  It is slower than an EMS
board that provides high-speed bank switching,
because the emulator copies data within memory or
between memory and disk.

   Since the 386, it refers to a memory manager
(EMM) that runs in 386s and up and creates EMS out
of extended memory.  Technically, the 386 is really
not emulating anything.  The 386 can map any memory
to any other memory, thus it is merely mapping
memory according to the EMS specification.


EMS memory manager
See EMM and EMS emulator.


emulation mode
Operational state of a computer when it is running
a foreign program under emulation.


emulator
Device that is built to work like another.  A
computer can be designed to emulate another model
and execute software that was written to run in the
other machine.  A terminal can be designed to
emulate various communications protocols and
connect to different networks.  The emulator can be
hardware, software or both.


en
In typography, a unit of measure equal to one half
the width of an em.  An en is typically the width
of one numeric digit.


enable
To turn on.  Contrast with disable.


Enable/OA
Integrated software package for PCs from Enable
Software, Inc., Ballston Lake, NY.  It is noted for
being a very comprehensive package rivaling many
stand-alone programs.  Version 4.0 also runs under
UNIX.


Encapsulated PostScript
PostScript file format that contains PostScript
code for the document as well as optional preview
images in TIFF, Windows Metafile or Macintosh PICT
formats.  The PostScript code drives a PostScript
printer directly, and the preview formats allow the
image to be manipulated on screen.  DOS and OS/2
files use an EPS extension.


encapsulation
(1) In object-oriented programming, making the data
and processing private within an object, which
allows it to be modified without causing problems
elsewhere in the program.

(2) In communications, inserting the frame header
and data from a higher level protocol into the data
frame of a lower level protocol.


encipher
To encode data for security purposes.  See
encryption.


encode
(1) To assign a code to represent data, such as a
parts code.

(2) Same as encipher or encrypt.


encryption
Encoding data for security purposes by converting
it into a proprietary code.  To be used, it must be
decoded.  It is used to transmit documents over a
network or to encode data so that it cannot be
easily changed with common software.  See DES.


end key
Keyboard key commonly used to move the cursor to
the bottom of the screen or file or to the next
word or end of line.


end points
In vector graphics, the two ends of a line
(vector).  In 2-D graphics, each end point is
typically two numbers representing coordinates on x
and y axes.  In 3-D, each end point is made up of
three numbers representing coordinates on x, y and
z axes.


end user
Same as user.


end user computing
Using personal computers.


endian
See big endian.


endless loop
Series of instructions that are constantly
repeated.  It can be caused by an error in the
program or it can be intentional; for example, a
screen demo on continuous replay.


endnote
See footnote.


engine
(1) Specialized processor, such as a graphics
processor.  Like any engine, the faster it runs,
the quicker the job gets done.

(2) Software that performs a primary and highly
repetitive function such as a database engine,
graphics engine or dictionary engine.

(3) Slang for processor.


engineering cylinder
See diagnostic tracks.


engineering drawing sizes
A - 8 1/2 x 11
B - 11 x 17
C - 17 x 22
D - 22 x 34
E - 34 x 44


Enhanced keyboard
IBM 101-key keyboard that superseded the PC and AT
keyboards.  It has a separate cursor key cluster
located between the original numeric/cursor keypad
and the letter keys.


enhancement
Any improvement made to a software package or
hardware device.


ENIAC
(Electronic Numerical Integrator And Calculator)
First operational electronic digital computer
developed for the U.S. Army by John Eckert and John
Mauchly at the Univ. of Pennsylvania.  Completed in
1946, it was decimal-based, used 18,000 vacuum
tubes, took up 1,800 square feet and performed
5,000 additions/second.


enquiry character
In communications, a control character that
requests a response from the receiving station.


enter key
See return key.


enterprise data
Centralized data that is shared by many users
throughout the organization.


enterprise model
Model of how an organization does business.
Information systems are designed from this model.


enterprise network
Geographically-dispersed network under the
jurisdiction of one organization.  It often
includes several different types of networks and
computer systems from different vendors.


entity
In a database, anything about which information can
be stored; for example, a person, concept, physical
object or event.  Typically refers to a record
structure.


entity relationship model
In a database, a data model that describes
attributes of entities and the relationships among
them.


entity type
In a database, a particular kind of file; for
example, a customer or product file.


entropy
In data compression, a measure of the amount of
non-redundant, non-compressible information in an
object.


entry
Input of an item or set of items at a terminal.
See data entry.


entry point
In programming, the starting point of the
instructions in a subroutine.


enumerate
To count or list one by one.  An enumerated data
type defines a list of all possible values for a
variable, and no other value can then be placed
into it.


envelope
(1) Range of frequencies for a particular
operation.

(2) Group of bits or items that is packaged and
treated as a single unit.


environment
Computer configuration that includes the CPU model
and system software (operating system, data
communications and database systems).  It may also
include the programming language used.  It sets the
standards for the applications that run in it.

   The term often refers only to the operating
system; for example, "This program is running in a
UNIX environment."


environment variable
See DOS Set.


EOF
(End Of File)  File status when its end has been
reached or when an instruction or command resets
the file pointer to the end.


EOL
(End Of Line)


EOM
(End Of Message)


EOT
(End Of Transmission)


epitaxial layer
In chip making, a semiconductor layer that is
created on top of the silicon base rather than
below it.  See molecular beam epitaxy.


epoch date
Starting point from which time is measured as the
number of days, minutes, etc., from that time.


EPP
(1) (Enhanced Parallel Port)  Standard that
provides fast parallel port transfer, up to
2Mbytes/sec.  It is built into the 386SL chip set.

(2) (Ethernet Packet Processor)  Chip from Kalpana,
Inc., Santa, Clara, CA, that doubles speed of
Ethernet transmission to 20Mbits/sec.


EPROM
(Erasable Programmable ROM)  Reusable PROM chip
that holds its content until erased under
ultraviolet light.  See PROM programmer.


EPS
See Encapsulated PostScript.


Epson emulation
Compatible with Epson dot matrix printers.  The
command set in the Epson MX, RX and FX printers has
become an industry standard.  Useful codes are:


  ASCII VALUE  COMMAND

          12  Form feed
       27 48  8 LPI
       27 50  6 LPI
          15  Condensed on
          18  Condensed off
     27 81 1  Double width on
     27 81 0  Double width off
       27 69  Emphasized on
       27 70  Emphasized off
     27 83 1  Subscript on
     27 83 0  Superscript on
       27 84  Sub/super off
     27 45 1  Underline on
     27 45 0  Underline off


EPSS
(Electronic Performance Support System)  Computer
system that provides quick assistance and
information without requiring prior training to use
it.  It may incorporate all forms of multimedia
delivery as well as AI techniques such as expert
systems and natural language recognition.


EQ
(EQual to)  See relational operator.


equalization
In communications, techniques used to reduce
distortion and compensate for signal loss
(attenuation) over long distances.


equation
Arithmetic expression that equates one set of
conditions to another; for example, A = B + C.  In
a programming language, assignment statements take
the form of an equation.  The above example would
assign the sum of B and C to the variable A.


ER model
See entity relationship model.


ERA
(Electrically Reconfigurable Array)  Programmable
logic chip (PLD) technology from Plessey
Semiconductor that allows the chip to be
reprogrammed electrically.


erase
See delete.


erase head
In a magnetic tape drive, the device that erases
the tape before a new block of data is recorded.


ergonomics
Science of people-machine relationships.  An
ergonomically-designed product implies that the
device blends smoothly with a person's body or
actions.


Erlang
Unit of traffic use that specifies the total
capacity or average use of a telephone system.  One
Erlang is equivalent to the continuous usage of a
telephone line.  Traffic in Erlangs is the sum of
the holding times of all lines divided by the
period of measurement.


error checking
(1) Testing for accurate transmission of data over
a communications network or internally within the
computer system.  See parity checking and CRC.

(2) Same as validity checking.


error control
Same as error checking.


error detection & correction
See error checking and validity checking.


error-free channel
Interface (wire, cable, etc.) between devices that
is not subject to external interference;
specifically not the dial-up telephone system.


error handling
Routines in a program that respond to errors.  The
measurement of quality in error handling is based
on how the system informs the user of such
conditions and what alternatives it provides for
dealing with them.


error rate
Measurement of the effectiveness of a
communications channel.  It is the ratio of the
number of erroneous units of data to the total
number of units of data transmitted.


ES
See expert system.


ES/3090
High-end IBM mainframe that incorporates the
ESA/370 enhancements.


ES/9000
IBM System/390 computer line introduced in late
1990 that uses 31-bit addressing with maximum
memory capacities from 256MB to 9GB.  It's 18
models (Model 120 to Model 900) introduced the
widest range of power in a single series at one
time with prices ranging from $70K to $23M.  Vector
processing is optional on high-end water-cooled and
certain air-cooled models.  See System/390.


ESA/370
(Enterprise System Architecture/370)  IBM
enhancements that increase the performance of high-
end 4381 and 3090 mainframes.  Introduced in 1988,
it increases virtual memory from 2GB to 16TB and
adds techniques for managing it more effectively.
This architecture is built into System/390 ES/9000
computers.


ESA/390
(Enterprise System Architecture/390)  Extensions to
ESA/370 for System/390 series.  It includes
MVS/ESA, VM/ESA and VSE/ESA operating systems.


Esc
See escape character and escape key.


escape character
Control character often used to precede other
characters to control a printer or other device.
For example, escape, followed by &l10, sets the
LaserJet to landscape mode.  In ASCII, escape is
decimal 27, hex 1B; in EBCDIC, it is hex 27.


escape key
Keyboard key commonly used to exit a mode or
routine, or cancel some function.


escape sequence
(1) Machine command that starts with an escape
character.  Printers are often commanded by escape
sequences.  See escape character.

(2) In a modem, a unique sequence of characters
that precedes a command.  It allows modem commands
(dial, hang up, etc.) to be transmitted with the
data.  See TIES and Hayes Smartmodem.


ESCON
(Enterprise Systems CONnection)  IBM System/390
fiber optic channel that transfers 10 Mbytes/sec up
to 5.6 miles.  An ESCON Director is the coupling
device that provides 8-16 ports (Model 1) or 28-60
ports (Model 2).


ESD
(1) (ElectroStatic Discharge)  Sparks (electrons)
that jump from an electrically-charged object to an
approaching conductive object.

(2) (Electronic Software Distribution)  Installing
software by transmitting it to the destination
machines over a network.

(3) (Entry Systems Division)  Personal computer and
workstation division within IBM.


ESDI
(Enhanced Small Device Interface)  Hard disk
interface that transfers data in the one to three
MByte/sec range.  ESDI has always been the high-
speed interface for small computers, but is now
being superseded by IDE and SCSI drives.  See hard
disk.


ESDS
(Entry Sequence DataSet)  VSAM structure that
stores records one after the other without regard
to content.  Records are retrieved by address.
Contrast with KSDS.


ESF
(1) (Extended SuperFrame)  Enhanced T1 format that
allows a line to be monitored during normal
operation.  It uses 24 frames grouped together
(instead of the 12-frame D4 superframe) and
provides room for CRC bits and other diagnostic
commands.

(2) (External Source Format)  Specification
language for defining an application in IBM's
CSP/AD application generator.


ESP
(1) (Enhanced-Service Provider)  Organization that
adds value to basic telephone service by offering
such features as call-forwarding, call-detailing
and protocol conversion.

(2) (E-tech Speedy Protocol)  Proprietary protocol
of E-Tech Research used in its modems.

(3) (Electronic Still Photography)  Digitizing and
transmitting images over a telephone line.

(4) (Emulex SCSI Processor)  Proprietary chip used
in Emulex's SCSI disk controller.


ESS
(1) (Electronic Switching System)  Large-scale
computer used to switch telephone conversations in
a central office.

(2) (Executive Support System)  See EIS.

(3) (Electronic SpreadSheet)  See spreadsheet.


Ethernet
Local area network (LAN) that conforms to the IEEE
802.3 standard, originally developed by Xerox,
Digital and Intel.  It uses the CSMA/CD access
method, transmits at 10Mbps and can connect up to
1,024 nodes in total.

   Standard Ethernet (also called thick Ethernet)
uses a bus topology with a maximum cable segment
length of 1,640 ft. without the use of a repeater.
Attachment is made to the cable by clamping a
transceiver onto it.

   Thin Ethernet (also called ThinNet and
CheaperNet) uses a bus topology with a maximum
cable length of 607 feet.  Nodes are daisy chained
together with T-type BNC connectors as the
transceivers are contained within the network
adapter cards.

   Twisted pair Ethernet allows installed telephone
wire to be used (if the right type) and Fiber Optic
Ethernet is impervious to external radiation.  Both
use a star topology, which is considered easier to
debug as networks expand.

           Maximum devices per segment
      Maximum segment length     │
   Ethernet type        │        │  Topology

 10Base5 Standard    1,640 ft.  100   bus
 10Base2 Thin          607 ft.   30   bus
 10BaseT Twisted pair  328 ft.    2   star
 10BaseF Fiber Optic   1.3 mi.    2   star

   An emerging Ethernet standard is Fast Ethernet
(10BaseX), which proposes 100Mbits/sec speeds over
twisted pair.  Details to be ironed out in 1993.


EtherTalk
Macintosh software from Apple that accompanies its
Ethernet Interface NB Card and adapts the Mac to
Ethernet networks.


Eurocard
Family of European-designed printed circuit boards
that uses a 96-pin plug rather than edge
connectors.  The 3U is a 4x6" board with one plug;
the 6U is a 6x12" board with two plugs; the 9U is a
14x18" board with three plugs.


even parity
See parity checking.


event driven
Application that responds to input from the user or
other application at unregulated times.  It's
driven by choices that the user makes (select menu,
press button, etc.).  Contrast with procedure
oriented.


EVGA
(Extended VGA)  See VGA.


Exabyte
(Exabyte Corp., Boulder, CO)  Maker of high-
capacity, proprietary 8mm tape backup systems.
Single-tape units are in the 2 to 25GB range, and
multi-tape library units can hold terabytes.


Excel
Full-featured spreadsheet for PCs and the Macintosh
from Microsoft.  It can link many spreadsheets for
consolidation and provides a wide variety of
business graphics and charts for creating
presentation materials.


exception report
Listing of abnormal items or items that fall
outside of a specified range.


exclusive NOR
See NOR.


exclusive OR
See OR.


EXE file
(EXEcutable file)  Runnable program in DOS, OS/2
and VMS.  In DOS, if a program fits within 64K, it
may be a COM file.


executable
Program in machine language that is ready to run in
a particular computer environment.


execute
To follow instructions in a program.  Same as run.


execution time
Time in which a single instruction is executed.  It
makes up the last half of the instruction cycle.


executive
Same as operating system.


exit
(1) To get out of the current mode or quit the
program.

(2) In programming, to get out of the loop, routine
or function that the computer is currently in.


expanded memory
See EMS, EMM and expanded storage.


expanded memory emulator
Memory manager for 386s and up that converts
extended memory into EMS memory.  See EMM.


expanded storage
Auxiliary memory in IBM mainframes.  Data is
usually transferred in 4K chunks from expanded
storage to central storage (main memory).


expansion board
(1) Printed circuit board that plugs into an
expansion slot.

(2) See bus extender.


expansion bus
(1) The computer's bus comprised of a series of
receptacles or slots into which expansion boards
(video display, disk controller, etc.) are plugged.

(2) Sometimes refers to bus extender (3).


expansion card
Same as expansion board.


expansion slot
Receptacle inside a computer or other electronic
system that accepts printed circuit boards.  The
number of slots determines future expansion.  In
personal computers, expansion slots are connected
to the bus.


ExperLogo
Macintosh version of Logo from ExperTelligence,
Inc., Goleta, CA.  It contains more functions
similar to LISP than most versions of Logo.


expert system
AI application that uses a knowledge base of human
expertise for problem solving.  Its success is
based on the quality of the data and rules obtained
from the human expert.  In practice, expert systems
perform both below and above that of a human.

   It derives its answers by running the knowledge
base through an inference engine, which is software
that interacts with the user and processes the
results from the rules and data in the knowledge
base.

   Examples of uses are medical diagnosis,
equipment repair, investment analysis, financial,
estate and insurance planning, vehicle routing,
contract bidding, production control and training.
See EPSS.


┌─────────┐     ┌─────────┐     ┌─────────┐
│Knowledge│     │Inference│     │  User   │
│  Base   ├────│ Engine  ├────│Interface│
└─────────┘     └─────────┘     └─────────┘
If-then-else   Forward chain   Ability to ask
   rules       Backward chain  questions, get
                               input and explain
                               rationale for answer

                Expert System



expireware
Software with a built-in expiration date, either by
date or number of uses.


explode
(1) To break down an assembly into its component
pieces.  Contrast with implode.

(2) To decompress data back to its original form.


exponent
Number written above the line and to the right of a
number that indicates the power of a number, or how
many zeros there are in it.  For example 10 to the
3rd power indicates three zeros.  The number
467,000 can be stated as 467 x 10 to the 3rd.  On a
screen or printout, the number is expressed as
467E3.  See floating point.


exponential growth
Extremely fast growth.  On a chart, the line curves
up rather than being straight.  Contrast with
linear.


exponential smoothing
Widely-used technique in forecasting trends,
seasonality and level change.  Works well with data
that has a lot of randomness.


export
To convert a data file in the current application
program into the format required by another
application program.


expression
In programming, a statement that describes data and
processing.  For example, VALUE=2*COST and
PRODUCT="HAT" AND COLOR="GRAY".


extended application
DOS application that runs in extended memory under
the control of a DOS extender.


extended ASCII
Second half of the ASCII character set (128 through
255).  The symbols are defined by ANSI, by IBM for
the PC (see ASCII chart or hex chart) and by other
vendors for proprietary uses.  It is non-standard
ASCII.


Extended Edition
IBM version of OS/2 that includes communications
and database management.  The Communications
Manager has built-in LU 6.2 and X.25 protocols.
The Database Manager uses IBM's SQL.


extended maintenance
On-call service that is ordered for periods in
addition to the primary period of maintenance.


extended memory
In Intel 286s and up, standard memory above one
megabyte.  Extended memory is used directly by
Windows and OS/2 as well as DOS applications that
run with DOS extenders.  It is also used under DOS
for RAM disks and disk caches.  Contrast with
expanded memory (EMS), which is specialized memory
above one megabyte.  Memory boards can usually be
set up as a mix of the two.  See EMS, XMS and DOS
extender.


extender
See bus extender.


extensible
Capable of being expanded or customized.  For
example, with extensible programming languages,
programmers can add new control structures,
statements or data types.


extension
DOS and OS/2 file category added to the end of the
file name with a dot.  An extension can have up to
three letters or digits.  Executable files use
.EXE, .COM and .BAT extensions; for example,
GLOSS.EXE is the software program for the DOS
version of this Glossary.

   All programs and most data files use extensions.
However, some word processing files do not, in
which case you could create your own filing system;
for example, CHAP1.NOV and CHAP2.NOV could be
chapters in a novel.


 ┌── File extension
 │        Type of file
ABC  Glossary configuration
AD   After Dark image
AFM  Windows Type 1 font metrics
AI   Adobe Illustrator graphics
ARC  ARC, ARC+ compressed
ASM  Assembly source code

BAK  Backup
BAS  BASIC source code
BAT  DOS, OS/2 batch file
BIN  Driver, overlay
BMP  Windows & OS/2 bitmap

C    C source code
CAL  Windows calendar
CAL  SuperCalc spreadsheet
CAP  Ventura Pub. captions
CDR  Corel Draw vector graphics
CFG  Configuration

CGM  CGM vector graphics
CHP  Ventura Pub. chapter
CHK  DOS Chkdsk chained file
CIF  Ventura Pub. chapter info.
COB  COBOL source code
CLP  Windows clipboard

COM  Executable program
CPI  DOS code page
CPP  C++ source code
CSV  Comma delimited
CUT  Dr. Halo graphics

DAT  Data
DB   Paradox table
DBF  dBASE database
DBT  dBASE text
DCA  IBM text
DCT  Dictionary

DIB  Device independent BMP
DIC  Dictionary
DIF  Spreadsheet
DLL  Dynamic link library
DOC  Document (Multimate, Word...)
DOX  MultiMate V4.0 document

DPI  Pointline raster graphics
DRV  Driver
DRW  Micrografx Designer vector graphics
DWG & DXF  AutoCAD vector formats

EPS  Encapsulated PostScript
EXE  Executable program

FAX  Group 3 fax
FDX  Force index
FLC, FLI  AutoDesk animation
FMT  dBASE Screen format
FNT  Windows font
FON  Font or telephone no.

FOR  FORTRAN source code
FOT  Windows TrueType font info.
FOX  FoxBase compiled program
FRM  dBASE report layout

GCA  IBM MO:DCA graphics
GED  Arts & Letters graphics
GEM  GEM vector graphics
GIF  CompuServe raster graphics
GRF  Micrografx Charisma vector graphics
GRP  Windows ProgMan Group
GX1 & GX2  Show Partner raster graphics


HLP  Help text
HPL  HP Graphics language
HYC  WordPerfect hypen list

ICA  IBM MO:DCA raster graphics
ICO  Windows icons
IDX  FoxBase index
IL   Icon library (hDC Computer)
IMG  GEM Paint raster graphics
INF  Information
INI  Initialization

JT   JT Fax

LBL  dBASE label
LBM  Deluxe Paint graphics
LIB  Function library
LZH  LHARC compressed

MAC  MacPaint raster
MAP  Linkage editor map
MET  OS/2 Metafile
MEU  Menu items
MDX  dBASE IV multi-index
MID  MIDI sound file
MSP  Microsoft Paint raster graphics

NDX  dBASE index
NG   Norton Guides text

OAZ  OAZ Fax
OBJ  Object module
OVL  Overlay module
OVR  Overlay module

PAS  Pascal source code
PCL  HP LaserJet
PCM  LaserJet cartridge info.
PCT  PC Paint raster and
      Mac PICT format
PCW  PC Write document
PCX  PC Paintbrush raster graphics

PDF  Printer driver
PDV  PC Paintbrush printer driver
PFA  Type 3 font
PFB  Type 1 font
PFM  Windows Type 1 font metrics
PGL  HPGL graphics

PIC  Vector vector formats:
      Lotus 1-2-3, Micrografx Draw,
      Mac PICT format
     IBM Storyboard raster format
PIF  Windows info. for DOS programs,
     IBM Picture Interchange
PM   PageMaker graphics/text
PMx  PageMaker document (x=ver.)
PTx  PageMaker template (x=ver.)
PRD  Word printer driver

PRG  dBASE source code
PRN  XyWrite printer driver
PRN  Temporary print file
PRS  WordPerfect printer driver
PRT  Formatted text
PS   PostScript page description

QLC  ATM font info.

RAS  Sun raster graphics
RIB  Renderman graphics
RIC  Roch FaxNet
RIX  RIX virtual screen
RLE  Compressed
RTF  Microsoft text/graphics

R8P  LaserJet portrait font
R8L  LaserJet landscape font

SAM  Ami Pro document
SBP  IBM Storyboard vector graphics
SC   Paradox source code
SCx  ColoRIX raster (x=res.)
SCR  dBASE screen layout
SCR  Script

SCT  Lotus Manuscript screen capture text
SET  Setup parameters
SFP  LaserJet portrait font
SFL  LaserJet landscape font
SFS  PCL 5 scalable font
SLD  AutoCAD slide

SND  Aristosoft sound
SPD  Speedo scalable font
STY  Ventura Pub. style sheet
SYL  SYLK format (spreadsheets)
SYS  DOS, OS/2 driver

TAL  Adobe Type Align shaped text
TDF  Speedo typeface definition
TFM  Intellifont font metrics
TIF  TIFF raster graphics
TMP  Temporary
TTC  TrueType font compressed

TTF  TrueType font
TXT  ASCII text

USP  LaserJet portrait font
USL  LaserJet landscape font

VGR  Ventura Pub. chapter info.
VOC  Sound Blaster sound
VUE  dBASE relational view

WAV  Windows sound
WKQ  Quattro spreadsheet
WKS  Lotus 1-2-3 ver. 1a spreadsheet
WK1  Lotus ver. 2.x
WK3  Lotus ver. 3.x & Windows
WMF  Windows Metafile
WPG  WordPerfect vector graphics

WPM  WordPerfect macro
WRI  Windows Write document
WRK  Sympohony spreadsheet

XFX  JetFax
XLS  Excel spreadsheet
XLC  Excel chart

ZIP  PKZIP compressed
ZOO  Zoo compressed

$$$  Temporary


extent
Contiguous space on a disk reserved for a file or
application.


external command
(1) In DOS and OS/2, a function performed by a
separate utility program that accompanies the
operating system.

(2) A user-developed HyperCard command.  See XCMD.


external interrupt
Interrupt caused by an external source such as the
computer operator, external sensor or monitoring
device, or another computer.


external modem
Self-contained modem that can be connected to the
serial port of any computer.  It gets its power
from a wall outlet.  Contrast with internal modem.


external reference
In programming, a call to a program or function
that resides in a separate, independent library.


external sort
Sort program that uses disk or tape as temporary
workspace.  Contrast with internal sort.


external storage
Storage outside of the CPU, such as disk and tape.



f
See farad.


F connector
Coaxial cable connector used to connect antennas,
TVs and VCRs.  It is easily recognized: the plug's
inner wire is stripped bare and sticks out of the
connector looking very unfinished.


F keys
See function keys.


facilities management
Management of a user's computer installation by an
outside organization.  All operations including
systems, programming and the datacenter can be
performed by the facilities management organization
on the user's premises.


facsimile
See fax.


factorial
Number of sequences that can exist with a set of
items, derived by multiplying the number of items
by the next lowest number until 1 is reached.  For
example, three items have six sequences (3x2x1=6):
123, 132, 231, 213, 312 and 321.


fail safe
Same as fault tolerant.


fail soft
Ability to fail with minimum destruction.  For
example, a disk drive can be built to automatically
park the heads when power fails.  Although it
doesn't correct the problem, it minimizes
destruction.


FAMOS
(Floating gate Avalanche-injection Metal Oxide
Semiconductor)  Type of EPROM.


fan-fold paper
Same as continous forms.


fan in
To direct multiple signals into one receiver.


fan out
To direct one signal into multiple receivers.


far pointer
In an Intel x86 segmented address, a memory address
that includes both segment and offset.  Contrast
with near pointer.


farad
Unit of electrical charge that is used to measure
the storage capacity of a capacitor.  In
microelectronics, measurements are usually in
microfarads or picofarads.


Fast
Asynchronous communications protocol used to
quickly transmit files over high-quality lines.
Error checking is done after the entire file has
been transmitted.


Fast Eddy
Code name for Apple/Sony devlopment of a consumer-
oriented CD ROM product that connects to the TV,
similar to CD-I and CDTV.


Fast Fourier Transform
Class of algorithms used in digital signal
processing that break down complex signals into
elementary components.


FastCAD
Full-featured PC CAD program from Evolution
Computing, Tempe, AZ, known for its well-designed
user interface.  It requires a math coprocessor.
Users with less sophisticated requirements can
start out with FastCAD's baby brother, EasyCAD.


FastDisk
Windows 3.1 driver that accesses the hard disk
directly to improve performance.  See WinDisk.


FAT
See DOS FAT.


fatal error
Condition that halts processing due to read errors,
program bugs or anomalies.


FatBits
MacPaint option in the "Goodies" menu that lets a
user edit an image a pixel at a time.


father file
See grandfather, father, son.


fault tolerant
Continous operation in case of failure.  A fault
tolerant system can be created using two or more
computers that duplicate all processing, or having
one system stand by if the other fails.  It can
also be built with redundant processors, control
units and peripherals architecturally integrated
from the ground up (Tandem, Stratus, etc.).

   Fault tolerant operation requires backup power
in the event of power failure.  It may also imply
duplication of systems in disparate locations in
the event of natural catastrophe or vandalism.


fax
(FACSimile)  Originally called telecopying, it is
the communication of a printed page between remote
locations.  Fax machines scan a paper form and
transmit a coded image over the telephone system.
The receiving machine prints a facsimile of the
original.  A fax machine is made up of a scanner,
printer and modem with fax signalling.

   Groups 1 and 2, used in the 1970s and 1980s,
transmit at six and three minutes per page
respectively.  Group 3 transmits up to 9,600 baud
using data compression at less than one minute per
page.  This speed increase led to the extraordinary
rise in usage in the late 1980s, resulting in
today's most universal form of electronic mail.

  Group 3 resolution is 203x98 dpi in standard mode
and 203x196 dpi in fine mode.  Higher-speed Group 4
machines rely on all-digital (ISDN) networks which
may not be prevalent until the mid 1990s.


fax board
Fax transmission on an expansion board.  It uses
software that generates fax signals directly from
disk files or the screen and transmits a sharper
image than a fax machine, which gets its image by
scanning.  Incoming faxes are printed on the
computer's printer.


fax/modem
Combination fax board and data modem available as
an external unit or expansion board.  It includes a
fax switch that routes the call to the fax or the
data modem.


fax switch
Device that tests a phone line for a fax signal and
routes the call to the fax machine.  When a fax
machine dials a number and the line answers, it
emits an 1,100Hz tone to identify itself.  Some
devices handle voice, fax and data modem switching
and may require keying in an extension number to
switch to the modem.


FCB
See DOS FCB.


FCC
(Federal Communications Commission)  Regulatory
body for U.S. interstate telecommunications
services as well as international service
originating in the U.S.  It was created under the
U.S. Communications Act of 1934, and its board of
commissioners is appointed by the President.


FCC Class
FCC certification of radiation limits on digital
devices.  Class A certification is for business
use.  Class B for residential use is more stringent
in order to avoid interference with TV and other
home reception.  See Part 15, Subpart B, of the
Federal Register (CFR 47, Parts 0-19).


FCFS
First come, first served.


fci
(Flux Changes per Inch) Measurement of polarity
reversals on a magnetic surface.  In MFM, each flux
change is equal to one bit.  In RLL, a flux change
generates more than one bit.


FD
(Floppy Disk)  For example, FD/HD refers to a
floppy disk/hard disk device.


FD:OCA
(Formatted Data:Object Content Architecture)  SAA-
compliant (CCS) specification for formatting data
in fields.


FDDI
(Fiber Distributed Data Interface)   ANSI standard
token passing LAN that uses optical fiber cabling
and transmits at 100 Mbits/sec up to 62 miles.
FDDI specifications deal with OSI layers 1 and 2.

   It provides an optional "dual counter-rotating
ring" topology that contains primary and secondary
rings with data flowing in opposite directions.  If
the line breaks, the secondary ring is used to
bypass the fault.


    ███─────P───███     ███─────P───███
    ███──────S──███     ███──────S──███
    ││            ││     ││            ││

    ││            ││     ││            ││
    ███─────────███     ███───    ───███
    ███─────────███     ███───    ───███

    Normal Operation        Rerouted


   Stations can be configured as Single Attached
Stations (SAS) connected to concentrators, or as
Dual Attached Stations (DAS), connected to both
rings.  Groups of stations are typically wired to
concentrators connected in a hierarchical tree to
the main ring.  Large networks may be configured as
a "dual ring of trees," in which the dual ring
provides the backbone to which multiple hierarchies
of concentrators are attached.

   FDDI provides a quantum leap in speed over
Ethernet, Token Ring and other LANs and allows
high-resolution graphics and digital video to be
quickly transmitted.  See CDDI.


FDISK
See DOS Fdisk.


FDM
(Frequency Division Multiplexing)  Method used to
transmit multiple signals over a single channel.
Each signal (data, voice, etc.) modulates a carrier
with a different frequency and all signals travel
simultaneously over the channel.  Contrast with
TDM.  See baseband.


FDX
See full-duplex.


FEA
(Finite Element Analysis)  Mathematical technique
for analyzing stress, which breaks down a physical
structure into substructures, called finite
elements.  The finite elements and their
interrelationships are converted into equation form
and solved mathematically.

   Graphics-based FEA software can display the
model on screen as it is being built and, after
analysis, display the object's reactions under load
conditions.  Models created in popular CAD packages
can often be accepted by FEA software.


feasibility study
Analysis of a problem to determine if it can be
solved effectively.  The operational (will it
work?), economical (costs and benefits) and
technical (can it be built?) aspects are part of
the study.  Results of the study determine whether
the solution should be implemented.


feature negotiation
See automatic feature negotiation.


FEC
See forward error correction.


federal regulations
See NCSC and Computer Security Act.


female connector
Receptacle into which the male counterpart of the
connector is plugged.


femtosecond
One quadrillionth of a second.  See space/time.


FEP
See front end processor.


ferric oxide
(Fe2O3)  Oxidation of iron used in the coating of
magnetic disks and tapes.


ferromagnetic
Capability of a material, such as iron and nickel,
to be highly magnetized.


FET
(Field Effect Transistor)  Type of transistor used
in MOS integrated circuits.


fetch
To locate the next instruction in memory for
execution by the CPU.


FF
See form feed.


FFT
See Fast Fourier Transform.


Fiber Channel
Future ANSI standard under development for a high-
speed computer channel that incorporates IPI, SCSI
and HiPPI command sets.  Speeds range from 12.5 to
100 MBytes/sec using coax and optical fiber.


fiber optic
Communications systems that use optical fibers for
transmission.  See optical fiber.


Fibonacci numbers
Series of whole numbers in which each number is the
sum of the two preceding ones: 1, 1, 2, 3, 5, 8,
13, etc.  It is used to speed up binary searches by
dividing the search into the two lower numbers; for
example, 13 items would be divided into 5 and 8
items; 8 items would be divided into 5 and 3.


fiche
Same as microfiche.


FidoNet
E-mail protocol that originated from the Fido BBS
created by Tom Jennings in 1984.  Over 10,000
FidoNet nodes are in use.  Users must have their
networks active for one universal hour in the early
morning, and the software must adhere to the FTSC-
001 specification.  The FidoNet address format is
zone:local net/node; for example, Boardwatch
Magazine's address is 1:104/555.


field
Physical unit of data that is one or more bytes in
size.  A collection of fields make up a record.  A
field also defines a unit of data on a source
document, screen or report.  Examples of fields are
NAME, ADDRESS, QUANTITY and AMOUNT DUE.

   The field is the common denominator between the
user and the computer.  When you interactively
query and update your database, you reference your
data by field name.

   A field is a physical unit of storage, whereas a
data item refers to the data itself.  For example,
the data items, Chicago, Dallas and Phoenix are
stored in the CITY field.

   The terms field, data element, data item and
variable refer to the same unit of data and are
often used interchangeably.


field engineer
Person who is responsible for hardware
installation, maintentance and repair.  Formal
training is in electronics, although many people
have learned on the job.


field name
Assigned name for a field (NAME, ADDRESS, CITY,
STATE, etc.) that will be the same in every record.


field separator
Character used to mark the separation of fields in
a record.  See comma delimited and tab delimited.


field service
See field engineer.


field squeeze
In a mail merge, a function that eliminates extra
blank spaces between words when fixed-length fields
are inserted into the document text.  See line
squeeze.


field template
See picture.


FIF
(Fractal Image Format)  Graphics file format from
Iterated Systems, Inc., Norcross, GA, that stores
fractal images with compression ratios as high as
2,500:1.


FIFO
(First In-First Out)  Storage method that retrieves
the item stored for the longest time.  Contrast
with LIFO.


fifth-generation computer
Computer designed for AI applications.  Appearing
in the late 1990s, these systems will represent the
next technology leap.


file
(1) In data management, a collection of related
records.

(2) In word processing, a single text document.

(3) In computer graphics, a set of image
descriptors for one picture, either in TV-like
format (raster graphics) or in line, or object,
format (vector graphics).

(4) In programming, the source program and machine
language program are stored as individual files.

(5) In computer operations, any collection of data
that is treated as a single unit on a peripheral
device, such as any of the examples in items 1
through 4 above.


file and record locking
First-come, first-served technique for managing
data in a multiuser environment.  The first user to
access the file or record prevents, or locks out,
other users from accessing it.  After the file or
record is updated, it is unlocked and available.


file attribute
File access classification that allows a file to be
retrieved or erased.  Typical attributes are
read/write, read only, archive and hidden.


file compression
See data compression.


file conversion.
See conversion.


file extension
See extension.


file extent
See extent.


file format
Structure of a file.  There are hundreds of
proprietary formats for database, word processing
and graphics files.  See record layout.


file layout
Same as record layout.


file maintenance
(1) Periodic updating of master files.  For
example, adding/deleting employees and customers,
making address changes and changing product prices.
It does not refer to daily transaction processing
and batch processing (order processing, billing,
etc.).

(2) Periodic reorganization of the disk drives.
Data that is continuously updated becomes
physically fragmented over the disk space and
requires regrouping.  An optimizing program is run
(daily, weekly, etc.) that rewrites all files
contiguously.


file manager
(1) Software that manages data files.  Often
erroneously called database managers, file managers
provide the ability to create, enter, change, query
and produce reports on one file at a time.  They
have no relational capabilty and usually don't
include a programming language.

(2) Software used to manage files on a disk.  It
provides functions to delete, copy, move, rename
and view files as well as create and manage
directories.


file name
Name assigned by the user or programmer that is
used to identify a file.


file protect ring
Plastic ring inserted into a reel of magnetic tape
for file protection.


file protection
Preventing accidental erasing of data.  Physical
file protection is provided on the storage medium
by turning a switch, moving a lever or covering a
notch.  On 1/2" tape, a plastic ring in the center
of the reel is removed (no ring-no write).  In
these cases, writing is prohibited even if the
software directs the computer to do so.

   Logical file protection is provided by the
operating system, which can designate a single file
as read only.  This method allows both regular
(read/write) and read only files to be stored on
the same disk volume.  Files can also be designated
as hidden files, which makes them invisible to most
software programs.


              Protecting Floppies

3.5"
On the back of the disk (metal door at top), slide
the square, plastic window (bottom right) downward
uncovering a hole through the disk.

5.25"
Cover the side notch with a stick-on label.

8"
Remove stick-on label covering the side notch.


file recovery program
Software that recovers disk files that have been
accidentally deleted or damaged.


file server
High-speed computer in a LAN that stores the
programs and data files shared by users on the
network.  Also called a network server, it acts
like a remote disk drive.  See database server.


file sharing protocol
Communications protocol that provides a structure
for file requests (open, read, write, close, etc.)
between stations in a network.  If file sharing is
strictly between workstation and server, it is also
called a client/server protocol.  It refers to
layer 7 of the OSI model.


file size
Length of a file in bytes.  See "Byte
Specifications" in the term byte.


file spec
(file SPECification)  Reference to the location of
a file on a disk, which includes disk drive,
directory name and file name.  For example, in DOS
and OS/2, c:\wordstar\books\chapter is a file spec
for the file CHAPTER in the BOOKS subdirectory in
the WORDSTAR directory on drive C.


file system
(1) Method for cataloging files in a computer
system.  See hierarchical file system.

(2) Data processing application that manages
individual files.  Files are related by customized
programming.  Contrast with relational database.


file transfer protocol
Communications protocol that can transmit files
without loss of data.  It implies that it can
handle binary data as well as ASCII data.  Common
examples are Xmodem, Ymodem, Zmodem and Kermit.


file viewer
Software that displays the contents of a file as it
would be normally displayed by the application that
created it.  It is usually capable of displaying a
variety of common formats.


FileMaker II
Macintosh file manager from Claris.  It is a
popular program for general data management and
provides a variety of statistical functions, fast
search capabilities and extensive reporting
features.


FileMan
(1) Public-domain MUMPS software that provides a
stand-alone, interactive DBMS as well as a set of
utilities for the MUMPS programmer.

(2) Slang for Windows' file manager, which is
precisely named "File Manager."


filespec
See file spec.


fill
(1) In a paint program, to change the color of a
bordered area.

(2) In a spreadsheet, to enter common or repetitive
values into a group of cells.


fill pattern
(1) Color, shade or pattern used to fill an area of
an image.

(2) Signals transmitted by a LAN station when not
receiving or transmitting data in order to maintain
synchronization.


film recorder
Device that takes a 35mm slide picture from a
graphics file, which has been created in a CAD,
paint or business graphics package.  It generates
very high resolution, typically 2,000 to 4,000
lines.

   It typically works by recreating the image on a
built-in CRT that shines through a color wheel onto
the film in a standard 35mm camera.  Some units
provide optional Polaroid camera backs for instant
previewing.  Film recorders can be connected to
personal computers by plugging in a controller
board cabled to the recorder.


filter
(1) Process that changes data, such as a sort
routine that changes the sequence of items or a
conversion routine (import or export filter) that
changes one data, text or graphics format into
another.

(2) Pattern or mask through which only selected
data is passed.  For example, certain E-mail
systems can be programmed to filter out important
messages and alert the user.  In dBASE, set filter
to file overdue, compares all data to the matching
conditions stored in OVERDUE.


financial planning language
Language used to create data models and command a
financial planning system.


financial planning system
Software that helps the user evaluate alternatives.
It allows for the creation of a data model, which
is a series of data elements in equation form; for
example, gross profit = gross sales - cost of goods
sold.  Different values can be plugged into the
elements, and the impact of various options can be
assessed (what if?).

   It is a step above spreadsheets by providing
additional analysis tools; however, some of these
capabilities are being added to spreasheets.  For
example, sensitivity analysis assigns a range of
values to a data element, which causes that data to
be highlighted if it ever exceeds that range.

   Goal seeking provides automatic calculation.
For example, by entering gross margin = 50% as well
as the minimums and maximums of the various inputs,
the program will calculate an optimum mix of inputs
to achieve the goal (output).


Finder
The part of the Macintosh operating system that
manages the desktop.  It keeps track of icons,
controls the Clipboard and Scrapbook and allows
files to be copied.  Finder manages one application
at a time.  Multifinder manages multiple
applications on screen.


fingerprint reader
Scanner used to identify a person's fingerprint for
security purposes.  After a sample is taken, access
to a computer or other system is granted if the
fingerprint matches the stored sample.  A PIN may
also be used with the fingerprint sample.


finite element
See FEA.


firmware
Category of memory chips that hold their content
without electrical power and include ROM, PROM,
EPROM and EEPROM technologies.  Firmware becomes
"hard software" when holding program code.


first-generation computer
Computer that used vacuum tubes as switching
elements; for example, the UNIVAC I.


fixed disk
Non-removable hard disk such as is found in most
personal computers.  Programs and data are copied
to and from the fixed disk.


fixed-frequency monitor
Monitor that accepts one type of video signal, such
as VGA only.  Contrast with multiscan monitor.


fixed head disk
Direct access storage device, such as a disk or
drum, that has a read/write head for each track.
Since there is no access arm movement, access times
are significantly improved.


fixed length field
Constant field size; for example, a 25-byte name
field takes up 25 bytes in each record.  It is
easier to program, but wastes disk space and
restricts file design.  Description and comment
fields are always a dilemma.  Short fields allow
only abbreviated remarks, while long fields waste
space if lengthy comments are not required in every
record.  Contrast with variable length field.


fixed length record
Data record that contains fixed length fields.


fixed point
Method for storing and calculating numbers in which
the decimal point is always in the same location.
Contrast with floating point.


Fkey
(Function key)  Macintosh command sequence using
command, shift and option key combinations.  For
example, Fkey 1 (command-shift 1) ejects the
internal floppy.


flag
(1) In communications, a code in the transmitted
message which indicates that the following
characters are a control code and not data.

(2) In programming, a "yes/no" indicator built into
certain hardware or created and controlled by the
programmer.


flame
Slang for communicating emotionally and/or
excessively via electronic mail.


flash memory
Memory chip that holds its content without power,
but must be erased in bulk.  Originally coined by
Toshiba, the term comes from its ability to be
erased "in a flash."  Derived from EEPROMs, flash
memory chips are less expensive and provide higher
bit densities.

   As future designs provide for less-than-whole-
chip erasure, and ultimately, byte by byte erasure,
flash memory may provide an alternative to current-
day RAM.


flat address space
Memory addressing in which each byte is referenced
by a different sequential number starting with 0.
Contrast with segmented address space.


flat file
Stand-alone data file that does not have any pre-
defined linkages or pointers to locations of data
in other files.  The term usually refers to files
managed by file managers with no relational
capability.  In the past, this referred to the very
type of file used in relational databases.


flat panel display
Thin display screen that uses any of a number of
technologies, such as LCD, electroluminscent or
plasma.  Used today in laptops to reduce size and
weight, they will eventually supersede CRTs.


flat shading
In computer graphics, a technique for computing a
one-tone shaded surface to simulate simple
lighting.


flatbed plotter
Graphics plotter that draws on sheets of paper that
have been placed in a bed.  The size of the bed
determines the maximum size sheet that can be
drawn.


flexible disk
Same as floppy disk and diskette.


flicker
Fluctuating image on a video screen.


flip-flop
Electronic circuit that alternates between two
states.  When current is applied, it changes to its
opposite state (0 to 1 or 1 to 0).  Made of several
transistors, it is used in the design of static
memories and hardware registers.


flippy board
PC expansion board that connects to both ISA/EISA
and Micro Channel buses.  ISA/EISA connectors are
on one edge of the board, MCA on the other.


flippy-floppy
Single-sided 5.25" floppy converted to double-sided
use by punching a second notch into the disk so
that it can be flipped over and inserted upside
down.  This is not recommended as the disk's
rotation is alternated.


float
In programming, a declaration of a floating point
number.


floating point
Method for storing and calculating numbers in which
the decimal points don't line up as in fixed point
numbers.  The significant digits are stored as a
unit called the mantissa, and the location of the
radix point (decimal point in base 10) is stored in
a separate unit called the exponent.  Floating
point methods are used for calculating a large
range of numbers quickly.

   Floating point operations can be implemented in
hardware (math coprocessor), or they can be done in
software.  They can also be performed in a separate
floating point processor that is connected to the
main processor via a channel.

         Mantissa Exponent    Value
        ┌────────┬────────┬──────────┐
        │  6508  │    0   │   6508   │
        │  6508  │    1   │  65080   │
        │  6508  │   -1   │    650.8 │
        └────────┴────────┴──────────┘

               Floating Point



floating point processor
Arithmetic unit designed to perform floating point
operations.  It may be a coprocessor chip in a
personal computer, a CPU designed with built-in
floating point capabilities or a separate machine,
often called an array processor, which is connected
to the main computer.


floppy disk
Reusable magnetic storage medium.  It is the
primary method for distributing personal computer
software.  It's also used to transfer data between
users, although local area networks can eliminate
much of this "sneakernet."

   Also called a diskette, the floppy is a flexible
disk, similar to tape, with both surfaces used for
magnetic recording.  The disk drive grabs the
floppy's center and spins it inside its housing,
and the read/write head makes contact with the
surface through an opening in the floppy's
envelope, case or cartridge.

   Floppies are much slower than hard disks,
because they spin at 300 rpm, a tenth the rotation
of a hard disk, and they are at rest until a data
transfer is requested.  In order of first to last
developed, the major types are:

 Creator   External format          Capacity
 IBM       8" flexible envelope     100 - 500KB
 Shugart   5.25" flexible envelope  100KB - 1.2MB
 Sony      3.5" rigid case          400KB - 4MB +

   Although floppy disks look the same, what's
recorded on them determines their capacity and
compatibility.  Each new floppy must be
"formatted," which records the sectors on the disk
that will hold the data.  PC, Mac, Apple II, Amiga
and Atari formats are different, although most can
read and write PC (DOS) diskettes.  See format
program, Floptical and magnetic disk.


FLOPS
(FLoating point Operations Per Second)  Unit of
measurement of floating point calculations.  For
example, 100 megaflops is 100 million floating
point operations per second.


Floptical
Floppy disk from Insite Peripherals, Inc., San
Jose, CA, that records data magnetically, but uses
grooves in the disk to optically align the head
over the tracks.  The first 3.5" Floptical drive
uses 21MB diskettes and can also read and write
720KB and 1.44MB diskettes.


flow chart
Graphical representation of the sequence of
operations in an information system or program.
Information system flow charts show how data flows
from source documents through the computer to final
distribution to users.  Program flow charts show
the sequence of instructions in a single program or
subroutine.  Different symbols are used to draw
each type of flow chart.


flow control
(1) In communications, the management of data
transmission.  It ensures that the receiving
station can process the data before the next block
is sent.

(2) In programming, the if-then and loop statements
that make up the program's logic.


flush
To empty the contents of a memory buffer onto disk.


flush center
               In typography,
       refers to centering text uniformly
       between the left and right margins
              as is this paragraph.


flush left
In typography, the alignment of all text uniformly
to the left margin.  All text is typically set
flush left as is this paragraph.


flush right
In typography, the alignment of all text
           uniformly to the right margin
            while the left margin is set
       ragged left as is this paragraph.


flux
Energy field generated by a magnet.


FM
(1) (Frequency Modulation)  Transmission technique
that blends the data signal into a carrier by
varying (modulating) the frequency of the carrier.
See modulate.

(2) (Frequency Modulation)  Earlier magnetic disk
encoding method that places clock bits onto the
medium along with the data bits.  It has been
superseded by MFM and RLL.


Fn key
(FuNction key)  Keyboard key that works like a
shift key to activate the second function on a
dual-purpose key, typically found on laptops to
reduce keyboard size.  It is different than the
function keys F1, F2, etc.


FOCA
(Font Object Content Architecture)  See MO:DCA.


FOCUS
(1) DBMS from Information Builders, Inc., New York,
that runs on PCs, mainframes and minis.  It allows
relational, hierarchical and network data
structures and can access a variety of databases,
including standard IBM mainframe files, DB2, IMS,
IDMS and others.  It includes a fourth-generation
language and a variety of decision support
facilities.

(2) (Federation On Computing in the U.S.)  U.S.
representative of IFIP.  Address: IEEE Computer
Society, 1730 Mass. Ave. N.W., Washington, DC
20036, 202/371-0101.


FOIRL
(Fiber Optic Inter Repeater Link) IEEE standard for
fiber optic Ethernet.


folder
In the Macintosh, a simulated file folder that
holds documents (text, data or graphics),
applications and other folders.  A folder is like a
DOS directory.  A folder within a folder is like a
DOS subdirectory.


Folio
(1) Text management software for PCs from Folio
Corp., Provo, UT, that provides storage, retrieval
and hypertext capability for text databases.  It
can import text from over 40 file formats.  Folio
files are called "Infobases."

(2) (folio) In typography, a printed page number.
For example, folio 3 could be the 27th physical
page in a book.


font
Set of type characters of a particular typeface
design and size.  Each typeface (Times Roman,
Helvetica, etc.) generally includes normal weight
and bold, italic and bold italic variations of the
typeface, which consitute four fonts.  For
bitmapped fonts, which include pre-defined bitmaps
for each point size, four fonts are required for
each point size.  For scalable fonts, which create
bitmaps in the required size on the fly, only four
fonts are required for each typeface.

   Fonts are either built into the printer or are
available as plug-in cartriges or as soft fonts,
which reside in the computer.  See bitmapped font
and scalable font.


font cartridge
Set of bitmapped or outline fonts for one or more
typefaces contained in a plug-in module for the
printer.  The fonts are stored in a ROM chip within
the cartridge.  Contrast with soft font and
internal font.


font characteristics
Font selection in an HP LaserJet is made by sending
a coded command to the printer with the following
criteria:

  Code               Characteristic

Typeface     Design (Courier, Times Roman, etc.)
Orientation  Portrait or landscape
Symbol set   Country or special characters
Spacing      Proportional or fixed spacing (width)
Pitch        Characters per inch (if fixed spacing)
Point size   Height of characters
Style        Upright or italic
Stroke       Light, medium or bold appearance
 weight


font compiler
Same as font generator.


font editor
Software that allows fonts to be designed and
modified.


font family
Set of fonts of the same typeface in assorted
sizes, including bold, italic and bold italic
variations.


font generator
Software that converts an outline font into a
bitmap (dot pattern required for a particular font
size).  Font generation is not linear, simply
expanding a letter to any size.  As fonts get
bigger, their characteristics must change in order
to make them attractive.  Font generation implies
creating fonts in advance of printing and storing
them on disk.  Font scaling implies creating fonts
on the fly as needed.  See font scaler.


font metric
Typographic information (width, height, kerning)
for each character in a font.


font number
Identification number assigned to a font.  A
program references the font by this number.


font rasterizer
See font scaler.


font scaler
Software that converts scalable fonts into bitmaps
on the fly as required for display or printing.
Examples are TrueType, Adobe Type Manager and
Bitstream's Facelift.  See font generator and
scalable font.


font style
Typeface variation (normal, bold, italic, bold
italic).


font utility
Software that provides functions for managing
fonts, including the ability to download, install,
design and modify fonts.


font weight
Thickness of characters (light, medium or bold).


Fontware
Font generator for PCs from Bitstream Inc.,
Cambridge, MA, that includes a library of outline
fonts.  Typeface packages include normal, italic,
bold and bold italic weights.


foo
Popular name for a temporary file, function or
variable, or example of same.  Often used in
conjunction with "bar," from "fubar" (Fouled Up
Beyond All Recognition).


footer
In a document or report, common text that appears
at the bottom of every page.  It usually contains
the page number.


footnote
Text that appears at the bottom of a page, which
adds explanation.  It is often used to give credit
to the source of information.  When accumulated and
printed at the end of a document, they are called
endnotes.


footprint
Amount of geographic space covered by an object.  A
computer footprint is the desk or floor surface it
occupies.  A satellite's footprint is the earth
area covered by its downlink.


for statement
High-level programming language structure that
repeats a series of instructions a specified number
of times.  It creates a loop that includes its own
control information.  The following examples print
"Hello" 10 times:

     BASIC                       C
  for x = 1 to 10     for (x = 0;  x < 10;  x++)
   print "hello"       printf ("hello\n");
  next x



Force
dBASE compiler from Sophco, Inc., Boulder, CO, that
combines C and dBASE structures.  It is noted for
generating very small executable programs.


foreground/background
Priority assigned to programs running in a
multitasking environment.  Foreground programs have
highest priority, and background programs have
lowest.  Online users are given the foreground, and
batch processing activities (sorts, updates, etc.)
are given the background.  If batch activities are
given a higher priority, terminal response times
may slow down considerably.

   In a personal computer, the foreground program
is the one the user is currently working with, and
the background program might be a print spooler or
communications program.


Forest & Trees
Data analysis program for PCs from Channel
Computing, Inc., Newmarket, NH, that integrates
data from a variety of applications.  It provides a
control room interface that lets users monitor
important business information.


form
(1) Paper form used for printing.

(2) Screen display designed for a particular
application.


form factor
Physical size of a device.


form feed
Advancing a printer form to the top of the next
page.  It is done by pressing the printer's form
feed (FF) button or by sending the form feed code
(ASCII 12) to the printer from the computer.


form view
Screen display showing one item or record arranged
like a preprinted form.  Contrast with table view.


format
Structure, or layout, of an item.  Screen formats
are fields on the screen.  Report formats are
columns, headers and footers on a page.

   Record formats are the fields within a record.
File formats are the structure of data files, word
processing documents and graphics files (display
lists and bitmaps) and all associated codes.  See
format program, disk format, DOS Format and style
sheet.


format program
Software that initializes a disk.  There are two
formatting levels.  The low-level initializes the
disk surface by creating the physical tracks and
storing sector identification in them.  Low-level
format programs are geared to the drive technology
used (IDE, SCSI, etc.).

   The high-level format lays out the indexes used
by the operating system (Mac, DOS, etc.) to keep
track of data stored in the sectors.

   Floppy disk format programs perform both levels
on a diskette.  See DOS Format.


formula
(1) Arithmetic expression that solves a problem.
For example, (fahrenheit-32)*5/9 is the formula for
converting fahrenheit to centigrade.

(2) In spreadsheets, an algorithm that identifies
how the data in a specific number of cells is to be
calculated.  For example, +C3*D8 means that the
contents of cell C3 are to be multipled by the
contents of cell D8 and the results are to be
placed where the formula is located.


FORTH
(FOuRTH-generation language)  High-level
programming language created by Charles Moore in
the late 1960s as a way of providing direct control
of the computer.  Its syntax resembles LISP, it
uses reverse polish notation for calculations, and
it is noted for its extensibility.

   It is both compiler and interpreter.  The source
program is compiled first and then executed by its
operating system/interpreter.  It is used in
process control applications that must quickly
process data acquired from instruments and sensors.
It is also used in arcade game programming as well
as robotics and other AI applications.  The
following polyFORTH example converts Fahrenheit to
Celsius:

   : CONV ( n) 32 - 5 9 * / . ." Celsius
   : USER_INPUT  ." Enter Fahrenheit " CONV ;



FORTRAN
(FORmula TRANslator)  First high-level programming
language and compiler, developed in 1954 by IBM.
It was originally designed to express mathematical
formulas, and although it is used occasionally for
business applications, it is still the most widely
used language for scientific, engineering and
mathematical problems.

   FORTRAN IV is an ANSI standard, but FORTRAN V
has various proprietary versions.
   The following example converts Fahrenheit to
Celsius:

   WRITE(6,*) 'Enter Fahrenheit '
   READ(5,*) XFAHR
   XCENT = (XFAHR - 32) * 5 / 9
   WRITE(6,*) 'Celsius is ',XCENT
   STOP
   END



FORTUNE 500
The following figures are the 1991 and 1992 FORTUNE
500 ranking of computer and electronics firms.
Reprinted with permission of FORTUNE Magazine.  See
vendors and software vendors.

(c) 1992-1993 The Time Inc. Magazine Company.
            All rights reserved.


  1 9 9 2  COMPUTERS/OFFICE EQUIPMENT
                         Sales  Profit Employees
Rank  Company              (000,000)     (000)
  4  IBM                 65,096  (4,965)  308
 24  Hewlett-Packard     16,427     549    93
 27  Digital Equipment   14,027  (2,796)  114
 62  Unisys               8,422     361)   54
 76  Apple Computer       7,087     530    15

119  Compaq Computer      4,132     213    10
139  Sun Mircosystems     3,628     173    13
144  Pitney Bowes         3,460     100    29
164  Seagate Technology   2,889      63    43
182  Amdahl               2,554     (7)     9

203  Conner Peripherals   2,273     121    13
217  Tandem Computers     2,058     (41)   11
225  Wang Laboratories    1,910    (357)   13
270  Storage Technology   1,521      15    10
315  Intergraph           1,182       8    10

327  Quantum              10,128      47    18
328  Data General         1,127     (63)    7
331  Gateway 2000         1,107      70    18
348  SCI Systems          1,045       4    10
351  Maxtor               1,039       7     8

367  AST Research           951      69     4
370  Western Digital        940     (73)    7
385  Dell Computer          890      51     3
392  Silicon Graphics       867    (118)    4
408  Cray Research          798     (15)    5
               TOTAL    146,557  (6,051)  794


  1 9 9 2  ELECTRONICS/ELECTRICAL
                         Sales  Profit Employees
Rank  Company              (000,000)     (000)
5    General Electric    62,202   4,725    268
32   Motorola            13,341     453    107
35   Westinghouse        12,100  (1,291)   109
43   Rockwell Int'l.     10,995  (1,036)    79
54   Raytheon             9,119     635     64

70   Emerson Electric     7,706     663     69
71   Texas Instruments    7,470     247     61
73   Whirlpool            7,309     205     39
89   Cooper Industries    6,159    (229)    53
90   N. American Philips  6,138      50     43

93   Intel                5,922   1,067     26
95   Litton Industries    5,741     174     50
148  AMP                  3,337     290     25
151  Harris               3,042      75     28
157  Maytag               3,041    (315)    21

163  Teledyne             2,891      33     24
165  Loral                2,882     122     22
214  E-Systems            2,099     (69)    19
243  Nat'l Semiconductor  1,726    (120)    27
255  Nat'l Service Ind.   1,634      74     20

257  General Signal       1,623     (83)    14
259  Duracell Int'l.      1,617     128      8
266  Reliance Electric    1,553      26     14
269  Advanced Micro Dev.  1,531     245     12
295  Raychem              1,296     (25)    11

304  Zenith Electronics   1,271    (106)    25
310  Magnetek             1,230      22     16
333  J.M. Huber           1,102      43      7
340  General Instrument   1,076     (53)     9
344  Thomas & Betts       1,057      51      8

354  Pittway              1,019      47      5
364  Sunbeam/Oster          967      48      9
407  Hubbell                800      78      6
415  Molex                  782      67      7
455  Vishay Intertechnology 664      30     11

482  LSI Logic              617    (110)      3
490  Harman Int'l Ind.      604       3       5
495  Exide                  594       7       5
               TOTAL    194,259   6,172   1,326


  1 9 9 1  COMPUTERS/OFFICE EQUIPMENT
                         Sales  Profit Employees
Rank  Company              (000,000)     (000)
  4  IBM                 64,792  (2,827)  345
 26  Hewlett-Packard     14,541     755    89
 28  Digital Equipment   14,024    (617)  121
 58  Unisys               8,696  (1,393)   60
 81  Apple Computer       6,309     310    14

137  Pitney Bowes         3,417     295    29
145  Compaq Computer      3,271     131    10
146  Sun Microsystems     3,260     190    12
166  Seagate Technology   2,691      67    43
201  Wang Laboratories    2,127    (386)   18

217  Tandem Computers     1,940      35    11
233  Amdahl               1,702      11     9
239  Storage Technology   1,653      93    10
248  Conner Peripherals   1,627      92     8
272  DR Holdings          1,391       -     7

295  Data General         1,237      86     9
300  Intergraph           1,205      71    10
314  SCI Systems          1,129      13    10
363  Quantum                878      74     1
365  Maxtor                 875     (45)    8

370  Cray Research          862     113     5
431  AST Research           697      65     3
457  Bell & Howell          625      (5)    6
488  Silicon Graphics       557      33     3
490  Dell Computer          546      27     2
               TOTAL    140,054  (2,812)  845


  1 9 9 1  ELECTRONICS/ELECTRICAL
                         Sales  Profit Employees
Rank  Company              (000,000)     (000)
5    General Electric    60,236   2,636    284
30   Westinghouse        12,794  (1,086)   114
35   Rockwell Int'l.     12,028     601     87
39   Motorola            11,341     454    102
51   Raytheon             9,356     592     72

64   Emerson Electric     7,427     632     70
77   Texas Instruments    6,812    (409)    63
78   Whirlpool            6,770     170     38
86   Cooper Industries    6,163     393     54
91   N. American Philips  6,065       8     43

99   Litton Industries    5,313      64     52
106  Intel                4,779     819     25
147  Teledyne             3,218     (25)    29
150  AMP                  3,095     260     25
151  Harris               3,081      19     31

153  Maytag               2,971      79     23
200  Loral                2,136      90     24
210  E-Systems            1,998     110     19
229  Nat'l Semiconductor  1,711    (151)    30
251  General Signal       1,620      54     15

254  Nat'l Service Ind.   1,602      32     21
260  Duracell Int'l.      1,524     (34)     8
261  Reliance Electric    1,516      34     14
274  Varian Associates    1,381      58      9
282  Zenith Electronics   1,322     (52)    28

291  Raychem              1,250     (23)    11
296  Advanced Micro Dev.  1,227     145     11
312  Magnetek             1,134      35     15
339  Western Digital        986    (134)     7
340  Pittway                984      26      8

349  Mark IV Industries     937      26     11
356  Sunbeam/Oster          886      48     11
407  Hubbell                768      91      6
413  Exide                  743     (12)     6
418  Molex                  716      65      7

422  LSI Logic              713       8       4
473  Harman Int'l Ind.      587     (20)      4
478  Thomas & Betts         573      48       5
493  Analog Devices         539       8       5
               TOTAL    188,298   5,656   1,389



forward chaining
In AI, a form of reasoning that starts with what is
known and works toward a solution.  Known as
bottom-up approach.  Contrast with backward
chaining.


forward compatible
Same as upward compatible.


forward error correction
Communications technique that can correct bad data
on the receiving end.  Before transmission, the
data is processed through an algorithm that adds
extra bits for error correction.  If the
transmitted message is received in error, the
correction bits are used to repair it.


fourth-generation computer
Computer made up almost entirely of chips with
limited amounts of discrete components.  We are
currently in the fourth generation.


fourth-generation language
Computer language that is more advanced than
traditional high-level programming languages.  For
example, in dBASE, the command LIST displays all
the records in a data file.  In second- and third-
generation languages, instructions would have to be
written to read each record, test for end of file,
place each item of data on screen and go back and
repeat the operation until there are no more
records to process.

   First-generation languages are machine
languages; second-generation are machine dependent
assembly languages; third-generation are high-level
programming languages, such as FORTRAN, COBOL,
BASIC, Pascal, and C.  Although many languages,
such as dBASE, are called fourth-generation
languages, they are actually a mix of third and
fourth.  The dBASE LIST command is a fourth-
generation command, but applications programmed in
dBASE are third-generation.

   Query language and report writers are also
fourth-generation languages.  Any computer language
with English-like commands that doesn't require
traditional input-process-output logic falls into
this category.


FoxBASE+
dBASE III PLUS-compatible DBMS for the Macintosh
from Microsoft.  Originally developed by Fox
Software for the PC, FoxBASE gained a reputation
for its speed and compatibility.


FoxPro
dBASE IV-compatible DBMS from Microsoft for PCs.
An enhanced version of FoxBASE, FoxPro includes
windowing, SQL and QBE interfaces and "Rushmore"
technology for fast queries on large databases.


FPGA
(Field Programmable Gate Array)  Programmable logic
chip with a high density of gates.


fps
(1) (Frames Per Second)  See frame.

(2) (FPS) (Floating Point Systems, Inc., Beaverton,
OR)  Supercomputer manufacturer.


FPU
(Floating Point Unit)  Computer circuit that
handles floating point operations.


fractals
Technique for describing and greatly compressing
images, especially natural objects, such as trees,
clouds and rivers.  Fractals, or "fractional
mathematics," comes from the science of chaos.  It
turns an image into a set of data and an algorithm
for expanding it back to the original.


fractional T1
Service that provides less than full T1 capacity.
One or more 64Kbits/sec channels are provided.


fragmentation
Non-contiguous storage of data on disk.  As files
are updated, new data is stored in available free
space, which may not be contiguous.  Fragmented
files cause extra head movement, slowing disk
accesses.  A disk maintenance, or optimizer,
program is used to rewrite and reorder all the
files.


FRAM
(1) (Ferroelectronic RAM)  Non-volatile
semiconductor memory that retains its content
without power for up to 10 years.

(2) (Ferromagnetic RAM)  Non-volatile memory that
records microscopic bits on a magnetic surface.


frame
(1) In computer graphics, one screenful of data or
its equivalent storage space.

(2) In communications, a group of bits that make up
an elementary block of data for transmission by
certain protocols.

(3) In AI, a data structure that holds a general
description of an object, which is derived from
basic concepts and experience.


frame buffer
Separate memory component that holds a graphic
image.  It can have one plane of memory for each
bit in the pixel; for example, if eight bits are
used per pixel, there are eight separate memory
planes.


frame grabber
Device that accepts standard TV signals and
digitizes the current video frame into a bitmap
image.


frame relay
High-speed packet switching protocol that provides
faster transmission than X.25.  It is suited for
data and image transfer rather than voice.


FrameMaker
Desktop publishing program from Frame Technology
Corp., San Jose, CA, that runs on UNIX platforms,
Macintosh and Windows.  It is noted for its
integrated text and graphics capabilities.
Optional viewers let documents run on machines
without FrameMaker, providing a way to distribute
hypertext-based help systems.


framework
(1) In object-oriented programming, a generalized
subsystem design for building applications.  It
consists of abstract classes and their object
collaboration as well as concrete classes.  While
object-oriented programming supports software
reuse, frameworks support design reuse.

(2) (FrameWork)  One of the first integrated
software packages for PCs that included a
programming language.  From Ashton-Tate.


framing bit
Same as start bit and stop bit.


free-form database
Database system that allows entry of text without
regard to length or order.  Although it accepts
data as does a word processor, it differs by
providing better methods for searching, retrieving
and organizing the data.


free-form language
Language in which statements can reside anywhere on
a line or even cross over lines.  It does not imply
less syntax structure, just more freedom in placing
statements.  For example, any number of blank
spaces are allowed between symbols.  Most high-
level programming languages are free-form.


Free Software Foundation
Non-profit organization founded in 1985 by Richard
Stallman, dedicated to eliminating restrictions on
copying and modifying programs by promoting the
development and use of freely re-distributable
software.  It is developing the GNU computing
environment, including kernel, utilities, editor,
compiler and debugger.  GNU programs, X Windows and
others are available for a transaction charge.
Address: 675 Mass. Ave., Cambridge, MA 02139,
617/876-3296, Internet: [e-mail].  See
League for Programming Freedom.


FreeHand
Full-featured Macintosh drawing program from Aldus
Corp., Seattle, WA, that combines a wide range of
drawing tools with special effects.


freeware
Software distributed without charge.  Ownership is
retained by the developer who has control over its
redistribution, including the ability to change the
next release of the freeware to payware.  See
shareware and public domain software.


frequency
Number of oscillations (vibrations) that are in an
alternating current within one second.  See
carrier.


frequency division multiplexing
See FDM.


frequency modulation
See FM.


frequency shift
See FSK.


friction feed
Mechanism that allows cut paper forms to be used in
a printer.  The paper is passed between the platen
and a roller that presses tightly against it.
Contrast with tractor feed.


frob
From frobnicate.  Slang for manipulating and
adjusting dials and buttons for fun.


front-end CASE
CASE tools that aid in systems analysis and design.
Contrast with back-end CASE.


front end processor
Computer that handles communications processing for
a mainframe.  It connects to the communications
lines on one end and the mainframe on the other.
It transmits and receives messages, assembles and
dissassembles packets and detects and corrects
errors.  It is sometimes synonymous with a
communications controller, although the latter is
usually not as flexible.


frontware
Software that adds a graphical user interface to
mainframe applications.  The frontware application
is processed in the personal computer which is used
as a terminal to the mainframe.


FSK
(Frequency Shift Keying)  Simple modulation
technique that merges binary data into a carrier.
It creates only two changes in frequency: one for
0, another for 1.


FSR
(Free System Resource)  In Windows, the amount of
unused memory in a 64K block (128K for Version 3.1)
reserved for managing current applications.  Every
open window takes some space in this area.


FT1
See fractional T1.


FTAM
(File Transfer Access and Management)
Communications protocol for the transfer of files
between systems of different vendors.


FTP
(File Transfer Protocol)  TCP/IP protocol that is
used to log onto the network, list directories and
copy files.  It can also translate between ASCII
and EBCDIC.  See TFTP.


FTS 2000
(Federal Telecommunications System 2000)  Digital
fiber-optic network providing voice, video, e-mail
and high-speed data communications for the U.S.
government.  AT&T and Sprint are the major
equipment providers.


FUD factor
(Fear Uncertainty Doubt factor)  Marketing strategy
by a dominant or privileged organization that
restrains competition by not revealing future
plans.


full backup
See backup types.


full-duplex
Transmitting and receiving simultaneously.  In pure
digital networks, this is achieved with two pairs
of wires.  In analog networks or in digital
networks using carriers, it is achieved by dividing
the bandwidth of the line into two frequencies, one
for sending, one for receiving.


full featured
Hardware or software that provides capabilities and
functions comparable to the most advanced models or
programs of that category.


full path
Path name that includes the drive, starting or root
directory, all attached subdirectories and ending
with the file or object name.


full project life cycle
Project from inception to completion.


full-screen mode
Programming capability that allows data to be
displayed in any row or column on screen.  Contrast
with teletype mode.


fully populated
Circuit board whose sockets are completely filled
with chips.


function
In programming, a software routine that does a
particular job.  The function performs the job and
returns control to the instruction following the
calling instruction.  Programming languages provide
a set of standard functions and may allow
programmers to define others.  The C language is
built entirely of functions.


function keys
Set of keyboard keys used to command the computer
(F1, F2, etc.).  F1 is often the help key, but the
purpose of any function key is determined by the
software currently running.


function library
Collection of program routines.  See function.


functional decomposition
Breaking down a process into non-redundant
operations.


functional specification
Blueprint for the design of an information system.
It provides documentation for the database, human
and machine procedures, and all the input,
processing and output detail for each data entry,
query, update and report program in the system.


fuse
(1) Protective device that is designed to melt, or
blow, when a specified amount of current is passed
through it.  PROM chips are created as a series of
fuses that are selectively blown in order to create
the binary patterns in the chip.

(2) To bond together.


fusible link
Circuit line in a PROM chip or similar device that
is designed to be blown apart.  See PROM
programmer.


Futurebus+
IEEE standard multisegment bus that can transfer
data at 32, 64, 128 and 256-bits and can address up
to 64 bits.  Clock speeeds range from 25 to 100MHz.
At 100MHz and 256 bits, it transfers 3.2
Gbytes/sec.


fuzzy computer
Specially-designed computer that employs fuzzy
logic.  Using such architectural components as
analog circuits and parallel processing, fuzzy
computers are designed for AI applications.


fuzzy logic
Mathematical technique for dealing with imprecise
data and problems that have many solutions rather
than one.  It can deal with values between 0 and 1
and is more analogous to human logic than digital
logic.  Results can be mostly true and mostly false
rather than true and false.


fuzzy search
Inexact search for data that finds answers that
come close to the desired data.  It can get results
when the exact spelling is not known or help users
obtain information that is loosely related to a
topic.



G
See giga.


G-byte
See gigabyte.


gain
Amount of increase that an amplifier provides on
the output side of the circuit.


GAL
(Generic Array Logic)  Programmable logic chip
(PLD) technology from Lattice Semiconductor.


gallium arsenide
Alloy of gallium and arsenic compound (GaAs) that
is used as the base material for chips.  It is
several times faster than silicon.


game port
I/O connector used to attach a joy stick.  It is
typically a 15-pin socket on the back of a PC.


gamma correction
In computer graphics, using a formula to provide a
range of intensities that appear uniform to the
human eye.


gang punch
To punch an identical set of holes into a deck of
punched cards.


Gantt chart
Form of floating bar chart usually used in project
management to show resources or tasks over time.


gap
(1) Space between blocks of data on magnetic tape.

(2) Space in a read/write head over which magnetic
flux (energy) flows causing the underlying magnetic
tape or disk surface to become magnetized in the
corresponding direction.


gapless
Magnetic tape that is recorded in a continuous
stream without interblock gaps.


garbage collection
Routine that searches memory for program segments
or data that are no longer active in order to
reclaim that space.


garbage in...
See GIGO.


gas discharge display
See plasma display.


gas plasma
See plasma display.


gate
(1) Open/closed switch.

(2) Pattern of transistors that makes up an AND, OR
or NOT Boolean logic gate.  See gate array.

(2) In a MOS transistor, the line that triggers the
switch.


gate array
Chip type that contains unconnected logic elements.
The finished, customized chip is obtained by
adhering the top metal layer of pathways between
the elements.  This final masking stage is less
costly than designing the chip from scratch.

   It usually contains only two-input NAND gates,
which can be used singularly or connected with
other NAND gates to provide all the Boolean
operations required for digital logic.


gated
Switched "on" or capable of being switched on and
off.


gateway
Computer that interconnects and performs the
protocol conversion between two types of networks.
For example, a gateway between a personal computer
LAN and a mainframe network.  See bridge.


gather write
To output data from two or more noncontiguous
memory locations with one write operation.  See
scatter read.


GatorBox
Gateway from Cayman Systems, Inc., Cambridge, MA,
that interconnects LocalTalk and Ethernet networks
and supports TCP/IP and NFS protocols.  It also
functions as a router to connect AppleTalk-based
computers on a LAN with remote AppleTalk devices.


gauss
Unit of measurement of magnetic energy.


Gaussian distribution
Random distribution of events that is often graphed
as a bell-shaped curve.  It is used to represent a
normal or statistically probable outcome.


Gaussian noise
In communications, a random interference generated
by the movement of electricity in the line.  Also
called white noise.


GB, Gb
See gigabyte and gigabit.


Gbit
See gigabit.


Gbits/sec
(GigaBITS per SECond)  Billion bits per second.


GBps, Gbps
(GigaBytes Per Second, GigaBits Per Second)
Billion bytes per second.  Billion bits per second.


GByte
See gigabyte.


Gbytes/sec
(GigaBYTES per SECond)  Billion bytes per second.


GCOS
Bull HN operating system used in its minis and
mainframes (formerly Honeywell's product).


GCR
(1) (Group Code Recording)  Encoding method used on
magnetic tapes and Apple II and Mac 400K and 800K
floppy disks.

(2) (Gray Component Replacement)  Method for
reducing amount of printing ink used.  It
substitutes black for the amount of gray contained
in a color, thus black ink is used instead of the
three CMY inks.  See UCR and dot gain.


GDDM
(Graphical Data Display Manager)  Software that
generates graphics images in the IBM mainframe
environment.  It contains routines to generate
graphics on terminals, printers and plotters as
well as accepting input from scanners.  Programmers
use it for creating graphics, but users can employ
its Interactive Chart Utility (ICU) to create
business graphics without programming.

   GDDM/graPHIGS is a programming environment that
combines graphics capability with a user interface
similar to the Presentation Manager in OS/2.


GDI
(Graphics Device Interface)  Windows graphics
language used to provide output to the screen,
printer or other device.  Applications create
images on screen by calling GDI functions.  A GDI
driver executes these Windows functions directly.


GDM
See CGM.


GE
(Greater than or Equal to)  See relational
operators.


GEM
(Graphics Environment Manager)  Graphical user
interface from Digital Research similar to the
Mac/Windows environment.  It is built into ROM in
several Atari computers, and the DOS version of
Ventura Publisher comes with a runtime version.


gender changer
Coupler that reverses the gender of one of the
connectors in order that two male connectors or two
female connectors can be joined together.


General Magic
(General Magic, Inc., Cupertino, CA)  Spin off of
Apple Computer in 1990.  Its mission is to create
new personal intelligent communications products
and services by developing and licensing technology
to a wide variety of manufacturers and service
providers.  It has formed an alliance with large
organizations such as AT&T, Sony, Philips and
Motorola in order to reach the widest possible
audience.  See Telescript and Magic Cap.


general-purpose computer
Refers to computers that follow instructions, thus
virtually all computers from micro to mainframe are
general purpose.  Even computers in toys, games and
single-function devices follow instructions in
their built-in program.  In contrast, computational
devices can be designed from scratch for special
purposes (see ASIC).


general-purpose controller
Peripheral control unit that can service more than
one type of peripheral device; for example, a
printer and a communications line.


general-purpose language
Programming language used to solve a wide variety
of problems.  All common programming languages
(FORTRAN, COBOL, BASIC, C, Pascal, etc.) are
examples.  Contrast with special-purpose language.


generalized program
Software that serves a changing environment.  By
allowing variable data to be introduced, the
program can solve the same problem for different
users or situations.  For example, the electronic
versions of this Glossary could be programmed to
read in a different title and thus be used for any
type of dictionary.


generator
(1) Software that creates software.  See
application generator and macro generator.

(2) Device that creates electrical power or
synchonization signals.


Generic CADD
Full-featured PC CADD package from Generic
Software, Inc., Bothell, WA, that offers levels for
beginner, intermediate and advanced users.


GEnie
(General Electric Network for Information Exchange)
Online information service from GE Information
Services that provides business information, news
and access to special interest groups.  See online
services.


Genifer
dBASE application generator from Bytel Corp.,
Berkeley, CA, that creates dBASE source code.


genlock
(generator lock)  Circuitry that synchronizes video
signals for mixing.  In personal computers, a
genlock display adapter converts screen output into
an NTSC video signal, which it synchronizes with an
external video source.


geostationary
Same as geosynchronous.


geosynchronous
Earth aligned.  Refers to communications satellites
that are placed 22,300 miles above the equator and
travel at the same speed as the earth's rotation,
thus appearing stationary.


GeoWorks Ensemble
Popular graphical operating environment for DOS
from GeoWorks, Inc., Berkeley, CA, that includes
word processing, drawing, communications, card file
and calendar applications.  It provides complete
DOS file management and simulates file folders like
the Macintosh.  Users can launch all applications
from within Ensemble.  GeoWorks Pro includes the
Quattro Pro spreadsheet.


germanium
(Ge) Material used in making the first transistors.
Although still used in very limited applications,
germanium was replaced by silicon years ago.


gesture recognition
Ability to interpret simple hand-written symbols
such as check marks and slashes.


get
In programming, a request for the next record in an
input file.  Contrast with put.


Gflops
See gigaflops.


ghost
(1) Faint second image that appears close to the
primary image on a display or printout.  In
transmission, it is a result of secondary signals
that arrive ahead of or later than the primary
signal.  On a printout, it is caused by bouncing
print elements as the paper passes by.

(2) To display a menu option in a dimmed, fuzzy
typeface, indicating it is not selectable at this
time.


GHz
(GigaHertZ)  One billion cycles per second.


GIF
(Graphics Interchange Format)  Popular raster
graphics file format developed by CompuServe that
handles 8-bit color (256 colors) and uses the LZW
method to achieve compression ratios of
approximately 1.5:1 to 2:1.


giga
Billion.  Abreviated "G."  It often refers to the
precise value 1,073,741,824 since computer
specifications are usually binary numbers.  See
binary values and space/time.


gigabit
One billion bits.  Also Gb, Gbit and G-bit.  See
giga and space/time.


gigabyte
One billion bytes.  Also GB, Gbyte and G-byte.  See
giga and space/time.


gigaflops
(GIGA FLoating point OPerations per Second)  One
billion floating point operations per second.


GIGO
(Garbage In Garbage Out)  "Bad input produces bad
output."  Data entry is critical.  All possible
tests should be made on data entered into a
computer.

   GIGO also means "Garbage In, Gospel Out."
People put too much faith in computer output!


GIS
(1) (Geographic Information System)  Digital
mapping system used for exploration, demographics,
dispatching and tracking.

(2) (Generalized Information System) Early IBM
mainframe query and data manipulation language.


GKS
(Graphical Kernel System)  Device-independent
graphics language for 2-D, 3-D and raster graphics
images.  It allows graphics applications to be
developed on one system and easily moved to another
with minimal or no change.  It was the first true
standard for graphics applications programmers and
has been adopted by both ANSI and ISO.


glare filter
Fine mesh screen that is placed over a CRT screen
to reduce glare from overhead and ambient light.


glitch
Temporary or random hardware malfunction.  It's
possible that a bug (permanent error) in a program
may cause the hardware to appear as if it had a
glitch in it and vice versa.  At times it can be
extremely difficult to determine whether a problem
lies within the hardware or the software.


global
Pertaining to an entire file, database, volume,
program or system.


global variable
In programming, a variable that is used by all
modules in a program.


glossary
Term used by Microsoft Word and adopted by other
word processors for the list of shorthand, keyboard
macros created by a particular user.


glue chip
Support chip that adds functionality to a
microprocessor, for example, an I/O processor or
extra memory.


GNU
(Gnu's Not UNIX)  Project sponsored by the Free
Software Foundation that is developing a complete
software environment including operating system
kernel and utilities, editor, compiler and
debugger.  Many consultants and organizations
provide support for GNU software.


goal seeking
Ability to calculate a formula backward to obtain a
desired input.  For example, given the goal gross
margin = 50% as well as the range of possible
inputs, goal seeking attempts to obtain the optimum
input.


GOCA
(Graphics Object Content Architecture)  See MO:DCA.


gooey
See GUI.


GOSIP
(Government Open Systems Interconnection Profile)
U.S. government mandate that after 8/15/90, all new
network procurements must comply with OSI.  Testing
is performed at the NIST, which maintains a
database of OSI-compliant commercial products.
(TCP/IP protocols can also still be used.)


GOTO
(1) In a high-level programming language, a
statement that directs the computer to go to some
other part of the program.  Low-level language
equivalents are branch and jump.

(2) In dBASE, a command that directs the user to a
specific record in the file.

(3) In word processing, a command that directs the
user to a specific page number.


GOTO-less programming
Writing a program without using GOTO instructions,
an important rule in structured programming.  A
GOTO instruction points to a different part of the
program without a guarantee of returning.  Instead
of using GOTOs, structures called subroutines or
functions are used, which automatically return to
the next instruction after the calling instruction
when completed.


Gouraud shading
In computer graphics, a technique developed by
Henri Gouraud that computes a shaded surface based
on the color and illumination at the corners of
polygonal facets.


GPF
(1) (General Protection Fault)  Application program
abend in Windows 3.1.  See UAE.

(2) (GUI Programming Facility)  OS/2 application
generator from GPF Systems, Inc., Moodus, CT.


GPI
(Graphical Programming Interface)  Graphics
language in OS/2 Presentation Manager.  It is a
derivative of the GDDM mainframe interface and
includes Bezier curves.


GPIB
(General Purpose Interface Bus)  IEEE 488 standard
parallel interface used for attaching sensors and
programmable instruments to a computer.  It uses a
24-pin connector.  HP's version is the HPIB.


GPS
(Global Positioning System)  Series of
continuously-transmitting satellites used for
identifying earth locations.  By triangulation from
three satellites, a receiving unit can pinpoint
where it is on earth.


GPSS
(General Purpose Simulation System)  Programming
language for discrete event simulation, which is
used to build models of operations such as
manufacturing environments, communications systems
and traffic patterns.  Originally developed by IBM
for mainframes, PC versions are available, such as
GPSS/PC by Minuteman Software and GPSS/H by
Wolverine Software.


grabber hand
Pointer in the shape of a hand that is moved by a
mouse to "grab" and relocate objects on screen.


graceful degradation
A system that continues to perform at some reduced
level of performance after one of its components
fails.


graceful exit
Ability to get out of a problem situation in a
program without having to turn the computer off.


grade
Transmission capacity of a line.  It refers to a
range or class of frequencies that it can handle;
for example, telegraph grade, voice grade and
broadband.


gradient
Color spread from light to dark to shade an object
or give it a sense of depth.  It is also used to
create a colorful background.


GRAFCET
(GRAPHe de Commande Etape-Transition - stage
transition command graph)  PLC specification and
programming language.


GrafPort
See graphics port (2).


grammar checker
Software that checks the grammar of a sentence.  It
can check for and highlight incomplete sentences,
awkward phrases, wordiness and poor grammar.


Grammatik
Popular grammar checking program for DOS, Windows,
Macintosh and UNIX from Reference Software, Int'l,
San Francisco.  U.S. Government versions check for
usage according to the Government Printing Office
and other military and civilian guides.


grandfather, father, son
Method for storing previous generations of master
file data that are continuously updated.  The son
is the current file, the father is a copy of the
file from the previous cycle, and the grandfather
is a copy of the file from the cycle before that
one.


granularity
Degree of modularity of a system.  The more
granularity (grains or granules), the more
customizable or flexible the system.


graph
Pictorial representation of information.  See
business graphics.


graphic character
Printable symbol that includes digits and letters.


graphical interface
See GUI.


graphics
Usually called "computer graphics," it is the
creation and management of picture images in the
computer.  It is defined as "graphics" in this
Glossary to keep it next to other "graphics"
entries.

   A graphics computer system requires a graphics
display screen, a graphics input device (tablet,
mouse, scanner, camera, etc.), a graphics output
device (dot matrix printer, laser printer, plotter,
etc.) and a graphics software package; for example,
a CAD, drawing or paint program.


        Vector Graphics and Raster Graphics
Two methods are used for storing and maintaining
pictures in a computer.  The first method, called
vector graphics (also known as object-oriented
graphics), maintains the image as a series of
points, lines, arcs and other geometric shapes.

   The second method, called raster graphics,
resembles television, where the picture image is
made up of dots.

   Understanding these two methods and how they
intertwine in today's graphics systems is essential
for mastering computer graphics.  When you create
an image on the computer, you may not know which
method is used, but when you try to manipulate that
image, it will become obvious.


        Vector Graphics for CAD and Drawing
Vector graphics is the method employed by CAD
(computer-aided design) and drawing packages.  As
you draw, each line of the image is stored as a
vector (two end points on an x-y matrix).  For
example, a square becomes four vectors, one for
each side.  A circle is turned into dozens or
hundreds of tiny straight lines, the number of
which is determined by the resolution of the
drawing.  The entire image is commonly stored in
the computer as a list of vectors, called a display
list.

  Older CAD systems used vector display screens
that "drew" the image directly from the vectors.
Today, most screens are raster graphics displays
(made up of dots), and the vectors are "rasterized"
into the required dot patterns by hardware or
software.

   Vector graphics is used when you need geometric
knowledge about the object created.  Geometric
shapes keep their integrity: a line can always be
picked, extended or erased.  It never turns into
just a string of dots in the database.

   Vector graphics can be transmitted directly to
x-y plotters that "draw" the images from the list
of vectors.


     Raster Graphics for Imaging and Painting
Raster graphics is the TV-like method that uses
dots to display an image on screen.  Raster
graphics images are created by scanners and cameras
and are also generated by paint packages.  A
picture frame is divided into hundreds of
horizontal rows, with each row containing hundreds
of dots, called pixels.

   Unlike TV, which uses one standard (NTSC) for
the country, there are dozens of raster graphics
standards.  Also, unlike TV, which records and
displays the dots as infinitely variable shades and
colors (analog), computer graphics have a finite
number of shades and colors (digital).

   When you scan an image or paint an object into
the computer, the image is created in a reserved
area of memory called a bitmap, with some number of
bits corresponding to each dot (pixel).  The
simplest monochrome bitmap uses one bit (on/off)
for each dot.  Gray scale bitmaps (monochrome
shades) hold a number for each dot large enough to
hold all the gray levels.  Color bitmaps require
three times as much storage in order to hold the
intensity of red, green and blue.

   The image in the bitmap is continuously
transmitted to the video screen, dot for dot, a
line at a time, over and over again.  Any changes
made to the bitmap are instantly reflected on the
screen.

   Since colors are designated with numbers,
changing red to green is simply searching for the
red number and replacing it with the green number.
Animation is accomplished by continuously copying
new sequences from other areas in memory into the
bitmap, one after the other.

   Raster graphics images may take up more space on
disk than their vector graphics counterpart,
because storage for each pixel is required even if
it's part of the background.  A small object in
vector graphics format will take up only a few
vectors in the display list file.


graphics accelerator
High-performance video display board for graphical
user interfaces that has line drawing and pixel
block move functions (bitblt) built into hardware.
In Windows, such boards provide fast scrolling and
line drawing.  Windows applications will run better
on a slower PC with a graphics accelerator than on
a faster PC without one.  See Winmark and graphics
engine.


graphics adapter
Same as video display board


graphics based
Display of text and pictures as graphics images;
typically bitmapped images.  Contrast with text
based.


graphics card
Same as video display board.


graphics engine
Hardware that performs graphics processing
independently of the computer's CPU.  Under
directives from a graphics language, it can perform
a variety of functions, such as converting vectors
to rasters, compression and matrix multiplication
(for fast rotation).  It is typically designed for
CAD systems and is more specialized than a graphics
accelerator.


graphics file
File that contains only graphics data.  Contrast
with text file and binary file.


graphics interface
See graphics language and GUI.


graphics language
High-level language used to create graphics images.
The language is translated into images by software
or specialized hardware.  See graphics engine.


graphics mode
Screen display mode that displays graphics.
Contrast with text mode and character mode.


graphics port
(1) Socket on the computer for connecting a
graphics monitor.

(2) Macintosh graphics structure that defines all
the characteristics of a graphics window (also
called GrafPort).


graphics primitive
Elementary graphics building block, such as a
point, line or arc.  In a solid modeling system, a
cylinder, cube and sphere are examples of
primitives.


graphics processor
Same as graphics engine.


graphics tablet
See digitizer tablet.


graphics terminal
(1) I/O device that displays pictures in raster
graphics, vector graphics format or both.  Images
are received via communications or entered with a
mouse or light pen.  The keyboard may have
specialized function keys, wheels or dials.

(2) Terminal or personal computer that displays
graphics.


graPHIGS
See GDDM.


gray scale
Series of shades from white to black.  The more
shades, or levels, the more realistic an image can
be recorded and displayed, especially a scanned
photo.  Scanners differentiate typically from 16 to
256 gray levels.

   Although compression techiques help reduce the
size of graphics files, high-resolution gray scale
requires huge amounts of storage.  At a printer
resolution of 300 dpi, each square inch is made up
of 90,000 pixels.  At 256 levels, it takes one byte
per pixel, or 90,000 bytes per square inch of
image.  See halftone.


greek
To display text in a representative form in which
the actual letters are not discernible, because the
screen resolution isn't high enough to display them
properly.  Desktop publishing programs let you set
which font sizes should be greeked.


grep
(Global Regular Expression and Print)  UNIX pattern
matching utility that searches for a string of text
and outputs any line that contains the pattern.


ground
Electrically conductive body, such as the earth,
which maintains a zero potential (not positively or
negatively charged) for connecting to an electrical
circuit.


ground current
Current found in a ground line.  May be caused by
imbalanced electrical sources; for example, the
ground line in a communications channel between two
computers deriving power separately.


ground fault
Temporary current in the ground line, caused by a
failing electrical component or interference from
an external electrical source such as a
thunderstorm.


ground loop
Unwanted ground current flowing back and forth
between two devices that are grounded at two or
more points.


ground noise injection
Intentional insertion of unwanted noise by a power
supply into the ground line.


groupware
Software that is designed for use in a network and
serve a group of users that work on a related
project.


GSOS
(GS Operating System)  Graphical operating system
for the Apple IIGS that also accepts ProDOS
applications.


GT
(Greater Than)  See relational operator.


guard band
Frequency that insulates one signal from another.
In an analog telephone line, the low band is 0-300;
the high band is 3300-4000Hz.


GUI
(Graphical User Interface)  Graphics-based user
interface that incorporates icons, pull-down menus
and a mouse.  Macintosh, Windows, Presentation
Manager (OS/2), OSF/Motif and Open Look are
examples.  See desktop manager and window manager.
See also Star.  Contrast with CUI.


GUI accelerator
See graphics accelerator.


gulp
Some number of bytes!


gutter
In typography, the space between two columns.


GVPN
(Global Virtual Private Network)  Service from
cooperating carriers that provides international
digital communications for multinational companies.


GW-BASIC
(Gee Whiz-BASIC)  BASIC interpreter that
accompanied MS-DOS in versions prior to 5.0.  See
QBasic.



h
(Hexadecimal)  Symbol that refers to a hex number.
For example, 09h has a numeric value of 9, whereas
0Ah has a value of 10.  See hex chart.


H&J
(Hyphenation and Justification)  Alignment of the
right margin in a document.  Hyphenation breaks up
words that exceed the margin.  Justification aligns
text uniformly at the right margin while spacing
text evenly between both margins.


H.261
CCITT standard for a video codec that uses
intraframe and interframe compression and transmits
over Px64 ISDN lines.  It transmits at 9.115
Mbits/sec (QCIF), with 36.45 Mbits/sec (CIF)
optional.


hacker
Person who writes programs in assembly language or
in system-level languages, such as C.  Although it
may refer to any programmer, it implies very
tedious "hacking away" at the bits and bytes.

   The term has become widely used for people that
gain illegal entrance into a computer system.


HAL
(1) (Hardware Abstraction Layer)  Hardware-
dependent routines within Windows NT, which
provides the translation layer between hardware-
independent applications.

(2) Spaceship computer in the film, "2001," which
takes command by itself.  From I-B-M, the letters
preceding H-A-L.


half-adder
Elementary electronic circuit in the ALU that adds
one bit to another, deriving a result bit and a
carry bit.


half-duplex
Transmission of data in both directions, but only
one direction at a time.  Two-way radio was the
first to use half-duplex, for example, while one
party spoke, the other party listened.  Contrast
with full-duplex.


half height drive
5.25" disk drive that takes up half the vertical
space of first-generation drives.  It is 1 5/8"
high by 5.75" wide.


halftone
In printing, the simulation of a continuous-tone
image (shaded drawing, photograph) with dots.  All
printing processes, except for Cycolor, print dots.
In photographically-generated halftones, a camera
shoots the image through a halftone screen,
creating smaller dots for lighter areas and larger
dots for darker areas.  Digitally-composed printing
prints only one size of dot.

   In order to simulate varying size halftone dots
in computer printers, dithering is used, which
creates clusters of dots in a "halftone cell."  The
more dots printed in the cell, the darker the gray.
As the screen frequency gets higher (more lines per
inch), there is less room for dots in the cell,
reducing the number of gray levels that can be
generated.

   This tradeoff is a compromise in a 300 dpi
printer, since realistic gray-scale printing
reduces the resolution; for example, the 8x8
halftone cell required to create 64 grays results
in a coarse 38 lpi resolution (300 dpi ÷ 8).  In
high-resolution imagesetters, the highest screen
frequencies can be used with ample gray scale.

       ┌──┬──┬─── cells
    ─┼──┼──┼──┼───────
  │   │▄█│██│  │  This simplistic example uses
lpi  ─┼──┼──┼──┼─ a 2x2 halftone cell
  │   │▄▀│▄ │     allowing only white (no dots),
  │  ─┼──┼──┼─    black (all four dots) and three
                 interim shades (1, 2 and 3 dots).
      In a 300 dpi printer, this would allow for a
      150 lpi resolution (300÷2).  A 4x4 cell would
      provide 16 shades and 75 lpi.

                   Halftone Cell


hammer
In a printer, the mechanism that pushes the
typeface onto the ribbon and paper or pushes the
paper into the ribbon and typeface.


Hamming code
Communications error correction method that
intersperses three check bits at the end of each
four data bits.  At the receiving station, the
check bits are used to detect and correct one-bit
errors automatically.


handle
(1) In computer graphics, a location on an image
that can be grabbed for reshaping.  It is usually a
tiny square.

(2) Temporary name or number assigned to a file,
font or other object.  For example, an operating
system may assign a sequential number to each file
that it opens as a way of identifying and keeping
track of it.

(3) Nickname used when teleconferencing on a
bulletin board, like a "CB handle" used between
truck drivers.


handler
Software routine that performs a particular task.
For example, upon detection of an error, an error
handler is called to recover from the error
condition.


handset
The part of the telephone that contains the speaker
and the microphone.


handshaking
Signals transmitted back and forth over a
communications network that establish a valid
connection between two stations.


hanging paragraph
Paragraph in which the first line starts at the
    left margin, but subsequent lines are indented
    as is this paragraph.


hard boot
Same as cold boot.


hard coded
Software that performs a fixed number of tasks or
works with only a fixed number of devices.  For
example, a program could be written to work with
only two types of printers and not allow any other
types to be introduced.  Hard coded solutions to
problems are usually the fastest, but do not allow
for future flexibility.


hard copy
Printed output.  Contrast with soft copy.


hard disk
Primary computer storage medium that is made of
rigid disks with a magnetic recording surface.
Personal computer hard disks hold from 20MB to over
1GB.  Mini and mainframe hard disks can hold
several gigabytes.

   Fixed hard disks are permanently sealed in the
drive.  Removable hard disks are encased in disk
pack or disk cartridge modules that can be moved
between computers with the same kinds of drives.

   Hard disks provide fast retrieval because they
rotate at 3,600 rpm and higher and spin constantly,
although laptops turn them off to preserve battery.
Hard disks are made of one or more aluminum
platters (two to 15" diameter), each side coated
with a ferromagnetic material.

   Hard disks are usually low-level formatted from
the factory, which records the original sector
identification on them.  See floppy disk, magnetic
disk and format program.


            HARD DISK SPECIFICATIONS

Interface  Encoding   Transfer Rate    Storage
  Type      Method*    (Bytes/sec)    Capacities

  ST506       MFM          625K        5M - 100M
  ST506 RLL   RLL          937K       30M - 200M
  IDE         RLL       .625-2M       20M - 1G
  ESDI        RLL          1-3M       80M - 2G
  SCSI-1      RLL          1-5M       20M - 1.5G
  SCSI-2      RLL         1-40M       40M - 3G
  SMD         RLL          1-4M      200M - 2G
  IPI         RLL        10-25M      200M - 3G

*(Most disks use RLL, but the encoding method is
not prescribed by all interfaces.)


              Hard Disk Measurements
Capacity is measured in bytes, and speed is
measured in bytes per second (transfer rate) and in
milliseconds (access time).  Fast personal computer
hard disk access times range from 12 to 28ms; in
larger computers as fast as 1ms.


                For Technical Specs

   "Hard Drive Bible," $24.95
    Corporate Systems Center, Sunnyvale, CA
    408/737-7312.

   "Hard Disk Technical Guide," $49.95
   "Hard Disk Encyclopedia." $119.95
    Micro House, Clearwater, FL, 800/741-3282


hard error
(1) Permanent, unrecoverable error such as a disk
read error.  Contrast with soft error.

(2) Group of errors that requires user intervention
and includes disk read errors, disk not ready (no
disk in drive) and printer not ready (out of
paper).


hard hyphen
Hyphen that always prints.  Contrast with soft
hyphen.


hard return
Code entered into a text document by pressing the
return (enter) key.  DOS and OS/2 text files use a
CR/LF (carriage return/line feed) pair, but this is
not standard (WordPerfect uses only an LF).  The
Macintosh uses a CR and UNIX uses an LF.

   It may be represented by a visible symbol on
screen, such as the "<" in WordStar or the "" in
XyWrite, or it may remain invisible until revealed
in an expanded screen mode.  Contrast with soft
return.


hard sectored
Sector identification technique that uses a
physical mark.  For example, hard sectored floppy
disks have a hole in the disk that marks the
beginning of each sector.  Contrast with soft
sectored.


hard space
Special space character that acts like a letter or
digit, used to prevent multiple-word proper names
from breaking between lines.


Hardcard
Family of hard disks from Plus Development Corp.,
Milpitas, CA, that house the disk drive and the
controller electronics on an expansion board that
plugs into a PC.  It allows for a simple
installation and does not use up a drive bay.


HardFacts
Database service for PC hardware from HardFacts,
Inc., Beverly, MA, that includes retail and street
prices, distributor and mail order info on 14,000+
PCs and peripherals.  Monthly updates, product
review abstracts and manufacturer's data sheets by
fax are included in the subscription.


hardware
Machinery and equipment (CPU, disks, tapes, modem,
cables, etc.).  In operation, a computer is both
hardware and software.  One is useless without the
other.  The hardware design specifies the commands
it can follow, and the instructions tell it what to
do.  See instruction set.


                    Hardware Is
            "Storage and Transmission"
The more memory and disk storage a computer has,
the more work it can do.  The faster the memory and
disks transmit data and instructions to the CPU,
the faster it gets done.  A hardware requirement is
based on the size of the databases that will be
created and the number of users or applications
that will be served at the same time.  How much?
How fast?


                    Software Is
               "Logic and Language"
Software deals with the details of an ever-changing
business and must process transactions in a logical
fashion.  Languages are used to program the
software.  The "logic and language" involved in
analysis and programming is generally far more
complicated than specifying a storage and
transmission requirement.


hardware failure
Malfunction within the electronic circuits or
electromechanical components (disks, tapes) of a
computer system.  Contrast with software failure.


hardware interrupt
Interrupt caused by some action of a hardware
device, such as the depression of a key or mouse
movement.  See interrupt.


hardware key
Copy protection device supplied with software that
plugs into a computer port.  The software
interrogates the key's serial number during
execution to verify its presence.  The hardware key
acts as a pass-through, but tests for a special
code that reads the serial number.


hardware monitor
Device connected to the circuits of a computer in
order to analyze its performance.


hardware virtual memory
Virtual memory management built into a chip.
Although virtual memory can be performed by
software only, it is far more efficient to do it in
hardware.  See DAT and PMMU.


hardwired
(1) Electronic circuitry that is designed to
perform a specific task.  See hard coded.

(2) Devices that are closely or tightly coupled.
For example, a hardwired terminal is directly
connected to a computer without going through a
switched network.


harmonic distortion
In communications, frequencies that are generated
as multiples of the original frequency due to
irregularities in the transmission line.


Harvard Graphics
Popular PC business graphics program from Software
Publishing Corp., Mountain View, CA.  It was one of
the first business graphics packages and provides
the ability to create columnar and free form text
charts.


hash total
Method for ensuring the accuracy of processed data.
It is a total of several fields of data in a file,
including fields not normally used in calculations,
such as account number.  At various stages in the
processing, the hash total is recalculated and
compared with the original.  If any data has been
lost or changed, a mismatch signals an error.


Hayes compatible
Refers to modems controlled by the Hayes command
language.  See AT command set.


Hayes Smartmodem
Family of intelligent modems for personal computers
from Hayes Microcomputer Products, Inc., Atlanta,
GA.  Hayes developed the intelligent modem for
first-generation personal computers in 1978, and
its command language (Hayes Standard AT Command
Set) for modem control has become an industry-
standard.

               The Intelligent Modem
An intelligent modem has a command state and an
online state.  In the command state, it accepts
instructions.  In the online state, it dials,
answers, transmits and receives.

   Once connected, it performs the handshaking with
the remote modem, which is similar to the opening
exchange of a telephone call.  The called party
says "hello," the calling party says "hello, this
is..."  After this, the real conversation begins.
If the modem's speaker is on, you can hear the
whistles and tones used in the handshake.

   Once the handshake is completed, you are online
with the other computer, and data can be
transmitted back and forth.

   An important part of the Hayes standard is the
escape sequence, which tells the modem to switch
from online to the command state.  It usually
consists of three plus signs in sequence (+++) with
a Hayes-patented, one-second guard time interval
before and after it, which prevents the modem from
mistaking a random occurrence of the escape
sequence.  The escape sequence and guard time
interval can be programmed in the modem's Status
registers.

   To issue an escape sequence, hold down the shift
key and press + + +.  Pause one second before and
after the sequence.  The modem will return the OK
result code, indicating it is ready to accept
commands.


HC
See high color.


HD
(1) (High Density)  Designation for high-density
diskettes; for example, the 5.25" 1.2MB and 3.5"
1.44MB floppies.  Contrast with DD.

(2) (Hard Disk)  For example, FD/HD refers to a
floppy disk/hard disk device such as a controller.


HDA
(Head Disk Assembly)  Mechanical components of a
disk drive (minus the electronics), which includes
the actuators, access arms, read/write heads and
platters.


HDD
(Hard Disk Drive)  See hard disk.


HDLC
(High-level Data Link Control)  ISO communications
protocol used in X.25 packet switching networks.
It provides error correction at the data link
layer.  SDLC, LAP and LAPB are subsets of HDLC.


HDTV
(High Definition TV)  TV standard with 1125 lines
of resolution compared to the 525-line NTSC
standard.  Japan is currently broadcasting HDTV,
and 36" to 50" TV sets cost as much as $15,000.
U.S. standards are forthcoming.


HDX
See half-duplex.


head
See read/write head.


head crash
Physical destruction of a hard disk.  Misalignment
or contamination with dust can cause the read/write
head to collide with the disk's recording surface.
The data is destroyed, and both the disk platter
and head have to be replaced.

   The read/write head touches the surface of a
floppy disk, but on a hard disk, it hovers above
its surface at a distance that is less than the
diameter of a human hair.  It has been said that
the read/write head flying over the disk surface is
like trying to fly a jet plane six inches above the
earth's surface.


head-per-track disk
Disk drive that has a read/write head positioned
over each track, thus eliminating the access arm
movement from track to track.


head skew
Offset distance from the start of the previous
track so that the head has time to switch from top
of platter to bottom of platter and be at the start
of the new track.  See cylinder skew.


header
(1) In data processing, the first record in a file,
used for identification.  File name, date of last
update and other status data are stored in it.

(2) In a document or report, common text printed at
the top of every page.

(3) In communications, the first part of the
message, which contains controlling data, such as
originating and destination stations, message type
and priority level.

(4) Any caption or description used as a headline.


header label
Record used for file identification that is
recorded at the beginning of the file.


heap
In programming, the free memory currently available
to load and run programs.


heat sink
Material that absorbs heat.


helical scan
Diagonal tracking used on videotape and digital
audio tape (DAT), which increases storage capacity
over parallel methods.


help
On-screen instruction regarding the use of a
program.  On PCs, pressing F1 is the de facto
standard for getting help.  With graphics-based
interfaces (Mac, Windows, etc.), clicking a "?" or
HELP button gets help.  See context sensitive help.


help compiler
Software that translates text and compiler
instructions into an online help system.


Hercules Graphics
Video display standard for PCs from Hercules
Computer Technology Inc., Berkeley, CA, that
provides monochrome graphics and text with a
resolution of 720x348 pixels.  IBM's first PC
monochrome display did not provide graphics, and
Hercules introduced its display adapter to fill the
void in 1982.  It quickly became a de facto
standard incorporated into all monochrome display
boards.


Hermes
Code name for Microsoft's enterprisewide network
management system that will provide centralized
control of resources and manage Windows and Windows
NT environments.  Expected late 1993.


Hertz
Frequency of electrical vibrations (cycles) per
second.  Abbreviated "Hz," one Hz is equal to one
cycle per second.  In 1883, Heinrich Hertz detected
electromagnetic waves.


heterogeneous environment
Equipment from a variety of manufacturers.


heuristic
Method of problem solving using exploration and
trial and error methods.  Heuristic program design
provides a framework for solving the problem in
contrast with a fixed set of rules (algorithmic)
that cannot vary.


Hewlett-Packard
See HP.


hex
(HEXadecimal)  Hexadecimal means 16.  Base 16
numbering system used as a shorthand for
representing binary numbers.  Each half byte (four
bits) is assigned a hex digit as follows:

 Dec Hex Binary   Dec Hex Binary  Dec Hex Binary
  0   0  0000      6   6  0110     10  A  1010
  1   1  0001      7   7  0111     11  B  1011
  2   2  0010      8   8  1000     12  C  1100
  3   3  0011      9   9  1001     13  D  1101
  4   4  0100                      14  E  1110
  5   5  0101                      15  F  1111


   In a hex number, each digit position has a value
16 times greater than the one to its right.  Two
hex digits make up one byte; for example, A7h (h
means hex) is equivalent to decimal 167 (10x16 +
7x1).  See hex chart.

                         A    7
            ┌────┬────┬────┬────┐
            │4096│ 256│ 16 │  1 │
            └────┴────┴────┴────┘


   The hex number A000 (pronounced "A thousand") is
equivalent to 40,960 in decimal (4096x10); however,
for PC addressing, hex addresses are interpreted
uniquely (see paragraph).

                    $, h and H
Sometimes a $ is used to represent hex values as
well as upper and lower-case H; for example, $3E0,
3E0h and 3E0H are the same hex number.



hex chart
The following chart is ASCII code in hexadecimal.

╔═══════════════════════════════╦═════════════════╗
║         Standard ASCII        ║ Extended ASCII  ║
║  The first 32 characters are  ║    (IBM PC)     ║
║        control codes.         ║                 ║
║                               ║                 ║
║00 Null             │21 !│ 51 Q║ 80 Ç│ AE «│ DC ▄║
║01 Start of heading │22 "│ 52 R║ 81 ü│ AF »│ DD ▌║
║02 Start of text    │23 #│ 53 S║ 82 é│ B0 ░│ DE ▐║
║03 End of text      │24 $│ 54 T║ 83 â│ B1 ▒│ DF ▀║
║04 End of transmit  │25 %│ 55 U║ 84 ä│ B2 ▓│ E0 α║
║05 Enquiry          │26 &│ 56 V║ 85 à│ B3 ││ E1 ß║
║06 Acknowledge      │27 '│ 57 W║ 86 å│ B4 ┤│ E2 Γ║
║07 Audible bell     │28 (│ 58 X║ 87 ç│ B5 ╡│ E3 π║
║08 Backspace        │29 )│ 59 Y║ 88 ê│ B6 ╢│ E4 Σ║
║09 Horizontal tab   │2A *│ 5A Z║ 89 ë│ B7 ╖│ E5 σ║
║0A Line feed        │2B +│ 5B [║ 8A è│ B8 ╕│ E6 µ║
║0B Vertical tab     │2C ,│ 5C \║ 8B ï│ B9 ╣│ E7 τ║
║0C Form feed        │2D -│ 5D ]║ 8C î│ BA ║│ E8 Φ║
║0D Carriage return  │2E .│ 5E ^║ 8D ì│ BB ╗│ E9 Θ║
║0E Shift out        │2F /│ 5F _║ 8E Ä│ BC ╝│ EA Ω║
║0F Shift in         │30 0│ 60 `║ 8F Å│ BD ╜│ EB δ║
║10 Data link escape │31 1│ 61 a║ 90 É│ BE ╛│ EC ∞║
║11 Device control 1 │32 2│ 62 b║ 91 æ│ BF ┐│ ED φ║
║12 Device control 2 │33 3│ 63 c║ 92 Æ│ C0 └│ EE ε║
║13 Device control 3 │34 4│ 64 d║ 93 ô│ C1 ┴│ EF ∩║
║14 Device control 4 │35 5│ 65 e║ 94 ö│ C2 ┬│ F0 ≡║
║15 Neg. acknowledge │36 6│ 66 f║ 95 ò│ C3 ├│ F1 ±║
║16 Synchronous idle │37 7│ 67 g║ 96 û│ C4 ─│ F2 ≥║
║17 End trans. block │38 8│ 68 h║ 97 ù│ C5 ┼│ F3 ≤║
║18 Cancel           │39 9│ 69 i║ 98 ÿ│ C6 ╞│ F4 ⌠║
║19 End of medium    │3A :│ 6A j║ 99 Ö│ C7 ╟│ F5 ⌡║
║1A Substitution     │3B ;│ 6B k║ 9A Ü│ C8 ╚│ F6 ÷║
║1B Escape           │3C <│ 6C l║ 9B ¢│ C9 ╔│ F7 ≈║
║1C Figures shift    │3D =│ 6D m║ 9C £│ CA ╩│ F8 °║
║1D Group separator  │3E >│ 6E n║ 9D ¥│ CB ╦│ F9 ∙║
║1E Record separator │3F ?│ 6F o║ 9E ₧│ CC ╠│ FA ·║
║1F Unit separator   │40 @│ 70 p║ 9F ƒ│ CD ═│ FB √║
║20 Blank space      │41 A│ 71 q║ A0 á│ CE ╬│ FC ⁿ║
║                    │42 B│ 72 r║ A1 í│ CF ╧│ FD ²║
║                    │43 C│ 73 s║ A2 ó│ D0 ╨│ FE ■║
║                    │44 D│ 74 t║ A3 ú│ D1 ╤│ FF  ║
║                    │45 E│ 75 u║ A4 ñ│ D2 ╥│     ║
║                    │46 F│ 76 v║ A5 Ñ│ D3 ╙│     ║
║                    │47 G│ 77 w║ A6 ª│ D4 ╘│     ║
║                    │48 H│ 78 x║ A7 º│ D5 ╒│     ║
║                    │49 I│ 79 y║ A8 ¿│ D6 ╓│     ║
║                    │4A J│ 7A z║ A9 ⌐│ D7 ╫│     ║
║                    │4B K│ 7B {║ AA ¬│ D8 ╪│     ║
║                    │4C L│ 7C |║ AB ½│ D9 ┘│     ║
║                    │4D M│ 7D }║ AC ¼│ DA ┌│     ║
║                    │4E N│ 7E ~║ AD ¡│ DB █│     ║
║                    │4F O│ 7F ║     │     │     ║
║                    │50 P│     ║     │     │     ║
╚════════════════════╧════╧═════╩═════╧═════╧═════╝


hexadecimal
See hex.


HFS
(Hierarchical File System)  Macintosh file system
that allows files to be placed into folders, and
folders to be placed within other folders.


HGC
See Hercules Graphics.


hi res
Same as high resolution.


hidden file
File classification that prevents a file from being
accessed.  It is usually an operating system file;
however, utility programs let users hide files to
prevent unauthorized access.


hierarchical
Structure made up of different levels like a
company organization chart.  The higher levels have
control or precedence over the lower levels.
Hierarchical structures are a one to many
relationship; each item having one or more items
below it.

   In communications, a hierarchical network refers
to a single computer that has control over all the
nodes connected to it.


hierarchical communications
Network controlled by a host computer that is
responsible for managing all connections.  Contrast
with peer-to-peer communications.


hierarchical file system
File organization method that stores data in a top-
to-bottom organization structure.  All access to
the data starts at the top and proceeds throughout
the levels of the hierarchy.

   In DOS and OS/2, the root directory is the
starting point.  Files can be stored in the root
directory, or directories can be created off the
root that hold files and subdirectories.

   In the Macintosh, the disk window is the
starting point.  Files can be stored in the disk
window, or folders can be created that can hold
files and additional folders.


high color
Ability to generate 32,768 colors (15 bits) or
65,536 colors (16-bit).  15-bit color uses five
bits for each red, green and blue pixel.  The 16th
bit may be a color, such as XGA with 5-red, 6-green
and 5-blue, or be an overlay bit that selects
pixels to display over video input.  See true
color.


high definition TV
See HDTV.


high density
Refers to increased storage capacity of bits and/or
tracks per square inch.  See HD.


high DOS memory
Same as UMA.


high-level format
Indexes on a disk that the operating system uses to
keep track of the data stored on the disk.  See
format program.


high-level language
Machine-independent programming language, such as
FORTRAN, COBOL, BASIC, Pascal and C.  It lets the
programmer concentrate on the logic of the problem
to be solved rather than the intricacies of the
machine architecture such as is required with low-
level assembly languages.


high memory
(1) Uppermost end of memory.

(2) In PCs, the area between 640K and 1M, or the
64K high memory area (HMA) between 1024 and 1088K.


High-Performance Computing
Federal initiative to enhance U.S. computing
capability that includes a T3-speed network linking
agencies, private companies and schools to
supercomputer centers.


high resolution
High-quality image on a display screen or printed
form.  The more dots used per square inch, the
higher the quality.  To display totally realistic
images including the shades of human skin requires
about 1,000x1,000 pixels on a 12" diagonal screen.
Desktop laser printers print respectable text and
graphics at 300 dpi, but typesetting machines print
1,270 and 2,540 dpi.


High Sierra
First CD ROM standard named for an area near Lake
Tahoe where it was conceived in 1985.  Later
evolved into the ISO 9660 standard.


high tech
Refers to the latest advancements in computers and
electronics as well as to the social and political
environment and consequences created by such
machines.


highlight
To identify an area on screen in order to select,
move, delete or change it in some manner.


highlight bar
Currently-highlighted menu item.  Choice is made by
moving the bar to the desired item and pressing
enter or clicking the mouse.  The bar is a
different color on color screens or reverse video
on monochrome screens.


HiJaak
Graphics file conversion and screen capture program
for PCs from Inset Systems Inc., Brookfield, CT.
It supports a wide variety of raster and vector
graphics formats as well as fax boards.  It also
handles conversion between PC and Mac formats.


HIMEM.SYS
XMS driver in DOS 5 and Windows 3.0 that allows
programs to cooperatively allocate extended memory
in 286s and up.  See XMS and DOS HIMEM.SYS.


hints
Font instructions that alter space and other
features to improve the typeface image at low
resolutions.  Hints help to make a character
uniform and legible especially at small point
sizes; for example, they ensure that serifs and
accents appear in proper proportion.  Hints will
have less meaning for printing as common desktop
resolutions approach 600 and 800 dpi and more, but
rendering typefaces on screens, which have less
resolution than printers, will still be valuable.


HIPO
(Hierarchy plus Input-Process-Output)  Pronounced
"hy-po."  IBM flow-charting technique that provides
a graphical method for designing and documenting
programs.


HiPPI
(HIgh Performance Parallel Interface channel)
ANSI-standard high-speed (100 Mbytes/sec)
supercomputer channel.


histogram
Chart displaying horizontal or vertical bars.  The
length of the bars are in proportion to the values
of the data items they represent.


history
User input within the current session.  A history
feature keeps track of user commands and/or
retrieved items so that they can be quickly reused
or reviewed.


HLLAPI
(High Level Language Application Program Interface)
IBM programming interface that allows a PC
application to communicate with a mainframe
application.  The hardware hookup is handled via
normal micro to mainframe 3270 emulation.


HLS
(Hue Lightness Saturation)  Variation of the HSV
color model that uses double hexcones (six-sided
pyramids).  Black is at the bottom, white on top,
and the hue coordinates surround the center.


HMA
(High Memory Area)  In PCs, the first 64K of
extended memory from 1024K to 1088K, which can be
accessed by DOS.  It is managed by the HIMEM.SYS
driver.


HMOS
(High-density MOS)  Chip with a high density of
NMOS transistors.


Hobbit
Microprocessor from AT&T used in a variety of
portable devices.


hog
Program that uses an excessive amount of computer
resources, such as memory or disk, or takes a long
time to execute.


Hollerith machine
First automatic data processing system.  It was
used to count the 1890 U.S. census.  Developed by
Herman Hollerith, a statistician who had worked for
the Census Bureau, the system used a hand punch to
record the data in dollar-bill-sized punched cards
and a tabulating machine to count them.

   It was estimated that, with manual methods, the
1890 census wouldn't be completed until after 1900.
With Hollerith's machines, it took two years and
saved five million dollars.

   Hollerith formed the Tabulating Machine Company
and sold his machines throughout the world for a
variety of accounting functions.  In 1911, his
company was merged into the company that was later
renamed IBM.


home brew
Products that are developed at home by hobbyists.


home button
Icon that represents the beginning of a file or a
set of operations.


home computer
Low-priced personal computer such as the Apple II,
Commodore 64 and 128, Tandy Color Computer and
Atari ST.


home key
Keyboard key used to move the cursor to the top of
the screen or file or to the previous word or
beginning of line.  See home button.


Honeywell
See Bull HN.


hook
In programming, instructions that provide logical
breakpoints for future expansion.  Hooks may be
changed to call some outside routine or function or
may be places where additional processing is added.


hooked vector
Trapped interrupt in a PC.  The pointer for a
particular interrupt in the interrupt vector table
has been modified to jump to a new routine to
service that interrupt.


hookemware
Free software that contains a limited number of
features designed to entice the user into
purchasing the more comprehensive version.


hop count
Number of gateways and routers in a transmission
path.


hopper
Tray, or chute, that accepts input to a mechanical
device, such as a disk duplicator.


horizontal resolution
Number of elements, or dots, on a horizontal line
(columns in a matrix).  Contrast with vertical
resolution.


horizontal scan frequency
Number of lines illuminated on a video screen in
one second.  For example, a resolution of 400 lines
refreshed 60 times per second requires a scan rate
of 24KHz plus overhead (time to bring the beam back
to the beginning of the next line).  Same as
horizontal sync frequency in TV.  Contrast with
vertical scan frequency.


horizontal sync
See horizontal scan frequency.


HOS
(Higher Order Software)  Design and documentation
technique used to break down an information system
into a set of functions that are mathematically
correct and error free.  It uses a rigid set of
rules for the decomposition of the total system
into its elementary components.  The resulting
specifications are complete enough to have machine
language programs generated directly from them.


host
Main computer in a distributed processing
environment.  It typically refers to a large
timesharing computer or a central computer that
controls a network.


host adapter
Device that connects a peripheral unit to a
computer (computer may be any size).  It contains
less electronics than a controller.  For example,
an IDE disk drive has a built-in controller and
connects to a non-IDE-ready motherboard via an IDE
host adapter (often erroneously called an IDE
controller).


host based
Communications system that is controlled by a
large, central computer system.


host mode
Communications mode that allows a computer to
answer an incoming telephone call and receive data
without human assistance.


hot fix
Capability of being repaired while in operation.
For example, many SCSI drives can move the data in
sectors that are becoming hard to read to spare
sectors on the fly without even the SCSI host
adapter being aware of it.  In some fault tolerant
systems, circuit boards and components can be
removed and replaced without turning the system off
(also called hot swapping).


hot link
Predefined connection between programs so that when
information in one database or file is changed,
related information in other databases and files
are also updated.  See compound document and OLE.


hot spot
Exact location of the screen cursor that points to
and affects the screen object when the mouse is
clicked.  It is typically the tip of an arrow or
finger pointer, but can be elsewhere with other
cursor designs.


hot swap
~See hot fix.


hotkey
Key or key combination that causes some function to
occur in the computer, no matter what else is
currently running.  It is commonly used to activate
a memory resident (TSR) program.


housekeeping
Set of instructions that are executed at the
beginning of a program.  It sets all counters and
flags to their starting values and generally
readies the program for execution.


HP
(Hewlett-Packard Company, Palo Alto, CA)  Major
manufacturer of computers and electronics.  It was
founded in 1939 by William Hewlett and David
Packard in a garage behind the Packard's California
home.  Its first product, an audio oscillator for
measuring sound, was the beginning of a line of
electronics that made HP an international supplier
of electronic test and measurement instruments.
Walt Disney Studios, HP's first big customer,
purchased eight oscillators to develop and test a
new sound system for the movie "Fantasia."

   HP entered the computer field in 1966 with the
2116A, the first of the HP 1000 series designed to
gather and analyze the data produced by HP
instruments.  HP 1000 computers are used for CIM
applications, such as process monitoring and
control, alarm management and machine monitoring.

   In 1972, HP branched into business computing
with the 3000 series, a multiuser system that
became well known for its extremely high
reliability, especially for that time.  The
successful 3000 family has continued to be HP's
major computer series and has evolved into a full
family of computers from micro to mainframe.  Also
in 1972, HP introduced the first scientific
handheld calculator, the HP-35, obsoleting the
slide rule and ushering in a new age of pocket-
sized calculators.  In 1982, the first HP 9000
workstation was introduced.

   HP's first personal computer was the Touchscreen
150, an MS-DOS personal computer that gained only
modest acceptance.  In 1985, it introduced the
Vectra, a 286-based machine that was the first of a
complete line of IBM-compatible PCs.

   In 1984, HP revolutionized the printer market
with its desktop LaserJet printer, which has set
the standard for the industry.

   In 1986, it introduced a new internal design for
its 3000 and 9000 families that will carry the
company into the 1990s.  The new HP Precision
Architecture provides a significant increase in
performance.

   In 1989, HP acquired Apollo Computer, which
combined with its own line, made HP the market
leader in workstations.

   HP sells over 10,000 different products in the
electronics and computer field, and it has gained a
worldwide reputation for its rugged and reliable
engineering.


HP 1000
Family of realtime computers from HP introduced in
1966.  They are sensor-based computers used
extensively in laboratory and manufacturing
environments for collecting and analyzing data.


HP 3000
Family of business-oriented computers from HP.
Introduced in 1972, these midrange computers set a
standard for reliability and rugged engineering.
It evolved into a complete line from micros to
medium-scale mainframes and has been HP's major
computer line.  New models are RISC machines that
are compatible with the original 3000s.


HP 9000
Family of high-performance UNIX workstations and
business servers from HP.  Introduced in 1982, it
is used extensively in CAD and engineering
applications.  Business servers provide commercial
functionality.  New models use HP's RISC
architecture.


HP-PA
See HP Precision Architecture.


HP Precision Architecture
Proprietary RISC architecture from HP introduced in
1986 that is incorporated into new models of its
3000 and 9000 computer families.


HP-UX
HP's version of UNIX that runs on its 9000 family.
It is based on SVID and incorporates features from
BSD UNIX along with several HP innovations.


HPC
See High-Performance Computing.


HPFS
(High Performance File System)  File system,
introduced with OS/2 Version 1.2, that handles
larger disks (2TB volumes; 2GB files), long file
names (256 bytes) and can launch the program by
referencing the data as in the Macintosh.  It
coexists with the existing FAT system.


HPGL
(Hewlett-Packard Graphics Language)  Vector
graphics file format from HP that was developed as
a standard plotter language.  Most plotters support
the HPGL and DMPL standards.


HPIB
(Hewlett-Packard Interface Bus)  HP's version of
the IEEE 488 standard GPIB.


HSB
(Hue Saturation Brightness)  See HSV.


HSL
(Hue Saturation Lightness)  See HLS.


HST
(1) Asymetrical modem protocol from U.S. Robotics
that includes error control and compression and
transmits from 4800 to 14400 bps in one direction
and from 300 to 400 bps in the other.

(2) (Hubble Space Telescope)  Launched in April
1990, it views star material some 10 to 12 billion
light years from earth.


HSV
(Hue Saturation Value)  Color model that uses a
cylindrical coordinate system structured as an
inverted hexcone (six-sided pyramid).  Hue is
measured by the angle around the vertical axis with
red at 0°, yellow 60°, green 120°, cyan 180°, blue
240° and magenta 300°.  Saturation is amount of
color from 0 to 1 or 0 to 100%.  Value is from
black to white (0-1 or 0-100%).  Pure green would
be H=120, S=1 and V=1.


hub
Central connecting device for communications lines
in a star topology.  "Passive hubs" add nothing to
the data being transmitted.  "Active hubs"
regenerate signals and may monitor traffic for
network management.  "Intelligent hubs" are
computers that provide network management and may
also include bridging, routing and gateway
capabilities.

   The hub's star topology improves troubleshooting
over bus topology, in which all nodes are connected
to a common cable.  Hubs can be added to Ethernet
(bus) networks for improved network management.
Both hubs and routers may be inserted into the
middle of a network in order to improve performance
and network management.  See router.


hub ring
Flat ring pressed around the hole in a 5.25" floppy
disk for rigidity.  The drive's clamping ring
presses the hub ring onto the spindle.


hue
In computer graphics, a particular shade or tint of
a given color.


Huffman coding
Statistical compression method that converts
characters into variable length bit strings.  Most-
frequently-ocurring characters are converted to
shortest bit strings; least frequent, the longest.
Compression takes two passes.  The first pass
analyzes a block of data and creates a tree model
based on its contents.  The second pass compresses
the data via the model.  Decompression decodes the
variable length strings via the tree.  See LZW.


hybrid circuit
See hybrid microcircuit.


hybrid computer
Digital computer that processes analog signals
which have been converted into digital form.  It is
used in process control and robotics.


hybrid microcircuit
Electronic circuit composed of different types of
integrated circuits and discrete components,
mounted on a ceramic base.  Used in military and
communications applications, it is especially
suitable for building customized analog circuits
(A/D, D/A converters, amplifiers, modulators,
etc.).


hybrid network
In communications, a network made up of equipment
from multiple vendors.


Hydra
(1) (Hybrid Document Reproduction Apparatus)  A
printer, photocopier, scanner and fax built into
one machine.

(2) Device that converts analog signals to ISDN
Basic Rate Interface (BRI).

(3) Utility from the Austin Mac Developer's Assn.
that tests Macintosh graphics card performance.


Hyperaccess
PC communications program from Hilgraeve, Inc.,
Monroe, MI, that provides data compression, has its
own script language and supports a variety of
terminals and protocols.


HyperCard
Application development system from Apple that runs
on the Macintosh and Apple IIGS.  Using visual
tools, users build "stacks" of "cards" that hold
data, text, graphics, sound and video with
hypertext links between them.  The HyperTalk
programming language allows complex applications to
be developed.  Third-party compilers can compile
HyperCard stacks into executable programs,
eliminating the need to have HyperCard running in
order to execute the stacks.

   HyperCard used to be more popular with many
commercial and shareware stacks being developed
routinely.  Today Apple includes only a runtime
version with its Macs, not the full development
version, which is available from Claris.

   HyperCard's visual programming approach was
brought to PCs with Brightbill-Robert's HyperPad
and Asymetrix's ToolBook.


hypercube
Parallel processing architecture made up of binary
multiples of computers (4, 8, 16, etc.).  The
computers are interconnected so that data travel is
kept to a minimum.  For example, in two eight-node
cubes, each node in one cube would be connected to
the counterpart node in the other.


hypermedia
Use of data, text, graphics, video and voice as
elements in a hypertext system.  All the various
forms of information are linked together so that a
user can easily move from one to another.


HyperPAD
Application development system for PCs from
Brightbill-Roberts & Company, Ltd., Syracuse, NY.
It is a HyperCard-like program that works in text
mode and includes the PADtalk scripting language.


HyperScript
Advanced macro (scripting) language that is
provided with the WINGZ spreadsheet.


HyperTalk
Programming language used in HyperCard.


hypertext
Linking related information.  For example, by
selecting a word in a sentence, information about
that word is retrieved if it exists, or the next
occurrence of the word is found.  The concept was
coined by Ted Nelson as a method for making the
computer respond to the way humans think and
require information.

   In the electronic versions of this Glossary, you
can hypertext to the definition of any term used
within the definitions by clicking on it or
highlighting it with the mouse.


hyperware
Hypertext products.


hyphen ladder
Hyphens on two or more consecutive lines, which
causes distraction to the reader.


hyphenation
Breaking words that extend beyond the right margin.
Software hyphenates words by matching them against
a hyphenation dictionary or by using a built-in set
of rules, or both.  See discretionary hyphen.


hyphenation dictionary
Word file with predefined hyphen locations.


hyphenation zone
Distance from the right margin within which a word
may be hyphenated.


hysteresis
Lag between making a change, such as increasing or
decreasing power, and the response or effect of
that change.


Hz
(HertZ)  See Hertz.



I-CASE
(Integrated CASE)  CASE systems that generate
applications code directly from design
specifications.  Features include support for rapid
prototyping, modeling the data and processing and
drawing logic diagrams.


I/E time
See instruction cycle.


I/O
(Input/Output)  Transferring data between the CPU
and a peripheral device.  Every transfer is an
output from one device and an input into another.


I/O area
Reserved segment of memory used to accept data from
an input device or to accumulate data for transfer
to an output device.  See buffer.


I/O bound
Refers to an excessive amount of time getting data
in and out of the computer in relation to the time
it takes for processing it.  Faster channels and
disk drives improve the performance of I/O bound
computers.


I/O card
See expansion board and PC card.


I/O channel
See channel.


I/O interface
See port and expansion slot.


I/O processor
Circuitry specialized for I/O operations.  See
front end processor.


I/O statement
Programming instruction that requests I/O.


I-time
See instruction time.


i486
See 486.


i750
Programmable compression chip from Intel that
supports a variety of techniques including DVI,
MPEG and JPEG.


i860
RISC-based, 64-bit from Intel that uses a 64-bit
data bus, has built-in floating point and 3-D
graphics capability and contains over one million
transistors.  It can be used as a stand-alone CPU
or to accelerate performance in existing systems.


IAC
(InterApplication Communications)  IPC capability
in Macintosh System 7.0.


IBM
(International Business Machines Corp., Armonk, NY)
World's largest computer company.  It started in
New York in 1911 when the Computing-Tabulating-
Recording Co. (CTR) was created by a merger of The
Tabulating Machine Co. (Hollerith's punched card
company in Washington), International Time
Recording Co. (time clock maker in NY state),
Computing Scale Co. (maker of scales and food
slicers in Dayton, Ohio), and Bundy Manufacturing
(time clock maker in Poughkeepsie, NY).  CTR
started out with 1,200 employees and a capital
value of $17.5 million.

   In 1914, Thomas J. Watson, Sr., became general
manager.  During the next 10 years, he dispensed
with all non-tabulating business and turned it into
an international enterprise renamed IBM in 1924.
Watson instilled a strict, professional demeanor in
his employees that set IBMers apart from the rest
of the crowd.

   IBM achieved spectacular success with its
tabulating machines and the punched cards that were
fed into them.  From the 1920s through the 1960s,
it developed a huge customer base that was ideal
for conversion to computers.

   IBM launched its computer business in 1953 with
the 701 and introduced the 650 a year later.  By
the end of the 1950s, the 650 was the most widely
used computer in the world with 1,800 systems
installed.  The 1401, announced in 1959, was its
second computer winner, and by the mid 1960s, an
estimated 18,000 were in use.

   In 1964, it announced System/360, the first
family of compatible computers ever developed.  The
360s were enormously successful and set a standard
underlying IBM mainframes to this day.

   During the 1970s and 1980s, IBM made a variety
of incompatible minicomputer systems, including the
System/36 and System/38.  Its highly-successful
AS/400, introduced in 1988, provides a broad family
of compatible machines in this segment.

   In 1981, IBM introduced the PC into a chaotic
personal computer field and set the standard almost
overnight.  IBM is still the largest single
supplier of PCs, but the majority of sales come
from the PC industry at large, from companies such
as Compaq and Dell to mom and pop shops by the
thousands.

   The 1990s will be the most challenging era for
this industry giant.  With technology advancing in
an never-ending spiral, with PC networks springing
up daily, and with downsizing on the lips of every
budget-conscious IS manager, IBM will use every
ounce of its marketing genius.

   In 1991, IBM surprised everyone by forming an
alliance with Apple to integrate Macintoshes into
IBM enterprise networks and to jointly develop a
new line of future desktop systems (see Apple for
details).

   No doubt, more surprises are in store!


IBM-compatible PC
Personal computer that is compatible with the IBM
PC and PS/2 standards.


IBM mainframes
Large-scale computers from IBM.  The following
series all stem from the System/360 architecture
introduced in 1964.

 Date
 Intro. Series name and models
 1964   System/360  (Models 20 thru 195)
 1970   System/370  (Models 115 thru 168)
 1977   303x series (3031, 3032, 3033)
 1979   43xx series (4300 thru 4381, ES/4381)
 1980   308x series (3081, 3083, 3084)
 1986   3090 series (Models 120 thru 600, ES/3090)
 1986   9370 series (Entry level; 9370, ES/9370)
 1990   System/390  (ES/9000 Models 120 to 900)


IBM minicomputers
Midrange computers from IBM.  The following series
comprise IBM's minicomputers over the years.

 Date
 Intro. Series name
 1969   System/3
 1975   System/32
 1976   Series/1
 1977   System/34
 1978   System/38
 1978   8100
 1983   System/36
 1985   System/88
 1988   AS/400


IBM PC
Personal computer from IBM.  May refer to the first
IBM PC (1981) or to any IBM personal computer
model.

PC     Yr. Intro. CPU   Features
PC          '81  8088  No. 1 (floppy only)
XT          '83  8088  Slow hard disk
XT 286      '86   286  Slow hard disk
XT/370      '83  8088  370 emulation
AT          '84   286  Medium-speed hard disk
3270 PC     '83  8088  3270 emulation
PCjr        '83  8088  Floppy-based home use
PC Portable '84  8088  Floppy-based portable
Convertible '86  8088  Microfloppy laptop

PS/2   Intro. CPU Features
(MCA bus unless noted otherwise)
25      '87  8086, PC bus (limited expansion)
30      '87  8086, PC bus
30-286  '88  286, ISA bus
35 LS   '91  386SX, ISA bus, diskless
35 SX   '91  386SX, ISA bus
L40 SX  '91  386SX, ISA bus, laptop
40 SX   '91  386SX, ISA bus
50      '87  286
50 Z    '88  286, faster 50
N51 SX  '92  386SX, notebook
N51 SLC '92  386SLC, notebook
55 SX   '89  386SX
55 LS   '90  386SX, diskless
56 SLC  '92  386SLC
56 SX   '92  386SX, upgradeable
57 SLC  '92  386SLC
57 SX   '91  386SX, 2.88MB floppy
CL57 SX '92  386SX, notebook, active matrix color
60      '87  286
65      '90  386SX
70      '88  386
70 486  '89  486
P70     '89  386 portable
P75 486 '90  486 portable, 22 lbs.
76      '92  486SX, OS/2
77      '92  486SX, OS/2
80      '87  386, tower
90      '90  486, XGA, SCSI, upgradable
90      '92  486DX2/66
95      '90  486, tower
90 SX   '91  486SX
95 SX   '91  486SX, tower
Thinkpad laptops
 300    '92  386SLC
 700    '92  486SLC
 700C   '92  486SLC, active matrix color


IC
See integrated circuit and information center.


IC card
See PC card and memory card.


ICCP
(Institute for Certification of Computer
Professionals)  Organization founded in 1973 that
offers industry certification and provides
worldwide test centers.  The Associate Computer
Professional exam is open to all.  The Certified
Computer Programmer (CCP), Certified Data Processor
(CDP) and Certified Systems Professional (CSP)
require job experience (academic credit may
substitute).  Address: 2200 E. Devon Ave., Des
Plaines, IL 60018, 708/299-4227.


icon
Small, pictorial, on-screen representation of an
object (file, program, disk, etc.) used in
graphical interfaces.  For example, to delete a
file in the Macintosh, the file icon is moved into
the wastebasket icon.


iconic interface
User interface that uses icons.


IDA
(Intelligent Drive Array)  High-performance hard
disk interface from Compaq that controls a disk
array via the EISA bus.


IDAPI
(Independent Database API)  Programming interface
for accessing databases on a network proposed by
Borland and supported by IBM, Novell and others.


IDC
(Int'l. Data Corp., Framingham, MA)  Largest market
research, analysis, consulting and publishing firm
in the information field.  It provides annual
briefings and in-depth reports on all aspects of
the industry.


IDE
(1) (Integrated Drive Electronics)  Hard disk that
contains a built-in controller.  IDE drives are
widely used in PCs and range in capacity from 40MB
up to 1GB.  The drive connects via a 40-line flat
ribbon cable to an IDE host adapter (often called
an IDE controller) that plugs into an expansion
slot in the PC.  The host adapter controls up to
two IDE drives, but advanced host adapters control
up to four.

   Some motherboards are built with a 40-pin IDE
connector directly on the board thus freeing up an
expansion slot for use by another device.  The IDE
drive uses the ATA interface (AT Attachment),
although ATA is often only referenced in technical
manuals.  See hard disk.


           Installing a Second IDE Drive
Installing a disk drive correctly requires more
mechanical skill than it does knowledge of
computers or electronics.  Fitting the drive into
the bays and pushing and pulling on wires is the
hard part.

   Many PCs come with one IDE drive, but the IDE
host adapter can usually control two, and the 40-
line flat, signal cable between the host adapter
and the first drive generally has an open connector
for the second drive.  Be sure you have two jumpers
in hand (available from your hardware supplier) and
follow this procedure to install the second drive:

1. DETERMINE IF YOUR BIOS SUPPORTS THE NEW DRIVE
Note the cylinder, heads and sectors (spt)
identified on the second drive.  Go into your BIOS
setup and determine if you can define this new
drive properly.  To get into setup, many PCs
display on startup the key to press (often the Del
key).  If not, look in your hardware manual for the
keys to press (sometimes Ctrl-Alt-Esc).

   Cursor down to the second hard drive, which is
either D: or 1 (drives are either indicated as C
and D or 0 and 1) and see if you can select either
a predefined type that matches your new drive or
select User-defined type 47 and enter the
cylinders, heads and sectors to derive the total
size in megabytes.  This time, exit setup without
saving anything.

   If you were able to define the new drive
successfully, proceed with step #2, otherwise do
not proceed and review the problem with your
hardware support personnel.

2. INSTALL THE DRIVE
Turn the computer off.  Look at your drives and
make sure each drive has two sets of pins, one
named Master, the other named Slave (possibly only
M and S will be printed).  Do not proceed if the
pins are not present on both drives.  Next, place a
jumper on Master on the first drive and Slave on
the second.

   Insert the new drive into a drive bay and screw
it in.  Do not over-tighten screws into the drive.
If you want to put a 3.5" drive into a 5.25" drive
bay, get an adapter that holds the drive and fits
into the 5.25" bay.

   Plug an available four-wire (red-black-black-
yellow/orange) power cable into the drive (it only
fits one way).  If none is available, get a power
cable splitter, pull out an existing power
connection to another drive and insert the
splitter.  Attach both drives to the splitter.

   The connectors on the flat signal cable can be
inserted up or down, so be sure to connect the
second drive in the same direction as the first
drive.  If the cable isn't long enough, a longer
40-pin IDE ribbon cable can be purchased.  The
three connectors on the cable are common, and
either one can be used for either drive or the host
adapter.  One side of the cable is usually colored.
Line that side up with pin 1 on the host adapter
and the drives if you have to start from scratch.

   After installing the drives, turn on the
computer and go immediately into setup mode and re-
enter the data from step #1 above.  This time,
select the option that saves the new data to the
CMOS RAM.  The computer will reboot, and the second
drive is now ready for Fdisk and Format (see
Formatting a Hard Disk under DOS Format).


(2) (Integrated Development Environment)  Set of
programs run from a single user interface.  For
example, programming languages often include a text
editor, compiler and debugger, which are all
activated and function from a common menu.


IDE controller
(1) Controller built into an IDE drive.

(2) Often (erroneously) refers to an IDE host
adapter that connects an IDE drive to a non-IDE-
ready motherboard.


IDMS
(Integrated Data Management System)  Full-featured
relational DBMS from Computer Associates that runs
on minis and mainframes.  It was developed at GE in
the 1960s and marketed by Cullinane, later renamed
Cullinet.  In 1989, Cullinet was acquired by
Computer Associates and IDMS was renamed CA-
IDMS/DB.


IE
See information engineering.


IEC
(Int'l. Electrotechnical Commission)  Organization
that sets international electrical and electronics
standards founded in 1906 and headquartered in
Geneva.  It is made up of national committees from
over 40 countries.  Contact via ANSI, New York, NY.


IEEE
(Institute of Electrical and Electronic Engineers)
Membership organization that includes engineers,
scientists and students in electronics and allied
fields.  Founded in 1963, it has over 300,000
members and is involved with setting standards for
computers and communications.  Address: 345 E. 47th
St., New York, NY 10017, 212/705-7900.

   The Computer Society of the IEEE has over
100,000 members and holds meetings and technical
conferences on computers.  Address: 1730 Mass. Ave.
N.W., Washington, DC 20036, 202/371-0101.


IEEE 488
See GPIB.


IEEE 802
IEEE standard for local area networks.  See "LANs"
under data link protocol.

  ┌─802.1───Covers network management, etc.───────┐
  │  ┌────────────────────────────────────────────┘
  │  │ ┌─802.2───Specifies data link layer for────┐
  │  │ │         the following access methods     │
  │  │ └──────────────────────────────────────────┘
  │  │  ┌───802.3──┐ ┌──802.4──┐ ┌─────802.5──────┐
  │  │  │ CSMA/CD  │ │  token  │ │   token ring   │
  │  │  │"Ethernet"│ │   bus   │ │"IBM Token Ring"│
  └──┘  └──────────┘ └─────────┘ └────────────────┘


IEF
(Information Engineering Facility)  CASE software
from TI that runs on PCs and MVS mainframes and
generates COBOL code for PCs, MVS mainframes, VMS,
Tandem, AIX, HP-UX and other UNIX platforms.  It is
a fully-integrated set of CASE tools.


IEW
(Information Engineering Workbench)  CASE software
from Knowledgeware, Inc., Atlanta, GA, that runs on
DOS PCs and generates COBOL, CICS and IMS code for
MVS mainframes.


if-then-else
High-level programming language statement that
compares two or more sets of data and tests the
results.  If the results are true, the THEN
instructions are taken; if not, the ELSE
instructions are taken.  The following is a BASIC
example:

   10  IF ANSWER = "Y"  THEN PRINT "Yes"
   20  ELSE PRINT "No"


   In certain languages, THEN is implied.  All
statements between IF and ELSE are carried out if
the condition is true.  All instructions between
ELSE and ENDIF are carried out if not true.  The
following dBASE example produces the same results
as above:

   IF ANSWER = "Y"
       ? "Yes"
     ELSE
       ? "No"
   ENDIF



IFIP
(Int'l. Federation of Information Processing)
Multinational affiliation of professional groups
concerned with information processing, founded in
1960.  There is one voting representative from each
country (U.S. representative is FOCUS).  Address:
16 Place Longemalle, CH-1204 Geneva, Switzerland,
41 22 28 2649.


IFS
(Installable File System)  OS/2 feature that
supports multiple file systems.  Different systems
can be installed (UNIX, CD ROM, etc.) just like
drivers are installed for new peripherals.


IGES
(Initial Graphics Exchange Specification)  ANSI
graphics file format that is system independent and
also intended for human interpretation.  It evolved
out of the Air Force's Integrated Computer
Automated Manufacturing (ICAM) program in 1979.
For more on IGES and PDES, contact: IGES
Organization, National Institute of Standards &
Technology, Building 220, Room A-353, Gaithersburg,
MD 20899, 301/921-3691.


IIA
(1) (Information Industry Assn.)  Trade
organization that includes members from all aspects
of the information field.  Its purpose is to
conduct active government relations that safeguard
the interests of a healthy, competitive information
industry.  IIA sponsors seminars and conferences
and provides newsletters, newspapers and books.
Address: 555 New Jersey Ave. N.W., Washington, DC
20001, 201/639-8262.

(2) (Information Interchange Architecture)  IBM
formats for exchanging documents between different
systems.


illustration program
Same as drawing program.


Illustrator 88
Macintosh drawing program from Adobe Systems, Inc.,
that enhanced the original Illustrator program in
1988.  It provides sophisticated tracing and text
manipulation capabilities, as well as colors and
color separations.


IM
See information management.


image
(1) A picture (graphic).

(2) See system image.


image enhancement
Improving graphics images either manually using a
paint program or by using software routines that
change contrast, smooth lines or filter out
unwanted data.  See anti-aliasing.


image processing
(1) Analysis of a picture using techniques that can
identify shades, colors and relationships that
cannot be perceived by the human eye.  It is used
to solve identification problems, such as in
forensic medicine or in creating weather maps from
satellite pictures and deals with images in raster
graphics format that have been scanned in or
captured with digital cameras.

(2) Image improvement, such as refining a picture
in a paint program that has been scanned or entered
from a video source.

(3) Same as imaging.


imagesetter
Typesetting machine that handles text and graphics
and typically accepts PostScript input.  See
phototypesetter.


imaging
Creating a film or electronic image of any picture
or paper form.  It is accomplished by scanning or
photographing an object and turning it into a
matrix of dots (raster graphics), the meaning of
which is unknown to the computer, only to the human
viewer.  Scanned images of text may be encoded into
computer data (ASCII or EBCDIC) with page
recognition software (OCR).  See micrographics,
image processing and document imaging.


imaging model
Set of rules for representing images.


imaging system
See document imaging, image processing and image
enhancement.


immediate access
Same as direct access.


impact printer
Printer that uses a printing mechanism that bangs
the character image into the ribbon and onto the
paper.  See printer for examples.


impedance
Resistance to the flow of alternating current in a
circuit.


implementation
(1) Computer system implementation is the
installation of new hardware and system software.

(2) Information system implementation is the
installation of new databases and application
programs and the adoption of new manual procedures.


implode
To link component pieces to a major assembly.  It
may also refer to compressing data using a
particular technique.  Contrast with explode.


import
To convert a file in a foreign format to the format
of the program being used.


Improv
Multidimensional Windows spreadsheet from Lotus
that allows for easy switching to different views
of the data.  Data is referenced by name as in a
database rather than the typical spreadsheet row
and column coordinates.  Improv was originally
developed for the NeXt computer.


IMS
(Information Management System)  IBM hierarchical
DBMS for mainframes under MVS.  It was widely
implemented throughout the 1970s and continues to
be used.  IMS/DC is its transaction processing
component (like CICS) that handles the details of
communications and SNA networking.  IMS/DC is also
used to access DB2 databases.


in hardware
Refers to logic that has been placed into the
electronic circuits of the computer.


in software
Refers to logic in a program.  For example, "that
routine is done in software."


incident light
In computer graphics, light that strikes an object.
The color of the object is based on how the light
is absorbed or reflected by the object.


increment
To add a number to another number.  Incrementing a
counter means adding 1 to its current value.


incremental backup
See backup types.


incremental spacing
See microspacing.


IND$FILE
IBM mainframe program that transfers files between
the mainframe and a PC functioning as a 3270
terminal.


indent
To align text some number of spaces to the right of
the left margin.  See hanging paragraph.


index
(1) In data management, the most common method for
keeping track of data on a disk.  Indexes are
directory listings maintained by the OS, DBMS or
the application.

   An index of files contains an entry for each
file name and the location of the file.  An index
of records has an entry for each key field (account
no., name, etc.) and the location of the record.

(2) In programming, a method for keeping track of
data in a table.  See indexed addressing.


index hole
Small hole punched into a hard sectored floppy disk
that serves to mark the start of the sectors on
each track.


index mark
Physical hole or notch, or a recorded code or mark,
that is used to identify a starting point for each
track on a disk.


index register
High-speed circuit used to hold the current,
relative position of an item in a table (array).
At execution time, its stored value is added to the
instructions that reference it.


indexed addressing
Technique for referencing memory that automatically
increments the address with the value stored in an
index register.  See subscript (2).


indexed sequential
See ISAM.


indexing
(1) Creating indexes based on key data fields or
key words.

(2) Creating timing signals based on detecting a
mark, slot or hole in a moving medium.


indirect addressing
Address mode that points to another pointer rather
than the actual data.  This mode is prohibited in
RISC architecture.


inductance
Opposition to the changing flow of current in a
circuit, measured in Henrys.


induction
Process of generating an electric current in a
circuit from the magnetic influence of an adjacent
circuit as in a transformer or capacitor.


inference engine
Processing program in an expert system.  It derives
a conclusion from the facts and rules contained in
the knowledge base using various artificial
intelligence techniques.


infix notation
Common way arithmetic operators are used to
reference numeric values.  For example, A+B/C is
infix notation.  Contrast with Polish notation and
reverse Polish notation.


Info Select
Popular personal information manager (PIM) for PCs
from Micro Logic Corp., Hackensack, NJ, that
includes automatic phone dialing via modem.  It is
noted for its exceptional ease of use and ability
to store random information and instantly retrieve
it.  It is based on an earlier product called
Tornado conceived by Paul Mendelsohn.


infopreneur
Person who is in business to gather and disseminate
electronic information.


informate
To dispense information, as coined by Harvard
Professor Shoshana Zuboff.


information
Summarization of data.  Technically, data are raw
facts and figures that are processed into
information, such as summaries and totals.  But
since information can also be raw data for the next
job or person, the two terms cannot be precisely
defined.  Both terms are used synonymously and
interchangeably.

   As office automation and data processing merge,
it may be more helpful to view information the way
data is defined and used, namely: data, text,
spreadsheets, pictures, voice and video.  Data are
discretely defined fields.  Text is a collection of
words.  Spreadsheets are data in matrix (row and
column) form.  Pictures are lists of vectors or
frames of bits.  Voice is a continuous stream of
sound waves.  Video is a sequence of frames.

   Future databases will routinely integrate all
these forms of information.


information appliance
Type of future home or office device that can
transmit to or plug into common public or private
networks.  Envisioned is a "digital highway," like
telephone and electrical power networks.


information center
Division within the IS department that supports
end-user computing.  Responsible for training users
in applications and solving related personal
computer problems.


information engineering
Integrated set of methodologies and products used
to guide and develop information processing within
an organization.  It starts with enterprise-wide
stategic planning and ends with running
applications.


information hiding
Keeping details of a routine private.  Programmers
only know what input is required and what outputs
are expected.  See encapsulation and data
abstraction.


information industry
(1) Information publishing.  Organizations that
provide information via online services or through
distribution by diskette or CD ROM.

(2) All computer, communications and electronics-
related organizations, including hardware, software
and services.


information management
Discipline that analyzes information as an
organizational resource.  It covers the
definitions, uses, value and distribution of all
data and information within an organization whether
processed by computer or not.  It evaluates the
kinds of data/information an organization requires
in order to function and progress effectively.

   Information is complex because business
transactions are complex.  It must be analyzed and
understood before effective computer solutions can
be developed.  See data administration.


information processing
Same as data processing.


information resource management
See Information Systems and information management.


information science
See information management.


information service
Any information retrieval, publishing, timesharing
or BBS facility.  See online services.


Information Services
See Information Systems.


information system
Business application of the computer.  It is made
up of the database, application programs, manual
and machine procedures and encompasses the computer
systems that do the processing.

   The database stores the subjects of the business
(master files) and its activities (transaction
files).  The application programs provide the data
entry, updating, query and report processing.  The
manual procedures document how data is obtained for
input and how the system's output is distributed.
Machine procedures instruct the computer how to
perform the batch processing activities, in which
the output of one program is automaticaly fed into
another program.

   The daily processing is the interactive,
realtime processing of the transactions.  At the
end of the day or other period, the batch
processing programs update the master files that
have not been updated since the last cycle.
Reports are printed for the cycle's activities.

   The periodic processing of an information system
is the updating of the master files, which adds,
deletes and changes the information about
customers, employees, vendors and products.


         Relationships Between Systems

    STRUCTURE (is)           FUNCTION (does)

 ──Management system───┬───────────────────────────
                       │Sets organization's goals
   1.  PEOPLE          │and objectives, strategies
   2.  MACHINES        │and tactics, plans,
                       │schedules and controls
 ──Information system──┼───────────────────────────
                       │
   1. DATABASE         │ Defines data structures
   2. APPLICATION      │ ┌Data entry, updating,
       PROGRAMS        │ └ queries and reporting
   3. PROCEDURES       │ Defines data flow
                       │
 ──Computer system─────┼───────────────────────────
                       │
   1. CPU              │  Processes (The 3 C's)
   2. PERIPHERALS      │  Store and retrieve
   3. OPERATING SYSTEM │  Manages computer system


Information Systems
Formal title for a data processing, MIS, or IS
department.  Other titles are Data Processing,
Information Processing, Information Services,
Management Information Systems, Management
Information Services and Information Technology.


information theory
Study of encoding and transmitting information.
From Claude Shannon's 1938 paper, "A Mathematical
Theory of Communication," which proposed the use of
binary digits for coding information.


information utility
(1) Service bureau that maintains up-to-date
databases for public access.

(2) Central source of information for an
organization or group.


information warehouse
Collection of all databases in an enterprise across
all platforms and departments.


INFORMIX
Family of DBMSs from Informix Software, Inc., Menlo
Park, CA, that includes an SQL-based relational
DBMS, fourth-generation language and toolkits for
embedding SQL in application programs.


infoware
Information sold electronically, such as the
electronic versions of this Glossary.


InfoWindow
Trade name for IBM display screens.


infrared
Invisible band of radiation at the low-frequency
end of the light spectrum.  Contrast with
ultraviolet.


INGRES
(INteractive Graphics and REtrieval System)
Relational DBMS from Ingres Corp., Alameda, CA,
that runs on VAXs and UNIX workstations.  It
includes a 4GL, QBE and lets users create and
manage a database as a series of forms.  Its
Knowledge Management extension allows rules to be
programmed into the database.

   Ingres Corp. was formerly Relational Technology,
a company founded in 1980 to market a commercial
version of INGRES, which was developed at the Univ.
of California at Berkeley in the early 1970s.


inheritance
In object-oriented programming, the ability of one
class of objects to inherit properties from a
higher class.


inhouse
Operation that takes place on the user's premises.


INIT
(INITiate)  Macintosh routine that is run when the
computer is started or restarted.  It is used to
load and activate drivers and system routines.
Many INITs are memory resident and may conflict
with each other like TSRs in the PC environment.


initial program load
See IPL.


initialization string
Same as setup string.


initialize
To start anew, which typically involves clearing
all or some part of memory or disk.


ink jet
Printer mechanism that sprays one or more colors of
ink onto paper and produces high-quality printing
like that of a laser printer.

   The continuous stream method produces droplets
that are aimed onto the paper by electric field
deflectors.

   The drop-on-demand method uses a set of
independently controlled injection chambers, the
newest of which use solid ink developed by Exxon in
1983.  Solid ink liquefies quickly when heated and
solidifies instantly when it reaches the paper.


INMARSAT
(INternational MARitime SATellite)  International
organization involved in providing satellite
communications to and from ships and offshore rigs.
It is represented in the U.S. and partially owned
by COMSAT.


innoculate
To store characteristics of an executable program
in order to detect a possible unknown virus if the
file is changed.


input
(1) Data that is ready for entry into the computer.

(2) To enter data into the computer.


input area
Reserved segment of memory that is used to accept
data from a peripheral device.  Same as buffer.


input device
Peripheral device that generates input for the
computer such as a keyboard, scanner, mouse or
digitizer tablet.


input/output
See I/O.


input program
Same as data entry program.


input queue
Reserved segment of disk or memory that holds
messages that have been received or job control
statements describing work to be done.


input stream
Collection of job control statements entered in the
computer that describe the work to be done.


inquiry program
Same as query program.


Ins key
(INSert key)  A keyboard key that is used to switch
between insert and overwrite mode or to insert an
object at the current cursor location.


insert mode
Data entry mode that causes new data typed on the
keyboard to be inserted at the current cursor
location on screen.  Contrast with overwrite mode.


install program
Software that prepares a software package to run in
the computer.  It copies the files from the
distribution diskettes to the hard disk and
decompresses them, if required.  It may ask you to
identify your computer environment in order to link
in the drivers for the display, printer and other
devices that you have.


installation conflicts
See PC conflicts.


installation spec
Documentation from an equipment manufacturer that
describes how a product should be properly
installed within a physical environment.


instance
In object-oriented programming, a member of a
class; for example, "Lassie" is an instance of the
class "dog."  When an instance is created, the
initial values of its instance variables are
assigned."


instance variable
In object-oriented programming, the data in an
object.


instant print
Ability to use the computer as a typewriter.  Each
keystroke is transferred to the printer.


instantiate
In object-oriented programming, to create an object
of a specific class.  See instance.


instruction
(1) Statement in a programming language.

(2) Machine instruction.


instruction cycle
Time in which a single instruction is fetched from
memory, decoded and executed.  The first half of
the cycle transfers the instruction from memory to
the instruction register and decodes it.  The
second half executes the instruction.


instruction mix
Blend of instruction types in a program.  Often
refers to writing generalized benchmarks, which
requires that the amount of I/O versus processing
versus math instructions, etc., reflects the type
of application the benchmark is written for.


instruction register
High-speed circuit that holds an instruction for
decoding and execution.


instruction repertoire
Same as instruction set.


instruction set
Repertoire of machine language instructions that a
computer can follow (from a handful to several
hundred).  It is a major architectural component
and is either built into the CPU or into microcode.
Instructions are generally from one to four bytes
long.


instruction time
Time in which an instruction is fetched from memory
and stored in the instruction register.  It is the
first half of the instruction cycle.


insulator
Material that does not conduct electricity.
Contrast with conductor.


int
Programming statement that specifies an interrupt
or that declares an integer variable.  See
interrupt and integer.


int 13
DOS interrupt used to activate disk functions, such
as seek, read, write and format.


integer
Whole number.  In programming, the integer function
would yield 123 from 123.898.


Integer BASIC
Apple version of BASIC for the Apple II that
handles only fixed point numbers (non-floating
point).  Due to its speed, many games are written
in it.


integrated
Collection of distinct elements or components that
have been built into one unit.


integrated CASE
See I-CASE.


integrated circuit
Formal name for chip.


integrated injection logic
Type of bipolar transistor design known for its
fast switching speeds.


integrated software package
Software that combines several applications in one
program, typically database management, word
processing, spreadsheet, business graphics and
communications.  Such programs (Microsoft Works,
AppleWorks, etc.) provide a common user interface
for their applications plus the ability to cut and
paste data from one to the other.

   User interfaces, such as found on the Macintosh
and Windows, provide this capability with all
applications written for their environments.


integrator
In electronics, a device that combines an input
with a variable, such as time, and provides an
analog output; for example, a watt-hour meter.


integrity
See data integrity.


Intel
(Intel Corp., Santa Clara, CA)  Leading
manufacturer of semiconductor devices founded in
1968 by Bob Noyce and Gorden Moore in Mountain
View, CA.  A year later it introduced its first
product, a 64-bit bipolar static RAM chip.  By
1971, its very successful memory chips began to
obsolete magnetic core storage.

   Intel is known for its x86 microprocessor
family, but it also developed the first
microprocessor in 1971.  In response to a
calculator chip order from Japanese manufacturer
Busicom, Intel engineer Marcian E. "Ted" Hoff
decided it would make more sense to design a
general-purpose machine.  The resulting 4004 chip
was the world's first microprocessor.

   Over the years, Intel has developed a wide
variety of chips and board-level products,
including the MULTIBUS bus used in industrial
applications.  Intel started with 12 people and
first year revenues of $2672.  In 1990, it had
24,000 employees and revenues of four billion.


Intellect
Natural language query program from AI Corp.,
Waltham, MA, that runs on IBM mainframes and other
computers.  It can answer many English language
questions; for example, "Tell me the number of
employees in the personnel department."


Intellifont
Scalable font technology from Agfa CompuGraphic.
Intellifont typefaces are built into LaserJet IIIs
and 4s (see LaserJet).  The Intellifont for Windows
font scaler creates matching screen fonts for
Windows from Intellifont and compatible typefaces.


intelligence
Processing capability.  Every computer is
intelligent!


intelligent cable
Same as smart cable.


intelligent controller
Peripheral control unit that uses a built-in
microprocessor for controlling its operation.


intelligent database
Database that contains knowledge about the content
of its data.  A set of validation criteria are
stored with each field of data, such as the minimum
and maximum values that can be entered or a list of
all possible entries.  See DBMS (Intelligent
Databases).


intelligent form
Data entry application that provides help screens
and low levels of AI in aiding the user to enter
the correct data.


intelligent hub
Network hub that performs a variety of functions
such as regenerating signals, monitoring
transmission for network management, allowing
connections to a variety of cable types and
routing.  Contrast with passive hub.  See hub.


intelligent modem
Modem that responds to commands and can accept new
instructions during online transmission.  It was
originally developed by Hayes.


intelligent paper
Same as intelligent form.


intelligent terminal
Terminal with built-in processing capability, but
no local disk or tape storage.  It may use a
general-purpose CPU or may have specialized
circuitry as part of a distributed intelligence
system.  Contrast with dumb terminal.


INTELSAT
(INt'l. TELecommunications SATellite)
International organization involved in launching
and operating commercial satellites.  It was
created in 1964 with only 11 countries
participating.  Today, over 100 nations have
ownership.  It is represented in the U.S. and
partially owned by COMSAT.


inter
To cross over boundaries; for example, internetwork
means from one network to another.  Contrast with
intra.


interactive
Back-and-forth dialog between the user and a
computer.


interactive cable TV
Service in which viewers take part in TV programs
by reacting to issues.  It implies full TV viewing,
in contrast with videotex or teletext.  In time,
all of these services may be provided over cable TV
channels.  A decoder and keyboard are required.


interactive session
Back-and-forth dialogue between user and computer.
Contrast with batch session.


interactive video
Use of videodisc or CD ROM controlled by computer
for an interactive education or entertainment
program.  See videodisc and CD ROM.


InterBase
Relational DBMS from Borland that runs on UNIX
workstations and VAXes, designed to handle online
complex processing (OLCP).  It can be a peer-to-
peer or client/server system and uses SQL plus its
own data manipulation language.


interblock gap
Same as interrecord gap.


interface
Connection and interaction between hardware,
software and the user.

   Hardware interfaces are the plugs, sockets,
wires and the electrical pulses travelling through
them in a particular pattern.  Also included are
all electrical timing considerations.  Examples are
RS-232 transmission, the Ethernet and Token Ring
network topologies and the IDE, ESDI, SCSI, ISA,
EISA and Micro Channel interfaces.

   Software, or programming, interfaces are the
languages, codes and messages programs use to
communicate with each other and to the hardware.
Examples are the applications that run under the
Mac, DOS and Windows operating systems as well as
the SMTP e-mail and LU 6.2 communications
protocols.

   User interfaces are the keyboards, mice,
commands and menus used for communication between
you and the computer.  Examples are the command
lines in DOS and UNIX and the Mac, Windows and
Motif graphical interfaces.

   Interfacing is a major part of what engineers,
programmers and consultants do.  Users "talk to"
the software.  The software "talks to" the hardware
and other software.  Hardware "talks to" other
hardware.  All this is interfacing.  It has to be
designed, developed, tested and redesigned, and
with each incarnation, a new specification is born
that may become yet one more de facto or regulated
standard.


                 Format & Function
Every interface implies a structure.  Electrical
signals are made up of voltage levels, frequencies
and duration.  The data passed from one device or
program to another has a precise format (header,
body, trailer, etc.).

   Every interface implies a function.  At the
hardware level, electronic signals activate
functions; data is read, written, transmitted,
received, analyzed for error, etc.  At the software
level, instructions activate the hardware (access
methods, data link protocols, etc.).  At higher
levels, the data transferred or transmitted may
itself request functions to be performed
(client/server, program to program, etc.).


              Language & Programming
An interface is activated by programming language
commands.  The complexity of the functions and the
design of the language determine how difficult it
is to program.


         Interface, Protocol, API and ABI
The interface between the user and the computer is
called a user interface; between components in a
network, a protocol; between two programs, an API,
and between an application and a computer
environment, an API or ABI.

   All these interactions are interfaces, and the
terms are used interchangeably.  Regardless of what
they're called, they all imply a set of rules that
must be followed.


interface adapter
In communications, a device that connects the
computer or terminal to a network.


interframe coding
In video compression, coding only the differences
between frames.  See intraframe coding.


interlaced
Illuminating a CRT by displaying odd lines and then
even lines (every other line first; then filling in
the gaps).  TV signals are interlaced and generate
60 half frames (30 full frames) per second.
Computer display systems may also be interlaced,
but usually only at the highest resolution.

   Rather than send every line of information to
the screen (non-interlaced), interlacing sends half
the information in the same time frame, thus
requiring less-complicated and less-expensive
circuits.

   TV's constant animation has always provided
acceptable viewing using the interlaced method,
although reading a still image on TV is not all
that pleasing.  Interlaced screens used on
computers can provide an annoying flicker that
causes headaches and eye strain (see below).


      Interlaced       Non-interlaced
   1 ▓▓▓▓▓▓▓▓▓▓▓▓▓     ▓▓▓▓▓▓▓▓▓▓▓▓▓▓
   2 ░░░░░░░░░░░░░     ▓▓▓▓▓▓▓▓▓▓▓▓▓▓
   3 ▓▓▓▓▓▓▓▓▓▓▓▓▓     ▓▓▓▓▓▓▓▓▓▓▓▓▓▓
   4 ░░░░░░░░░░░░░     ▓▓▓▓▓▓▓▓▓▓▓▓▓▓
   5 ▓▓▓▓▓▓▓▓▓▓▓▓▓     ▓▓▓▓▓▓▓▓▓▓▓▓▓▓


               Where's the Flicker?
When you purchase a video display adapter and
monitor, the interlaced vs non-interlaced issue
comes up when you get into the highest modes.  For
example, most VGA adapters and monitors support the
following three resolutions: 640x480, 800x600 and
1024x768.  Advanced models support 1280x1024 and
higher.

   The lower resolutions (640x480 and 800x600) are
usually non-interlaced, but the highest mode
1024x768 or 1280x1024 may be interlaced.  When you
start up under DOS, you are always at the lowest,
non-interlaced 640x480 resolution.  It's only when
you get into Windows or AutoCAD that you get into
the higher modes.

   An interlaced resolution does not cause flicker
like a badly-synchronized movie projector.  Rather
it provides a faint overall flutter that is often
very noticeable on tiny, complex graphic elements
such as icons.

   A related issue is the vertical scan frequency,
or the number of times the entire screen is
refreshed per second.  Since the refresh rate may
go down as resolution goes up, this is another
consideration.  The number can range from 45 to
over 100; however, 60 is the smallest refresh
recommended.

   For CAD and destop publishing, a non-interlaced
1280x1024 resolution with a 70Hz refresh rate on a
21" monitor is recommended.  Depending on the size
of the page you are working with, a non-interlaced
1024x768 resolution on a 17" screen may suffice.

   The high resolutions required to see full pages
and facing pages of text provide enough strain on
the eyes.  Interlaced screens and low refresh rates
only add to the burden.



Interleaf
Full-featured desktop publishing software for 386
and higher PCs from IBM.  Includes text and
graphics editing, free-hand drawing, supports
PostScript and provides connectivity to shared
AS/400 folders.


interleave
See sector interleave and memory interleaving.


interlock
Device that prohibits an action from taking place.


intermediate language
Same as pseudo language.


intermediate node routing
Routing a message to non-adjacent nodes; for
example, if three computers are connected in series
A--B--C, data transmitted from A to C can be routed
through B.


intermittent error
Error that occurs sporadically, not consistently.
It is very difficult to diagnose and repair.


internal bus
Data pathway between closely-connected components,
such as between the CPU and memory.  See local bus.


internal font
Set of characters for a particular typeface that is
built into a printer.  Contrast with font cartridge
and soft font.


internal interrupt
Interrupt that is caused by processing, for
example, a request for input or output or an
arithmetic overflow error.  Contrast with external
interrupt.


internal modem
Modem that plugs into a particular computer's
expansion slot from which it derives its power.
Contrast with external modem.


internal sort
Sorting accomplished entirely in memory without
using disks or tapes for temporary files.


internal storage
Same as memory.


internet
(1) Large network made up of a number of smaller
networks.

(2) (Internet)  National research-oriented network
comprised of over 3,000 government and academic
networks in more than 40 countries.  Access to the
Internet is available through many online services
such as CompuServe, BIX and America Online.  See
online services.


Internet address
The format for addressing a message to an Internet
user is: [e-mail].  For example,
the address of the Free Software Foundation is
[e-mail], which means transmitting to
the GNU mailbox via nodes PREP, AI and MIT.

  Internet Domains
  com - business
  edu - educational
  gov - government
  mil - military site
  net - gateway or host
  org - other organization


InterNet Router
Macintosh software from Apple that internetworks
different access methods (LocalTalk, EtherTalk,
TokenTalk, etc.) and can reside in any network
station.  Each Router can connect up to eight
networks with a maximum of 1,024 networks and 16
million nodes.


internetwork
To go between one network and another.


interoperable
Ability for one system to communicate or work with
another.


interpolate
To estimate values that lie between known values.


Interpress
Page description language from Xerox used on the
2700 and 9700 page printers (medium to large-scale
laser printers).  Ventura Publisher provides output
in Interpress.


interpret
To run a program one line at a time.  Each line of
source language is translated into machine language
and then executed.


interpreter
High-level programming language translator that
translate and runs the program at the same time.
It translates one program statement into machine
language, executes it, then proceeds to the next
statement.

   Interpreted programs run slower than their
compiler counterparts, because the compiler
translates the entire program before it is run.
However, it's convenient to write an interpreted
program, since a single line of code can be tested
interactively.

   Interpreted programs must always be run with the
interpreter.  For example, in order to run a BASIC
or dBASE program, the BASIC or dBASE interpreter
must be in the computer.

   If a language can be both interpreted and
compiled, a program may be developed with the
interpreter and compiled for production.


interpretive language
Programming language that requires an interpreter
to run it.


interprocess communication
See IPC.


interrecord gap
Space generated between blocks of data on tape,
created by the starting and stopping of the reel.


interrogate
(1) To search, sum or count records in a file.  See
query.

(2) To test the condition or status of a terminal
or computer system.


interrupt
Signal that gets the attention of the CPU and is
usually generated when I/O is required.  For
example, hardware interrupts are generated when a
key is pressed or when the mouse is moved.
Software interrupts are generated by a program
requiring disk input or output.

   An internal timer may continually interrupt the
computer several times per second to keep the time
of day current or for timesharing purposes.

   When an interrupt occurs, control is transferred
to the operating system, which determines the
action to be taken.  Interrupts are prioritized;
the higher the priority, the faster the interrupt
will be serviced.


interrupt-driven
Computer or communications network that uses
interrupts.


interrupt latency
Time it take to service an interrupt.  It becomes a
critical factor when servicing realtime functions
such as a communications line.  See UART overrrun.


interrupt mask
Internal switch setting that controls whether an
interrupt can be processed or not.  The mask is a
bit that is turned on and off by the program.


interrupt priorities
Sequence of importance assigned to interrupts.  If
two interrupts occur simultaneously, the interrupt
with the highest priority is serviced first.  In
some systems, a higher-priority interrupt can gain
control of the computer while it's processing a
lower-priority interrupt.


interrupt vector
In the PC, one of 256 pointers that reside in the
first 1KB of memory.  Each vector points to a
routine in the ROM BIOS or elsewhere in memory,
which handles the interrupt.


intersect
In relational database, to match two files and
produce a third file with records that are common
in both.  For example, intersecting an American
file and a programmer file would yield American
programmers.


intra
Within a boundary; for example, intraoffice refers
to operations that take place within the office.
Contrast with inter.


intraframe coding
Compressing redundant areas within a video frame.
See interframe coding.


inverse video
Same as reverse video.


inverted file
In data management, a file that is indexed on many
of the attributes of the data itself.  For example,
in an employee file, an index could be maintained
for all secretaries, another for managers.  It's
faster to search the indexes than every record.
Inverted file indexes use lots of disk space;
searching is fast, updating is slower.


inverted list
Same as inverted file.


inverter
(1) Logic gate that converts the input to the
opposite state for output.  If the input is true,
the output is false, and vice versa.  An inverter
performs the Boolean logic NOT operation.

(2) Circuit that converts DC current into AC
current.  Contrast with rectifier.


invoke
To activate a program, routine, function or
process.


IOCA
(Image Object Content Architecture)  See MO:DCA.


IOCS
(Input Output Control System)  Early, rudimentary
IBM operating system (1950s).  It was a set of I/O
routines for tapes and disks.  Today's counterpart
in the PC is the ROM BIOS.


ion deposition
Printing technology used in high-speed page
printers.  It is similar to laser printing, except
instead of using light to create a charged image on
a drum, it uses a printhead that deposits ions.
After toner is attracted to the ions on the drum,
the paper is pressed directly against the drum
fusing toner to paper.

   Quality approaches that of a laser printer;
however, the ink has not been embedded as deeply,
and the paper can smear more easily.


IOS
(Integrated Office System)  See office automation.


IP
(1) (Internet Protocol)  IP part of the TCP/IP
protocol, which routes a message across networks.
See TCP/IP and datagram.

(2) See image processing.


IPC
(InterProcess Communication)  Exchange of data
between one program and another either within the
same computer or over a network.  It implies a
protocol that guarantees a response to a request.
Examples are OS/2's Named Pipes, Windows' DDE,
Novell's SPX and Macintosh's IAC.

   Although IPCs are performed automatically by the
programs, an analogous function is performed
interactively when users cut and paste data from
one file to another using the clipboard.


IPDS
(Intelligent Printer Data Stream)  IBM format for
sending full pages of text and graphics from a
mainframe or mini to a laser printer.


IPI
(Intelligent Peripheral Interface)  High-speed hard
disk interface used with minis and mainframes that
transfers data in the 10 to 25 MBytes/sec range.
IPI-2 and IPI-3 refer to differences in the command
set that they execute.   See hard disk.


IPL
(Initial Program Load)  Same as boot.


ips
(Inches Per Second)  Measures the speed of tape
passing by a read/write head or paper passing
through a pen plotter.


IPX
(Internet Packet EXchange)  NetWare communications
protocol used to route messages from one node to
another.  Application programs that manage their
own client/server or peer-to-peer communications in
a Novell network can access IPX, or NetWare's SPX
protocol, directly.  IPX does not guarantee
delivery of a message as does SPX.


IR
(Industry Remarketer)   Same as VAR or VAD.


IRG
(InterRecord Gap)  See interrecord gap.


IRM
(Information Resource Management)  See Information
Systems and information management.


IRMAboard
Micro to mainframe board for PCs from DCA, Inc.,
Alpharetta, GA.  It emulates the common IBM 3270
mainframe terminal allowing a PC access to
centralized mainframe applications.  IRMA is DCA's
trade name for a variety of communications
products.  It is the lady's name, not an acronym.


IRMALAN
Family of gateway products from DCA, Inc.,
Alpharetta, GA, that allow PC users connected to
NetBIOS-compatible LANs to access an SNA host.  It
includes gateways for IEEE 802.2, SDLC and DFT
environments.


iron oxide
Material used to coat the surfaces of magnetic
tapes and lower-capacity disks.


IRQ
(Interrupt ReQuest)  Hardware interrupt on a PC.
Eight lines (0-7 on 8086/88s) and 16 lines (0-15 on
286s and up) accept interrupts from devices such as
a scanner and network adapter.  Unless specifically
programmed to interact together, two devices cannot
use the same line.  If a new expansion board is
preset to the IRQ used by an existing board, one of
them must be changed.  See PC conflicts.

   Starting with the 286, the PC uses two 8259A
controller chips to handle the IRQs.  The chips are
cascaded together.  IRQ 2 connects to IRQ 9 of the
second chip.

     IRQ  Assignment

      0   System timer
      1   Keyboard
      2   Connects to IRQ 9
      3   COM2, COM4
      4   COM1, COM3
      5   LPT2
      6   Floppy disk
      7   LPT1
      8   Realtime clock
      9   3270 emulation
     10   -
     11   -
     12   -
     13   Math coprocessor
     14   Hard disk
     15 -



IS
See Information Systems.


ISA
(Industry Standard Architecture)  Pronounced "eye-
suh."  Expansion bus commonly used in PCs.  It
accepts the plug-in boards that control the video
display, disks and other peripherals.  The majority
of PC expansion boards on the market are ISA
boards.

   ISA was originally called the AT bus, because it
was first used in the IBM AT (1984), and it
extended the original PC bus from eight to 16 bits.
Most ISA PCs provides a mix of 8-bit and 16-bit
expansion slots.  Contrast with EISA ("ee-sa") and
Micro Channel.

                 ISA vs Local Bus
Starting with the 386, when CPU speeds began to
dramatically accelerate, PCs have been built with
two buses.  The CPU communicates with its memory
chips via a 32-bit internal path, known as the
local bus, at its full clock speed, which can be as
high as 50MHz.  RAM chips are directly connected to
the motherboard to allow for this high-speed
transfer.

   In contrast, the PC transfers data between its
peripheral devices over the 16-bit ISA bus at only
8MHz.  Even the 32-bit EISA and Micro Channel buses
do not normally run much faster.

   This local bus, reserved for high-speed memory
transfer, is now being tapped to transfer data to
and from peripheral devices.  See local bus.


ISAM
(Indexed Sequential Access Method)  Common disk
access method that stores data sequentially, while
maintaining an index of key fields to all the
records in the file for direct access.  The
sequential order would be the one most commonly
used for batch processing and printing (account
number, name, etc.).


ISDN
(Integrated Services Digital Network)
International telecommunications standard for
transmitting voice, video and data over a digital
line.  It uses 64Kbps circuit-switched B (Bearer)
channels to carry voice and data and uses a
separate D (Data) channel to carry control signals
via a packet-switched network.  This out-of-band D
channel allows a variety of services to be
provided, including call forwarding, call waiting
and advice of charge.  The two types of service
are:

BASIC RATE INTERFACE (BRI) 144Kbps
Includes two B channels and one 16Kbps D channel
(2B+D).

PRIMARY RATE INTERFACE (PRI) 1.544Kbps
In North America, it includes 23 B channels and one
64Kbps D channel (23B+D), equivalent to T1.  In
Europe, it includes 30 B channels and one 64Kbps D
channel (30B+D), equivalent to European E1 service.


                The Future of ISDN
ISDN's 64Kbps channel speed is a big boost over
today's fastest analog modems, but it can't match
Ethernet and Token Ring speeds of 10Mbps and
16Mbps.  However, Broadband ISDN (BISDN) should
materialize by the mid 1990s, which utilizes
broadband transmission and fiber optic cables, to
attain speeds of 150Mbps.


ISO
(Int'l. Standards Organization)  Organization that
sets international standards, founded in 1946 and
headquartered in Geneva.  It deals with all fields
except electrical and electronics, which is
governed by the older Int'l. Electrotechnical
Commission (IEC), also in Geneva.  With regard to
information processing, ISO and IEC created JTC1,
the Joint Technical Committee for information
technology.

   It carries out its work through more than 160
technical committees and 2,300 subcommittees and
working groups and is made up of standards
organizations from more than 75 countries, some of
them serving as secretariats for these technical
bodies.  ANSI is the U.S. member body.  Address:
ANSI, 1430 Broadway, New York, NY 10018.


isochronous
Time dependent.  Realtime voice, video and
telemetry are examples of isochronous data.


isometric view
In computer graphics, a picture of a 3-D object
that shows all three dimensions in equal
proportions.  Isometric views do not show true
perspective.


isotropic
Refers to properties, such as transmission speed,
that are the same regardless of the direction that
is measured.  Contrast with anisotropic.


ISPF
(Interactive System Productivity Facility)  IBM
mainframe software that executes interactive user
interfaces on 3270 terminals.  It is created with
ISPF's PDF (Program Development Facility) software.


ISR
(Interrupt Service Routine)  Software routine that
is executed in response to an interrupt.


ISV
(Independent Software Vendor)  Person or company
that develops software.


IT
(Information Technology)  Same as Information
Systems.


ITAA
(Information Technology Assn. of America)  Formerly
Assn. of Data Processing Service Organizations
(ADAPSO).  Membership organization founded in 1960
that defines performance standards, improves
management methods and monitors government
regulations in the computer services field.
Address: 1616 N. Fort Myer Dr., Arlington, VA
22209, 703/522-5055.


item
One unit or member of a group.  See data item.


iteration
One repetition of a sequence of instructions or
events.  For example, in a program loop, one
iteration is once through the instructions in the
loop.


iterative operation
Operation that requires successive executions of
instructions or processes.


ITSEC
See NCSC.


IV
See interactive video.


IVD
(Interactive VideoDisc)  See interactive video.


Iverson notation
Set of symbols developed by Kenneth Iverson for
writing statements in APL.


IVR
(Interactive Voice Response)  See voice response.


iWARP
Systolic-array microprocessor from Intel that was
originally funded by DARPA and developed by
Carnegie-Mellon.


IXC
(IntereXchange Carrier)  Organization that provides
interstate communications services, such as AT&T,
MCI and Sprint.


IZE
PC text management system from Persoft, Inc.,
Madison, WI, noted for its flexible searching.  Key
words can be entered manually or can be created
from a list or condition, such as the name between
"Dear" and a comma.



J-lead
See SOJ.


jack
Receptacle into which a plug is inserted.


jacket
Plastic housing that contains a floppy disk.  The
5.25" disk is built into a flexible jacket; the
3.25" disk uses a rigid jacket.


Jacquard loom
Automated loom that transformed the 19th century
textile industry and became the inspiration for
future calculating and tabulating machines.
Developed by the French silk-weaver, Joseph-Marie
Jacquard (1752-1834), it used punched cards to
control its operation.  Although punched cards were
used in earlier looms and music boxes, Jacquard's
loom was a vast improvement and allowed complex
patterns to be created swiftly.


JAD
(Joint Application Development)  Approach to
systems analysis and design introduced by IBM in
1977 that emphasizes teamwork between user and
technician.  Small groups meet to determine system
objectives and the business transactions to be
supported.  They are run by a neutral facilitator
who can move the group toward well-defined goals.
Results include a prototype of the proposed system.


jaggies
Stairstepped appearance of diagonal lines on a low-
resolution graphics screen.


Javelin Plus
PC spreadsheet from Information Resources, Inc.,
Waltham, MA.  Instead of row and column numbers, it
uses names to identify cells and consolidate data.


Jazz
Integrated Macintosh software package from Lotus.
Modeled after Symphony, it never caught on.


JCL
(Job Control Language)  Command language for mini
and mainframe operating systems that launches
applications.  It specifies priority, program size
and running sequence, as well as the files and
databases used.


JEDEC
(Joint Electronic Device Engineering Council)
International body that sets integrated circuit
standards.


JEIDA
(Japanese Electronic Industry Development Assn.)
Japanese trade and standards organization.  PCMCIA
has joined with JEIDA to standardize on a 68-pin
memory card.


JES
(Job Entry Subsystem)  Software that provides batch
communications for IBM's MVS operating system.  It
accepts data from remote batch terminals, executes
them on a priority basis and transmits the results
back to the terminals.  The JES counterpart in VM
is called RSCS.


jiff
See GIF.


jitter
Flickering transmission signal or display image.


job
Unit of work running in the computer.  A job may be
a single program or a group of programs that work
together.


job class
Descriptive category of a job that is based on the
computer resources it requires when running.


job control language
See JCL.


job management language
Same as JCL.


job processing
Handling and processing jobs in the computer.


job queue
Lineup of programs ready to be executed.


job stream
Series of related programs that are run in a
prescribed order.  The output of one program is the
input to the next program and so on.


join
(1) In relational database management, to match one
file against another based on some condition
creating a third file with data from the matching
files.  For example, a customer file can be joined
with an order file creating a file of records for
all customers who purchased a particular product.

(2) See DOS Join.


Josephson junction
Ultra-fast switching technology that uses
superconductor materials, originally conceived by
Brian Josephson.  Circuits are immersed in liquid
helium to obtain near-absolute zero degrees
required for operation.  A Josephson junction has
been observed to switch in as little as 50
femtoseconds.


journal
Same as log.


JOVIAL
(Jules' Own Version of the Int'l. Algebraic
Language)  ALGOL-like programming language
developed by Systems Development Corp. in the early
1960s and widely used in the military.  Its key
architect was Jules Schwartz.


joy stick
Pointing device used to move an object on screen in
any direction.  It employs a vertical rod mounted
on a base that contains one or two buttons.  It is
used extensively in video games and in some CAD
systems.


JPEG
(Joint Photographic Experts Group)  ISO/CCITT
standard for compressing images using discrete
cosine transform.  It provides lossy compression at
variable ratios, providing 20 to 30:1 without
noticeable loss.  Ratios of 50:1 to 100:1 may be
used if the loss in image can be tolerated.

   JPEG is implemented in hardware as well as
software; for example, a PC with a 1992-vintage
JPEG board can compress a full-color 25MB image
into 1MB in one second.  C-Cube Microsystems
introduced the first JPEG chip.  See MPEG.


JRP
(Joint Requirements Planning)  Systems planning
performed cooperatively by a team of users and
technicians.  Functions should be prioritized and
related to the organization's goals and business
opportunities.


JTC1
(Joint Technical Committee 1)  See ISO.


Julian date
Representation of month and day by a consecutive
number starting with Jan. 1.  For example, Feb. 1
is Julian 32.   Dates are converted into Julian
dates for calculation.


jump
Same as GOTO.


jumper
Metal bridge used to close a circuit.  It can be a
short length of wire or a plastic-covered metal
block that is pushed onto two pins on a circuit
board.  It is often used in place of DIP switches.


junction
Point at which two elements make contact.  In a
transistor, a junction is the point where an N-type
material makes contact with a P-type material.


justification
In typography, the alignment of text evenly between
left and right margins.  Contrast with ragged
right.


justify
(1) To shift the contents of a field or register to
the right or left.

(2) To align text evenly between left and right
margins.



K
See kilo.


K-byte
See kilobyte.


K&R C
(Kernighan and Ritchie C)  Version of C defined by
Brian Kernighan and Dennis Ritchie that preceded
the ANSI standard.


Kaleida
(Kaleida Labs, Inc., Mountain View, CA)  Joint
venture of IBM and Apple that is developing
multimedia software.  See ScriptX.


KB, Kb
See kilobyte and kilobit.


Kbit
See kilobit.


Kbits/sec
(KiloBITS per SECond)  Thousand bits per second.


KBps, Kbps
(KiloBytes Per Second, KiloBits Per Second)
Thousand bytes per second.  Thousand bits per
second.


Kbyte
See kilobyte.


Kbytes/sec
(KiloBYTES per SECond)  Thousand bytes per second.


Kerberos
Security system developed at MIT that authenticates
users.  It does not provide authorization to
services or databases; it establishes identity at
logon, which is used throughout the session.


Kermit
Aynchronous file transfer protocol developed at
Columbia Univ., noted for its accuracy over noisy
lines.  Several extensions exist, including
SuperKermit, a full-duplex, sliding window version.
Kermit is popular on minis and mainframes and can
also handle byte-oriented transfers over 7-bit
ASCII systems.


kernel
Fundamental part of a program, such as an operating
system, that resides in memory at all times.


kerning
In typography, the spacing of letter combinations,
such as WA, MW and TA, where each character
overlaps into some of the space of the other for
improved appearance.


Kerr effect
Change in rotation of light reflected off a
magnetic field.  The polarity of a magneto-optic
bit causes the laser to shift one degree clockwise
or counterclockwise.


key
(1) Keyboard button.

(2) Data that identifies a record.  Account number,
product code and customer name are typical key
fields used to identify a record in a file or
database.  As an identifier, each key value must be
unique in each record.  See sort key.

(3) Numeric code used by an algorithm to create a
code for encrypting data for security purposes.


key cap
Replaceable, top part of a keyboard key.  To
identify commonly-used codes, it can be replaced
with a custom-printed key cap.


key click
Audible feedback provided when a key is pressed.
It may be adjustable by the user.


key command
Key combination (Alt-G, Ctrl-B, Command-M, etc.)
used as a command to the computer.


key driven
Any device that is activated by pressing keys.


key entry
Data entry using a keyboard.


key field
See key (2).


key in
To enter data by typing on a keyboard.


key rollover
See n-key rollover.


key-to-disk machine
Stand-alone data entry machine that stores data on
magnetic disk for computer entry.


key-to-tape machine
Stand-alone data entry machine that stores data on
magnetic tape for computer entry.  Introduced by
Mohawk Data Sciences in the mid 1960s, it was the
first advancement in data entry since the card
keypunch.  Mohawk's stock went from $2 to $200 in a
couple of years.


key word
(1) Word used in a text search.

(2) Word in a text document that is used in an
index to best describe the contents of the
document.

(3) Reserved word in a programming or command
language.


keyboard
Set of input keys.  On terminals and personal
computers, it includes the standard typewriter
keys, several specialized keys and features
outlined below.  See PC keyboard, AT keyboard and
Enhanced keyboard.


                Enter (Return) Key
In text applications, it ends a paragraph or short
line.  In data applications, it signals the end of
the input for that field or line.


                    Cursor Keys
The four arrow keys move the cursor on screen.
They are used in conjunction with shift, alt and
control to move the cursor in bigger jumps; for
example, CONTROL UP ARROW might scroll the screen.
Some earlier keyboards didn't have cursor keys, in
which case, control or alt was used with some
letter key.


       Control, Alt, Command and Option Keys
Used like a shift key, these keys are held down
while another key is pressed to command the
computer in a variety of ways.


                    Escape Key
Commonly used to exit or cancel the current mode
such as exiting from a menu.  Also used to clear an
area or repeat a function such as redrawing the
screen.


                   Numeric Lock
Locks a combination number/cursor keypad into
numeric mode only.


                 Home and End Keys
Commonly used to move the cursor to the extreme
left or right side of the current line.  Often used
in conjunction with shift, control and alt; for
example, CONTROL HOME and CONTROL END usually move
the cursor to the beginning and end of file.


            Page Up and Page Down Keys
Used to move the cursor up and down a page, screen
or frame.  Often used in combination with shift,
control and alt.


                   Function Keys
Used to call up a menu or perform a function, they
are located in a cluster on the left side or in a
row across the top of the keyboard (labelled F1,
F2, etc.).  Often used with the shift, control and
alt keys providing 40 separate functions with F1
through F10.


                   Backspace Key
Used to delete the character to the left of the
cursor (erase typos) and may be used with the
shift, control and alt keys to erase segments of
text.  The extra-wide, typewriter-style key is
preferred.


                    Delete Key
Used to erase the character at the current cursor
location.  Used in conjunction with the shift,
control and alt keys, it is used to erase any
segment of text, such as a word, sentence or
paragraph.


                    Insert Key
Usually a toggle switch to go back and forth
between insert and overwrite mode.  Also used to
"paste" a segment of text or graphics into the
document at the current cursor location.


                  Repeating Keys
Most computer keys repeat when held down, a
phenomenon first-time computer users must get used
to.  If you hold a key down that is used to command
the computer, you'll be entering the command
several times.


                 Audible Feedback
Keyboards may cause a click or beep to be heard
from the computer when keys are pressed.  This is
done to acknowledge that the character has been
entered.  It should be adjustable for personal
preference.


            All Keyboards Are Not Equal
Keyboard quality is critical for experienced
typists.  The feel (tension and springiness) varies
greatly.  Key placement is important.  Older
keyboards and new laptop keyboards may have awkward
return and shift key placements.


keyboard buffer
Memory bank or reserved memory area that stores
keystrokes until the program can accept them.  It
lets fast typists continue typing while the program
catches up.


keyboard controller
Circuit that monitors keystrokes and generates the
required data bits when pressed.


keyboard enhancer
Same as macro processor.


keyboard interrupt
Signal that gets the attention of the CPU each time
a key is pressed.  See interrupt.


keyboard macro processor
See macro processor.


keyboard processor
See keyboard controller and keyboard enhancer.


keyboard template
Plastic card that fits over the function keys to
identify each key's purpose in a particular
software program.


keyframe
In computer graphics animation, a frame that
indicates the beginning or end of an object in
motion.


keypad
Small keyboard or supplementary keyboard keys; for
example, the keys on a calculator or the
number/cursor cluster on a computer keyboard.


keypunch
To punch holes in a punched card.  It is sometimes
used to refer to typing on a computer keyboard.


keypunch department
Same as data entry department.


keypunch machine
Punched-card data entry machine.  A deck of blank
cards is placed into a hopper, and, upon operator
command, the machine feeds one card to a punch
station.  As characters are typed, a series of dies
at the punch station punch the appropriate holes in
the selected card column.


Khornerstones
Benchmark program that tests CPU, I/O and floating
point performance.


KHz
(KiloHertZ)  One thousand cycles per second.  See
horizontal scan frequency.


kicks
See CICS.


kilo
Thousand.  Abbreviated "K."  It often refers to the
precise value 1,024 since computer specifications
are usually binary numbers.  For example, 64K means
65,536 bytes when referring to memory or storage
(64x1024), but a 64K salary means $64,000.  The
IEEE uses "K" for 1,024, and "k" for 1,000.  See
binary values and space/time.


kilobit
One thousand bits.  Also KB, Kb, Kbit and K-bit.
See kilo and space/time.


kilobyte
One thousand bytes.  Also KB, Kbyte and K-byte.
See kilo and space/time.


Kinetics FastPath
Gateway from the Kinetics division of Excelan,
Inc., that connects LocalTalk and PhoneNet systems
and LaserWriters to VAXs, UNIX-based computers, PCs
and other Ethernet-based hosts.  It supports
AppleTalk, TCP/IP and DECnet protocols.


kiosk
Small, self-standing structure such as a newstand
or ticket booth.  Unattended, multimedia kiosks
dispense public information.


kludge
Also spelled "kluge" and pronounced "klooj."  A
crude, inelegant system, component or program.  It
may refer to a makeshift, temporary solution to a
problem as well as to any product that is poorly
designed or that becomes unwieldy over time.


knowledge acquisition
Process of acquiring knowledge from a human expert
for an expert system, which must be carefully
organized into IF-THEN rules or some other form of
knowledge representation.


knowledge base
Database of rules about a subject used in AI
applications.  See expert system.


knowledge based system
AI application that uses a database of knowledge
about a subject.  See expert system.


knowledge domain
Specific area of expertise of an expert system.


knowledge engineer
Person who translates the knowledge of an expert
into the knowledge base of an expert system.


knowledge representation
Method used to code knowledge in an expert system,
typically a series of IF-THEN rules (IF this
condition occurs, THEN take this action).


Korn shell
See UNIX.


KSDS
(Keyed Sequence DataSet)  VSAM structure that uses
an index to store records in available free space.
Retrieval is by key field or by address.  Contrast
with ESDS.


KSR terminal
(Keyboard Send Receive terminal)  Same as
teleprinter.  Contrast with RO terminal.


kwem
See QEMM.



label
(1) In data management, a made-up name that is
assigned to a file, field or other data structure.

(2) In spreadsheets, descriptive text that is
entered into a cell.

(3) In programming, a made-up name used to identify
a variable or a subroutine.

(4) In computer operations, a self-sticking form
attached to the outside of a disk or tape in order
to identify it.

(5) In magnetic tape files, a record used for
identification at the beginning or end of the file.


label prefix
In a spreadsheet, a character typed at the
beginning of a cell entry.  For example, in 1-2-3,
a single quote (') identifies what follows as a
descriptive label even if it's a number.


LAN
(Local Area Network)  Communications network that
serves users within a confined geographical area.
It is made up of servers, workstations, a network
operating system and a communications link.

   Servers are high-speed machines that hold
programs and data shared by all network users.  The
workstations, or clients, are the users' personal
computers, which perform stand-alone processing and
access the network servers as required.  Diskless
and floppy-only workstations are sometimes used,
which retrieve all software and data from the
server.  A printer can be attached to a workstation
or to a server and be shared by network users.

   Small LANs can allow each workstation to
function as a server, allowing all users access to
data on all machines.  These peer-to-peer networks
are often simpler to install and manage, but
dedicated servers provide better performance and
can handle higher transaction volume.  Multiple
servers are used in large networks.

   The controlling software in a LAN is the network
operating system, such as NetWare, LANtastic and
Appletalk, which resides in the server.  A
component part of the software resides in each
workstation and allows the application to read and
write data from the server as if it were on the
local machine.

   The physical transfer of data is performed by
the access method (Ethernet, Token Ring, etc.)
which is implemented in the network adapters that
plug into the workstations and servers.  The actual
communications path is the cable (twisted pair,
coax, optical fiber) that interconnects each
network adapter.  See MAN, WAN, bridge, router,
gateway and hub.


LAN administrator
See network administrator.


LAN Manager
Network operating system from Microsoft that runs
as a server application under OS/2 and supports
both DOS, Windows and OS/2 clients.  It uses the
Microsoft File Sharing protocol (SMB) for file
sharing, the NetBIOS protocol for its transport
mechanism and uses Named Pipes for interprocess
communication (IPC).  See LAN Server.

   LAN Manager for Windows NT is a different
product.  It adds network management and services
to Windows NT, which includes peer-to-peer
networking.


LAN Network Manager
IBM Token Ring network management software.  LAN
Station Manager is the workstation counterpart that
collects data for LAN Network Manager.


LAN Requester
LAN Server software that resides in the
workstation.


LAN Server
(1) Network operating system from IBM that runs as
a server application under OS/2 and supports both
DOS, Windows and OS/2 clients.  Originally based on
LAN Manager when OS/2 was jointly developed by IBM
and Microsoft, Version 3.0 runs under IBM's own
OS/2 Version 2.0.

   Version 3.0 provides disk mirroring, CID
capability and Network Transport Services/2 (NTS/2)
for concurrent access to NetWare servers.  Options
are Lan Server for the Macintosh for Mac client
access and System Performance/2 (SP/2), a series of
network management utilities.

(2) (LAN server)  Generically, a file server in a
network.


LAN station
(1) Workstation in a local area network.

(2) See LAN Network Manager.


LAN Workplace
Family of software products from Novell that allows
DOS, Windows, Macintosh and OS/2 clients in a
NetWare environment to access resources on a TCP/IP
network.  LAN Workplace for DOS can also
encapsulate NetWare protocols and run NetWare-
dependent applications entirely within a TCP/IP
network.


landing zone
Safe non-data area on a hard disk used for parking
the read/write head.


Landmark rating
Widely-used PC performance test from Landmark
Research Int'l., Clearwater, FL, that measures CPU,
video and coprocessor speed.  CPU speed is rated as
the clock speed required in an AT-class machine
that would provide equivalent performance.


landscape
Printing orientation that prints data across the
wider side of the form.  Contrast with portrait.


landscape monitor
Monitor that is used to display facing text pages.
It is wider than it is high.


language
Set of symbols and rules used to convey
information.  See machine language, programming
language, graphics language, page description
language, fourth-generation language, standards &
compatibility and user interface.


language processor
Language translation software.  Programming
languages, command languages, query languages,
natural languages and foreign languages are all
translated by software.


LanguageAccess
SAA-compliant query language from IBM that
translates a user's English-language request into
SQL language for QMF.  QMF retrieves the data.


LANtastic
Popular peer-to-peer LAN operating system for PCs
from Artisoft, Inc., Tucson, AZ, that is noted for
its ease of use.  It supports Ethernet, ARCNET and
Token Ring adapaters as well as its own twisted-
pair adapater at two Mbits/sec.  Artisoft also
makes Ethernet adapters.  Included are e-mail and
chat functions.  Voice mail and conversation are
optional.


LAP
(Link Access Procedure)  CCITT family of error
correction protocols originally derived from the
HDLC standard and used on X.25 packet networks.

LAP-B (LAP-Balanced) Used in current X-25 networks.

LAP-D (LAP-D channel)  Used in the data channel of
                       an ISDN transmission.

LAP-M (LAP-Modem)  Defined in CCITT V.42, which
                   uses some of the LAPD methods
                   and adds additional ones.

LAP-X (LAP-Half-dupleX)  Used for ship to shore
                         transmission.


LapLink
PC file transfer program from Traveling Software,
Inc., Bothell, WA, that transfers data between
laptops and desktop computers.  LapLink Mac
transfers files between PCs and Macs.


laptop computer
Portable computer that has a flat screen and
usually weighs less than a dozen pounds.  It uses
AC power and/or batteries.  Most have connectors
for an external monitor transforming them into
desktop computers.  See notebook computer and
pocket computer.

                 Laptop Features

KEYBOARD
Keyboard layout is often sacrificed.  The Home,
End, PageUp and PageDn keys may not be dedicated
keys, requiring that you hold down the Fn key in
conjunction with them.  This is more cumbersome.

   Function keys and cursor keys are often made
smaller.  If you have large hands, test the
keyboard carefully.

   A full-size external keyboard can be connected
to an external keyboard connector or through the
serial or parallel ports with an adapter.

SCREEN QUALITY
Monochrome LCD screens translate colors into shades
of gray.  The more shades, the better the
representation of full-color images.  Passive
matrix LCD screens provide a subdued color.  Active
matrix LCD screens are sharp and rich, but are
costly and use more power.  Stay tuned for active
addressing LCD screens (see LCD).

EXTERNAL DISPLAY AND KEYBOARD CONNECTORS
Connect a full-size CRT and keyboard for
home/office.  Even if you like your laptop
keyboard, you may want to use an external keyboard
with your external monitor, because the laptop
screen usually doesn't move out of the way for
direct viewing of the monitor.

LOW POWER CPU
Intel's 386SL and 486SL and AMD's Am386-SXL are
low-power CPUs that prolong battery life.

BUILT-IN TRACKBALL
Very convenient, but placement is not standard.
Try it first!  Keyboard keys or a specially-
designed key may also be used as a mouse
substitute.  Barring any of these, a built-in mouse
port lets you use an external mouse or trackball
and frees up the serial port for something else.

BUILT-IN MODEM
Saves lugging an external modem.

EXPANSION SLOTS
Some laptops connect to an optional docking station
that provides one or more slots for future
expandability.

AUTO RESUME
Lets you return to the computer and pick up where
you left off without having to reload your
applications.

DUAL DISPLAY
Using an external monitor and laptop display at the
same time.  For presentations with a data
projector, it may be difficult to look at a
projected image off in the distance.

NICKEL HYDRIDE BATTERY
Provides about 20% more power per pound than NiCad
and doesn't have its associated memory problem.
Recharge life may be shorter, however.

TRANSFORMER WEIGHT
Transformer weight (often not published) is a
consideration, since it is usually carried with the
computer.


laser
(Light Amplification from the Stimulated Emission
of Radiation)  Device that creates a very uniform
light that can be precisely focused.  It generates
a single wavelength or narrow band of wavelengths
and is used in applications such as communications,
printing and disk storage.  Unlike the transmission
of electricity, transmission of light pulses over
optical fibers is not affected by nearby electrical
interferences.  See LED.


                The Laser Discovery
In 1957, the laser was conceived by Gordon Gould, a
graduate student in physics at Columbia Univ.  When
Gould filed for patents in 1959, he found that
Columbia professor Charles Townes and Arthur
Schawlow of Bell Labs had already filed for them.
The year before, AT&T had, in fact, demonstrated a
working laser at Bell Labs.  In 1977, after years
of litigation, a court awarded Gould rights to the
first of three patents and later to all of them.
He finally reaped millions in royalties.


laser printer
Printer that uses the electrophotographic method
used in copy machines to print a page at a time.  A
laser "paints" the dots of light onto a
photographic drum or belt.  The toner is applied to
the drum or belt and then transferred onto the
paper.  Desktop printers use cut sheets like a copy
machine.  Large printers may use rolls of paper.

   In 1975, IBM introduced the first laser printer,
the high-speed model 3800.  Later, Siemens
introduced the ND 2 and Xerox introduced the 9700.
These self-contained printing presses are online to
a mainframe or offline, accepting print image data
on tape reels or disk packs.  Large-scale machines
provide collating and stacking, and some models can
print on very wide paper.

   In 1984, HP introduced the LaserJet, the first
desktop laser printer, which propelled desktop
publishing.  The desktop laser printer has
obsoleted the daisy wheel printer and competes
directly with the dot matrix printer.

   Although high-resolution color laser printers
are also available, less expensive desktop versions
will become widely used throughout the 1990s.

   Note: All large-scale printers that print a page
at a time do not use a laser.  Some use ion
deposition, which creates the image with
electricity rather than light.


laserdisc
See videodisc.


LaserJet
Family of desktop laser printers from HP.
Introduced in 1984 at $3,495, the first LaserJet
revolutionized the desktop laser printer market.
LaserJets print at 300 dpi and starting with the
LaserJet 4, at 600 dpi.  Third-party enhancements,
such as the WinJet, increase resolution to 1200
dpi.  PCL is the printer command language.

   LaserJets accept bitmapped fonts from plug-in
cartridges or, except for the original model, from
the computer (soft fonts).  PostScript cartridges
are available either from HP or from third parties
for all models starting with the Series II.
Starting with the LaserJet 4, native PostScript
models are available.

   Starting with the III (PCL 5), Intellifont
scalable fonts are included.  In addition, the III
overcomes previous limitations and can print
portrait and landscape fonts on the same page and
print white text on a black background.


              LASERJET SPECIFICATIONS

     Input paper capacity  Built in fonts    Canon
          Year Speed   │    │ Cartridges    Printer
 Model   Intro (ppm)   │    │   │     RAM   Engine
───────────────┬──┬──────┬────┬───┬─────────┬─────
*LaserJet  1984│ 8│  100 │  2 │ 1 │ 128K-2M │ CX
*PLUS      1985│ 8│  100 │  2 │ 1 │ 512K-2M │ CX
*500 PLUS  1986│ 8│  500 │  2 │ 1 │ 512K-2M │ CX
*2000 *1   1987│20│  500 │ 34 │ 3 │ 1½-5½M  │LPB20
*Series II 1987│ 8│  200 │  6 │ 2 │ 512K-4M │ SX
*IID *1    1989│ 8│  400 │ 22 │ 2 │ 640K-4M │ SX
*IIP       1989│ 4│50-300│ 14 │ 1 │ 512K-4.5│ LX
 IIP+      1991│  Slightly faster than IIP  │ LX
*III       1990│ 8│  200 │ *3 │ 2 │ 1-5M    │ SX
*IIID *1   1990│ 8│  400 │ *3 │ 2 │ 1-5M    │ SX
 IIIP      1991│ 4│70-320│ *3 │ 1 │ 1-5M    │ LX
*IIIsi *2  1991│17│ 1000 │ *3 │ 2 │ 1-17M   │ NX
───600 dpi──────────────────────────────────────
 4         1992│ 8│  350 │ *4 │ 1 │ 2-32M   │ EX
 4M        1992│ 8│  350 │ *5 │ 1 │ 6-26M   │ EX
 4si *2    1993│17│ 1000 │ *4 │ 2 │ 2-34M   │ *6
 4siMX *2  1993│17│ 1000 │ *5 │ 2 │ 2-26M   │ *6
───────────────┴──┴──────┴────┴───┴─────────┴─────
   *=No longer made as of 4/93
  *1=Double sided printing
  *2=Double sided optional
  *3=14 bitmapped fonts, plus two
     Intellifont typeface families (IIIsi has four)
  *4=35 Intellifont scalable fonts plus
     10 TrueType scalable fonts
  *5=*4 plus 35 Type 1 PostScript fonts (Level 2)
  *6=Similar to NX (designation not yet announced)


LaserMaster
See WinJet.


LaserWriter
Family of 300 dpi desktop laser printers from Apple
introduced in 1985.  All models handle bitmapped
fonts, and, except for the SC models, include
PostScript, built-in AppleTalk connections, as well
as RS-232 ports for connecting PCs via Diablo
emulation.


LAT
(Local Area Transport)  Communications protocol
from Digital for controlling terminal traffic in a
DECnet environment.


LATA
(Local Access and Transport Area)  Geographic
region set up to differentiate local and long
distance telephone calls.  Any telephone call
between parties within a LATA is handled by the
local telephone company.


latch
Electronic circuit that maintains one of two
states.  See flip-flop.


late binding
Linking routines at runtime.


latency
Time between initiating a request for data and the
beginning of the actual data transfer.  On a disk,
latency is the time it takes for the selected
sector to come around and be positioned under the
read/write head.  Channel latency is the time it
takes for a computer channel to become unoccupied
in order to transfer data.


latent image
Invisible image typically of electrical charges.
For example, in a copy machine, a latent image of
the page to be copied is created on a plate or drum
as an electrical charge.


launch
To cause a program to load and run.


LAWN
(Local Area Wireless Network)  Transmitter/receiver
from O'Neill Communications, Inc., Princeton, NJ,
that connects devices using radio transmission.


layer
(1) In computer graphics, one of several on-screen
"drawing boards" for creating elements within a
picture.  Layers can be manipulated independently,
and the sum of all layers make up the total image.

(2) In communications, a protocol that interacts
with other protocols to provide all the necessary
transmission services.  See OSI.


layout setting
Value used to format a printed page.  Margins,
tabs, indents, headers, footers and column widths
are examples.


LBRV
(Low Bit Rate Voice)  Voice sampling technique that
analyzes each 15-30 millisecond speech segment
independently and converts it into a 30-byte frame.


LC
(Low cost Color)  See Macintosh.


LCC
See leaded chip carrier.


LCD
(Liquid Crystal Display)  Display technology that
uses rod-shaped molecules (liquid crystals) that
flow like liquid and bend light.  Unenergized, the
crystals direct light through two polarizing
filters, allowing a natural background color to
show.  When energized, they redirect the light to
be absorbed in one of the polarizers, causing the
dark appearance of crossed polarizers to show.  The
more the molecules are twisted, the better the
contrast and viewing angle.

   Because it takes less power to move molecules
than to energize a light-emitting device, LCDs
replaced LEDs in digital watches years ago.

                   TYPES OF LCDs

                  Passive Display
Called "passive matrix" when used for computer
screens.  Called "passive display" when used for
digital readouts, icons, etc.  All active
electronics (transistors) are outside of the
display screen.  Provides a sharp image for
monochrome screens, but more subdued for color.
Submarining is common.  Passive display types are:

  TN (twisted nematic) - low-cost displays for
     consumer products, instruments, etc.
     90° twist; black on gray/silver background

  STN (supertwisted nematic) - used extensively on
     laptops for mono and color displays.
       180° twist; green/blue on yellow background
       270° twist; blue on white/blue background

  Active Addressing - Improves passive display by
     addressing pixels differently.  Eliminates
     submarining and less expensive than active
     displays.  Available end 1993/early 1994.


             Active Display (TFT LCD)
Typically used for laptop color screens, thus
called "active matrix" displays.  Transistors are
built into each pixel within the screen.  For
example, 640x480 color VGA screen requires 921,600
transistors; one for each red, green and blue dot.
Provides a sharp, clear image with good contrast
and eliminates submarining, but fabrication costs
are high.  Uses a 90° (TN) twist.  Also called TFT
LCD (thin film transistor LCD).


               Reflective vs Backlit
Reflective screens used in many consumer appliances
and some lightweight laptops require external light
and only work well in a bright room or with a desk
lamp.  Backlit and sidelit screens have their own
light source and work well in dim lighting.


LCD panel
Data projector that accepts computer output and
displays it on a see-through liquid crystal screen
placed on top of an overhead projector.


LCD printer
Electrophotographic printer that uses a single
light source directed by liquid crystal shutters.


LE
(Less than or Equal to)  See relational operator.


lead acid
Rechargeable battery technology widely used in
portable gardening tools, but has been used in some
portable computers.  It uses lead plates and an
acid electrolyte.  It provides the least amount of
charge per pound of the rechargeable technologies.
See NiCad, nickel hydride and zinc air.


leaded chip carrier
Square chip housing with pin connectors on all four
sides (provides more I/O paths than a DIP).
Contrast with leadless chip carrier.


leader
(1) Length of unrecorded tape used to thread the
tape onto the tape drive.

(2) Dot or dash used to draw the eye across the
printed page, such as in a table of contents.


leading
In typography, the vertical spacing between lines
of type (between baselines).  The name comes from
the early days of typesetting when the space was
achieved with thin bars of lead.


leading edge
(1) Edge of a punched card or document that enters
the reading station first.

(2) In digital electronics, a pulse as it changes
from a 0 to a 1.

(3) In programming, a loop that tests a condition
before the loop is entered.

(4) (Leading Edge Products, Inc., Westborough, MA)
PC manufacturer founded in 1980.  Its Model M in
1982 was the first PC-compatible from overseas.
Korean Daewoo Corp. supplied it with products since
1984 and acquired it in 1989.


leading zeros
Zeros used to fill a field that do not increase the
numerical value of the data.  For example, all the
zeros in 0000006588 are leading zeros.


leadless chip carrier
Square chip housing with flat contact connectors on
all four sides (provides more I/O paths than a
DIP).  Contrast with leaded chip carrier.


leaf
In database management, the last node of a tree.


League for Programming Freedom
Organization of professors, students and
businessmen who believe that software copyrights
and patents jeopardize the industry.  They are
dedicated to "bringing back the freedom to write
programs."  Address: 1 Kendall Square, P.O. Box
9171, Cambridge, MA 02139.


leapfrog test
Storage diagnostic routine that replicates itself
throughout the storage medium.


leased line
Private communications channel leased from a common
carrier.  It can be ordered in pairs, providing a
four-wire channel for full-duplex transmission
(dial-up system provides only two-wire lines).  To
improve line quality, it can also be conditioned.


leased line modem
High-speed modem used in private lines.  It may
have built-in lower speeds for alternate use in
dial-up lines.


least significant digit
Rightmost digit in a number.


LEC
(Local Exchange Carrier)  Organization that
provides local telephone services.


LED
(Light Emitting Diode)  Display technology that
uses a semiconductor diode that emits light when
charged.  It usually gives off a red glow, although
other colors can be generated.  It is used in
readouts and on/off lights in myriads of electronic
appliances.  It was the first digital watch
display, but was superseded by LCD, which uses less
power.


LED printer
~Electrophotographic printer that uses a matrix of
LEDs as its light source rather than a laser.


left justify
Same as flush left.


Lempel Ziv
Data compression algorithm that uses an adaptive
compression technique.


LEN
(Low Entry Networking)  In SNA, peer-to-peer
connectivity between adjacent Type 2.1 nodes, such
as PCs, workstations and minicomputers.  LU 6.2
sessions are supported across LEN connections.


Lessons
Following are lists of definitions based on
subject.  Use them as a springboard to other terms.
Either print the list and check off your progress
on paper or set a bookmark here and return to the
bookmark.


Lessons Associations
(Set a bookmark to return here.)

  ACM    (Information processing)
  BCS    (Personal computers)
  CBEMA  (Equipment vendors)
  CPA    (Computer press)
  DPMA   (DP management)

  ICCP   (Industry certificatesion)
  ITAA   (Information technology)
  MMA    (Microcomputer managers)
  MUG    (Mac users)
  NASI   (Systems integrators)

  NCF    (Channel for donating old equipment)
  NCGA   (Computer graphics)
  SPA    (Software publishers)
  WUGNET (Windows users)

 STANDARDS BODIES
  ANSI   (U.S. standards)
  NIST   (U.S. standards)
  CCIA   (Computer/communications industry)
  CCITT  (International standards)
  IEC    (International standards)

  ISO    (International standards)
  EIA    (Interface standards; RS-232)
  IEEE   (Electronics standards)
  JEDEC  (IC standards)
  JEIDA  (Japanese electronics)

  PCMCIA (PC memory card standards)
  XAPIA  (X.400 standards)


Lessons Basics
(Set a bookmark to return here.)

  hardware
  software
  data
  computer
  computer system

  analog
  digital
  bit
  binary
  byte

  peripheral
  magnetic recording
  floppy disk
  hard disk
  printer

  monitor
  modem
  operating sytem
  bus
  space/time

  chip
  PC
  Macintosh
  personal computer
  office automation
  standards & compatibility


Lessons Communications
(Set a bookmark to return here.)

  communications
  LAN
  OSI & OSI model
  data link protocol
  baseband

  Ethernet
  ARCNET
  token ring network
  NetWare
  Lantastic

  Appletalk
  SNA
  TCP/IP
  X Window

 LAN CONNECTIVITY
   repeater
   bridge
   router
   brouter
   gateway
   hub

 MODEMS
   BBS
   online services
   modem
   emoticon
   RS-232

   V.22bis    2200 bps standard
   V.32       9600 bps standard
   V.32bis   14400 bps standard
   V.42      error checking
   V.42bis   compression
   MNP       error checking/compression


Lessons Desktop pub.
(Set a bookmark to return here.)

  desktop publishing
  font
  typeface
  scalable font
  outline font
  vector font

  halftone
  bitmap
  kerning
  leading
  color separation

  colors
  point
  prepress
  imagesetter
  phototypesetter

  page description language
  PDL
  PCL
  PostScript


Lessons Graphics
(Set a bookmark to return here.)

  graphics
  paint program
  drawing program
  CAD
  CAD/CAM

  wireframe modeling
  solid modeling
  surface modeling
  ray tracing
  Renderman

  JPEG
  AutoCAD
  FastCAD
  Bezier
  spline

  GKS
  PHIGS
  bitblt
  PCX
  GIF

  TIFF
  PIC
  HSV


Lessons History
(Set a bookmark to return here.)

  Pascaline
  Hollerith machine
  ABC
  ENIAC
  UNIVAC I

  punched card
  1401
  650
  IBM mainframes
  IBM minicomputers

  personal computer
  PDP
  VAX
  Altair 8800
  TRS

  PET
  System/360
  Trilogy


Lessons Multimedia
(Set a bookmark to return here.)

  multimedia
  MPC
  CD
  CD ROM
  CD-I

  DVI
  CDTV
  THOR
  audio board
  hypertext

  Private Eye
  virtual reality


Lessons Personal Computers
(Set a bookmark to return here.)

 CATEGORIES
   personal computer
   PC
   Macintosh
   Amiga
   MEGA

   laptop
   palmtop

 HARDWARE
   computer
   memory
   floppy disk
   hard disk
   magnetic disk

   keyboard
   modem
   optical disk
   laser printer
   serial port

   parallel port
   game port
   mouse
   tape backup
   PC conflicts

 BUSES
   bus
   ISA
   EISA
   Micro Channel
   NuBus

   local bus
   VL-bus

 ENVIRONMENTS
   operating system
   DOS
   DOS abc's
   Windows
   DESQview

   DESQview/X
   OS/2
   UNIX

 SOFTWARE
   word processing
   DBMS
   spreadsheet
   business graphics
   communications program

   integrated software package
   paint program
   drawing program


Lessons Programming
(Set a bookmark to return here.)

  programming
  assembly language
  high-level language
  machine language
  microcode

  reentrant code
  function
  object-oriented programming
  COBOL
  BASIC

  FORTRAN
  Pascal
  C
  C++
  LISP

  Prolog
  LOGO
  MUMPS
  REXX

 PC PROGRAMMING
   ASCII chart
   hex chart
   binary values
   PC display modes
   PC memory map

   PC color codes
   paragraph
   Turbo C
   Microsoft C
   Borland C++


Lessons Slang
(Set a bookmark to return here.)

  flame
  frob
  droupie
  trashware
  shelfware

  kludge
  RTFM
  hookemware
  phone hawk
  Big Blue

  foo
  TLA
  write only code


Lessons System design
(Set a bookmark to return here.)

 OVERVIEW
   information system
   system development cycle
   Systemantics

 PEOPLE
   systems analyst
   application programmer
   programmer analyst
   systems programmer
   operator

 DEVELOPMENT
   data administration
   prototyping
   functional specification
   documentation
   CASE
   standards & compatibility

 SOFTWARE
   query language
   report writer
   spreadsheet
   DBMS
   financial planning system

   DSS
   EIS
   EPSS
   expert system
   case-based reasoning


Lessons UNIX
(Set a bookmark to return here.)

  UNIX
  TCP/IP
  NFS
  NIS
  SMTP

  SNMP
  Motif
  Open Look
  USL
  OSF

  X Window
  X terminal
  BSD UNIX
  STREAMS
  emacs

  vi
  awk
  sed
  grep

 UNIX/PC INTEGRATION
   DESQview/X
   SCO Open Desktop
   Solaris 2.0
   Lan Workplace
   UnixWare
   NetWare NFS


Lessons Vendors
(Set a bookmark to return here.)

  FORTUNE 500
  vendors
  software vendors
  IBM
  Apple

  Atari
  Commodore
  HP
  Digital Equipment
  Data General

  Bull HN
  Intel
  Motorola
  TI
  Tandy

  Tandem
  Microsoft
  Borland
  Digital Research
  Computer Associates
  D&B Software


letter quality
Print quality of an electric typewriter.  Laser
printers, ink jet printers and daisy wheel printers
provide letter quality printing.  24-pin dot matrix
printers provide near letter quality (NLQ), but the
characters are not as dark and crisp.


lexicographic sort
Arranging items in alphabetic order like a
dictionary.  Numbers are located by their
alphabetic spelling.


LF
See line feed.


LHARC
Popular freeware compression program developed by
Haruyasu Yoshizaki that uses a variant of the LZW
(LZ77) dictionary method followed by a Huffman
coding stage.  It runs on PCs, UNIX and other
platforms as its source code is also free.


librarian
Person who works in the data library.


library
(1) Collection of programs or data files.

(2) Collection of functions (subroutines) that are
linked into the main program when it is compiled.

(3) See data library.


library routine
Subroutine that is part of a macro or function
library.


LIFO
(Last In First Out)  Queueing method in which the
next item to be retrieved is the item most recently
placed in the queue.  Contrast with FIFO.


ligature
Two or more typeface characters that are designed
as a single unit (physically touch).  Fi, ffi, ae
and oe are common ligatures.


light bar
Same as highlight bar.


light guide
Transmission channel that contains a number of
optical fibers packaged together.


light pen
Light-sensitive stylus wired to a video terminal
used to draw pictures or select menu options.  The
user brings the pen to the desired point on screen
and presses the pen button to make contact.

   Screen pixels are constantly being refreshed.
When the user presses the button, allowing the pen
to sense light, the pixel being illuminated at that
instant identifies the screen location.


light source
In computer graphics, used to simulate the visual
effect of a light on a 3-D object.  Some programs
can compute multiple light sources.


lightwave
Light in the infrared, visible and ultraviolet
ranges, which falls between x-rays and microwaves.
Wavelengths are between 10 nanometers and one
millimeter.


lightwave system
Device that transmits light pulses over optical
fibers at extremely high speeds (Gbits/sec range).
Many intercity telephone trunks have been converted
to lightwave systems.


LIM EMS
See EMS.


limited distance modem
Same as short-haul modem.


limulator
See EMS emulator.


Linda
Set of parallel processing functions added to
languages, such as C and C++, that allows data to
be created and transferred between processes.  It
was developed by Yale professor David Gelernter,
when he was a 23-year old graduate student.


line
(1) In text-based systems, a row of characters.

(2) In graphics-based systems, a row of pixels.

(3) Any communications channel.


line adapter
In communications, a device similar to a modem,
that converts a digital signal into a form suitable
for transmission over a communications line and
vice versa.  It provides parallel/serial and
serial/parallel conversion, modulation and
demodulation.


line analyzer
Device that monitors the transmission of a
communications line.


line concentration
See concentrator.


line conditioning
See conditioning.


line dot matrix printer
Line printer that uses the dot matrix method.  See
printer.


line drawing
Graphic image outlined by solid lines.  The mass of
the drawing is imagined by the viewer.  See wire
frame.


line driver
In communications, a device that is used to extend
the transmission distance between terminals and
computers that are connected via private lines.  It
is used for digital transmission and is required at
each end of the line.


line editor
Simple editing program that allows text to be
created and changed one line at a time.


line feed
(1) Character code that advances the screen cursor
or printer to the next line.  The line feed is used
as an end of line code in UNIX.  In DOS and OS/2
text files, the return/line feed pair (ASCII 13 10)
is the standard end of line code.

(2) Printer button that advances paper one line.


line frequency
Number of times each second that a wave or some
repeatable set of signals is transmitted over a
line.  See horizontal scan frequency.


line level
In communications, the signal strength within a
transmission channel, measured in decibels or
nepers.


line load
(1) In communications, the percentage of time a
communications channel is used.

(2) In electronics, the amount of current that is
carried in a circuit.


line number
(1) Specific line of programming language source
code.

(2) On display screens, a specific row of text or
row of dots.

(3) In communications, a specific communications
channel.


line of code
Statement in a source program.  In assembly
language, it usually generates one machine
instruction, but in a high-level language, it may
generate a series of instructions.

   Lines of code are used to measure the complexity
of a program.  However, comparisons are misleading
if the programs are not in the same language or
category.  For example, 20 lines of code in COBOL
might require 200 lines of code in assembly
language.


line of sight
Unobstructed view from transmitter to receiver.


line printer
Printer that prints one line at a time.  Line
printers are usually connected to mainframes and
minicomputers.  See printer.


line segment
In vector graphics, same as vector.


line speed
See data rate.


line squeeze
In a mail merge, the elimination of blank lines
when printing names and addresses that contain no
data in certain fields, such as title, company and
second address line.  See field squeeze.

   Without line squeeze     With line squeeze

   Pat Smith                 Pat Smith
                             10 South Main
   10 South Main             Bearcat, OR 80901
   Bearcat, OR 80901


linear
Sequential or having a graph that is a straight
line.


linear address space
See flat address space.


linear programming
Mathematical technique used to obtain an optimum
solution in resource allocation problems, such as
production planning.


linear video
Continuous playback of videotape or videodisc.
Contrast with interactive video.


link
(1) In communications, a line, channel or circuit
over which data is transmitted.

(2) In data management, a pointer embedded within a
record that refers to data or the location of data
in another record.

(3) In programming, a call to another program or
subroutine.


link edit
To use a linkage editor to prepare a program for
running.


linkage editor
Utility program that links a compiled or assembled
program to a particular environment.  It formally
unites references between program modules and
libraries of subroutines.  Its output is a load
module, a program ready to run in the computer.


linked list
In data management, a group of items, each of which
points to the next item.  It allows for the
organization of a sequential set of data in
noncontiguous storage locations.


linker
See linkage editor.


Linpack
Package of FORTRAN programs for numerical linear
algebra that is commonly used to create benchmark
programs for testing a computer's floating point
performance.


Linux
Freeware version of a clone of the UNIX System V
Release 3.0 kernel that runs on x86 machines.  It
is available on programming BBSs and on the
Internet.


LIPS
(Logical Inferences Per Second)  Unit of
measurement of the thinking speed of an AI
application.  Humans do about 2 LIPS.  In the
computer, one LIPS equals from 100 to 1,000
instructions.


liquid crystal shutters
Method of directing light onto the drum in an
electrophotographic printer.  A matrix of liquid
crystal dots function as shutters that are opened
and closed.  See LCD.


Lisa
First personal computer to include integrated
software and use a graphical interface.  Modeled
after the Xerox Star and introduced in 1983 by
Apple, it was ahead of its time, but never caught
on due to its $10,000 price and slow speed.


LISP
(LISt Processing)  High-level programming language
used in non-numeric programming.  Developed in 1960
by John McCarthy, its syntax and structure is very
different than traditional programming languages.
For example, there is no syntactic difference
between data and instructions.

   LISP, available in both interpreter and compiler
versions, is used extensively in AI applications as
well as in compiler creation.  The language can be
modified and expanded by the programmer.  Many
varieties of LISP have been developed, including
versions that perform calculations efficiently.
The following Common LISP example converts
Fahrenheit to Celsius:

   (defun convert ()
     (format t "Enter Fahrenheit ")
     (let ((fahr (read)))
      (format t "Celsius is <126>D"
        (truncate (*(-fahr 32)
            (/ 5 9))))))


list
(1) Arranged set of data, often in row and column
format.

(2) In fourth-generation languages, a command that
displays/prints selected records.  For example, in
dBASE, list name address displays all names and
addresses in the current file.


list processing
Processing non-numeric data.


list processing language
Programming language, such as LISP, Prolog and
Logo, used to process lists of data (names, words,
objects).  Although operations such as selecting
the next to first, or next to last element, or
reversing all elements in a list, can be programmed
in any language, list processing languages provide
commands to do them.  Recursion is also provided,
allowing a subroutine to call itself over again in
order to repetitively analyze a group of elements.


listing
Any printed output.


literal
In programming, any part of an instruction that
remains unchanged when translated into machine
language, such as an output message.


little endian
See big endian.


liveware
People.


LLC
(Logical Link Control)  See "LANs" under data link
protocol.


LLCC
See leadless chip carrier.


lo-res
See low resolution.


load
(1) To copy a program from some source, such as a
disk or tape, into memory for execution.

(2) To fill up a disk with data or programs.

(3) To insert a disk or tape into a drive.

(4) In programming, to store data in a register.

(5) In performance measurement, the current use of
a system as a percentage of total capacity.

(6) In electronics, the flow of current through a
circuit.


load high
To load programs into high memory.  See DOS
Loadhigh.


load module
Program in machine language form ready to run in
the computer.  It is the output of a link editor.


load sharing
Sharing the workload in two or more computers.


loaded line
Telephone line from customer to central office that
uses loading coils to reduce distortion.


loader
Program routine that copies a program into memory
for execution.


loader routine
Same as loader.


loading coil
Device used in local telephone loops (exceeding
18,000 ft.) that boosts voice-grade transmission.
It often adds noise to high-speed data transmission
and must be removed for such traffic.


local area network
See LAN.


local bus
In a 386 and higher PC, a pathway from the CPU to
peripheral devices that runs at higher clock rates
than the ISA, EISA and Micro Channel expansion
buses.  Although CPU speeds have increased
dramatically over the years, the expansion buses
have remained slow to accommodate all the existing
expansion boards, designed for the slower speed.

   The local bus provides a channel that transfers
data to and from the CPU at the clock speed of the
CPU.  For example, in a 386/33, the 16 bit ISA bus,
which runs at 8MHz, can transfer 16 megabytes per
second (16 bits, or two bytes, times eight
million).  A local bus, which uses the full 32 bits
of the 386 and runs at the 33MHz clock rate can
theoretically transfer 132MB/sec (four bytes times
33 million).  In practice, transfers are slower
than maximum in both types.

   First implementations of the local bus used
proprietary designs and have since faded; however,
VESA has standardized the VL-bus, and Intel will
introduce its PCI local bus in 1993.  See VL-bus,
PCI and "ISA vs Local Bus" under ISA.


local bypass
Interconnection between two facilities without the
use of the local telephone company.


local loop
Communications line between a customer and the
telephone company's central office.  See loop
carrier.


local memory
Memory used by a single CPU or allocated to a
single program or function.


local storage
Disk storage used by a single CPU.


local variable
In programming, a variable used only within the
routine or function it is defined in.


LocalTalk
LAN access method from Apple that uses twisted pair
wires and transmits at 230,400 bps.  It runs under
AppleTalk and uses a daisy chain topology that can
connect up to 32 devices within a distance of 1,000
feet.  Third party products allow it to hook up
with bus, passive star and active star topologies.

   Apple's LocalTalk PC Card lets a PC gain access
to an AppleTalk network.


lockup
Refers to a computer's inability to respond to user
input.  See abend.


log
Record of computer activity used for statistical
purposes as well as backup and recovery.


logic
Sequence of operations performed by hardware or
software.  Hardware logic is made up of circuits
that perform an operations.  Software logic
(program logic) is the sequence of instructions in
a program.

   Note: Logic is not the same as logical.  See
logical vs physical and logical expression.


logic analyzer
(1) Device that monitors computer performance by
timing various segments of the running programs.
The total running time and the time spent in
selected progam modules is displayed in order to
isolate the the least efficient code.

(2) Device used to test and diagnose an electronic
system, which includes an oscilloscope for
displaying various digital states.


logic array
Same as gate array or PLA.


logic bomb
Program routine that destroys data; for example, it
may reformat the hard disk or insert random bits
into data files.  It may be brought into a personal
computer by downloading a corrupt public-domain
program.  Once executed, it does its damage right
away, whereas a virus keeps on destroying.


logic chip
Processor or controller chip.  Contrast with memory
chip.


logic circuit
Circuit that performs some processing or
controlling function.  Contrast with memory.


logic controller
See PLC.


logic diagram
Flow chart of hardware circuits.


logic error
Program bug due to an incorrect sequence of
instructions.


logic gate
Collection of transistors and electronic components
that make up a Boolean logical operation, such as
AND, NAND, OR and NOR.  Transistors make up logic
gates.  Logic gates make up circuits.  Circuits
make up electronic systems.


logic operation
Operation that analyzes one or more inputs and
generates a particular output based on a set of
rules.  See AND, OR and NOT and Boolean logic.


logic-seeking printer
Printer that analyzes line content and skips over
blank spaces at high speeds.


logical
(1) Reasonable solution to a problem.

(2) Higher level view of an object; for example,
the user's view versus the computer's view.  See
logical vs physical.


logical data group
Data derived from several sources.  Same as view.


logical drive
Allocated part of a physical drive that is
designated and managed as an independent unit.


logical expression
Expression that results in true or false.  Same as
Boolean expression.


logical field
Data field that contains a yes/no, true/false
condition.


logical lock
Prevention of user access to data that is provided
by marking the file or record through the use of
software.  Contrast with physical lock.


logical operator
One of the Boolean logical operators (AND, OR and
NOT).


logical record
Reference to a data record that is independent of
its physical location.  It may be physically stored
in two or more locations.


logical vs physical
High-level versus low-level.  Logical implies a
higher view than the physical.  Users relate to
data logically by data element name; however, the
actual fields of data are physically located in
sectors on a disk.  For example, if you want to
know which customers ordered how many of a
particular product, your logical view is customer
name and quantity.  Its physical organization might
have customer name in a customer file and quantity
in an order file cross referenced by customer
number.  The physical sequence of the customer file
could be indexed, while the sequence of the order
file could be sequential.

   A message transmitted from Phoenix to Boston
logically goes between two cities; however, the
physical circuit could be Phoenix to Chicago to
Philadelphia to Boston.

   When you command your program to change the
output from the video screen to the printer, that's
a logical request.  The program will perform the
physical change of address from, say, device number
02 to device number 04.


login
Same as logon.


Logo
High-level programming language noted for its ease
of use and graphics capabilities.  It is a
recursive language that contains many list
processing functions that are in LISP, although
Logo's syntax is more understandable for novices.

   Logo's graphics language is called turtle
graphics, which allows complex graphics images to
be created with a minimum of coding.  The turtle is
a triangular-shaped cursor, which is moved on
screen with commands that activate the turtle as if
you were driving it, for example, go forward 100
units, turn right 45 degrees, turn left 20 degrees.

   Stemming from a National Science Foundation
project, Logo was created by Seymour Papert in the
mid 1960s along with colleagues at MIT and members
of Bolt Beranek & Newman.  Originally developed on
large computers, it has been adapted to most
personal computers.

   The following Object Logo example converts
Fahrenheit to Celsius:

   convert
   local [fahr]
   print "|Enter Fahrenheit |
   make "fahr ReadWord
   print "|Celsius is |
   print (:fahr - 32) * 5 / 9
   end



logoff
To quit, or sign off, a computer system.


logon
To gain access, or sign in, to a computer system.
If restricted, it requires users to identify
themselves by entering an ID number and/or
password.  Service bureaus base their charges for
the time between logon and logoff.


logout
Same as logoff.


long
In programming, an integer variable.  In C, a long
is four bytes and can be signed (-2G to +2G) or
unsigned (4G).  Contrast with short.


long card
In PCs, a full-length controller board that plugs
into an expansion slot.  Contrast with short card.


long-haul
In communications, modems or communications devices
that are capable of transmitting over long
distances.


long lines
In communications, circuits that are capable of
handling transmissions over long distances.


longitudinal redundancy check
See LRC.


LONWORKS
Control network from Echelon Corp., Palo Alto, CA,
that uses Echelon's NEURON CHIP (made by Motorola
and Toshiba) and LONTALK protocol.  Each NEURON
CHIP uses a 48-bit number for identification.
Control modules that contain the NEURON CHIP and
transceivers for transmitting via RS-485, twisted
pair, coax and AC power lines are available on
credit card-sized boards.

   The LONBUILDER development system is used to
create applications, which are written into PROM
chips.  LONWORKS software, as well as programming
interfaces for DOS and Windows, provide node
installation and network management.


lookup
Data search performed within a predefined table of
values (array, matrix, etc.) or within a data file.


loop
In programming, a repetition within a program.
Whenever a process must be repeated, a loop is set
up to handle it.  A program has a main loop and a
series of minor loops, which are nested within the
main loop.  Learning how to set up loops is what
programming technique is all about.

   The following example prints an invoice.  The
main loop reads the order record and prints the
invoice until there are no more orders to read.
After printing date and name and addresses, the
program prints a variable number of line items.
The code that prints the line items is contained in
a loop and repeated as many times as required.

   main┌──────────────┐
   loop│           Get next order
       │               │
       │           Print date
                  Print bill to
       │           Print ship to
       │   line┌──────┤
       │   item│
       │   loop│   Print line item
              │       │
       │       └──────┤
       │               │
       │           Print totals
       └───────────────┘

   Loops are accomplished by various programming
structures that have a beginning, body and end.
The beginning generally tests the condition that
keeps the loop going.  The body comprises the
repeating statements, and the end is a GOTO that
points back to the beginning.  In assembly
language, the programmer writes the GOTO, as in the
following example that counts to 10.

          MOVE     "0" TO COUNTER
   LOOP   ADD      "1" TO COUNTER
          COMPARE  COUNTER TO "10"
          GOTO     LOOP IF UNEQUAL
          STOP

   In high-level languages, the GOTO is generated
by the interpreter or compiler; for example, the
same routine as above using a WHILE loop.

       COUNTER = 0
       DO WHILE COUNTER <> 10
          COUNTER = COUNTER + 1
       ENDDO
       STOP



loop carrier
In telephone communications, a system that
concentrates a number of analog or digital lines
from a remote termination station into the central
office.  It normally converts analog voice into
digital at the remote station; however, it can be
adapted to provide ISDN service to a customer.


loopback plug
Diagnostic connector that directs the sending line
back into the receiving line for test purposes.


loosely coupled
Refers to stand-alone computers connected via a
network.  Loosely coupled computers process on
their own and exchange data on demand.  Contrast
with tightly coupled.


lossless compression
Compression techniques that decompress data 100%
back to original.  Contrast with lossy compression.


lossy compression
Compression techniques that do not decompress data
100% back to original.  Images and audio samples
may be able to afford small losses of resolution in
order to increase compression.  Contrast with
lossless compression.


lost cluster
Disk records that have lost their identification
with a file name.  This can happen if a file is not
closed properly, which can sometimes occur if the
computer is turned off without formally quitting an
application.  See DOS Chkdsk.


Lotus
(Lotus Development Corp., Cambridge, MA)  Software
company founded in 1981 by Mitch Kapor.  It
achieved outstanding success by introducing the
first spreadsheet for the IBM PC (see Lotus 1-2-3).
Over the years, it has developed a variety of
applications and has helped set industry standards.
In 1990, it acquired Samna Corp., makers of the
popular, Windows-based Ami word processors.


Lotus 1-2-3
Spreadsheet for DOS, Windows, Macintosh, Sun, VAX,
OS/2 and IBM mainframe platforms from Lotus.
Introduced in 1982, it was the first, new and
innovative spreadsheet for the PC.  It included
graphics, file management and limited word
processing along with spreadsheet capabilities.
Its ability to instantly convert numeric data into
a graph was a dazzling feature for its time.  The
program's user interface was also easy to use (see
Lotus menu).  Over 20 million copies of Lotus are
in use today.

   In 1989, Lotus upgraded Version 2.01 for DOS
into two versions: 2.2 and 3.0.  Version 2.2 and
succeeding 2.x versions run in a 640K PC.  They
include macro recording, an undo and a dynamic link
from one spreadsheet to another.  Version 3.0 and
succeeding 3.x versions take advantage of extended
and expanded memory and can build very large
spreadsheets.  They include 3-D and dynamic linking
capabilities as well as more sophisticated
graphing.


Lotus Add-in Toolkit
Pascal-like programming language from Lotus that
allows automated processes to be created and
executed in Lotus 1-2-3 Version 3.x.


Lotus menu
Menu introduced with Lotus 1-2-3 that became a de
facto standard.  It is a row of words, each of
which is an option that can be selected by
highlighting it and pressing Enter or by pressing
the first letter of the word.  When the word is
highlighted, an explanation line is displayed above
or below it.  Contrast with pull-down menu.


Lotus Notes
Distributed document database system from Lotus
that runs in a client/server environment under
Windows, OS/2 and various UNIX platforms.  Designed
for workgroups that need to exchange information,
all types of files can be attached to a Notes
document.  It includes e-mail and outbound fax and
keeps distributed documents in sync in an
enterprise-wide environment.  As of Release 3, it
allows a Windows PC to act as a server and will run
with any VIM-compliant e-mail system such as
cc:Mail.


low density
Refers to an earlier version of a storage device
with less bits per inch than today's version.  See
DD and double density.


low entry networking
See LEN.


low frequency
Electromagnetic wave that vibrates in the range
from 30 to 300,000 Hertz.


low-level format
Sector identification on a disk that the drive uses
to locate sectors for reading and writing.  See
format program.


low-level language
Programming language that is very close to machine
language.  All assembly languages are low-level
languages.  Contrast with high-level language.


low radiation
Refers to video terminals that emit less VLF (Very
Low Frequency) and ELF (Extremely Low Frequency)
radiation.  This level of radiation cannot be
shielded by office partitions.  It must be
cancelled out from the CRT.  Health studies on this
are not conclusive and are very controversial.  See
MPR II.


low resolution
Low-grade display or printing quality due to a
lower number of dots or lines per inch.


lower CASE
See back-end CASE.


lpi
(Lines Per Inch)  The number of lines printed in a
vertical inch.


lpm
(Lines Per Minute)  Number of lines a printer can
print or a scanner can scan in a minute.


LPT1
Logical name assigned to parallel port #1 in DOS
and OS/2 (usually connected to a printer).  A
second parallel device is assigned LPT2.  Contrast
with COM1.


LQ
See letter quality.


LRC
(Longitudinal Redundancy Check)  Error checking
method that generates a parity bit from a specified
string of bits on a longitudinal track.  In a row
and column format, such as on magnetic tape, LRC is
often used with VRC, which creates a parity bit for
each character.


LSAPI
(Licensing Service API)  Programming interface from
Microsoft that allows a licensing server to track
applications in use for managing multiuser software
licenses.


LSI
(Large Scale Integration)  Between 3,000 and
100,000 transistors on a chip.  See SSI, MSI, VLSI
and ULSI.


LSI-11
Family of board-level computers from Digital that
uses the micro version of the PDP-11.  Introduced
in 1974, it was the first to use the Q-bus.


LT
(Less Than)  See relational operator.


LU
(Logical Unit)  In SNA, one end of a communications
session.  The complete LU to LU session is defined
by session type.  Common types are:

     1  Host to 3770 RJE terminal
     2  Host to 3270 mainframe terminal
     3  Host to 3270 printer
   6.2  Program-to-program
     7  Host to 5250 midrange terminal


LU 6.2
SNA protocol that establishes a session between two
programs.  It allows peer-to-peer communications as
well as interaction between programs running in the
host with PCs and other midrange computers.

   Before LU 6.2, processing was done only in the
mainframe.  LU 6.2 allows processing to take place
at both ends of the communications, necessary for
today's distributed computing and client/server
environment.  See APPC and CPI-C.


lumen
Unit of measurement of the flow (rate of emission)
of light.  A wax candle generates 13 lumens; a 100
watt bulb generates 1,200.  See candela.


Lumena
PC paint program from Time Arts, Inc., Santa Rosa,
CA, that provides sophisticated, special effects.
It accepts and generates NTSC video output and
requires a video graphics board.


luminance
In computer graphics, the amount of brightness,
measured in lumens, that is given off by a pixel or
area on a screen.


LZW
(Lempel-Ziv-Welch)  Widely-used dictionary
compression method that stems from two techniques
introduced by Jacob Ziv and Abraham Lempel.  LZ77
scans a fixed length block of data and creates
pointers back to data when it repeats.  LZ78 scans
the data and creates a dictionary of repeating
phrases.  Pointers are created to those phrases.



M
See mega.


M-byte
See megabyte.


M Technology Assn.
See MUMPS.


Mac
(1) See Macintosh.

(2) (MAC) (Media Access Control)  Sublayer that
controls the access method in an IEEE 802 LAN.  See
"LANs" under data link protocol.


Mac to midrange
Using the Macintosh as the terminal to IBM S/3x and
AS/400 computers.  Apple and third party
connectivity products add local processing and a
friendly interface to IBM midrange computers.


MacAPPC
LU 6.2-compliant software from Apple Computer that
allows a Macintosh to be a peer to an IBM APPC
application.


MacDFT
Software that provides 3270 emulation for the
Macintosh from Apple.  It accompanies Apple's
TwinAx/Coax board and supports CUT and DFT modes
and DFT multiple sessions under SNA.


MacDraw Pro
Macintosh drawing program from Claris Corp. that is
an enhanced version of the original MacDraw from
Apple and includes full on-screen slide
presentation capability.  It is used for
illustrations and elementary CAD work.  MacDraw
files are a subset of the Claris CAD file format.


Mach
UNIX-like operating system developed at Carnegie-
Mellon Univ.


machine
Any electronic or electromechanical unit of
equipment.  A machine is always hardware; however,
"engine" refers to hardware or software.


machine address
Same as absolute address.


machine code
Same as machine language.


machine cycle
Shortest interval in which an elementary operation
can take place within the processor.  It is made up
of some number of clock cycles.


machine dependent
Refers to software that accesses specific hardware
features and runs in only one kind of computer.
Contrast with machine independent.  See device
dependent.


machine independent
Refers to software that runs in a variety of
computers.  The hardware-specific instructions are
in some other program (operating system, DBMS,
etc.).  Contrast with machine dependent.  See
device independent.


machine instruction
Instruction in machine language.  Its anatomy is a
verb followed by one or more nouns:

     OP CODE    OPERANDS (one or more)
     (verb)     (nouns)

   The op code is the operation to be performed
(add, copy, etc.), while the operands are the data
to be acted upon (add a to b).  There are always
machine instructions to INPUT and OUTPUT, to
process data by CALCULATING, COMPARING and COPYING
it, and to go to some other part of the program
with a GOTO instruction.  See computer.


machine language
Native language of the computer.  In order for a
program to run, it must be in the machine language
of the computer that is executing it.  Although
programmers are sometimes able to modify machine
language in order to fix a running program, they do
not create it.  It is created by programs called
assemblers, compilers and interpreters, which
convert programming language into machine language.

   Machine language tells the computer what to do
and where to do it.  When a programmer writes:
total = total + subtotal, that statement is
converted into a machine instruction that tells the
computer to add the contents of two areas of memory
(where TOTAL and SUBTOTAL are stored).

   A programmer deals with data logically, "add
this, subtract that," but the computer must be told
precisely where this and that are located.

   Machine languages differ substantially.  What
may take one instruction in one machine can take 10
instructions in another.  See assembly language.


machine readable
Data in a form that can be read by the computer,
which includes disks, tapes and punched cards.
Printed fonts that can be scanned and recognized by
the computer are also machine readable.


Macintosh
Series of 32-bit personal computers from Apple
introduced in 1984.  It uses the Motorola 68000 CPU
family and an operating system that simulates a
user's desktop on screen.  The Mac's graphics-based
user interface has provided a measure of
consistency and ease of use that is unmatched.  The
Macintosh family is the largest non-IBM compatible
personal computer series in use.

   Introduced in 1984 as a floppy-based computer
with 128K of memory, its "high-rise" cabinet and
built-in 9" monochrome screen were unique.  This
design is retained in the Classic models, while the
rest of the line is now clothed in traditional
cabinetry.


            MACINTOSH SPECIFICATIONS

                             3.5"
             Clock Bus      Floppy Hard    Screen
       68xxx Speed Size RAM  Disk  Disk      Res.
Model     CPU  Mhz Bits(--Bytes--)(Mbytes)
──────────────┬───┬───┬─────┬─────┬───────┬────────
128*       000│  8│ 16│128K │400K │  20   │ 512x342
512*       000│  8│ 16│512K │400K ├───────┤ 9" Mono
Plus*      000│  8│ 16│1-4M │800K │       │Black on
              │   │   │     ├─────┤       │ White
SE*        000│  8│ 16│1-4M │3.5" │ 20-160│
SE30*      030│ 16│ 32│1-8M │Super│       │
Classic*   000│  8│ 16│1-4M │Drive│       │
Classic II 030│ 16│ 16│2-10M│     │ 40-80 │
Color Classic │   │   │     │     │       ├────────
 256 cols  030│ 16│ 16│4-10M│     │ 40-160│10" diag
II*        020│ 16│ 32│1-8M │     │       ├────────
IIx*       030│ 16│ 32│1-8M │     │       │640x480
IIcx*      030│ 16│ 32│1-8M │     │       │14" B/W
IIci       030│ 25│ 32│5-32M│     │ 80-230│or 256
IIfx*      030│ 40│ 32│4-32M│     │ 80+   │ cols.
IIsi       030│ 20│ 32│3-17M│     │ 40-80 │
IIvi       030│ 16│ 32│4-20M│     │ 40-400│640x870
IIvx       030│ 32│ 32│4-20M│     │ 40-400│15" B/W
LC*        020│ 16│ 16│1-10M│     │ 40-80 │
LC II      030│ 16│ 16│2-10M│     │ 40-80 │1152x870
LC III     030│ 25│ 32│4-36M│     │ 40-160│1152x870
Quadra 700*040│ 25│ 32│4-20M│     │ 80-400│21" B/W
Quadra 800 040│ 33│ 32│8-136│     │230-1G │
Quadra 900*040│ 25│ 32│4-64M│     │160-400│
Quadra 950 040│ 33│ 32│8-256│     │230-1G │**
Centris610 040│ 20│ 32│4-68M│     │80-500 │
Centris650 040│ 25│ 32│4-132│     │80-500 ├────────
Portable*  000│ 16│ 32│1-9M │     │  40   │am

Performa (consumer product line)
200        030│ 16│ 16│4-10M│     │ 80-160│640x480
400        030│ 16│ 16│4-10M│     │ 80-160│14"
600        030│ 32│ 16│4-68M│     │ 80-160│256 cols

PowerBook Portables
100*       000│ 16│ 16│2-8M │     │  20   │pm
140*       030│ 16│ 16│2-8M │     │ 20-40 │pm
145        030│ 25│ 16│4-8M │     │ 40-80 │pm
160        030│ 25│ 16│4-14M│     │40-120 │pm
165c color 030│ 33│ 16│4-14M│     │80-160 │pm
170*       030│ 25│ 16│4-8M │     │  40   │am
180        030│ 33│ 16│4-14M│     │80-120 │am
210 Duo    030│ 25│ 16│4-24M│     │80     │pm
230 Duo    030│ 33│ 16│4-24M│     │80-120 │pm
──────────────┴───┴───┴─────┴─────┴───────┴────────
 * No longer made as of 2/93
** Built-in 24-bit color
pm passive matrix LCD
am active matrix LCD



Macintosh user interface
Method of operating a Macintosh, originally
developed by Xerox and introduced on the Xerox Star
in 1981.  It uses a graphics-based screen that
places familiar objects on a two-dimensional
desktop.  Programs, files, folders and disks are
represented by small pictures (icons).  An object
is selected by moving a mouse over the real
desktop, which correspondingly moves a pointer on
the screen desktop.  When the pointer touches an
icon, the object is selected by clicking the mouse
button.

   A hierarchical file system is provided that lets
a user "drag" a document icon into and out of a
folder icon.  Folders can also contain other
folders.  To delete a document, its icon is
literally dragged into a trash can icon.

   The Macintosh always displays a row of menu
titles at the top of the screen.  The full menu
appears as if it were pulled down from the top of
the screen when selected.  With the mouse button
held down, the option within the menu is selected
by pointing to it and releasing the button.

   Unlike the PC world, which, before Windows, left
the design of the user interface up to the software
developer, Macintosh developers always conform to
the Mac interface.  As a result, users feel more
comfortable with new programs from the start.

   In operation, the operating system and
applications are almost indistinguishable, and
Apple keeps technical jargon to a minimum.

   Early Mac applications had little regard for
experienced typists, forcing them to use the mouse
instead of well-designed keyboard commands.
Subsequent versions offer both methods and have
greatly improved.

   The Macintosh style has been adapted to many
environments, including Windows, Presentation
Manager, GEM and OSF/Motif.


MacIRMA
Micro to mainframe communications board for the
Macintosh from DCA, Inc., Alpharetta, GA.  It a
3270 terminal.


MacLink Plus
Macintosh file transfer program from DataViz Corp.,
Trumbull, CT, that provides document conversion for
over 45 Mac and PC formats.  Versions are available
for NeXt and Sun workstations and Wang OIS and VS
systems.


MacPaint II
Full-featured Macintosh paint program from Claris
that was originally developed by Apple and bundled
with every Mac up until the Mac Plus.  MacPaint's
PICT file format is used for printing the screen.
By pressing Command-shift-3, the current screen is
stored in a PICT file for printing either in
MacPaint or other program.


macro
(1) Series of menu selections, keystrokes and/or
commands that have been recorded and assigned a
name or key combination.  When the name is called
or the key is pressed, the macro is executed from
beginning to end.

   It is used to shorten long menu sequences into
one keystroke as well as to create miniature
programs within an application.  Macro languages
often include programming controls (IF THEN, GOTO,
WHILE, etc.) that automate sequences like any
programming language.  See macro recorder, batch
file and shell script.

(2) In assembly language, a prewritten subroutine
that is called for throughout the program.  At
assembly time, the macro calls are substituted with
the actual subroutine or instructions that branch
to it.  The high-level language equivalent is a
function.

(3) In dBASE programming, a variable which
references another variable that actually contains
the data.  At runtime, the macro variable is
substituted with the data variable.


macro assembler
Assembler program that lets the programmer create
and use macros.


macro call
Same as macro instruction.


macro generator
See macro recorder.


macro instruction
Instruction that defines a macro.  In assembly
language, MACRO and ENDM are examples that define
the beginning and end of a macro.  In C, the
#DEFINE statement is used.


macro language
(1) Commands used by a macro processor.  Same as
script.

(2) Assembly language that uses macros.


macro processor
(1) Software that creates and executes macros from
the keyboard.

(2) The part of an assembler that substitutes the
macro subroutines for the macro calls.


macro recorder
Program routine that converts menu selections and
keystrokes into a macro.  A user turns on the
recorder, calls up a menu, selects a variety of
options, turns the recorder off and assigns a key
command to the macro.  When the key command is
pressed, the selections are executed.


MacTerminal
Macintosh terminal emulation software from Apple
that allows a Mac to function as an IBM 3278 Model
2 (when used with an AppleLine Protocol Converter)
or Digital VT 52 or VT 100 terminal.


MacTwin
Mac to IBM midrange connectivity from Andrew/KMW,
which includes a card for the Mac that connects to
the twinax cabling from the S/3x or AS/400.
Software for the Mac provides 5250, 3196 and 3197
emulation.


MacWrite II
Full-featured Macintosh word processing program
from Claris Corp., that was originally packaged
with every Mac 128 and 512.


mag
Abbreviation for "magnetic."


Magellan
Disk management utility for PCs from Lotus that
searches for file names and contents.  It
popularized the file viewer, which lets you look
into various data files as if you were using the
applications that created them.


Magic Cap
(Magic Communicating Applications Platform)
Object-oriented control program from General Magic
for personal intelligent communicating devices
(PDAs, hand-held units, etc.) that includes the
Telescript language.


magnetic card
(1) See magnetic stripe.

(2) Magnetic tape strips used in early data storage
devices and word processors.  See CRAM, RACE and
Data Cell.


magnetic coercivity
Amount of energy required to alter the state of a
magnet.  The higher a magnetic disk's coercivity
index, the more data it can store.


magnetic disk
Primary computer storage device.  Like tape, it is
magnetically recorded and can be re-recorded over
and over.  Disks are rotating platters with a
mechanical arm that moves a read/write head between
the outer and inner edges of the platter's surface.
It can take as long as one second to find a
location on a floppy disk to as short as one
millisecond on an ultra-fast hard disk.  See floppy
disk and hard disk.


                Tracks and Sectors
The disk surface is divided into concentric tracks
(circles within circles).  The thinner the tracks,
the more storage.  The data bits are recorded as
tiny spots on the tracks.  The tinier the spot, the
more bits per inch and the greater the storage.
Most disks hold the same number of bits on each
track, even though the outer tracks are physically
longer than the inner ones.  Some disks pack the
bits as tightly as possible within each track.

   Tracks are further divided into sectors, which
hold the least amount of data that can be read or
written at one time; for example, READ TRACK 7
SECTOR 24.  In order to update the disk, one or
more sectors are read into the computer, changed
and written back to disk.  The operating system
figures out how to fit data into these fixed
spaces.  See hard disk and floppy disk.


magnetic disk & tape
Primary computer storage media.  The choice depends
on accessing requirements.  Disk is direct access;
tape is sequential access.  Locating a program or
data on disk can take a fraction of a second.  On
tape, it can take seconds or minutes.

   On minis and mainframes, disks are used for
daily transaction processing, and tapes are used
for backup and history.  Tapes have traditionally
been more economical for archival storage and
easier to transport than disk packs.

   For personal computers, hard disks are used for
all interactive processing, and both floppy disks
and tapes are used for backup.  Bernoulli disks and
removable hard disks are increasingly becoming
backup alternatives.

   In time, magnetic disks will be as obsolete as
punched cards.  Optical disks are getting faster
and cheaper, and optical technologies that employ
no moving parts will undoubtedly supersede them
all.  Compared to the magical technology within the
chip, whirling chunks of metal around is rather old
fashioned, don't you think?


magnetic drum
Early high-speed, direct access storage device that
used a magnetic-coated cylinder with tracks around
its circumference.  Each track had its own
read/write head.


magnetic field
Invisible energy emitted by a magnet.  Same as
flux.


magnetic ink
Magnetically detectable ink used to print the MICR
characters that encode account numbers on bank
checks.


magnetic oxide
See ferric oxide.


magnetic recording
With regard to computers, the technique used to
record, or write, digital data in the form of tiny
spots (bits) of negative or positive polarity on
tapes and disks.  A read/write head discharges
electrical impulses onto the moving ferromagnetic
surface.  Reading is accomplished by sensing the
polarity of the bit with the read/write head.


magnetic stripe
Small length of magnetic tape adhered to ledger
cards, badges and credit cards.  It is read by
specialized readers that may be incorporated into
accounting machines and terminals.  Due to heavy
wear, the data on the stripe is in a low-density
format that may be duplicated several times.


magnetic tape
Sequential storage medium used for data collection,
backup and historical purposes.  Like videotape,
computer tape is made of flexible plastic with one
side coated with a ferromagnetic material.  Tapes
come in reels, cartridges and cassettes of many
sizes and shapes.

   As with any tape, locating a specific item
requires reading everything in front of it.  There
is no way to fast forward.  In order to add and
delete records, the current tape is input to the
computer and a blank tape is used for output.  If
data on tape is only changed and the physical
number of records is not altered, some tape drives
can update in place by reading a block of data and
writing back over the same area.

   Except for tape cartridges that use the
serpentine or helical scan methods (see QIC and
DAT), data bits are recorded on parallel tracks
that run the length of the tape.  For example, 9-
track tape holds one byte of data across the tape's
width (8 bits plus parity).  Data is recorded in
blocks of contiguous bytes, separated by a space
called an interrecord or interblock gap.

   There are a variety of formats used in data
cartridges and data cassettes; however, open-reel
1/2" tape is a common standard among minis and
mainframes.  See tape backup.

   Tape is more economical than disks for
historical data.  When tapes are used for archival
storage, they must be periodically recopied or the
tightly coiled magnetic surfaces may contaminate
each other.

   Storage capacity is measured in bits per inch
(bpi).  With tape formatted in parallel tracks, bpi
is equivalent to bytes per inch.  Common 1/2"
recording densities are 1650 and 6250 bpi; early
densities were 200, 556 and 800 bpi.  Tape drive
speed is measured in inches per second (ips), thus,
transfer rate = ips X bpi.


magneto-optic
High-density, erasable recording method.  Data is
recorded magnetically like disks and tapes, but the
bits are much smaller, because a laser is used to
pinpoint the bit.  The laser heats the bit to 150°
Celsius, at which temperature the bit is realigned
when subjected to a magnetic field.  In order to
record new data, existing bits must first be set to
zero.  See Curie point, Kerr effect and optical
disk.


magnetographic
Non-impact printer technology from Groupe Bull that
prints up to 90 ppm.  A magnetic image is created
by a set of recording heads across a magnetic drum.
Monocomponent toner is applied to the drum to
develop the image, which is transferred to paper by
light pressure and an electrostatic field.  The
toner is then fused by heat.  The print quality is
not as good as a laser printer, but the machines
require less maintenance.


mail box
Computer storage assigned to a user for
electronically transmitted mail.


mail merge
Printing customized form letters.  A common feature
of a word processor, it uses a letter and a name
and address list.  In the letter, Dear A: Thank you
for ordering B from our C store..., A, B and C are
merge points into which data is inserted from the
list.  See field squeeze and line squeeze.


main line
See main loop.


main loop
Primary logic in a program.  It contains the
instructions that are repeated after each event or
transaction has been processed.  See loop.


main memory
Same as memory.


main storage
Same as memory.


mainframe
Large computer.  In the "ancient" mid 1960s, all
computers were called mainframes, since the term
referred to the main CPU cabinet.  Today, it refers
to a large computer system.

   There are small, medium and large-scale
mainframes, handling from a handful to several
thousand online terminals.  Large-scale mainframes
can have hundreds of megabytes of main memory and
terabytes of disk storage.  Large mainframes use
smaller computers as front end processors that
connect to the communications networks.

   The original mainframe vendors were Burroughs,
Control Data, GE, Honeywell, IBM, NCR, RCA and
Univac, otherwise known as "IBM and the Seven
Dwarfs."  After GE and RCA's computer divisions
were absorbed by Honeywell and Univac respectively,
the mainframers were known as "IBM and the BUNCH."


maintenance
(1) Hardware maintenance is the testing and
cleaning of equipment.

(2) Information system maintenance is the routine
updating of master files, such as adding and
deleting employees and customers and changing
credit limits and product prices.

(3) Software or program maintenance is the updating
of application programs in order to meet changing
information requirements.

(4) Disk or file maintenance is the periodic
reorganizing of online disk files that have
undergone fragmentation due to continuous updating.


maintenance credits
Monetary credits issued to a customer by the vendor
for qualified periods during which the vendor's
products are not functioning properly.


maintenance service
Service provided to keep a product in good
operating condition.


major key
Primary key used to identify a record, such as
account number or name.


make
To compile a multi-module program.  The make
utility recompiles only those modules that have
been updated since the last compilation.


male connector
Plug that is designed to fit into a particular
socket.


Maltron keyboard
Keyboard that uses independent left- and right-hand
modules shaped to conform to the natural position
of the hands, designed to prevent strain (RSI).


MAN
(Metropolitan Area Network)  Communications network
that covers a geographic area such as a city or
suburb.  See LAN and WAN.


management science
Study of statistical methods, such as linear
programming and simulation, in order to analyze and
solve organizational problems.  Same as operations
research.


management support
See DSS and EIS.


management system
Leadership and control within an organization.  It
is made up of people interacting with other people
and machines that, together, set the goals and
objectives, outline the strategies and tactics, and
develop the plans, schedules and necessary controls
to run an organization.


Manchester Code
Self-clocking data encoding method that divides the
time required to define the bit into two cycles.
The first cycle is the data value (0 or 1) and the
second cylce provides the timing by shifting to the
opposite state.


MANTIS
Application development language from Cincom
Systems, Inc., Cincinnati, OH, that runs on IBM
mainframes, VAXs and other mainframes.  It provides
procedural and non-procedural languages for
developing prototypes and applications and works
with Cincom's SUPRA database, DB2 and IMS.


mantissa
Numeric value in a floating point number.  See
floating point.


MAP
(Manufacturing Automation Protocol)  Communications
protocol introduced by General Motors in 1982.
MAP's goal is to provide common standards for the
interconnection of computers and programmable
machine tools used in factory automation.  At the
lowest physical level, it uses the IEEE 802.3 token
bus protocol.  Although MAP has provided vitally
needed consolidation of standards, it continues to
be in a constant state of revision.

   MAP is often used in conjunction with TOP, an
office protocol developed by Boeing Computer
Services.  TOP is used in the front office and MAP
is used on the factory floor.


map
(1) Set of data that has a corresponding
relationship to another set of data.

(2) List of data or objects as they are currently
stored in memory or disk.

(3) To transfer a set of objects from one place to
another.  For example, program modules on disk are
mapped into memory.  A graphic image in memory is
mapped onto the video screen.  An address is mapped
to another address.

(4) To relate one set of objects with another.  For
example, a logical database structure is mapped to
the physical database.  A vendor's protocol stack
is mapped to the OSI model.


MAPI
(Mail API)  Microsoft e-mail and messaging protcol.
See OMI and VIM.


MAPPER
(MAintaining, Preparing and Processing Executive
Reports)  Unisys mainframe fourth-generation
language.  In 1980, it was introduced as a high-
level report writer and was later turned into a
full-featured development system used successfully
by non-technical users.


mapping
See map and digital mapping.


marginal test
System test that introduces values far above and
far below the expected values.


mark
(1) Small blip printed on or notched into various
storage media used for timing or counting purposes.

(2) To identify a block of text in order to perform
some task on it such as deletion, copying and
moving.

(3) To identify an item for future reference.

(4) In digital electronics, a 1 bit.  Contrast with
space.

(5) On magnetic disk, a recorded character used to
identify the beginning of a track.

(6) In optical recognition and mark sensing, a
pencil line in a preprinted box.

(7) On magnetic tape, a tape mark is a special
character that is recorded after the last character
of data.


Mark I
Electromechanical calculator designed by professor
Howard Aiken, built by IBM and installed at Harvard
in 1944.  It strung 78 adding machines together to
perform three calculations per second.  It was 51
feet long, weighed five tons and used punched cards
and typewriters for I/O.  Made of 765,000 parts, it
sounded like a thousand knitting needles according
to Admiral Grace Hopper.  The experience helped IBM
develop its own computers a few years later.


MARK IV
See Crosstalk and MARK IX.


MARK IX
Application generator from Sterling Software's
Answer Systems Div., Woodland Hills, CA, that runs
on IBM mainframes and personal computers.  It stems
from MARK IV, the first report writer to use fill-
in-the-blanks forms.  MARK V was a subsequent
online version.


mark sensing
Detecting pencil lines in predefined boxes on paper
forms.  The form is designed with boundaries for
each pencil stroke that represents a yes, no,
single digit or letter, providing all possible
answers to each question.  A mark sense reader
detects the marks and converts them into digital
code.


mask
(1) Pattern used to transfer a design onto an
object.  See photomask.

(2) Pattern of bits used to accept or reject bit
patterns in another set of data.  For example, the
Boolean AND operation can be used to match a mask
of 0s and 1s with a string of data bits.  When a 1
occurs in both the mask and the data, the resulting
bit will contain a 1 in that position.

   Hardware interrupts are often enabled and
disabled in this manner with each interrupt
assigned a bit position in a mask register.


mask bit
1 bit in a mask used to control the corresponding
bit found in data.


maskable interrupts
Hardware interrupts that can be enabled and
disabled by software.


masked
State of being disabled or cut off.


MASM
(Macro ASeMbler)  Assembly language that allows
macros to be defined and used.


mass storage
High-capacity, external storage such as disk or
tape.


massage
To process data.


massively parallel
Parallel processing architecture that uses hundreds
or thousands of processors.


master
Primary, controlling.  See master-slave
communications and master file.


master card
Master record in punched card format.


master clock
Clock that provides the primary source of internal
timing for a processor or stand-alone control unit.


master console
Main terminal used by the computer operator or
systems programmer to command the computer.


master control program
See operating system.


master file
Collection of records pertaining to one of the main
subjects of an information system, such as
customers, employees, products and vendors.  Master
files contain descriptive data, such as name and
address, as well as summary information, such as
amount due and year-to-date sales.  Contrast with
transaction file.


master record
Set of data for an individual subject, such as a
customer, employee or vendor.  See master file.


master-slave communications
Communications in which one side, called the
master, initiates and controls the session.  The
other side (slave) responds to the master's
commands.


math coprocessor
Mathematical circuit that performs high-speed
floating point operations.  It increases the
performance of CAD applications, but the CAD
program must activate its use.  See array processor
and vector processor.


mathematical expression
Group of characters or symbols representing a
quantity or an operation.  See arithmetic
expression.


mathematical function
Rule for creating a set of new values from an
existing set; for example, the function f(x) = 2x
creates a set of even numbers (if x is a whole
number).


matrix
Array of elements in row and column form.  See x-y
matrix.


matrix printer
See dot matrix and printer.


MAU
(Multi-station Access Unit)  Central hub in a token
ring local area network.


maximize
In a graphical environment, to enlarge a window to
full size.  Contrast with minimize.


MB, Mb
See megabyte and megabit.


Mbit
See megabit.


Mbits/sec
(MegaBITS per SECond)  Million bits per second.


MBps, Mbps
(MegaBytes Per Second, MegaBits Per Second)
Million bytes per second.  Million bits per second.


Mbyte
See megabyte.


Mbytes/sec
(MegaBYTES per SECond)  Million bytes per second.


MC68000
See 68000.


MCA
See Micro Channel.


MCB
(Memory Control Block)  Identifier (16-bytes) that
DOS places in front of each block of memory it
allocates.


MCGA
(Multi Color Graphics Array)  IBM video display
standard built into low-end PS/2 models.  It is not
well supported by software vendors.  See PC display
modes.


MCI
(Media Control Interface)  High-level programming
interface from IBM/Microsoft for controlling
multimedia devices.  It includes text commands such
as open, play and close for languages such as
Visual BASIC, as well as functions for languages
such as C.  See RIFF and AVI.


MCI decision
FCC decree in 1969 that granted MCI the right to
compete with the Bell System by providing private,
intercity telecommunications services.


MCU
(1) (MicroController Unit)  Control unit on a
single chip.

(2) (Multipoint Control Unit)  Device that connects
multiple sites for audio and video conferencing.


MDA
(Monochrome Display Adapter)  First IBM PC
monochrome video display standard for text only.
Due to its lack of graphics, MDA cards were often
replaced with Hercules cards, which provided both
text and graphics.  See PC display modes.


MDI
(Multiple Document Interface)  In Windows, multiple
windows that are minimized or maximized as a group.
Contrast with SDI.


mechanical mouse
Mouse that uses a rubber ball that rolls against
wheels inside the unit.  Contrast with optical
mouse.


media
Material that stores or transmits data, for
example, floppy disks, magnetic tape, coaxial cable
and twisted wire pair.


media access method
See "LANs" under data link protocol.


media conversion
Converting data from one storage medium to another,
such as from disk to tape or from one type of disk
pack to another.


media failure
Condition of not being able to read from or write
to a storage device, such as a disk or tape, due to
a defect in the recording surface.


medium frequency
Electromagnetic wave that oscillates in the range
from 300,000 to 3,000,000 Hz.  See electromagnetic
spectrum.


meg
Same as mega.


mega
(1) Million.  Abreviated "M."  It often refers to
the precise value 1,048,576 since computer
specifications are usually binary numbers.  See
binary values and space/time.

(2) (MEGA)  Personal computer series from Atari
that is Motorola 68000 based, runs under GEM and
the TOS operating system and includes a MIDI
interface.  It is ST compatible.


Mega VGA
1024x768, 256 color Super VGA mode that requires
one megabyte of video RAM.


megabit
One million bits.  Also Mb, Mbit and M-bit.  See
mega and space/time.


megabyte
One million bytes.  Also MB, Mbyte and M-byte.  See
mega and space/time.


megaflops
(mega FLoating point OPerations per Second)  One
million floating point operations per second.


megahertz
One million cycles per second.  See MHz.


megapel display
In computer graphics, a display system that handles
a million or more pixels.  A resolution of 1,000
lines by 1,000 dots requires a million pixels for
the full screen image.


membrane keyboard
Dust and dirtproof keyboard constructed of two thin
plastic sheets (membranes) that contain flexible
printed circuits made of electrically conductive
ink.  The top membrane is the printed keyboard and
a spacer sheet with holes is in the middle.  When a
user presses a simulated key, the top membrane is
pushed through the spacer hole and makes contact
with the bottom membrane, completing the circuit.


memo field
Data field that holds a variable amount of text.
The text may be stored in a companion file, but it
is treated as if it were part of the data record.
For example, in the dBASE command list name,
biography, name is in the data file (DBF file) and
biography could be a memo field in the text file
(DBT file).


memory
The computer's workspace (physically, a collection
of RAM chips).  It is an important resource, since
it determines the size and number of programs that
can be run at the same time, as well as the amount
of data that can be processed instantly.

   All program execution and data processing takes
place in memory.  The program's instructions are
copied into memory from a disk or tape and are then
extracted from memory into an electronic circuit
for analysis and execution.  The instructions
direct the computer to input data into memory from
a keyboard, disk, tape or communications channel.

   As data is entered into memory, the previous
contents of that space is lost.  Once the data is
in memory, it can be processed (calculated,
compared and copied).  The results are sent to a
screen, printer, disk, tape or communications
channel.

   Memory is like an electronic checkerboard, with
each square holding one byte of data or
instruction.  Each square has a separate address
like a post office box and can be manipulated
independently.  As a result, the computer can break
apart programs into instructions for execution and
data records into fields for processing.


          Memory Doesn't Usually Remember
Oddly enough, the computer's memory doesn't
remember anything when the power is turned off.
That's why you have to save your files before you
quit your program.  Although there are memory chips
that do hold their content permanently (ROMs,
PROMs, EPROMs, etc.), they're used for internal
control purposes and not for the user's data.

     "Remembering" memory in a computer system is
its disks and tapes, and although they are also
called memory devices, many prefer to call them
storage devices (as we do) in order to
differentiate them from internal memory.  Perhaps
in time, memory will refer to disks exclusively and
RAM will refer to working memory.  Until then, its
usage for both RAM and disk only adds confusion to
the most confusing industry on earth.

   Other terms for memory are RAM, main memory,
main storage, primary storage, read/write memory,
core and core storage.


memory allocation
Reserving memory for specific purposes.  Operating
systems generally reserve all the memory they need
at startup.  Application programs use memory when
loaded and may allocate more after being loaded.
If there is not enough free memory, they cannot
run.

   On a personal computer, memory can be allocated
for a disk cache, which retains large chunks of
data from the disk in faster RAM.  However, a large
disk cache that speeds up one application may slow
down another because there is less normal memory
available.

   Memory can be allocated for a RAM disk, which
simulates a disk drive in memory.  Disk files are
copied to the RAM disk and all accesses take place
in faster memory.  RAM disks may dramatically speed
up one program and have little effect on others.
Like the disk cache, it takes away from the total
available memory.

   On DOS PCs, allocating a mix of extended memory
and EMS memory is often requried.  Windows 3.x and
DOS-extended applications use extended memory,
while other applications may use EMS memory.  On
286s, allocation requires changing parameters in
the CONFIG.SYS file and rebooting.  Older 286s may
require changing switches on the EMS boards.  On
386s and up, using advanced memory managers such as
QEMM386 and 386MAX, allocation can be done on
demand automatically.  See DOS memory manager.


memory bank
(1) Physical section of memory.  See memory
interleaving.

(2) Refers generically to a computer system that
holds data.


memory based
Programs that hold all data in memory for
processing.  Almost all spreadsheets are memory
based so that a change in data at one end of the
spreadsheet can be instantly reflected at the other
end.


memory cache
See cache.


memory card
(1) Credit-card-sized memory module used as a disk
alternative in portable computers.  Called IC
cards, ROM cards and RAM cards, they use a variety
of chip types, including RAM, ROM, EEPROM and flash
memory.  RAM cards use a battery to keep the cells
charged.  See PC card and PCMCIA.

(2) Printed circuit board that contains memory.


memory cell
One bit of memory.  In dynamic RAM memory, a cell
is made up of one transistor and one capacitor.  In
static RAM memory, a cell is made up of about five
transistors.


memory chip
Chip that holds programs and data either
temporarily (RAM), permanently (ROM, PROM) or
permanently until changed (EPROM, EEPROM).


memory cycle
Series of operations that take place to read or
write a byte of memory.  For destructive memories,
it includes the regeneration of the bits.


memory cycle time
Time it takes to perform one memory cycle.


memory dump
Display or printout of the contents of memory.
When a program abends, a memory dump can be taken
in order to examine the status of the program at
the time of the crash.  The programmer looks into
the buffers to see which data items were being
worked on when it failed.  Counters, variables,
switches and flags are also inspected.


memory effect
See NiCad and nickel hydride.


memory interleaving
Category of techniques for increasing memory speed.
For example, with separate memory banks for odd and
even addresses, the next byte of memory can be
accessed while the current byte is being refreshed.


memory management
Method used to control memory, which includes
memory protection, virtual memory and bank
switching techniques.  See virtual memory, EMS, EMM
and DOS memory manager.


memory map
Location of instructions and data in memory.


memory mapped I/O
Peripheral device that assigns specific memory
locations to input and output.  For example, in a
memory mapped display, each pixel or text character
derives its data from a specific memory byte or
bytes.  The instant this memory is updated by
software, the screen is displaying the new data.


memory protection
Technique that prohibits one program from
accidentally clobbering another active program.
Using various different techniques, a protective
boundary is created around the program, and
instructions within the program are prohibited from
referencing data outside of that boundary.


memory resident
Program that remains in memory at all times.  See
TSR.


memory sniffing
Coined by Data General, a diagnostic routine that
tests memory during normal processing.  The
processor uses cycle stealing techniques that allow
it to test memory during unused machine cycles.  A
memory bank can be "sniffed" every few minutes.


memory typewriter
Typewriter that holds a few pages of text in its
memory and provides limited word processing
functions.  With a display screen of only one or
two lines, editing is tedious.


menu
(1) List of available options on screen.  Selection
is accomplished by highlighting the option with a
mouse or cursor keys and clicking the mouse or
pressing Enter.  See Lotus menu and pull-down menu.

(2) (Menu)  Software subsidiary of Black Box Corp.,
Pittsburgh, PA, that offers the world's most
complete listing of software information for LANs
and personal computers.


menu bar
Row of on-screen menu options.


menu-driven
Using menus to command the computer.  Contrast with
command-driven.


menuing software
Software that provides a menu for launching
applications and running operating system commands.


merge
See mail merge and concatenate.


merge purge
To merge two or more lists together and eliminate
unwanted items.  For example, a new name and
address list can be added to an old list while
deleting duplicate names or names that meet certain
criteria.


mesa
Semiconductor process used in the 1960s for
creating the sublayers in a transistor.  Its deep
etching gave way to the planar process.


mesh network
Net-like communications network in which there are
at least two pathways to each node.  Since the term
network means net-like as well as communications
network, the term mesh is used to avoid saying
network communications network.


message
(1) In communications, a set of data that is
transmitted over a communications line.  Just as a
program becomes a job when it's running in the
computer, data becomes a message when it's
transmitted over a network.

(2) In object-oriented programming, communicating
between objects, similar to a function call in
traditional programming.


message handling
(1) In communications, a system of electronic mail
that handles text (memos, letters) in document
form.

(2) In communications, the lower level protocols
that transfer data over a network, which assemble
and disassemble the data into the appropriate codes
for transmission.


message queue
Storage space in memory or on disk that holds
incoming transmissions until the computer can
process them.


message switch
Computer used to switch data from one point to
another.  Computers have always been ideal message
switches due to their input/output and compare
capabilities.  It inputs the message, compares its
destination with a set of stored destinations and
routes it accordingly.


metafile
File that can define and store more than one type
of information.  For example, a Windows Metafile
(WMF) can hold pictures in vector graphics and
raster graphics formats as well as text.


metalanguage
Language used to describe another language.


meter
Basic unit of the metric system (39.37 inches).  A
yard is about 9/10ths of a meter (0.9144 meter).


method
In object-oriented programming, an algorithm that
governs an object's behavior and performance.  When
a message is sent to an object, a method is
implemented and data may or may not be returned.


methodology
Specific way of performing an operation that
implies precise deliverables at the end of each
stage.


Mflops
See megaflops.


MFM
(Modified Frequency Modulation)  Magnetic disk
encoding method used on most floppy disks and most
hard disks under 40MB.  It has twice the capacity
of the earlier FM method, transfers data at 625
Kbytes per second and uses the ST506 interface.
See hard disk.


MGA
(Monochrome Graphics Adapter)  Display adapter that
employs Hercules Graphics, combining graphics and
text on a monochrome monitor.


MGP
(Monochrome Graphics Printer port)  Display adapter
that employs Hercules Graphics and a parallel
printer port on the same expansion board.


MHS
(1) (Message Handling Service)  E-mail software
from Action Technologies, Inc., Alameda, CA,
licensed by Novell for its NetWare operating
systems.  It provides message routing and store and
forward capabilities.  It also provides gateways
into PROFS, All-in-1 and X.400 message systems.

(2) (Message Handling System)  Often refers to
e-mail systems that conform to the OSI model, which
is based on the X.400 protocol.


MHz
(MegaHertZ)  One million cycles per second.  Often
references a computer's clock rate, the raw measure
of internal speed.  For example, a 12MHz 286
computer processes data internally (calculates,
compares, etc.) twice as fast as a 6MHz 286.
However, disk speed and caching play a major role
in the computer's actual performance.


MIB
See SNMP.


mickey
Unit of mouse movement typically set at 1/200th of
an inch.


MICR
(Magnetic Ink Character Recognition)  Machine
recognition of magnetically-charged characters
typically found on bank checks and deposit slips.
MICR readers detect the characters and convert them
into digital data.


micro
(1) Microcomputer or personal computer.

(2) One millionth.  See space/time.

(3) Microscopic or tiny.


Micro Channel
Also known as MCA (Micro Channel Architecture), it
is an IBM 32-bit bus used in most PS/2s, the
RS/6000 series and certain ES/9370 models.  MCA
boards can be designed for bus mastering and also
contain built-in identification that eliminates
manual settings often required with ISA boards.

   MCA transfers data at 20MBytes/sec and has modes
for increasing speeds to 40 and 80MB.  Future
enhancements may take it to 64 bits and 160MB.  MCA
boards are not interchangeable with ISA and EISA
boards.


micro manager
Person who manages personal computer operations
within an organization and is responsible for the
analysis, selection, installation, training and
maintenance of personal computer hardware and
software.  See information center and MMA.


Micro PDP-11
Microcomputer version of the PDP-11 from Digital
introduced in 1975.  Uses the Q-bus and serves as a
stand-alone computer or is built into other
equipment.


micro to mainframe
Interconnection of personal computers to
mainframes.  See 3270 emulator.


microchip
Same as chip.


microcircuit
Miniaturized, electronic circuit, such as is found
on an integrated circuit.  See chip.


microcode
Permanent memory that holds the elementary circuit
operations a computer must perform for each
instruction in its instruction set.  It acts as a
translation layer between the instruction and the
electronic level of the computer and enables the
computer architect to more easily add new types of
machine instructions without having to design
electronic circuits.  See microprogramming.


Microcom Protocol
See MNP.


microcomputer
Same as personal computer.


microcontroller
See MCU.


microelectronics
Miniaturization of electronic circuits.  See chip.


microfiche
Pronounced "micro-feesh."  A 4x6" sheet of film
that holds several hundred miniaturized document
pages.  See micrographics.


microfilm
Continuous film strip that holds several thousand
miniaturized document pages.  See micrographics.


microfloppy disk
Floppy disk encased in a 3.5" wide, rigid plastic
shell.  Developed by Sony, it has become the medium
of choice as it holds more data and is easier to
handle than its 5.25" counterpart.


microform
In micrographics, a medium that contains
microminiaturized images such as microfiche and
microfilm.


micrographics
Production, handling and use of microfilm and
microfiche.  Images are created by cameras or by
COM units that accept computer output directly.
The documents are magnified for human viewing by
readers, some of which can automatically locate a
page using indexing techniques.

   Microfiche and microfilm have always been an
economical alternative for high-volume data and
picture storage.  However, optical disks are
competing with film-based systems and may become
the preferred storage medium.


microimage
In micrographics, any photographic image of
information that is too small to be read without
magnification.


microinstruction
Microcode instruction.  It is the most elementary
computer operation that can take place; for
example, moving a bit from one register to another.
It takes several microinstructions to carry out one
machine instruction.


microjacket
In micrographics, two sheets of transparent plastic
that are bonded together to create channels into
which strips of microfilm are inserted and stored.


micromainframe
Personal computer with mainframe or near mainframe
speed.


micromechanics
Microminiaturization of mechanical devices (gears,
motors, rotors, etc.) using similar photomasking
techniques as in chip making.


micromini
Personal computer with minicomputer or near
minicomputer speed.


micron
One millionth of a meter.  Approx. 1/25,000 of an
inch.  The tiny elements that make up a transistor
on a chip are measured in microns.  Measurements
below the micron level are made in Angstroms, in
which 10,000 Angstroms equals one micron.


microprocessor
CPU on a single chip.  In order to function as a
computer, it requires a power supply, clock and
memory.  First-generation microprocessors were
Intel's 8080, Zilog's Z80, Motorola's 6800 and
Rockwell's 6502.  The first microprocessor was
created by Intel.


microprogram
Same as microcode.


microprogramming
Programming microcode.


micropublishing
In micrographics, the issuing of new or reformatted
information on microfilm for sale or distribution.


microrepublishing
In micrographics, the issuing of microfilm that has
been previously or is simultaneously published in
hardcopy for sale or distribution.


microsecond
One millionth of a second.  See space/time.


Microsoft
(Microsoft Corp., Redmond, WA)  Leading software
company founded in 1975 by Paul Allen and Bill
Gates, two college students who wrote the first
BASIC interpreter for the Intel 8080 microprocessor
(Allen now runs Asymetrix Corp.).

   MBASIC was licensed to Micro Instrumentation and
Telemetry Systems to accompany its Altair 8800 kit.
By the end of 1976, more than 10,000 Altairs were
sold with MBASIC.  Versions were licensed to Radio
Shack, Apple and many other vendors.  Later, a
version called GW-BASIC (Gee Whiz BASIC) was
developed for 16-bit personal computers.

   Although Microsoft became a leader in
microcomputer programming languages, its
outstanding success is due to supplying IBM with
DOS and the compatible companies with MS-DOS.
Extending into graphical interfaces with Windows is
also proving highly successful, ever since Version
3.0 was introduced in 1990.

   Microsoft does very well in the applications
market with products such as Excel, Microsoft Word
and Word for Windows.  However, Microsoft's
position as the supplier of the major operating
system to the world's largest computer base gives
it considerable influence over this industry.


Microsoft C
C compiler from Microsoft used to create a wide
variety of commercial products.  Windows
programming also requires the Microsoft Windows
Software Development Kit.  Microsoft C and
Borland's Turbo C are the most widely used C
languages for PC application development.


Microsoft Word
Full-featured word processing program for PCs and
the Macintosh from Microsoft.  The DOS version
provides both graphics-based and text-based
interfaces for working with a document.  Microsoft
Word for Windows (WinWord) is a separate and
distinct Windows product with sophisticated
capabilities.


Microsoft Works
Integrated software package for PCs and the
Macintosh from Microsoft.  It provides file
management with relational-like capabilities, word
processing, spreadsheet, business graphics and
communications capabilities in one package.


microspacing
Positioning characters for printing by making very
small horizontal and vertical movements.  Many dot
matrix printers and all laser printers have this
ability.


MicroStation
Full-featured 2-D and 3-D CADD program from
Intergraph Corp., Huntsville, AL, for PCs, Macs and
Intergraph, Sun and HP workstations.


MicroVAX
Series of entry-level VAXs introduced in 1983 that
run under VMS or ULTRIX.  Some models use the Q-bus
architecture.


microwave
Electromagnetic wave that vibrates at 1GHz and
above.  Microwaves are the transmission frequencies
used in communications satellites as well as in
line-of-sight systems on earth.


middleware
Software that sits between the application and the
control program (operating system, network control
program, DBMS).  Similar in purpose to a pseudo
language, it provides a single programming
interface for an application, which will run in as
many different computer environments as the
middleware runs in.


MIDI
(Musical Instrument Digital Interface)  Standard
protocol for the interchange of musical information
between musical instruments, synthesizers and
computers.  It defines the codes for a musical
event, which includes the start of a note, its
pitch, length, volume and musical attributes, such
as vibrato.  It also defines codes for various
button, dial and pedal adjustments used on
synthesizers.

   MIDI is commonly used to synchronize notes
produced on several synthesizers.  Its control
messages can orchestrate a series of synthesizers,
each playing a part of the musical score.

   A computer with a MIDI interface can be used to
record a musical session, but instead of recording
the analog sound waves as in a tape recorder, the
computer stores the music as keystroke and control
codes.  The recording can be edited in an entirely
different manner than with conventional recording;
for example, the rhythm can be changed by editing
the timing codes in the MIDI messages.  In
addition, the computer can easily transpose a
performance from B major into D major.  MIDI files
also take up much less disk space than sound files
that contain the actual digitized music.

   The objective of MIDI was to allow the keyboard
of one synthesizer to play notes generated by
another.  However, since Version 1.0 in 1983, MIDI
has brought electronic control of music to
virtually everybody, benefiting musicians and
teachers alike.


midicomputer
Computer with performance and capacity between a
minicomputer and a mainframe.


midrange computer
Same as minicomputer, but excludes single-user
minicomputer workstations.


mill
Very old term for processor (number crunching!).


millimeter
One thousandth of a meter, or 1/25th of an inch.


million
One thousand times one thousand.  See mega and
microsecond.


millisecond
One thousandth of a second.  See space/time.


MIMD
(Multiple Instruction stream Multiple Data stream)
Computer architecture that uses multiple
processors, each processing its own set of
instructions simultaneously and independently of
the others.  Contrast with SIMD.


mini
See minicomputer.


mini-supercomputer
Computer that is 25% to 100% as fast as a
supercomputer, but costs less.  Note: A mini-
supercomputer is not the same as a supermini.


minicomputer
Medium-scale computer that functions as a single
workstation, or as a multiuser system with up to
several hundred terminals.  A minicomputer system
costs roughly from $20,000 to $250,000.

   In 1959, Digital launched the minicomputer
industry with its PDP-1.  Soon after, Data General
and HP introduced minis, and eventually Wang,
Tandem, Datapoint and Prime joined them.  IBM has
introduced several minicomputer series (see IBM
minicomputers).

   Today, the term "midrange" is becoming popular
for medium-sized computer.  High-end microcomputers
and low-end mainframes overlap in minicomputer
price and performance.


minifloppy
Floppy disk encased in a 5.25" wide, stiff plastic
jacket.  Introduced by Shugart in 1978, it
superseded IBM's 8" floppy and has been used
extensively ever since.


minimize
In graphical environments, to reduce a window to an
icon.


MINIX
Version of UNIX for the PC, Mac, Amiga and Atari ST
developed by Andrew Tannenbaum and published by
Prentice-Hall.  It comes with complete source code.


minor key
Secondary key used to identify a record.  For
example, if transactions are sorted by account
number and date, account number is the major key
and date is the minor key.


MIPS
(1) (Million Instructions Per Second)  Execution
speed of a computer.  For example, .5 MIPS is
500,000 instructions per second.  High-speed
personal computer and workstation CPUs perform in
the 20-50 MIPS range.  Digital's Alpha chip has a
peak rate of 400 MIPS.  Inexpensive microprocessors
used in toys and games may be in the .05-.1 MIPS
range.

   MIPS rates are not uniform.  Some are best-case
mixes while others are averages.  In addition, it
takes more instructions in one machine to do the
same thing as another (RISC vs CISC, mainframe vs
micro).  As a result, MIPS has been called
"MisInformation to Promote Sales."

   MIPS rate is just one factor in overall
performance.  Bus and channel speed and bandwidth,
memory speed, memory management techniques and
system software also determine total throughput.

(2) (MIPS Computer Systems, Inc., Sunnyvale, CA.)
Micro and minicomputer manufacturer.  See ACE.


Mirror II
PC communications program from Softklone
Distributing Corp., Tallahassee, FL, that supports
a variety of terminals and protocols and provides a
learn mode for recording common sequences.


mirroring
See disk mirroring.


Mirrors
Software from Micrografx, Inc., Richardson, TX,
that allows Windows programs to be converted to
OS/2 with minimal modification.


MIS
(1) (Management Information System)  Information
system that integrates data from all the
departments it serves and provides operations and
management with the information they require.

   It was "the" buzzword of the mid to late 1970s,
when online systems were implemented in all large
organizations.  See DSS.

(2) (Management Information Services)  See
Information Systems.


mission critical
Vital to the operation of an organization.


mixed object
Same as compound document.


ML
Symbolic programming language developed in the
1970s at Univ. of Edinburgh, Scotland.  Similar to
LISP, its commands and structures are like Pascal.


MM
See Multiple Master.


MMA
(Microcomputer Manager's Assn., Inc.)  Membership
organization with chapters throughout the U.S.
devoted to educating personnel responsible for
personal computers.  Provides seminars,
conferences, trade show events, job bank and
newsletters.  Address: P.O.Box 4615, Warren, NJ,
908/580-9091.


MME
See Multimedia Extensions.


MMF
(Multiple Mode Fiber)  Class of optical fiber used
in FDDI that transmits through multiple paths at
200MBits/sec up to 10 miles.  See SMF.


MMI
(Man Machine Interface)  Same as user interface.


MMU
(Memory Management Unit)  Virtual memory circuit
that translates logical addresses into physical
addresses.


mnemonic
Pronounced "nuh-monic."  Means memory aid.  A name
assigned to a machine function.  For example, in
DOS, COM1 is the mnemonic assigned to serial port
#1.  Programming languages are almost entirely
mnemonics.


MNP
(Microcom Networking Protocol)  Family of
communications protocols from Microcom, Inc.,
Norwood, MA, that have become de facto standards
for error correction (classes 2 though 4) and data
compression (class 5).

Class    Features

  1  Half-duplex asynchronous transmission.
     (Early mode, no longer used.)

  2  Full-duplex asynchronous transmission.

  3  Full-duplex synchronous transmission using
     HDLC framing techniques using 64-byte
     blocks.  Start/stop bits stripped.

  4  Increased throughput.  Shorter headers,
     frames up to 256 bytes.  Some vendors
     adjust frame size based on line quality.

  5  Compresses data up to two times.

  6  Starts at V.22bis modulation and switches
     to V.29 if possible.  Uses pseudo-
     duplexing ping-pong method for faster
     turnaround of V.29 transmission.

  7  Compresses data up to three times.

  8  Not in use.

  9  Adds Piggy-back Acknowledgement** and
     selective retransmission for more
     efficient transport of data.  Provides
     better performance over variety of links.

 10  Adds Adverse Channel Enhancements** for
     efficient operation on noisy lines (rural,
     cellular, international, etc.).

** Proprietary Microcom techniques.


MO
See magneto-optic.


MO:DCA
(Mixed Object:Document Content Architecure)  IBM
compound document format for text and graphics
elements in a document.  It supports Revisable
Documents, which are editable like revisable-form
DCA, Presentation Documents, which provide specific
output formatting similar to DCA final-form, and
Resource Documents, which hold control information
such as fonts.

   Formats for specific objects are specified in
OCAs (Object Content Architectures): PTOCA for
Presentation and Text that has been formatted for
output, GOCA for vector Graphics objects, IOCA for
bitmapped Images and FOCA for Fonts.


Mobiltex
Packet radio service from RAM Mobile Data (joint
venture of RAM Broadcasting and BellSouth).  By the
end of 1993, over 800 8Kbps base stations will
serve over 100 areas in the U.S.


mod
See modulo.


modal
Mode oriented.  A modal operation switches from one
mode to another.  Contrast with non-modal.


modal dispersion
Signal distortion in an optical fiber in which the
light pulses spread out, and the receiving device
cannot detect the beginnings and ends of pulses.


mode
Operational state that a system has been switched
to.  It implies at least two possible conditions.
There are countless modes for hardware and
software.  See Real Mode, Protected Mode, burst
mode, insert mode, supervisor state and program
state.


model
(1) Style or type of hardware device.

(2) Mathematical representation of a device or
process used for analysis and planning.  See data
model, data administration, financial planning
system and scientific applications.


model-based expert system
Expert system based on fundamental knowledge of the
design and function of an object.  Such systems are
used to diagnose equipment problems, for example.
Contrast with rule-based expert system.


modeling
Simulating a condition or activity by performing a
set of equations on a set of data.  See data
modeling, data administration, financial planning
system and scientific applications.


modem
(MOdulator-DEModulator)  Device that adapts a
terminal or computer to a telephone line.  It
converts the computer's digital pulses into audio
frequencies and converts them back into pulses at
the receiving side.

   For hookup, an internal modem needs a free
expansion slot, while an external modem requires a
free serial port.  A communications program
provides the user interface and the software
protocols (Xmodem, Kermit, etc.).

   The modem handles the dialing and answering of
the call and controls transmission speed, which
ranges from 300 to 14,400 bps and higher.  The
common dial-up modem speed is 2,400 bps with 9,600
becoming popular.  See the V dot standards (V.32,
V.42).  Private lines allow for faster transmission
speeds.  Very-high-speed modems are used to connect
to broadband LANs, which use frequencies like the
telephone.

  At 2,400 bps, it takes about seven seconds to
fill up a text-based screen of 2,000 characters,
but most interactive sessions display less than a
full screen.  The character rate is 10% of the bit
rate; thus, 2,400 bps is equivalent to 240 cps.

   Features to look for in a modem are high speed
(V.32, V.32bis), error checking (V.42, MNP 2-4) and
data compression (V.42bis, MNP 5).  New modems have
automatic feature negotiation, which adjusts to the
other modem's speed and hardware protocols.

   The term is also used as a verb; for example,
"I'll modem you later."


modem eliminator
Device that allows two close computers to be
connected without modems.  For personal computers,
it is the same as a null modem cable.  In
synchronous systems, it provides active
intelligence for synchronization.


modify structure
Database command that changes a file's structure.
Field lengths and field names can be changed, and
fields can be added or deleted.  It may convert the
old data file into the new structure without data
loss, unless fields have been truncated or deleted.


Modula-2
(MODUlar LAnguage-2)  Enhanced version of Pascal
introduced in 1979 by Swiss professor Nicklaus
Wirth, creator of Pascal.  It supports separate
compilation of modules.  The following example
changes Fahrenheit to Celsius:

      MODULE FahrToCent;
   FROM InOut IMPORT ReadReal,WriteReal,
   WriteString,WriteLn;
   VAR Fahr:REAL;
   BEGIN
   WriteString("Enter Fahrenheit ");
   ReadReal(Fahr);
   WriteLn;
   WriteString("Celsius is ");
   WriteReal((Fahr - 32) * 5 / 9);
      END  FahrToCent


modular programming
Breaking down the design of a program into
individual components (modules) that can be
programmed and tested independently.  It is a
requirement for effective development and
maintenance of large programs and projects.


Modular Windows
Subset of Windows for TV-based consumer
electronics.  It does not use Program Manager,
scroll bars and overlapping windows.  The
application is the window.


modulate
To vary a carrier wave.  Modulation blends a data
signal (text, voice, etc.) into a carrier for
transmission over a network.  Major methods are AM
(amplitude modulation) - modulate the height of the
carrier wave, FM (frequency modulation) - modulate
the frequency of the wave, and PM (phase
modulation) - modulate the polarity of the wave.
Contrast with demodulate.  See carrier.


module
Self-contained hardware or software component that
interacts with a larger system.  Hardware modules
are often made to plug into a main system.  Program
modules are designed to handle a specific task
within a larger program.


modulo
Mathematical operation (modulus arithmetic) in
which the result is the remainder of the division.
For example, 20 MOD 3 results in 2 (20/3 = 6 with a
remainder of 2.


moire
Pronounced "mor-ray."  Objectionable pattern that
sometimes results from scanning halftones or
scaling halftones that have already been scanned.


molecular beam epitaxy
Technique that "grows" atomic-sized layers on a
chip rather than creating layers by diffusion.


monadic
One.  Single item or operation that deals with one
item or operand.


monitor
(1) Display screen used to present output from a
computer, camera, VCR or other video generator.  A
monitor's clarity is based on video bandwidth, dot
pitch, refresh rate and convergence.  See analog
monitor, digital monitor and interlaced.

(2) Software that provides utility and control
functions such as setting communications
parameters.  It typically resides in a ROM chip and
contains startup and diagnostic routines.

(3) Software that monitors the progress of
activities within a computer system.

(4) Device that gathers performance statistics of a
running system via direct attachment to the CPU's
circuit boards.


monochrome
Also called "mono."  Display of one foreground
color and one background color; for example, black
on white, white on black and green on black.

   Non-color laptop PCs commonly use "monochrome
VGA" screens, which are actually gray-scale
screens.  This is like black and white TV and is
not the same as the monochrome screens widely used
over the years on mini and mainframe terminals and
PCs using the MDA adapter, which display a solid
color and no shades in between.


monolithic integrated circuit
Common form of chip design, in which the base
material (substrate) contains the pathways as well
as the active elements that take part in its
operation.


monophonic
Sound reproduction using a single channel.
Contrast with stereophonic.


monospacing
Uniform horizontal spacing, such as 10 characters
per inch.  Contrast with proportional spacing.


Monte Carlo method
Technique that provides approximate solutions to
problems expressed mathematically.  Using random
numbers and trial and error, it repeatedly
calculates the equations to arrive at a solution.


MORE II
Macintosh desktop presentation program and outline
processor from Symantec Corp., Cupertino, CA, that
includes writing, spell checking, presentation-
quality text and graphics and 35mm slide output.


morphing
Transforming one image into another; for example, a
car into a tiger.  From metamorphosis.  See
tweening.


morray
See moire.


Morse code
Data code represented by dots and dashes, developed
by Samuel Morse in the mid-19th century.  A dot can
be a voltage, carrier wave or light beam of one
duration, while a dash is a longer duration.  It
was used to send telegraph messages before the
telephone and was used in World War II for
signalling by light.


MOS
(Metal Oxide Semiconductor)  Pronounced "moss."
One of two major categories of chip design (the
other is bipolar).  It derives its name from its
use of metal, oxide and semiconductor layers.
There are several varieties of MOS technologies,
including PMOS, NMOS and CMOS.


MOSFET
(Metal Oxide Semiconductor Field Effect Transistor)
Common type of transistor fabricated as a discrete
component or into MOS integrated circuits.


most significant digit
Leftmost, non-zero digit in a number.  It is the
digit with the greatest value in the number.


motherboard
Main printed circuit board in an electronic device,
which contains sockets that accept additional
boards.  In a personal computer, the motherboard
contains the bus, CPU and coprocessor sockets,
memory sockets, keyboard controller and supporting
chips.

   Chips that control the video display, serial and
parallel ports, mouse and disk drives may or may
not be present on the motherboard.  If not, they
are independent controllers that are plugged into
an expansion slot on the motherboard.


Motif
Graphical user interface endorsed by the Open
Software Foundation.  It is widely used in the UNIX
world.  See OSF.


motion path
In computer graphics, the path to be followed by an
animated object.


Motorola
(Motorola, Inc., Schaumburg, IL)  Leading
manufacturer of semiconductor devices founded in
Chicago in 1928 by Paul V. Galvin as the Galvin
Manufacturing Corp.  Its first product allowed
radios to operate from household current instead of
batteries.  In the 1930s, the company
commercialized car radios under the Motorola brand
suggesting "sound in motion," and in 1947, changed
the company name.

   By the 1960s, it was a leader in communications
and consumer electronics and had built its first
semiconductor facility.  It eventually moved from
the consumer side, selling its color TV business in
the mid-1970s.

   Although Motorola is known in computers for its
68000 microprocessor family, it is also involved in
radio and data communications systems and
automotive and industrial products, among others.


mouse
Puck-like object used as a pointing and drawing
device.  As it is rolled across the desktop, the
screen cursor (pointer) moves correspondingly.

   It is similar to the tablet cursor on a
digitizer tablet; however, the tablet cursor makes
contact with the tablet with absolute reference.
Placing it on the upper left part of the tablet
moves the screen cursor to that same location on
screen.

   With a mouse, movement is relative; the screen
cursor moves from its existing location.  The mouse
could be moved across your arm, and the screen
cursor would move as well.  See mechanical mouse,
optical mouse, serial mouse, bus mouse and mickey.


mouse pad
Fabric-covered rubber pad roughly 9" square that
provides a smooth surface for rolling a mouse.


mouse port
Socket in the computer into which a mouse is
plugged.


MOV
(1) (Metal Oxide Varister)  Electronic component
that diverts excessive voltage to ground.

(2) Assembly language instruction that moves
(copies) data from one location to another.


move
(1) In programming, to copy data from one place in
memory to another.  At the end of the move, source
and destination data are identical.

(2) In word processing and graphics, to relocate
text and images to another part of the document or
drawing.


MPC
(Multimedia PC)  Microsoft minimum requirements for
a multimedia PC:

  10Mhz 286 CPU, VGA display
  2MB RAM, 30MB hard disk
  Two-button mouse
  CD ROM with CD ROM extensions 2.2
  Audio board with 8-bit Linear PCM sampling,
   music synthesizer and analog mixing capabilities
  Serial, parallel, MIDI and joystick ports
  DOS 3.1, Windows 3.0 with multimedia extensions


MPE
(MultiProgramming Executive)  Multitasking
operating system that runs on the HP 3000 series.


MPEG
(Moving Pictures Experts Group)  ISO/CCITT standard
for compressing full-motion video.  See JPEG.


MPR II
Swedish government standard for maximum video
terminal radiation.  The earlier MPR I is less
stringent.  See TCO.


MPU
(MicroProcessor Unit)  Same as microprocessor.


MRCI
(Microsoft Realtime Compression Interface)
Programming interface for Microsoft's DoubleSpace
technology used in DOS 6.


ms
(1) (MilliSecond)  See space/time.

(2) (MS) See Microsoft.


MS-DOS
(MicroSoft-Disk Operating System)  Single user
operating system for PCs from Microsoft.  It is
almost identical to IBM's DOS version, and both
versions are called DOS generically.  See PC
(Operating Environment).


MS-Net
(MicroSoft Network)  Microsoft's version of PC-
Network introduced in 1985.


MS-Windows
(MicroSoft Windows)  See Windows.


MSI
(Medium Scale Integration)  Between 100 and 3,000
transistors on a chip.  See SSI, LSI, VLSI and
ULSI.


MSP
(1) Microsoft Paint graphics file format.

(2) (Multiprocessing Server Pack)  Utility that
enables LAN Manager to utilize a computer's
multiprocessing capabilities.

(3) Operating system used in Fujitsu IBM-compatible
mainframes.


MTBF
(Mean Time Between Failure)  Average time a
component works without failure.  It is the number
of failures divided by the hours under observation.


MTS
(Modular TV System)  Stereo channel added to the
NTSC standard, which includes the SAP audio channel
for special use.


MTTR
(Mean Time To Repair)  Average time it takes to
repair a failed component.


MUG
(Macintosh User Group)  There are many Mac user
groups throughout the world.  One organization that
disseminates press releases and product ads to over
1,300 MUGs is Pawtuckaway Graphics, 53 Lakeview
Dr., Raymond, NH 03077, 603/895-6227.


multi mode fiber
Optical fiber with a core diameter of from 50 to
100 microns.  It is most commonly used, but light
rays tend to bounce around within the core causing
some distortion of the signal.  Contrast with
single mode fiber.


MULTIBUS
Advanced bus architecture from Intel used in
industrial, military and aerospace applications.
It includes message passing, auto configuration and
software interrupts.  MULTIBUS I is 16-bits;
MULTIBUS II is 32-bits.


multicomputer
See parallel computing.


MULTICS
(MULTiplexed Information and Computing Service)
Bull HN operating system.  Developed at MIT and
Bell Labs in the mid 1960s, it was the first
timesharing operating system.  It was used on GE's
mainframes, which were later absorbed into the
Honeywell product line.


multidrop line
See multipoint line.


MultiFinder
See Finder.


multifrequency monitor
Monitor that adjusts to all frequencies within a
range (multiscan) or to a set of specific
frequencies, such as VGA and Super VGA.


multiline
Cable, channel or bus that contains two or more
transmission paths (wires or optical fibers).


multimastering
See bus mastering.


MultiMate
PC word processing program from Ashton-Tate that
was originally noted for its similarity to the Wang
word processors of the 1970s.  Version 4.0 (1989)
introduced a number of advanced features.


multimedia
Disseminating information in more than one form.
Includes the use of text, audio, graphics, animated
graphics and full-motion video.  See MPC.


Multimedia Extensions
Windows routines that support audio recording and
playback, animation playback, joysticks, MIDI, the
MCI interface for CD ROM, videodiscs, videotapes,
etc., and the RIFF file format.  See MPC.


MultiPlan
Early spreadsheet for CP/M machines and PCs from
Microsoft.  It was one of the first spreadsheets.


Multiple Master
Font technology from Adobe Systems, Mountain View,
CA, that allows a typeface to be generated in
different styles, from condensed to expanded and
from light to heavy.


multiplexing
Transmitting multiple signals over a single
communications line or computer channel.  The two
common multiplexing techniques are FDM, which
separates signals by modulating the data onto
different carrier frequencies, and TDM, which
separates signals by interleaving bits one after
the other.


multiplexor
In communications, a device that merges several
low-speed transmissions into one high-speed
transmission and vice versa.


multiplexor channel
Computer channel that transfers data between the
CPU and several low-speed peripherals (terminals,
printers, etc.) simultaneously.  It may have an
optional burst mode that allows a high-speed
transfer to only one peripheral at a time.


multiplier-accumulator
General-purpose floating point processor that
multiplies and accumulates the results of the
multiplication.  Newer versions also perform
division and square roots.


multipoint line
In communications, a single line that interconnects
three or more devices.


multiported memory
Memory that provides more than one access path to
its contents.  It allows the same bank of memory to
be read and written simultaneously.


multiprocessing
Simultaneous processing with two or more processors
in one computer, or two or more computers
processing together.  When two or more computers
are used, they are tied together with a high-speed
channel and share the general workload between
them.  If one fails, the other takes over.

   It is also accomplished in special-purpose
computers, such as array processors, which provide
concurrent processing on sets of data.  Although
computers are built with various overlapping
features, such as executing instructions while
inputting and outputting data, multiprocessing
refers specifically to concurrent instruction
executions.  See parallel processing, bus mastering
and fault tolerant.


multiprogramming
Same as multitasking.


multiscan monitor
Monitor that adjusts to all frequencies within a
range.  See multifrequency monitor.


MultiSync monitor
Family of multiscan monitors from NEC Technologies,
Inc.  NEC popularized the multiscan monitor.


multitasking
Running two or more programs in one computer at the
same time.  It is controlled by the operating
system.  The number of programs that can be
effectively multitasked depends on the amount of
memory available, CPU speed, hard disk capacity and
speed, as well as the efficiency of the operating
system.

   Multitasking is accomplished due to the
differences in I/O and processing speed.  While one
program is waiting for input, instructions in
another program are executed.  In interactive
programs, the delay between keystrokes is used to
execute instructions in other programs.  In batch
processing systems, the milliseconds of delay
transferring data to and from a disk are used to
execute instructions in other programs.

   Before the early 1980s, multiprogramming meant
multitasking, and multitasking meant
multithreading!


multithreading
Multitasking within a single program.  It is used
to process multiple transactions or messages
concurrently.  It is also required for creating
synchronized audio and video applications.
Multithreading functions are often written in
reentrant code.


multiuser
Computer shared by two or more users.


multiuser DOS
(1) DOS-compatible operating system that runs
multiple terminals from a single PC.

(2) (Multiuser DOS)  Multiuser DOS-compatible
operating system from Novell that runs multiple
terminals from a single 386 or higher PC.
Supersedes Concurrent DOS.


multivariate
Use of multiple variables in a forecasting model.


MUMPS
Advanced, high-level programming language and
integrated database used for business applications.
It has extensive string handling making it suitable
for databases with vast amounts of free text.

   MUMPS has unique features including the ability
to store both data and program statements in its
database.  In addition, formulas written in a
program can be stored and used by other programs.
Developed in 1966 at Massachusetts General Hospital
(Mass. Utility MultiProgramming System), it has
been used extensively in health-care.

   The following example converts Fahrenheit to
Celsius:

   READ "Enter Fahrenheit ",FAHR
   SET CENT=(FAHR-32)*5/9
   WRITE "Celsius is", CENT


   The M Technology Association (formerly MUMPS
Users Group) is an organization that supports the
MUMPS community through training, meetings and
distribution of publications and software.
Address: 1738 Elton Rd., Suite 205, Silver Spring,
MD 20903, 301/431-4070.


MUX
(MUltipleXor)  See multiplexor.


MVGA
(Monochrome VGA)  Non-color VGA (gray scale).


MVS
(Multiple Virtual Storage)  Introduced in 1974, the
primary operating system used on IBM mainframes
(the others are VM and DOS/VSE).  MVS is a batch
processing-oriented operating system that manages
large amounts of memory and disk space.  Online
operations are provided with CICS, TSO and other
system software.

   MVS/XA (MVS/eXtended Architecture) manages the
enhancements, including 2GB of virtual memory,
introduced in 1981 with IBM's 370/XA architecture.

   MVS/ESA (MVS/Enterprise Systems Architecture)
manages the enhancements made to large scale
mainframes, including 16TB of virtual memory,
introduced in 1988 with IBM's ESA/370 architecture.
 MVS/ESA runs on all models of the System/390
ES/9000 product line introduced in 1990.


MVS/ESA
See MVS.


MVS/XA
See MVS.



n-dimensional
Some number of dimensions.


N-key rollover
Keyboard circuit design for fast typing.  To test
this, press four adjacent keys in sequence without
removing any finger from any of the keys.  If all
four letters appear on screen, it has this feature.


NACCB
(National Assn. of Computer Consultant Businesses)
Organization representing companies that provide
professional help in information and engineering
fields.  Founded in 1987, it is concerned with
legislation that affects computer consultants.
Address: 1250 Connecticut Ave. N.W., Suite 700,
Washington, DC 20036, 202/637-9134.


NACOMEX
(NAtional COMputer EXchange)  See computer
exchange.


NAEC
See NetWare.


NAK
(Negative AcKnowledgement)  Communications code
used to indicate that a message was not received,
or that a terminal does not wish to transmit.
Contrast with ACK.


name service
See naming service.


Named Pipes
IPC facility in LAN Manager that allows data to be
exchanged from one application to another either
over a network or running within the same computer.
The use of the term pipes for interprocess
communication was coined in UNIX.


naming service
Software that converts a name into a physical
address on a network, providing logical to physical
conversion.  Names can be user names, computers,
printers, services or files.  The transmitting
station sends a name to the server containing the
naming service software, which sends back the
actual address of the user or resource.  It serves
as a Yellow Pages for the network, which is
precisely what Sun's NIS system was originally
called.


NAND
(Not AND)  Boolean logic operation that is true if
any single input is false.  Two-input NAND gates
are often used as the sole logic element on gate
array chips, because all Boolean operations can be
created from NAND gates.

        Inputs  Output
       ┌───────┬─────┐
       │ 0   0 │  1  │
       │ 0   1 │  1  │
       │ 1   0 │  1  │
       │ 1   1 │  0  │
       └───────┴─────┘



nanometer
One billionth of a meter.


nanosecond
One billionth of a second.  Used to measure the
speed of logic and memory chips, a nanosecond can
be visualized by converting it to distance.  In one
nanosecond, electricity travels about six inches in
a wire.

   Even at 186,000 miles per second, electricity is
never fast enough for the hardware designer who
worries over a few inches of circuit path.  The
slightest delay is multiplied millions of times,
since millions of pulses are sent through a wire in
a single second.  See space/time.


NAPLPS
(North American Presentation-Level Protocol Syntax)
ANSI-standard protocol for videotex and teletext.
It compresses data for transmission over narrow-
bandwidth lines and requires decompression on the
receiving end.


narrowband
In communications, a voice grade transmission of
2,400 bps or less, or a sub-voice grade
transmission from 50 to 150 bps.


NAS
(Network Application Support)  Digital's
implementation of open systems, which provides
standards-based software that allows a variety of
workstations (VMS, ULTRIX, Sun, DOS, Windows, OS/2,
Mac, etc.) to interface via VAX and ULTRIX servers.
Connectivity to non-Digital server platforms is
planned for 1992 and beyond.


NASI
(National Assn. of Systems Integrators)
Organization of more than 5,000 members founded in
1991, dedicated to exchanging up-to-date
information on members' products and services.  Its
annual Computer Suppliers & Services Directory, in
print and on disk, is organized by zipcode.
Address: 412 High Plain Street, Unit #1, Walpole,
MA 02081, 508/668-8900.


National Computer Exchange
See computer exchange.


native language
Same as machine language.  See native mode.


native mode
(1) Normal running mode of a computer, executing
programs from its built-in instruction set.
Contrast with emulation mode.

(2) Highest-performance state of a computer, such
as the 386 running in Protected Mode.


NATURAL
Fourth-generation language from Software AG,
Reston, VA, that runs on a variety of computers
from micro to mainframe.


natural language
English, Spanish, French, German, Japanese,
Russian, etc.


NAU
(1) (Network Access Unit)  Interface card that
adapts a computer to a local area network.

(2) (Network Addressable Unit)  SNA component that
can be referenced by name and address, which
includes the SSCP, LU and PU.


NB card
(NuBus card)  See NuBus.


NC
See numerical control.


NCB
(Network Control Block)  Packet structure used by
the NetBIOS transport protocol.


NCF
(National Cristina Foundation)  Not-for-profit
organization, founded by Bruce McMahan and named
after his daughter, that channels used and surplus
computers to the disadvantaged.  Address: 42
Hillcrest Dr., Pelham Manor, NY 10803,
800/CRISTINA.


NCGA
(National Computer Graphics Assn.)  Organization
dedicated to developing and promoting the computer
graphics industry.  It maintains a clearinghouse
for industry information and strives to encourage
communication among computer graphics users,
consultants, educators and vendors.  Address: 2722
Merrilee Dr., Suite 200, Fairfax, VA 22031,
800/225-NCGA.


NCP
(1) (Network Control Program)  IBM's SNA network
control program.  See SNA and network control
program.

(2) (NetWare Core Protocol)  Internal NetWare
language used to communicate between workstation
and server.

(3) (Not Copy Protected)  Software that can be
easily copied.


NCR
(NCR Corp., Dayton, OH)  Major manufacturer of
computers and financial terminals.  In 1884, John
Henry Patterson purchased National Manufacturing
Company of Dayton, Ohio, and renamed it National
Cash Register.  It became the leading cash register
company and, by 1911, had sold its one millionth
machine.

   Starting in the 1930s, NCR made accounting
machines that posted customer accounts and became
successful in the banking and retail industries, in
which it has remained ever since.

   In 1957, it introduced the "304" transistorized
computer.  It accepted data from NCR cash registers
and banking terminals via paper tape.  The 304 was
very reliabile and widely accepted.

   NCR computer lines have included the Century
series (1960s), Criterion series (1970s) and the V
and I series (1980s).  Starting in 1982 with the
UNIX- and Motorola 68000-based Tower series, NCR
embraced open systems and industry standards.  In
1990, the x86-based System 3000 series was
introduced, a complete line from laptops to
massively parallel machines running DOS and OS/2 at
the low end and UNIX at the high end.

   In 1991, NCR was acquired by AT&T and operates
as a wholly-owned subsidiary.


NCR paper
(No Carbon Required paper)  Multiple-part paper
form that does not use carbon paper.  The ink is
adhered to the reverse side of the previous sheet.


NCSC
(National Computer Security Center)  Arm of the
U.S. National Security Agency that defines criteria
for trusted computer products.  Following are the
Trusted Computer Systems Evaluation Criteria
(TCSEC), DOD Standard 5200.28 (also known as the
Orange Book) and the European equivalent.

   Level D is a non-secure system.

   Level C provides discretionary control.  The
owner of the data can determine who has access to
it.

   C1  Requires user log-on, but allows group ID.

   C2  Requires individual user log-on with
       password and an audit mechanism.

   Levels B and A provide mandatory control.
Access is based on standard DOD clearances.

   B1  DOD clearance levels.

   B2  Guarantees path between user and the
       security system.  Provides assurances that
       system can be tested and clearances cannot
       be downgraded.

   B3  System is characterized by a mathematical
       model that must be viable.

   A1  System is characterized by a mathematical
       model that can be proven.  Highest
       security.


                 European Ratings
The European Information Technology Security
Evaluation Criteria (ITSEC) is similar to TCSEC,
but rates functionality (F) and effectiveness (E)
separately.

   Orange Book
      TCSEC      ITSEC
         D         E0
        C1      F-C1, E1
        C2      F-C2, E2
        B1      F-B1, E3
        B2      F-B2, E4
        B3      F-B3, E5
        A1      F-B3, E6



NDIS
(Network Driver Interface Spec)  Microsoft
specification for hardware-independent drivers at
the data link (media access control) layer.  When
transport protocols are written to NDIS, network
adapters with NDIS-compliant MAC drivers can be
freely interchanged.  See "LANs" under data link
protocol.


NE
(Not Equal to)  See relational operator.


near pointer
In an x86 segmented address, a memory address
within a single segment (the offset).  Contrast
with far pointer.


NEAT chipset
(New Enhanced AT chipset)  Set of chips used to
build an AT-class machine from Chips and
Technologies, Inc.  EMS capability is included.
The CPU, BIOS and NEAT chipset are the primary
logic chips on a 286-based PC.


negative logic
Use of high voltage for a 0 bit and low voltage for
a 1 bit.  Contrast with positive logic.


nematic
Stage between a crystal and a liquid that has a
threadlike nature; for example, a liquid crystal.


nemonic
See mnemonic.


neper
Unit of measurement based on Napierian logarithms
that represents the ratio between two values, such
as current or voltage.


nerd
Person typically thought of as dull socially.
Nerds often like technical work and are generally
introspective.  Contrast with hacker, a technical
person that may or may not be a nerd.


nesting
In programming, the positioning of a loop within a
loop.  The number of loops that can be nested may
be limited by the programming language.  See loop.


NetBEUI
(NetBIOS Extended User Interface)  Pronounced "net-
booey."  Implementation of the NetBIOS transport
protocol within LAN Manager and LAN Server.  It
communicates to the network adapter via NDIS.


NetBIOS
Commonly used transport protocol for PC local area
networks introduced with IBM's PC Network and
implemented in Microsoft's MS-Net and LAN Manager.
Application programs use NetBIOS for client/server
or peer-to-peer communications.

   There are two NetBIOS modes for communicating.
The Datagram is the fastest method, but does not
guarantee delivery of a message.  It is a self-
contained packet with sender and receiver name,
usually limited to 512 bytes.  If the recipient
device is not listening for messages, the datagram
is lost.

   The Session mode establishes a connection until
broken.  It guarantees delivery of messages up to
64K bytes long.

   NetBIOS-compliant protocols refer to layers 3, 4
and 5 on the OSI model.


NETROOM
DOS memory manager from Helix Software Co., Long
Island City, NY, noted for squeezing large network
drivers into high DOS memory.  Its DISCOVER utility
reports the system's current configuration.


NetView
IBM SNA network management software that provides
centralized monitoring and control for SNA, non-SNA
and non-IBM devices.  NetView/PC interconnects
NetView with Token Ring LANs, Rolm CBXs and non-IBM
modems, while maintaining control in the host.


NetWare
Family of network operating systems from Novell,
Inc., Provo, UT, that runs on 286s and up and
supports DOS, OS/2 and Mac workstations and a
variety of LAN access methods, including Token
Ring, Ethernet and ARCNET.  It is the most widely-
used LAN control program.  See IPX, SPX, NGM and
MHS.

   NetWare Lite is a peer-to-peer system, which
allows any workstation to be a server.  It provides
upward migration to larger NetWare systems.  A
starter kit connects two PCs.  NetWare Lite
supersedes ELS NetWare (Entry Level System),
Novell's first peer-to-peer network.

   NetWare 2.x (formerly Advanced NetWare 286) runs
in a dedicated file server and supports up to 100
users.  It is the sole control program in the
server.  NetWare 3.x (formerly NetWare 386) runs on
386 servers and up and takes advantage of the 32-
bit architecture.  Versions of 3.x are available
from 10 to 4,000 nodes.

   NetWare 4.0, due in 1993, is backward compatible
with 2.x and 3.x and includes the NDS (NetWare
Directory Service) naming service that provides
X.500 compatibility.

   SFT NetWare (System Fault Tolerant) provides
automatic recovery from network malfunctions.
NetWare for VMS provides NetWare connectivity to
VAX networks.  Portable NetWare provides NetWare
source code for conversion to other platforms.

               NetWare Certification
Novell provides certification for technical
competence with self-study tests and courses given
at National Authorized Education Centers (NAECs).
Certificates include CNE (Certified NetWare
Engineer), CNI (Certified NetWare Instructor) and
ECNE (Enterprise CNE), which includes wide area
network (WAN) expertise.


NetWare NFS
Software from Novell that implements the NFS
distributed file system on NetWare 3.11 servers.
It allows UNIX and other NFS client machines to
access files on the NetWare server.  See LAN
Workplace and UnixWare.


network
(1) Arrangement of objects that are interconnected.
See LAN and network database.

(2) In communications, the transmission channels
and supporting hardware and software.


network adapter
Printed circuit board that plugs into a workstation
or server and controls the exchange of data over a
network.  It performs the electronic functions of
the access method (data link protocol), such as
Ethernet, Token Ring and LocalTalk.  The
transmission medium (twisted pair, coax or fiber
optic cable) interconnects all adapters in the
network.


network administrator
Person who manages a communications network and is
responsible for its efficient operation.  Tasks
include installing new applications and monitoring
network activity.


network architecture
(1) Design of a communications system, which
includes the hardware, software, access methods and
protocols used.  It also defines the method of
control: whether computers can act independently or
are controlled by other computers monitoring the
network.  It determines future flexibility and
connectability to foreign networks.

(2) Access method in a LAN, such as Ethernet, Token
Ring and LocalTalk.


network card
See network adapter.


network control program
Software that manages the traffic between terminals
and the host mini or mainframe.  It resides in the
communications controller or front end processor.
In a personal computer LAN, it is called a network
operating system and resides in the server and
manages requests from the workstations.  IBM's SNA
network control program is called NCP.


network database
(1) Database that runs in a network.  It implies
that the DBMS was designed with a client/server
architecture.

(2) Database that holds addresses of other users in
the network.

(3) Database organization method that allows for
data relationships in a net-like form.  A single
data element can point to multiple data elements
and can itself be pointed to by other data
elements.  Contrast with relational database.


network management
Monitoring an active network in order to diagnose
problems and gather statistics for administration
and fine tuning.


network modem
Modem shared by all users in a network.  See ACS.


network operating system
Control program that resides in a file server in a
LAN.  It handles the requests for data from the
workstations in the network.


network ready
Software designed to run in a network.  It implies
that multiple users can share the databases without
conflict.


network server
See file server.


neural network
Modeling technique based on the observed behavior
of biological neurons and used to mimic the
performance of a system.  It consists of a set of
elements that start out connected in a random
pattern, and, based upon operational feedback, are
molded into the pattern required to generate the
required results.  It is used in applications such
as robotics, diagnosing, forecasting, image
processing and pattern recognition.


newline
End of line code.  See CR/LF.


NeWS
(Network Extensible Windowing Support)  Networked
windowing system (similar to X Windows) from
SunSoft that renders PostScript fonts on screen the
way they print on a PostScript printer.


Newton
Family of PDAs from Apple.  First model is a hand-
held personal organizer that recognizes hand
printing.  It can add an appointment to a calendar
and dial a phone or send a fax.


NewWave
PC operating environment from HP that runs between
DOS and Windows.  It integrates data and activates
tasks within the system.  Its object-management
facility allows data from different applications to
be merged to create a compound document.  Hot links
automatically update the document if data in one of
the source files is updated.

   It allows for the creation of agents (automatic
procedures) that can be activated based on time or
events.  For example, at month end, an agent could
extract data from the corporate mainframe and
prepare a report using several application
programs.  Programs must be modified to run under
NewWave.


NeXT Inc.
(Redwood City, CA)  Founded in 1985 by Steven Jobs,
co-founder of Apple, NeXT created a family of high-
resolution, UNIX-based workstations running its
NeXTstep environment.  The first machine was
introduced in 1988.  Manufacturing of the hardware
ceased Feb. 1993, but NeXT is continuing with its
NeXTstep software for the x86.


NeXTstep
UNIX-based, object-oriented development environment
from NeXT Computer, Redwood City, CA.  It runs on
NeXT computers and 386s and up providing an
advanced, integrated environment for creating
applications with a graphical user interface.


NFS
(Network File System)  Distributed file system from
SunSoft that allows data to be shared across a
network regardless of machine, operating system,
network architecture or protocol.  This de facto
UNIX standard lets remote files appear as if they
were local on a user's machine.


NGM
(NetWare Global Messaging)  E-mail software from
Novell for NetWare 3.x that includes directory
synchronization across distributed servers and
provides optional interfaces to X.400, SMTP and
SNADS.  See SMF.


nibble
Half a byte (four bits).


nibble mode memory
Type of dynamic RAM that outputs four consecutive
bits (nibble) at one time.


NIC
(Network Interface Card)  Same as network adapter.


NiCad
(Nickel CADmium)  Rechargeable battery technology
that has been widely used in portable applications,
including portable computers.  It provides more
charge per pound than lead acid batteries, but less
than nickel hydride or zinc air.  Its major problem
is a so-called "memory effect," in which the
battery seems to remember how full it was when you
last charged it, and it doesn't go past that point
the next time.  NiCads should be completely drained
periodically to maintain the longest charge.  It
uses a nickel and cadmium plate and potassium
hydroxide as the electrolyte.  See lead acid,
nickel hydride and zinc air.


nickel hydride
Rechargeable battery technology that provides more
charge per pound than lead acid and NiCad, but less
than zinc air.  It does not suffer from the NiCad
memory effect.  It uses nickel and metal hydride
plates with potassium hydroxide as the electrolyte.
See lead acid, NiCad and zinc air.


NIS
(Network Information Services)  Naming service from
SunSoft that allows resources to be easily added,
deleted or relocated.  Formerly called Yellow
Pages, NIS is a de facto UNIX standard.  NIS+ is a
redesigned NIS for Solaris 2.0 products.


NIST
(National Institute of Standards & Technology)
Standards-defining agency of the U.S. government,
formerly called the National Bureau of Standards.


NLM
(NetWare Loadable Module)  Software that enhances
or provides additional server functions in a server
running NetWare 3.x.  Support for different kinds
of workstations, database engines, fax and print
servers are examples.  The NetWare 2.x counterpart
is a VAP.


NLQ
(Near Letter Quality)  Print quality that is almost
as sharp as an electric typewriter.  The slowest
speed of a dot matrix printer often provides NLQ.


NMI
(NonMaskable Interrupt)  High-priority interrupt
that cannot be disabled by another interrupt.  It
is used to report malfunctions such as parity, bus
and math coprocessor errors.


NMOS
(N-Channel MOS)  Pronounced "N moss."  Type of
microelectronic circuit used for logic and memory
chips.  NMOS transistors are faster than their PMOS
counterpart and more of them can be put on a single
chip.  It is also used in CMOS design.


no-op
(NO OPeration)  Instruction that does nothing but
hold the place for a future machine instruction.


no wait state memory
Memory fast enough to meet the demands of the CPU.
Idle wait states do not have to be introduced.


node
(1) In communications, a network junction or
connection point (terminal or computer).

(2) In database management, an item of data that
can be accessed by two or more routes.

(3) In computer graphics, an endpoint of a
graphical element.


noise
Extraneous signal that invades an electrical
transmission.  It can come from strong electrical
or magnetic signals in nearby lines, from poorly
fitting electrical contacts, and from power line
spikes.


NOMAD
Relational DBMS from Must Software Int'l., Norwalk,
CT, that runs on IBM mainframes, PCs and VAXs.
Introduced in the mid 1970s, it was one of the
first database systems to provide a non-procedural
language for data manipulation.


non-blocking
Ability of a signal to reach its destination
without interference or delay.


non-breaking space
See hard space.


non-document mode
Word processing mode used for creating source
language programs, batch files and other text files
that contain only text and no proprietary headers
and format codes.  All text editors, as well as
XyWrite III Plus, automatically output this format.


non-impact printer
Printer that prints without banging a ribbon onto
paper, such as a thermal or ink jet printer.  See
printer.


non-interlaced
Illuminating a CRT by displaying lines sequentially
from top to bottom.  Non-interlaced monitors
eliminate annoying flicker found in interlaced
monitors, which illuminate half the lines in the
screen in the first cycle and the remaining half in
the second cycle.  Contrast with and see interlaced
for a diagram.


non-modal
Not mode oriented.  A non-modal operation moves
from one situation to another without apparent mode
switching.


non-numeric programming
Programming that deals with objects, such as words,
board game pieces and people, rather than numbers.
Same as list processing.


non-preemptive multitasking
Environment in which an application is able to give
up control of the CPU to another application only
at specific points in its running; for example,
when it's ready to accept user input.  One program
can dominate a machine with this method.  Contrast
with preemptive multitasking.


non-procedural language
Computer language that does not require traditional
programming logic to be stated.  For example, a
command, such as LIST, might display all the
records in a file on screen, separating fields with
a blank space.  In a procedural language, such as
COBOL, all the logic for inputting each record,
testing for end of file and formatting the screen
has to be explicitly programmed.

   Query languages, report writers, interactive
database programs, spreadsheets and application
generators provide non-procedural languages for
user operation.  Contrast with and see procedural
language for an example.


non-return-to-zero
See NRZ.


non trivial
Favorite word among programmers for a difficult
task.


non-volatile memory
Memory that holds its content without power.
Firmware chips (ROMs, PROMs, EPROMs, etc.) are
examples.  Disks and tapes may be called non-
volatile memory, but they are usually considered
storage devices.


nonlinear
System in which the output is not a uniform
relationship to the input.


nonpreemptive multitasking
See non-preemptive multitasking.


NonStop
Family of fault tolerant computer systems from
Tandem.


NOR
(Not OR)  Boolean logical operation that is true if
all inputs are false, and false if any input is
true.  An exclusive NOR is true if both inputs are
the same.

           NOR           EXCLUSIVE NOR
      Inputs  Output    Inputs  Output
      ┌───────┬─────┐   ┌───────┬─────┐
      │ 0   0 │  1  │   │ 0   0 │  1  │
      │ 0   1 │  0  │   │ 0   1 │  0  │
      │ 1   0 │  0  │   │ 1   0 │  0  │
      │ 1   1 │  0  │   │ 1   1 │  1  │
      └───────┴─────┘   └───────┴─────┘



normal wear
Deterioration due to natural forces that act upon a
product under average, everyday use.


normalization
In relational database management, a process which
breaks down data into record groups for efficient
processing.  There are six stages.  By the third
stage (third normal form), data is identified only
by the key field in the record.  For example,
ordering information is identified by order number,
customer information, by customer number.


Norton SI
(Norton System Information)  Norton utility that
measures computer performance.  It provides a
computing index (CI) for CPU speed, a disk index
(DI) for disk speed and a performance index (PI)
that blends CI and DI.  The IBM XT is used as a
reference of 1.0.


Norton Utilities
Disk management utility programs for the PC and
Macintosh from Symantec Corp., Cupertino, CA.
Includes programs to search and edit files,
undelete files and restore damaged files among
others.  Originally from Peter Norton Computing,
these programs were among the first to popularize
disk utilities for the PC.


NOS
(Network Operating System)  Software that controls
the transmission in a network.


NOS/VE
(Network Operating System/Virtual Environment)
Multitasking, virtual memory operating system from
Control Data that runs on its medium to large-scale
mainframes.


NOT
Boolean logic operation that reverses the input.
If a 0 is input, a 1 is output, and vice versa.
See AND, OR & NOT.


Nota Bene
See XyWrite III Plus.


notation
How a system of numbers, phrases, words or
quantities is written or expressed.  Positional
notation is the location and value of digits in a
numbering system, such as the decimal or binary
system.


notebook computer
Portable computer that typically weighs less than
six pounds (heavier than a pocket computer; lighter
than a laptop).


Nova
Minicomputer series from Data General.  When
introduced in 1969, it was the first 16-bit mini to
use four CPU accumulators, quite advanced for its
time.  Novas and its RDOS operating system were
used extensively in the OEM marketplace.


NovaNET
Satellite-based network for educational services
created by the Education Research Lab of the Univ.
of Illinois.  It includes over 10,000 hours of
lesson material from third grade to post graduate
work in over a hundred subject areas.


Novell network
LAN controlled by one of Novell's NetWare operating
systems.  See NetWare.


nroff
(Nontypesetting RunOFF)  UNIX utility that formats
documents for terminals and dot matrix printers.
Using a text editor, troff codes are embedded into
the text and the nroff command converts the
document into the required output.  Complex troff
codes are ignored.  See troff.


NRZ
(Non-Return-To-Zero)  Signalling method used in
magnetic recording and communications that does not
automatically return to a neutral state after each
bit is transmitted.


ns
(NanoSecond)  See nanosecond.


NSTL
(National Software Testing Lab, Philadelphia)
Independent organization that evaluates computer
hardware and software.  It adheres to controlled
testing methods to ensure objective results and
publishes its findings in Software Digest Ratings
Report and PC Digest.


NT
See Windows NT.


NTSC
(National TV Standards Committee)  U.S. TV standard
administered by the FCC that is currently 525 lines
transmitted at 60 half frames/sec (interlaced).  It
is a composite of red, green and blue signals for
color and includes an FM frequency for audio and an
MTS signal for stereo.  NTSC reconvenes to change
TV standards.


NuBus
Bus architecture (32-bits) originally developed at
MIT and defined as a Eurocard (9U).  Apple has
changed its electrical and physical specs for its
Macintosh series.  Many Macs have one or more NuBus
slots for peripheral expansion.


NUI
(1) (Notebook User Interface)  Term coined by Go
Corp. for its PenPoint pen-based interface.

(2) (NetWare Users International)  NetWare
operating systems user group.

(3) (Network User Identifier)  Code used to gain
access into local European packed-switched
networks.


NUL
See null.


null
First character in ASCII and EBCDIC.  In hex, it
prints as 00; in decimal, it prints as a blank.  It
is naturally found in binary numbers when a byte
contains no 1 bits.  It is also used to pad fields
and act as a delimiter; for example, in C, it
specifies the end of a character string.


null modem cable
RS-232 cable used to connect two personal computers
in close proximity.  It connects to both serial
ports and crosses the sending wire on one end to
the receiving wire on the other.


null pointer
In programming, a reference to zero.  May be the
response of an unsuccessful search function.


null string
In programming, a character string that contains no
data.


Num Lock
(NUMeric Lock)  Key used to switch a combination
number/cursor keypad into number key mode.


Number 9 board
Family of high-resolution display boards for PCs
from Number Nine Computer Corp., Lexington, MA,
noted for its features (virtual screen, built-in
zoom) and speed.  Products begin with #9, such as
#9GXi and #9GXe.


number crunching
Refers to computers running mathematical,
scientific or CAD applications, which perform large
amounts of calculations.


numbers
In a computer, numbers can be stored in several
forms.  Although they are all coded as binary
digits (bits), BCD and packed decimal numbers
retain the decimal relationship of a number,
whereas fixed and floating point do not.


            Binary Coded Decimal (BCD)
BCD encodes each decimal digit in a single byte.
The number 6508 would take four bytes.  A
variation, called packed decimal, encodes two
digits in one byte.  6508 would take two bytes.


         Decimal      Packed Decimal
      ┌──┬──┬──┬──┐       ┌──┬──┐
      │ 6│ 5│ 0│ 8│       │65│08│
      └──┴──┴──┴──┘       └──┴──┘
      ┌──┬──┬──┬──┐    ┌──┬──┬──┬──┬──┐
      │       6508│    │       6508│00│
      └──┴──┴──┴──┘    └──┴──┴──┴──┴──┘
       Fixed Point      Floating Point


                Binary Fixed Point
This method converts the entire decimal number into
a binary number, placing it in a fixed unit of
storage.  The number 6508 would require at least
two bytes.  Binary numbers are calculated faster
than decimal (BCD) numbers.

        Bytes  Bits   Values
          1     8     0 to 255
          2    16     0 to 65,535
          4    32     0 to 4,294,967,295


               Binary Floating Point
Floating point allows very small fractions and very
large numbers to be maintained and calculated
quickly.  Both the mantissa (significant digits)
and the exponent (power to which the base is
raised) are converted into binary numbers.  See
floating point.


numeric data
Refers to quantities and money amounts used in
calculations.  Contrast with string or character
data.


numeric field
Data field that holds only numbers to be
calculated.  Contrast with character field.


numeric keypad
Four-row keyboard.

   Calculator   Telephone
      789          123
      456          456
      123          789
       0            0


numerical control
Category of automated machine tools, such as drills
and lathes, that operate from instructions in a
program.  Numerical control (NC) machines are used
in manufacturing tasks, such as milling, turning,
punching and drilling.

   First-generation machines were hardwired to
perform specific tasks or programmed in a very low-
level machine language.  Today, they are controlled
by their own microcomputers and programmed in high-
level languages, such as APT and COMPACT II, which
automatically generate the tool path (physical
motions required to perform the operation).

   The term was coined in the 1950s when the
instructions to the tool were numeric codes.  Just
like the computer industry, symbolic languages were
soon developed, but the original term remained.


NZ
(Non Zero)  Value greater or less than 0.



OA
See office automation.


OADG
(Open Architecture Development Group)  Organization
founded by IBM Japan in 1991 to promote PC
standards in Japan.  See DOS/V.


OAI
(Open Application Interface)  Computer to telephone
interface that lets a computer control and
customize PBX and ACD operations.


object
(1) In object-oriented programming, a self-
contained module of data and its associated
processing.

(2) In a compound document, an independent block of
data, text or graphics that was created by a
separate application.


object code
Same as machine language.


object computer
Same as target computer.


object language
(1) Language defined by a metalanguage.

(2) Same as target language.

(3) Object-oriented programming language.


object module
Output of an assembler or compiler, which must be
linked with other modules before it can be
executed.


object-oriented analysis
Examination of a problem by modeling it as a group
of interacting objects.  An object is defined by
its class, data elements and behavior.  For
example; in an order processing system, an invoice
is a class, and printing, viewing and totalling are
examples of its behavior.   Objects (individual
invoices) inherit this behavior and combine it with
their own data elements.


object-oriented database
Database that holds abstract data types (objects).
It can store objects directly from an object-
oriented programming language.  Because any type of
data can be stored (the rules for processing the
data are part of an object), the object database
promises fully integrated databases that will hold
data, text, pictures and voice; essentially an
endless variety of ever-changing formats.


object-oriented DBMS
DBMS that manages an object-oriented database.  It
is capable of handling complex queries about
objects that would be difficult in relational
database programs.


object-oriented design
Transforming an object-oriented model into the
specifications required to create the system.
Moving from object-oriented analysis to object-
oriented design is accomplished by expanding the
model into more and more detail.


object-oriented graphics
Same as vector graphics.


object-oriented interface
Graphical interface that uses icons and a mouse,
such as the Macintosh, Windows and GEM
environments.


object-oriented programming
Abbreviated "OOP," a programming technology that is
more flexible than standard programming.  It is an
evolutionary form of modular programming with more
formal rules that allow pieces of software to be
reused and interchanged between programs.  Major
concepts are (1) encapsulation, (2) inheritance,
and (3) polymorphism.

   Encapsulation is the creation of self-sufficient
modules that contain the data and the processing
(data structure and functions that manipulate that
data).  These user-defined, or abstract, data types
are called classes.  One instance of a class is
called an object.

   Classes are created in hierarchies, and
inheritance allows the knowledge in one class to be
passed down the hierarchy.  New objects can be
created by inheriting characteristics from existing
classes. For example, the object MACINTOSH could be
one instance of the class PERSONAL COMPUTER, which
could inherit properties from the class COMPUTER
SYSTEMS.  Adding a new computer requires entering
only what makes it different from other computers,
while the general characteristics of personal
computers can be inherited.

   Object-oriented programming allows procedures
about objects to be created whose exact type is not
known until runtime.  For example, a screen cursor
may change its shape from an arrow to a line
depending on the program mode.  The routine to move
the cursor on screen in response to mouse movement
would be written for "cursor," and polymorphism
would allow that cursor to be whatever shape is
required at runtime.  It would also allow a new
shape to be easily integrated into the program.

   Xerox's Smalltalk was the first OOP language and
was used to create the graphical user interface
whose derivations are so popular today.  C++ is
becoming the mainstay OOP language, because it
combines traditional C programming with object-
oriented features.

   Following is a terminology comparison:

   Object-oriented   Traditional
   programming       programming

    class             data type + characteristics
    instance          variable
    instantiate       declare a variable
    method            processing code
    message           call
    object            data type + processing



object-oriented technology
Variety of disciplines that support object-oriented
programming, including object-oriented analysis and
object-oriented design.


object program
Machine language program ready to run in a
particular operating environment.  It has been
assembled, or compiled, and link edited.


Objective-C
Object-oriented C programming language from The
Stepstone Corp. that runs on PCs and popular
workstations.  It was the first commercial object-
oriented extension of the C language.


ObjectVision
Application development system from Borland for
creating Windows and OS/2 2.0 applications.  Uses
visual techniques for user interface design as well
as for programming logic.  It also provides links
to spreadsheets and databases.


ObjectWindows
Class library of Windows objects from Borland that
helps developers create Windows applications.  It
is an open standard available from Borland and the
Object Management Group.


occam
Parallel processing language designed to handle
concurrent operations.  The INMOS Transputer
executes occam almost directly.  In the following
statements, two items of data are read and
incremented at the same time.  PAR specifies that
following statements are to be executed
concurrently, and SEQ indicates that the following
statements are executed sequentially.

   PAR
    SEQ
      chan1 ? item1
      item1 := item1 + 1
    SEQ
      chan2 ? item2
      item2 := item2 + 1



OCE
(Open Collaboration Environment)  Extension to
System 7 from Apple that provides e-mail and
document sharing across multiple platforms in an
enterprise.


OCR
(Optical Character Recognition)  Machine
recognition of printed characters.  OCR systems can
recognize many different OCR fonts, as well as
typewriter and computer-printed characters.
Advanced OCR systems can recognize hand printing.


octal
Numbering system that uses eight digits.  It is
used as a shorthand method for representing binary
numbers that use six-bit characters.  Each three
bits (half a character) is converted into a single
octal digit.   Okta is Greek for 8.


   Decimal Binary  Octal
      0     000      0
      1     001      1
      2     010      2
      3     011      3
      4     100      4
      5     101      5
      6     110      6
      7     111      7



ODBC
(Open DataBase Connectivity)  Microsoft programming
interface for accessing databases on a network.  It
supports SQL and is part of WOSA.


odd parity
See parity checking.


ODI
(Open Data link Interface)  Novell driver
specification that allows multiple transport
protocols to be run on one network adapter.  For
example, a PC can connect to a NetWare network
running SPX/IPX and a UNIX network running TCP/IP.


ODT
See SCO Open Desktop.


Oe
See Oersted.


OEM
(Original Equipment Manufacturer)  Manufacturer
that sells equipment to a reseller.  Also refers to
the reseller itself.  OEM customers either add
value to the product before reselling it, private
label it, or bundle it with their own products.
See VAR.


Oersted
Pronounced "ers-ted," the measurement of magnetic
resistance.  The higher the "Oe," the more current
required to magnetize it.


off-hook
State of a telephone line that allows dialing and
transmission but prohibits incoming calls from
being answered.  The term stems from the days when
a telephone handset was lifted off of a hook.
Contrast with on-hook.


off-the-shelf
Refers to products that are packaged and available
for sale.


office automation
Integration of office information functions,
including word processing, data processing,
graphics, desktop publishing and e-mail.

   The backbone of office automation is a LAN,
which allows users to transmit data, mail and even
voice across the network.  All office functions,
including dictation, typing, filing, copying, fax,
Telex, microfilm and records management, telephone
and telephone switchboard operations, are
candidates for integration.


Office Vision
Integrated office automation applications from IBM
that run in all IBM computer families.  It was the
first major implementation of SAA and incorporates
the Presentation Manager interface across OS/2
networks, AS/400s and mainframes.

   Introduced in 1989, it includes e-mail,
scheduling, document creation and distribution as
well as decision support and graphics capabilities
among all users.


offline
Not connected to or not installed in the computer.
If a terminal, printer or other device is
physically connected to the computer, but is not
turned on or in ready mode, it is still considered
offline.

   Disks and tapes that have been demounted and
stored in the data library are considered offline.
Contrast with online.


offline storage
Disks and tapes that are kept in a data library.


offload
To remove work from one computer and do it on
another.  See cooperative processing.


offset
(1) Distance from a starting point, either the
start of a file or the start of a memory address.
Its value is added to a base value to derive the
actual value.  An offset into a file is simply the
character location within that file, usually
starting with 0; thus "offset 240" is actually the
241st byte of the file.  See relative address.

(2) In word processing, the amount of space a
document is printed from the left margin.


ohm
Unit of measurement for electrical resistance.  One
ohm is the resistance in a circuit when one volt
maintains a current of one amp.


OLCP
(OnLine Complex Processing)  Processing complex
queries, long transactions and simultaneous reads
and writes to the same record.  Contrast with OLTP,
in which records are updated in a more predictable
manner.


OLE
(Object Linking and Embedding)  Windows compound
document protocol.  The "client" application
creates the document; the "server" application
creates an object within the document.  When a user
double clicks on an embedded object in a client
app, the server app is loaded and the appropriate
data file is retrieved.


OLTP
(OnLine Transaction Processing)  See transaction
processing and OLCP.


OMG
(Object Management Group)  International
organization founded in 1989 to endorse
technologies as open standards for object-oriented
applications.  Address: 492 Old Connecticut Path,
Framingham, MA 01701, 508/820-4300.


OMI
(Open Messaging Interface)  E-mail protocol
developed by Lotus, now included in VIM.


omnidirectional
In all directions.  For example, an omnidirectional
antenna can pick up signals in all directions.


OmniPage
Character recognition software for PCs and the
Macintosh from Caere Corp., Los Gatos, CA.  It was
the first personal computer software that could
distinguish text from graphics and convert a wide
variety of fonts into text.


on-hook
State of a telephone line that can receive an
incoming call.  Contrast with off-hook.


on-line
See online.


on the fly
As needed.  Implies little or no degradation in
performance to accomplish the task.  See realtime
and realtime compression.


ONA
(Open Network Architecture)  FCC plan that allows
users and competing enhanced service providers
(ESPs) equal access to unbundled, basic telephone
services.  The Open Network Provision (ONP) is the
European counterpart.


ONC
(Open Network Computing)  Family of networking
products from SunSoft for implementing distributed
computing in a multivendor environment.  Includes
TCP/IP and OSI protocols, NFS distributed file
system, NIS naming service and TI-RPC remote
procedure call library.  ONC+ adds Federated
Services, which is an interface for third-parties
to connect network services into the Solaris
environment.


one-chip computer
See computer on a chip.


onion diagram
Graphical representation of a system that is made
up of concentric circles.  The innermost circle is
the core, and all outer layers are dependent on the
core.


online
(1) Peripheral device (terminal, printer, etc.)
that is ready to operate.  A printer can be
attached and turned on, yet still not online, if
the ONLINE or SEL light is out.  Pressing the
ONLINE button will usually turn it back online.

(2) An online computer system refers to a system
with terminals, but does not imply how the system
functions.  All the following are online systems.
Data collection systems accept data from terminals,
but do not update master files.  Interactive
systems imply data entry and updating.  Transaction
processing systems update necessary files as
transactions arrive (orders, financial quotes,
etc.).  Realtime systems provide an immediate
response to a question.

 ┌─Want to impress your friends?─────────────────┐
 │ Although complete overkill, it is not         │
 │ incorrect to say that one has an online,      │
 │ realtime, interactive, transaction processing │
 │ system.  However, don't say this to an        │
 │ experienced systems analyst!                  │
 └───────────────────────────────────────────────┘


online help
On-screen instruction that is immediately
available.


online industry
Collection of service organizations that provide
dial-up access to databases, shopping, news,
weather, sports, e-mail, etc.  See online services.


online services
Following are major online information service
organizations, including the types of databases
provided.  "Wide variety" generally includes news,
weather and shopping as well as information on a
host of topics.  Many services provide e-mail.

 America Online, Inc.
 Databases: wide variety, personal computer
 technical
  8619 Westwood Center Dr.
  Vienna, VA 22182
  800/827-6364
  703/448-8700

 BIX
 Databases: personal computer technical
  Byte Information Exchange
  General Videotex Corp.
  1030 Massachusetts Ave.
  Cambridge, MA 02138
  800/695-4775
  617/491-3393

 CompuServe Information Service, Inc.
 Databases: wide variety, personal computer
 technical
  P.O. Box 20212
  Columbus, OH 43220
  800/848-8199 (Ohio)
  800/848-8990
  614/457-8650

 DataTimes Corporation
 Databases: newspapers, magazines, financial
  14000 Quail Springs Pkwy., Suite 450
  Oklahoma City, OK 73134
  800/642-2525
  405/751-6400

 DELPHI
 Databases: wide variety, access to DIALOG
  General Videotex Corp.
  1030 Massachusetts Ave.
  Cambridge, MA 02138
  800/544-4005
  617/491-3393

 DIALOG Information Services, Inc.
 Databases: over 400 (largest)
  3460 Hillview Avenue
  Palo Alto, CA 94304
  800/334-2564
  415/858-2700

 Dow Jones News/Retrieval Service
 Databases: financial plus shopping
 airline reservations, etc.
  P.O. Box 300
  Princeton, NJ 08543
  800/522-3567
  609/520-4000

 EasyLink
 Services: e-mail, Telex, EDI
 Databases: access to major providers (DIALOG,
 CompuServe, etc.)
  AT&T EasyLink Services
  400 Interpace Pkwy.
  Parsippany, NJ 07054
  800/242-6005
  201/331-4000

 GEnie
 Databases: wide variety
  General Electric Information Services Co.
  401 N. Washington St.
  Rockville, MD 20850
  800/638-9636
  301/340-4000

 Mead Data Central
 Databases: news (NEXIS), legal (LEXIS)
  P.O. Box 933
  Dayton, OH 45401
  800/227-4908
  513/865-6800

 Maxwell Online
 Databases: medical (BRS),
 patent, trademark (ORBIT)
  8000 Westpark Dr.
  McClean, VA 22102
  ORBIT 800/456-7248
  BRS 800/289-4277

 MEDLARS
 Databases: medical
  National Library of Medicine
  8600 Rockville Pike
  Bethesda, MD 20894
  800/638-8480
  301/496-6193

 MCI Mail
 Services: e-mail, Telex, fax
 Databases: access to Dow Jones
  1133 19th St., NW
  Washington, DC 20036
  800/444-6245
  202/833-8484

 National Videotex Network
 Databases: wide variety
  5555 San Felipe, Suite 1200
  Houston, TX 77056
  800/336-9096
  713/877-4444

 NewsNet, Inc.
 Databases: newsletters
  945 Haverford Rd.
  Bryn Mawr, PA 19010
  800/952-0122
  215/527-8030

 PRODIGY
 Databases: wide variety, shopping
  445 Hamilton Ave.
  White Plains, NY 10601
  800/776-3449
  914/993-8848

 VU/TEXT Information Services, Inc.
 Databases: newspapers
  325 Chestnut St., Suite 1300
  Philadelphia, PA 19106
  800/323-2940
  215/574-4400

 WESTLAW
 Databases: legal (plus access to
 DIALOG and Dow Jones)
  West Publishing Co.
  610 Opperman Dr.
  St. Paul, MN 55123
  800/WESTLAW
  612/687-7000

 ZiffNet
 Databases: personal computer (technical,
 news, shopping)
  25 First St.
  Cambridge, MA 02141
  800/666-0330
  617/252-5000


OO
Object oriented.


OOA
See object-oriented analysis.


OOD
See object-oriented design.


OODB
See object-oriented database.


OODBMS
See object-oriented DBMS.


OOP
See object-oriented programming.


OOPL
(OOP Language)  See object-oriented programming.


OOPS
(Object Oriented Programming System)  See object-
oriented programming.


op amp
(Operational Amplifier)  Device that amplifies
analog signals.  It uses two inputs; one for power
and one for data.  It is used in myriads of
applications from communications to stereo.


op code
See operation code.


open
(1) To identify a disk or tape file for reading and
writing.  The open procedure "locks on" to an
existing file or creates a new one.

(2) With regard to a switch, open is "off."


open architecture
System in which the specifications are made public
in order to encourage third-party vendors to
develop add-on products.  Much of Apple's early
success was due to the Apple II's open
architecture.  The PC is open architecture.


Open Desktop
See SCO Open Desktop.


Open Look
X Window-based graphical user interface for UNIX
developed by Sun and defined and distributed by
AT&T.  It conforms to POSIX, ANSI C and XPG
standards.


open pipe
Continuous path from sender to receiver, such as
found in a circuit-switching network or leased
line.  Transmitted data is not broken up into
packets.


open shop
Computing environment that allows users to program
and run their own programs.  Contrast with closed
shop.


open system
Vendor-independent system that is designed to
interconnect with a variety of products.  It
implies that standards are determined from a
consensus of interested parties rather than one or
two vendors.  Contrast with closed system.  See
OSI.

   "Open systems" often refers to UNIX-based
computer systems, since UNIX runs on more different
kinds of hardware than any other operating
environment.  See OSF and X/Open.


OpenOSF
UNIX-based OSF/1 from Digital that runs on its
Alpha systems.


OpenView
Network management software from HP.  It supports
SNMP and CMIP protocols, and third-party products
that run under OpenView support SNA and DECnet
network management protocols.  OpenView is an
enterprise-wide network management solution.


OpenVMS
VMS operating system from Digital that is POSIX and
XPG3-compliant and runs on VAX and Alpha systems.


operand
The part of a machine instruction that references
data or a peripheral device.  In the instruction,
ADD A to B, A and B are the operands (nouns), and
ADD is the operation code (verb).  In the
instruction READ TRACK 9, SECTOR 32, track and
sector are the operands.


operating system
Master control program that runs the computer.  It
is the first program loaded when the computer is
turned on, and its main part, called the kernel,
resides in memory at all times.  It may be
developed by the vendor of the computer it's
running in or by a third party.

   It is an important component of the computer
system, because it sets the standards for the
application programs that run in it.  All programs
must "talk to" the operating system.

   Also called an executive or supervisor, it
performs the following functions.


                  Job Management
In small computers, it responds to commands from
the user and loads the requested application
program into memory for execution.  In large
computers, the operating system carries out its job
control instructions (JCL), which describe the
programs that must be run for an entire shift.


                  Task Management
In single tasking computers, the operating system
has virtually no task management to do, but in
multitasking computers, it is responsible for the
concurrent operation of one or more programs
(jobs).  Advanced operating systems have the
ability to prioritize programs so that one job gets
done before the other.

   In order to provide users at terminals with the
fastest response time, batch programs can be put on
lowest priority and interactive programs can be
given highest priority.  Advanced operating systems
can be fine-tuned by the computer operator so that
a specific job can be speeded up or slowed down.

   Multitasking is accomplished by executing
instructions for one function while data is coming
into or going out of the computer for another.
Large computers are designed to overlap these
operations, and data can move simultaneously in and
out of the computer through separate channels with
the operating system governing these actions.

   In small computers, the operating system can
monitor idle time when a user is interactively
working with a program to execute another program
in the background.  Even the milliseconds between
keystrokes can be used for something else.  A user,
pausing at the keyboard for just a couple of
seconds, is light years to the computer, which can
use that time to execute hundreds of thousands of
instructions.


                  Data Management
A major operating system function is to keep track
of data on disk; hence the term DOS, or disk
operating system.  The application program does not
know where the data is actually stored or how to
get it.  That knowledge is contained in the
operating system's access method, or device driver,
routines.  When a program is ready to accept data,
it signals the operating system with a message.
The operating system finds the data and delivers it
to the program.  Conversely, when the program is
ready to output, the operating system transfers the
data from the program onto the available space on
disk.


                 Device Management
In theory, the operating system is supposed to
manage all devices, not just disk drives.  It is
supposed to handle the input and output to the
display screen as well as the printer.  By keeping
the details of the peripheral device within the
operating system, a device can be replaced with a
newer model, and only the routine in the operating
system that deals with that device needs to be
replaced.

   In the PC world running DOS, software developers
often bypass the operating system, because DOS
either doesn't support the device or adds too much
performance overhead.  For example, developers with
graphics, word processing and desktop publishing
applications have become responsible for providing
drivers (routines) for all the popular displays and
printers, adding an enormous burden to their
development efforts.


                     Security
Multiuser operating systems maintain a list of
authorized users and provide password protection to
unauthorized users who may try to gain access to
the system.  Large operating systems also maintain
activity logs and accounting of the user's time for
billing purposes.  They also provide backup and
recovery routines to start over again in the event
of a system failure.


                      History
The earliest operating systems were developed in
the late 1950s to manage tape storage, but
programmers mostly wrote their own I/O routines.
In the mid 1960s, operating systems became
essential to manage disks, complex timesharing and
multitasking systems.

   Today, all multi-purpose computers from micro to
mainframe use an operating system.  Special-purpose
devices (appliances, games, toys, etc.) do not.
They usually employ a single program that performs
all the required I/O and processing tasks.


             Common Operating Systems
PCs use DOS, OS/2, SCO XENIX and AIX.  Apple II's
use ProDOS.  Macintoshes use the System along with
Finder and Multifinder, as well as A/UX.  Digital
uses VMS and ULTRIX.  IBM mainframes use MVS, VM
and VSE.

   In the past, when a vendor introduced a new
operating system, users had little understanding of
this behind-the-glass-enclosed-datacenter
phenomenon.  Today, it is squarely in their hands.

   Perhaps the Japanese have the right idea with
their TRON operating system.  It is intended to be
a common interface across all applications from a
microwave oven to the largest supercomputer!


operation code
The part of a machine instruction that tells the
computer what to do, such as input, add or branch.
The operation code is the verb; the operands are
the nouns.


operations
See datacenter.


operations research
See management science.


operator
Person who operates the computer and performs such
activities as commanding the operating system,
mounting disks and tapes and placing paper in the
printer.  Operators may also write the job control
language (JCL), which schedules the daily work for
the computer.


OPI
(Open Prepress Interface)  Extension to PostScript
by Aldus Corp. to provide a format for color
separations.


optical disk
Direct access disk written and read by light.  CDs,
CD ROMs and videodiscs are optical disks that are
recorded at the time of manufacture and cannot be
erased.  WORM disks are recorded in the user's
environment, but cannot be erased.

   Erasable optical disks function like magnetic
disks and can be rewritten over and over.  In the
late 1980s, a variety of erasable optical disks
were introduced that use magneto-optic, dye polymer
and phase change recording technologies.

   Throughout the 1990s, erasable optical disks may
become a viable alternative to magnetic disks.
Optical disks have greater storage capacity per
square inch than their magnetic counterparts, and
optical technology will eventually replace magnetic
media.  Lasers can be moved electronically and, in
time, will be built into a new breed of non-
spinning storage device that will dramatically
impact future computers.


optical fiber
Thin glass wire designed for light transmission,
capable of transmitting billions of bits per
second.  Unlike electrical pulses, light pulses are
not affected by random radiation in the
environment.

   When the telephone companies eventually replace
the copper wire from their central stations into
everyone's home with optical fiber, all varieties
of information services will be interactively
available to the consumer.  See FDDI, multi mode
fiber and single mode fiber.


optical isolator
Device used with current loop transmission that
uses an LED and photoresistor to detect current in
the line.


optical mouse
Mouse that uses light to get its bearings.  It is
rolled over a small desktop pad that contains a
reflective grid.  The mouse emits a light and
senses its reflection as it is moved.  Contrast
with mechanical mouse.


optical reader
Input device that recognizes typewritten or printed
characters and bar codes and converts them into
their corresponding digital codes.


optical recognition
See OCR.


optical scanner
See scanner.


optimizer
Hardware or software that improves performance.
See disk management.


optoelectronics
Merging light and electronics technologies, such as
in optical fiber communications systems.


OR
Boolean logic operation that is true if any of the
inputs is true.  An exclusive OR is true if only
one of the inputs is true, but not both.

             OR           EXCLUSIVE OR
       Inputs  Output    Inputs  Output
      ┌───────┬─────┐   ┌───────┬─────┐
      │ 0   0 │  0  │   │ 0   0 │  0  │
      │ 0   1 │  1  │   │ 0   1 │  1  │
      │ 1   0 │  1  │   │ 1   0 │  1  │
      │ 1   1 │  1  │   │ 1   1 │  0  │
      └───────┴─────┘   └───────┴─────┘



ORACLE
(1) Relational DBMS from Oracle Corp., Redwood
Shores, CA, that runs on a wide variety of
computers from micro to mainframe.  It was the
first DBMS to incorporate the SQL language.
Database applications can be created on a PC and
easily moved to other hardware platforms.

(2) (Oracle)  European broadcast television text-
message service.


Orange Book
See NCSC.



Order Info
DOS and Windows versions are available.  If you're
in Windows ALL THE TIME, order the Windows version.
It looks the same, but is a full Windows
application with scroll bars and buttons.

To order, contact Gary Smith at

              OEC SYSTEMS
       4646 North Shallowford Road
           Atlanta, GA 30338
            BBS [phone]
            FAX [phone]

          Voice [phone]
                [phone]

      Checks, M/C and Visa accepted.


   BE SURE TO MENTION THE NAME OF THIS BBS
        TO RECEIVE YOUR 20% DISCOUNT.


                    Regular   OEC/BBS
   Format            Price     price
  DOS 5.25"           $30       24
  DOS 3.5"            $30       24
  Windows 5.25"       $30       24
  Windows 3.5"        $30       24
   All disks are high-density!!

   GA residents, please add sales tax

   Shipping & handling, add:
                          U.S.   4.00
                        Canada   5.00
            To other countries  10.00

   COD, add $7

    FUTURE UPGRADES ARE ONLY $12.95


  ┌─────────────────────────────────────
  │ OTHER GLOSSARY PRODUCTS...


               **SITE LICENSES**
   Make everyone in your department "Computer
   Literate."  You can also add your own
   information to the Glossary and distribute it
   via the world's easiest-to-use dictionary
   software.


                  **BUNDLES**
   The Glossary is the perfect bundle or premium
   every PC user can enjoy.  The Glossary can be
   customized with "Compliments of..." on screen
   AT ALL TIMES.

      The Glossary helps users learn about the
   computers they just purchased.  It also adds
   value to software packages and membership
   promotions.  Some of the organizations that use
   the Glossary as a bundle or premium are...

         Acma Computer
         AICPA Information Technology Membership
         The Boston Computer Society
         Circuit Specialists
         ComputerWorld
         FM Computer
         HardFacts
         JM Computers
         Landmark Research Int'l.
         Personal Computing Tools
         Simply Better Computers
         ZiffNet


└───end of ordering information───────────────┘


ordinal number
Number that identifies the sequence of an item, for
example, record #34.  Contrast with cardinal
number.


orientation
In typography, the direction of print across a
page.  See portrait.


orphan
See widow & orphan.


OS
See operating system.


OS/2
Single user, multitasking operating system for PCs.
It is an advanced operating system that is not
confined to DOS' infamous 1MB limit.  Although new
commands have been added, many OS/2 commands are
the same as in DOS.  The first versions of OS/2
(Version 1.x) were written for 286s and were
developed jointly by IBM and Microsoft.  The
current OS/2 (Version 2.x) is written for 32-bit
386s and up and is solely the product of IBM.

   OS/2's graphical interface, called Presentation
Manager in Versions 1.x and the Workplace Shell in
Versions 2.x, is similar to Windows and the
Macintosh.  It is compliant with IBM's SAA and CUA
specfications.


              OS/2 16-bit Version 1.x
The first OS/2 versions (1.0, 1.1, etc.) are
written for the 16-bit 286.  Only one DOS
application of about 500K ran in compatibility
mode.  Version 1.3, called OS/2 Lite, requires 2MB
RAM instead of 4MB and includes Adobe Type Manager.
IBM's Extended Edition version includes
Communications Manager and Database Manager.


           OS/2 32-bit Version 2.x - IBM
Introduced in April 1992, this 32-bit version for
386s and up from IBM multitasks DOS, Windows and
OS/2 applications.  Data can be shared between
applications using the clipboard and between
Windows and PM apps using the DDE protocol.
Version 2.x provides each application with a 512MB
virtual address space, which allows huge and
complicated tasks to be easily managed.

   Version 2.1 supports Windows' Enhanced Mode and
applications that take full advantage of Windows
3.1.  It also provides support for more video
standards and CD ROM drives.

   IBM's Extended Services option adds
Communications Manager and Database Manager.


              Windows NT - Microsoft
Originally OS/2 Version 3.0, this 32-bit version
from Microsoft (to be released in 1993) was renamed
Windows NT.  OS/2 compatibility was dropped, then
reannounced.  Stay tuned!  See Windows NT.



OS/2 PM
(OS/2 Presentation Manager)  See OS/2.


OS/8
Single user, multitasking operating system from
Digital for its PDP-8 computers.  Variants run on
DECstation and DECmate systems.


OS/9
UNIX-like, realtime operating system from Microware
Systems Corp. for Motorola 68000 CPUs.  Originally
developed for the 6809 chip, a version was created
for CD-I players.


oscillate
To swing back and forth between the minimum and
maximum values.  An oscillation is one cycle,
typically one complete wave in an alternating
frequency.


oscillator
Electronic circuit used to generate high-frequency
pulses.  See clock.


oscilloscope
Test instrument that displays electronic signals
(waves and pulses) on a screen.  It creates its own
time base against which signals can be measured,
and display frames can be frozen for visual
inspection.


OSF
(Open Software Foundation)  Non-profit organization
dedicated to delivering an open computing
environment based on standards.  Formed in 1988, it
solicits technologies from industry, invites member
participation to set technical direction and
licenses software to members.  Address: 11
Cambridge Center, Cambridge, MA 02142, 617/621-
8700.  Following are the major OSF standards:

   OSF/1 is the operating system that uses Carnegie
Mellon's Mach kernel.  It is a B1-secure, symmetric
multiprocessing operating system that can run on
multiple processors within the same machine.
Compliant with POSIX, XPG3 and SVID base and kernel
extensions.

   Motif is a graphical user interface for
applications running on any system with X Window
Version 11.  Compliant with POSIX, ANSI C and XPG.

   Distributed Computing Environment (DCE) is a set
of integrated programs that provides an environment
for creating, using and maintaining client/server
applications on a network.  It includes security,
directory naming, time synchronization, file
sharing, RPCs and multithreading services.

   Distributed Management Environment (DME) is a
set of integrated programs that provides coherent
management of systems and networks.

   Architecture Neutral Distribution Format (ANDF)
supports developing portable applications.  The
developer generates an intermediate ANDF language
that can be shrink-wrapped.  The ANDF language is
compiled into machine language at install time in
the target machine.


OSI
(Open System Interconnection)  ISO standard for
worldwide communications that defines a framework
for implementing protocols in seven layers.

   Control is passed from one layer to the next,
starting at the application layer in one station,
proceeding to the bottom layer, over the channel to
the next station and back up the hierarchy.

   Similar functionality exists in all
communications networks; however, existing non-OSI
systems often incorporate two or three layers of
functionality into one.

   Most vendors have agreed to support OSI in one
form or another; however OSI serves more as a model
than a universal standard.  Many OSI components are
too loosely defined, and proprietary standards are
entrenched.  One exception is the OSI-compliant
X.400 e-mail protocol that is widely implemented.
See OSI model.


OSI model

      User
        │          Meaningful information.
  ┌─────┴──────┐   The purpose for communicating.
 7│Application │   E-mail, file transfers,
  └─────┬──────┘   transactions.
  ┌─────┴──────┐
 6│Presentation│   Transfer syntax.
  └─────┬──────┘
  ┌─────┴──────┐   Coordinates
 5│  Session   │   overall
  └─────┬──────┘   communications.
  ┌─────┴──────┐
 4│ Transport  │   End to end control.
  └─────┬──────┘
  ┌─────┴──────┐   Routes data from sending
 3│  Network   │   to receiving station.
  └─────┬──────┘
  ┌─────┴──────┐   Node to node control.
 2│ Data Link  │   (Token Ring, Ethernet, SDLC
  └─────┬──────┘    X.25, Xmodem, Zmodem)
        │
  ┌─────┴──────┐   Transmission type,
 1│  Physical  │   encoding method, speeds,
  │            │   cable, plugs.
  └─────▄──────┘   (RS-232, TDM, FDM)
        █
        █ Transmission medium (twisted pair,
        █                      coax, optical fiber)
  ┌─────▀──────┐
 1│  Physical  │
  └────────────┘


               Application - Layer 7
Defines the rules for gaining entrance into the
communications system.  Programs communicate with
other programs through this layer.


              Presentation - Layer 6
Negotiates and manages the way data is represented
and encoded.  Provides a common denominator for
transferring data from different systems, ASCII,
EBCDIC, binary, etc.


                 Session - Layer 5
Provides coordination of the communications in an
orderly manner.  For example, it marks significant
parts of the transmitted data to ensure that the
entire message is received properly.


                Transport - Layer 4
Responsible for end to end validity and integrity
of the transmission.  "OSI transport services"
include layers 1-4, collectively responsible for
getting the bits from the sending station to the
receiving station.


                 Network - Layer 3
Establishes the route between the sending and
receiving stations.  For example, this layer is the
switching function of the dial-up telephone system.


                Data Link - Layer 2
Responsible for node to node validity and integrity
of the transmission.  See data link protocol.


                Physical - Layer 1
Defines functional characteristics for passing data
bits onto and receiving them from the connecting
medium.  For example, it includes the RTS (request
to send) and CTS (clear to send) signals in an RS-
232 environment, as well as the TDM (time division
multiplexing) in an ISDN environment.

   Note: Electrical and mechanical characteristics
define the interface between the OSI environment
and the connecting transmission medium.


OTPROM
(One Time PROM)  PROM chip that can be programmed
only once.


out of band
See signaling out of band.


outdent
Same as hanging indent and hanging paragraph.


outline font
Type of font made from basic outlines of each
character.  The outlines are scaled into actual
characters (bitmaps) before printing.  See scalable
font.


outline processor
Software that allows the user to type in thoughts
and organize them into an outline form.


output
(1) Any computer-generated information displayed on
screen, printed on paper or in machine readable
form, such as disk and tape.

(2) To transfer or transmit from the computer to a
peripheral device or communications line.


output area
Reserved segment of memory used to collect data to
be transferred out of the computer.  Same as
buffer.


output bound
Excessive slowness due to output functions,
typically slow-speed communications lines or
printers.  See print buffer.


output device
Any peripheral that presents output from the
computer, such as a screen or printer.  Although
disks and tapes receive output, they are called
storage devices.


outsourcing
Contracting with outside consultants, software
houses or service bureaus to perform systems
analysis, programming and datacenter operations.
See facilities management.


OverDrive
Intel's 486 upgrade CPUs.  See 486.


overflow error
Error that occurs when calculated data cannot fit
within the designated field.  The result field is
usually left blank or is filled with some symbol to
flag the error condition.


overhead
(1) Amount of processing time used by system
software, such as the operating system, TP monitor
or database manager.

(2) In communications, the additional codes
transmitted for control and error checking.


overlay
(1) Preprinted, precut form placed over a screen,
key or tablet for indentification purposes.  See
keyboard template.

(2) Program segment called into memory when
required.  When a program is larger than the memory
capacity of the machine, the parts of the program
that are not in constant use can be set up as
overlays.  When called in, the contents of the
previous overlay is lost.  Virtual memory is a
system of automatic overlays.


overlay card
Controller that digitizes NTSC signals from a video
source for display in the computer.


overloading
In programming, the ability to use the same name
for more than one variable or procedure, requiring
the compiler to differentiate them based on
context.


overscan
Area outside of the normal rectangular viewing area
on a display screen.  Contrast with underscan.


overstrike
(1) To type over an existing character.

(2) Character with a line through it.


overwrite
(1) Data entry mode that writes over existing
characters on screen when new characters are typed
in.  Contrast with insert mode.

(2) To record new data on top of existing data such
as when a disk record or file is updated.



p-code
See pseudo language and UCSD p-System.


p-System
See UCSD p-System.


P24T
See Pentium.


P5
See Pentium.


PA
See HP Precision Architecture.


PABX
(Private Automatic Branch eXchange)  Same as PBX.


PACBASE
Integrated CASE software for IBM, Bull HN and
Unisys mainframes from CGI Systems, Pearl River,
NY.  It supports a wide variety of databases
including DB2 and Oracle.  PACLAN is the version
for PCs running on LANs.


pack
(1) To compress data in order to save space.
Unpack refers to decompressing data.  See data
compression.

(2) Instruction that converts a decimal number into
a packed decimal format.  Unpack converts a packed
decimal number into decimal.

(3) In database programs, a command that removes
records that have been marked for deletion.


package
See software package.


packaged software
See software package.


packed decimal
Storage mode that places two decimal digits into
one byte, each digit occupying four bits.  The sign
occupies four bits in the least significant byte.


packet
Frame or block of data used for transmission in
packet switching and other communications methods.


packet cellular
Transmission of data over the cellular network.
Data is divided into packets, or frames, for error
checking.  Contrast with circuit cellular.  See
CDPD and wireless.


packet radio
Wireless transmission of data, which is divided
into packets, or frames, for error checking.  See
Ardis, Mobiltex and wireless.


packet switching
Technique for handling high-volume traffic in a
network by breaking apart messages into fixed
length packets that are transmitted to their
destination through the most expedient route.  All
packets in a single message may not travel the same
route (dynamic routing).  The destination computer
reassembles the packets into their proper sequence.

   This method efficiently handles messages of
different lengths and priorities in large networks,
such as Telenet, Tymnet and AT&T's Accunet.  X.25
is the international standard for such a network.

   Packet switching networks also provide value
added services, such as protocol conversion and
electronic mail.


packetized voice
Transmission of realtime voice in a packet
switching network.


packing density
Number of bits or tracks per inch of recording
surface.  Also refers to the number of memory bits
or other electronic components on a chip.


pad
(1) To fill a data structure with padding
characters.

(2) (PAD)  (Packet Assembler Dissassembler)
Communications device that formats outgoing data
into packets of the required length for
transmission in a packet switching network.  It
also strips the data out of incoming packets.


padding
Characters used to fill up unused portions of a
data structure, such as a field or communications
message.  A field may be padded with blanks, zeros
or nulls.


paddle
Input device that moves the screen cursor in a
back-and-forth motion.  It has a dial and one or
more buttons and is typically used in games to hit
balls and steer objects.  See joy stick.


page
(1) In virtual memory systems, a segment of the
program that is transferred into memory.

(2) In videotex systems, a transmitted frame.

(3) In word processing, a printed page.


page break
In printing, a code that marks the end of a page.
A "hard" page break, inserted by the user, breaks
the page at that location.  "Soft" page breaks are
created by word processing and report programs
based on the current page length setting.


page description language
Device-independent, high-level language for
defining printer output.  If an application
generates output in a page description language,
such as PostScript, the output can be printed on
any printer that supports it.

   Much of the character and graphics shaping is
done within the printer rather than in the user's
computer.  Instead of downloading an entire font
from the computer to the printer, which includes
the design of each character, a command to build a
particular font is sent, and the printer creates
the characters from font outlines.  Likewise, a
command to draw a circle is sent to the printer
rather than sending the actual bits of the circle
image.


page fault
Virtual memory interrupt that reads the required
page from disk when the next instruction or item of
data is not in memory.


page frame
See EMS.


page header
Common text that is printed at the top of every
page.  It generally includes the page number and
headings above each column.


page makeup
Formatting a printed page, which includes the
layout of headers, footers, columns, page numbers,
graphics, rules and borders.


page mode memory
Common dynamic RAM chip design.  Memory bits are
accessed by row and column coordinates.  Without
page mode, each bit is accessed by pulsing the row
and column select lines.  With page mode, the row
(page) is selected only once for all bits (columns)
within the row, resulting in faster access.


page printer
Type of printer that prints a page at a time.  See
laser printer and ion deposition.


page recognition
Software that recognizes the content of a printed
page which has been scanned into the computer.  It
uses OCR to convert the printed words into computer
text and should be able to differentiate text from
other elements on the page, such as pictures and
captions.


PageMaker
Full-featured desktop publishing program for the PC
and Macintosh from Aldus Corp., Seattle, WA.
Originally introduced for the Mac in 1985, it set
the standard for desktop publishing.  In fact, Paul
Brainerd, president of Aldus, coined the term
desktop publishing.  The PC version was introduced
in 1987.


pagination
(1) Page numbering.

(2) Laying out printed pages, which includes
setting up and printing columns, rules and borders.
Although pagination is used synonymously with page
makeup, the term often refers to the printing of
long manuscripts rather than ads and brochures.


paging
In virtual memory, the transfer of program segments
(pages) into and out of memory.


paint
(1) In computer graphics, to "paint" the screen
using a tablet stylus or mouse to simulate a
paintbrush.

(2) To transfer a dot matrix image as in the phrase
"the laser printer paints the image onto a
photosensitive drum."

(3) To create a screen form by typing anywhere on
screen.  To "paint" the screen with text.


paint program
Graphics program that allows the user to simulate
painting on screen with the use of a graphics
tablet or mouse.  Paint programs create raster
graphics images.


PAL
(1) (Paradox Application Language)   Paradox's
programming language.

(2) (Programmable Array Logic)  Programmable logic
chip (PLD) technology from Advanced Micro Devices.

(3) (Phase Alternating Line)  European TV standard
that uses 625 lines of resolution (100 more than
NTSC).


palette
(1) In computer graphics, the total range of colors
that can be used for display, although typically
only a subset of them can be used at one time.  May
also refer to the collection of painting tools
available to the user.

(2) Set of functions or modes.


palmtop
Computer small enough to hold in one hand and
operate with the other.  Palmtops may have
specialized keyboards or keypads for data entry
applications or have small qwerty keyboards.


pan
(1) In computer graphics, to move (while viewing)
to a different part of an image without changing
magnification.

(2) To move (while viewing) horizontally across a
text record.


paper tape
(1) Slow, low-capacity, sequential storage medium
used in the first half of the 20th century to hold
data as patterns of punched holes.

(2) Paper roll printed by a calculator or cash
register.


paperless office
Long predicted, the paperless office is still a
myth.  Although paper usage has been reduced in
some organizations, it has increased in others.
Today's PCs make it easy to churn out documents.

   In time, laptop computers with immense storage
and high-resolution screens will serve to replace
paper when travelling.  Optical fiber networks will
make it easy to send data, pictures, voice and
video quickly.

   As color laser printers become commonplace, it
will be easy to reproduce any document, no matter
how complex.  People will eventually get used to
the idea that a paper document is no better proof
of a transaction than its electronic form.  When
this occurs, the paperless office will arrive.


paradigm
Pronounced "para-dime."  A model, example or
pattern.


Paradise
Video display boards from the Paradise subsidiary
of Western Digital Corp., Irvine, CA.


Paradox
Network-ready relational DBMS for PCs from Borland
known for its ease of use and query by example
method for asking questions.  Its PAL programming
language is unique.  Many PAL statements are
interactive Paradox commands, so that a Paradox
user can adjust to programming more easily.
Version 4.0 supports memo fields and BLObs.

   The Paradox engine (available separately) lets C
applications access Paradox databases.


paragraph
In DOS programming, a 16 byte block.  Memory
addresses are generated as "segment:offset," where
the segment is expressed in paragraphs.  To compute
an address, the segment register is shifted left
four bits (multiplying it by 16).  For example, the
address A000:0100 = 655,616:

     Segment    A000     655,360 (40,960 X 16)
     Offset      0100        256
     Result     A0100    655,616

   This means there are 4,096 possibilities for
expressing each memory byte, a situation that has
helped generate confusion and bugs.


paragraph tag
In desktop publishing, a style sheet assigned to a
text paragraph.  It defines font, tab, spacing and
other settings.


parallel computing
Solving a single problem with multiple computers or
computers made up of multiple processors.  See
array processor and hypercube.


parallel interface
Multiline channel that transfers one or more bytes
simultaneously.  For example, personal computers
often connect printers via a Centronics 36-wire
parallel interface, which transfers one byte at a
time over eight wires, the remaining wires used for
control signals.  Large computer parallel
interfaces transfer more than one byte at a time.
Contrast with serial interface.  See Centronics.


parallel port
I/O attachment used to hook up a printer or other
parallel interface device.  On a PC, it is a 25-pin
female DB-25 connector.  See printer cable.


parallel processing
(1) Architecture within a single computer that
performs more than one operation at the same time.
See pipeline processing and vector processor.

(2) Multiprocessing architecture made up of
multiple CPUs or computer systems.  Either one
operation is performed on many sets of data (SIMD),
or different parts of the job are worked on
simultaneously (MIMD).  See hypercube and
multiprocessing.


parallel transmission
Transmitting data one or more bytes at a time.
Contrast with serial transmission.


parallelizing
To generate instructions for a parallel processing
computer.


parameter
(1) Any value that customizes a program.
Parameters include such information as file names,
coordinates, ranges of values and specific codes.
They are often entered along with the program name
when the program is loaded.  See DOS switch.

(2) In programming, a value passed to a subroutine
or function for processing.


parameter-driven
Software that requires external values.  It solves
a problem that is partially or entirely described
by the values (parameters) that are entered.


PARC
(Palo Alto Research Center)  Xerox's research and
development center where the Smalltalk programming
language and GUI interface were developed.
Established in 1970, it is located in the Stanford
Univ. Industrial Park, Palo Alto, CA.


parent-child
In database management, a relationship between two
files.  The parent file contains required data
about a subject, such as employees and customers.
The child is the offspring; for example, the child
of a customer file may be the order file.


parent program
Main, or primary, program or first program loaded
into memory.  See child program.


parity bit
Extra bit attached to the byte, character or word
used to detect errors in transmission.


parity checking
Error detection technique that tests the integrity
of digital data within the computer system or over
a network.  Parity checking uses an extra ninth bit
that holds a 0 or 1 depending on the data content
of the byte.  Each time a byte is transferred or
transmitted, the parity bit is tested.

   Even parity systems make the parity bit 1 when
there is an even number of 1 bits in the byte.  Odd
parity systems make it 1 when there is an odd
number of 1 bits.


parity drive
Separate disk drive that holds parity bits in a
disk array.  See RAID.


parity error
Error condition that occurs when the parity bit of
a character is found to be incorrect.


park
To retract the read/write head on a hard disk to
its home location before the unit is physically
moved in order to prevent damage.  Most modern
drives park themselves when the power is turned
off.


parse
To analyze a sentence or language statement.
Parsing breaks down words into functional units
that can be converted into machine language.  For
example, to parse the dBASE expression

   sum salary for title = "MANAGER"

   SUM must be identified as the primary command,
FOR as a conditional search, TITLE as a field name
and MANAGER as the data to be searched.

   Parsing breaks down a natural language request,
such as "What's the total of all the managers'
salaries" into the commands required by a high-
level language, such as in the example above.


parser
Routine that performs parsing operations on a
computer or natural language.


partition
Reserved part of disk or memory that is set aside
for some purpose.


Pascal
High-level programming language developed by Swiss
professor Niklaus Wirth in the early 1970s and
named after the French mathematician, Blaise
Pascal.  It is noted for its structured
programming, which caused it to achieve popularity
initially in academic circles.  Pascal has had
strong influence on subsequent languages, such as
Ada, dBASE and PAL.  See Turbo Pascal.

   Pascal is available in both interpreter and
compiler form and has unique ways of defining
variables.  For example, a set of values can be
stated for a variable, and if any other value is
stored in it, the program generates an error at
runtime.  A Pascal set is an array-like structure
that can hold a varying number of predefined
values.  Sets can be matched and manipulated
providing powerful non-numeric programming
capabilities.

   The following Turbo Pascal example converts
Fahrenheit to Celsius:

   program convert;
   var
   fahr, cent : integer;
   begin
    write('Enter Fahrenheit ');
    readln(fahr);
    cent := (fahr - 32) * 5 / 9;
    writeln('Celsius is ',cent)
   end.



Pascaline
Calculating machine developed in 1642 by French
mathematician Blaise Pascal.  It could only add and
subtract, but gained attention because 50 units
were placed in prominent locations throughout
Europe.  Accountants expressed grave concern that
they might be replaced by technology!


passive matrix
Common LCD technology used in laptops.  See LCD.


passive star
Network topology that joins wires from several
nodes without providing any additional processing.
Contrast with active star.  See hub.


password
Word or code used to serve as a security measure
against unauthorized access to data.  It is
normally managed by the operating system or DBMS.
However, the computer can only verify the
legitimacy of the password, not the legitimacy of
the user.  See NCSC.


paste
See cut & paste.


patch
Temporary or quick fix to a program.  Too many
patches in a program make it difficult to maintain.
It may also refer to changing the actual machine
code when it is inconvenient to recompile the
source program.


path
(1) In communications, the route between any two
nodes.  Same as line, channel, link or circuit.

(2) In database management, the route from one set
of data to another, for example, from customers to
orders.

(3) The route to a file on a disk.  In DOS and
OS/2, the path for file MYLIFE located in
subdirectory STORIES within directory JOE on drive
C: looks like:

            c:\joe\stories\mylife


   The equivalent UNIX path is (UNIX knows which
drive is used):

            /joe/stories/mylife


   The Macintosh also uses a path in certain
command sequences; for example, with "hard disk" as
the drive, path is:

          hard disk:joe:stories:mylife


   See DOS Path and DOS abc's.


PATHWORKS
Family of network software from Digital that lets a
VAX function as a file and print server for DOS and
OS/2 workstations.  DOS and OS/2 servers may also
use PATHWORKS services.  Protocols such as DECnet,
TCP/IP, AppleTalk and NetWare, are supported.


PAX
(1) (Private Automatic Exchange) Inhouse intercom
system.

(2) (Parallel Architecture Extended)  Parallel
processing environment standard based on Intel's
i860 RISC chip, UNIX System V and Alliant
Computer's parallel and 3-D graphics technologies.


PAX-1
Software from VXM Technologies, Boston, MA, that
allows a network of computers to function as a
single parallel processing system.  It runs in an
Ethernet network under TCP/IP and supports personal
computers, minis and mainframes.


payware
Software distributed for money.  Contrast with
freeware.


PBX
(Private Branch eXchange)  Inhouse telephone
switching system that interconnects telephone
extensions to each other, as well as to the outside
telephone network.  It may include functions such
as least cost routing for outside calls, call
forwarding, conference calling and call accounting.

   Modern PBXs use all-digital methods for
switching and can often handle digital terminals
and telephones along with analog telephones.


PC
(1) (Personal Computer)  Machines that conform to
the PC standard, originally developed by IBM and
subsequently governed by Intel, Microsoft and major
PC vendors collectively.  The PC is the world's
largest computer base; 1992 estimates are from 50
to 80 million units.  A rather wide range, one
wonders who's keeping count.

(2) (Personal Computer)  Any personal computer.

(3) Sometimes refers to first-generation IBM models
PC, XT and AT in contrast with second-generation
PS/2s.

(4) See printed circuit board.


                      THE PC
In this Glossary, PC refers to definition #1 above.

   PCs are used as stand-alone personal computers
or as workstations and file servers in a local area
network.  They are predominantly used as single-
user systems under DOS; however, they are also used
as a central computer in a multiuser environment
under UNIX and other operating systems.

   IBM's first PCs used acronyms and names: XT, AT,
Convertible, etc.  The PS/2 series use numbers:
Model 30, 55, 80, etc. (see IBM PC).  Compatibles
often use the CPU designation in the name, such as
"386 Turbo."

   Although there are literally thousands of PC
vendors, from mom and pop shops to large mail order
houses to the major computer companies (Compaq, HP,
Digital, etc.), and IBM, the world's largest, all
PCs fit into the following categories:


                      THE CPU
The brains of the PC is a CPU, or processor, from
the Intel 8086 family (x86) of microprocessors.
Increasingly, Intel-compatible CPUs from Advanced
Micro Devices and Cyrix Corp. are being used.

XT CLASS - 8086, 8088
The original PC launched by IBM in 1981 used the
16-bit 8088 CPU.  This architecture was chosen by
IBM because it was similar to the major personal
computer base of that time (Z80 CPU running the
CP/M operating system).  It allowed vendors to
easily migrate their applications from CP/M to the
IBM PC, which they did rather quickly.

   Unfortunately, the design of the Intel 8088 was
not only limited to one megabyte of memory, but was
limited in scope and flexibility for the future
(who knew this would become the world's greatest
hardware standard).  This architecture has caused
enormous confusion and problems for software
developers and users alike.  Although more advanced
CPUs (286, 386, etc.) came later, they had to build
in operating modes that conformed to the original
standard in order to run all PC applications on the
market.  Even today, all DOS applications are still
written to the original limitations of the first
PC.

   Today, these first PCs, known as XT-class
machines, survive in a second-hand market.  They
are used for many data processing functions, but
are too slow for intensive graphics or Windows
applications.  Memory can be increased beyond one
megabyte using expanded memory (EMS).


AT CLASS - 286
First used in the IBM AT in 1984, the 286's 16-bit
CPU is capable of addressing up to 16 megabytes of
memory.  However, until DOS extenders and Windows
3.0 (see "Operating Environment" below), this
"extended memory" was not widely used.

   AT-class machines are fast enough for many
applications, but are still sluggish under Windows
and are not geared for future 32-bit applications
and operating systems, such as Windows NT.


386, 486, Pentium
First used by Compaq in 1986, the 386, or 386DX, is
a 32-bit machine that runs faster than the 286 and
can address an unbelievable four gigabytes of
memory, although motherboards generally only have
slots for up to 16, 32 or 64 megabytes.  Its
flexible architecture allows both extended and
expanded (EMS) memory to be allocated on demand
(see memory allocation).  386s will also run
Windows NT and other future 32-bit applications and
operating systems.

   The 386SX is slower than the 386, but retains
its same advanced features.  The 386SL is designed
for battery conservation in laptops.

   With initial models introduced in late 1989, the
486, or 486DX, is about twice as fast as the 386
and has a built-in math coprocessor, which is
typically required by CAD programs.  The 486 is
suited for today's demanding applications.  The
486SX runs at slower speeds than the 486DX and
makes the coprocessor an optional item.

   Introduced in 1993, the Pentium is the successor
to the 486 and is currently the fastest CPU in the
Intel x86 family.  It will linitially be used as a
server and high-end CAD workstation.


                │
                │Extended│
                │ Memory │
                │ 1MB and│
                │   up   │
   ┌──────┐- - -├────────┤- - - - - - -
   │ 8088 │     │  286   │ Conventional
   │ 8086 │     │  386   │    Memory
   │ (XT) │     │  486   │  Up to 1MB
   │      │     │Pentium │
   └─────┘     └───────┘
      │             │
   ┌───────────────────────────────
   │   Expanded memory (EMS)
   └──────────────────────────────────

          CPUs AND MEMORY TYPES



   ┌───────────────────────────────────┐
   │  For more details on Intel CPUs,  │
   │  look up x86 in this Glossary.    │
   │                                   │
   │ Also look up the invidivual CPUs: │
   │ 286, 386, 486, etc.               │
   └───────────────────────────────────┘




               OPERATING ENVIRONMENT
Almost all PCs use Microsoft's DOS operating
system, which was developed for the 8088 CPU that
could only address one megabyte of RAM.  The PC was
also designed so that the first 640K of the one
megabyte is used for applications, while the next
384K (upper memory area, UMA) is used by the
operating system to control peripheral devices (see
PC memory map).  Since some of the 640K is also
used by DOS, only about 570K to 600K is available
to user programs.

   As users became comfortable with PCs, they
wanted more than one application open and active at
the same time.  In order to get around DOS' single
task nature and the PC's 640K limit, a variety of
add-ons, techniques and remedies have been created
to solve this dilemma.  Following is a synopsis.


TSRs
In 1984, Borland introduced Sidekick and
popularized the TSR, or popup, program.  Sidekick
stayed in memory but swapped in and out of view by
pressing a hotkey, and users could instantly switch
to a handy phone directory or notepad.  However,
keeping many TSRs in memory may not leave room for
important, big applications, and TSRs are known to
cause conflicts.


EXPANDED MEMORY
In 1984, expanded memory (EMS) was created to break
the one megabyte barrier.  An EMS board with
multiple megabytes of RAM could be plugged in, and
its memory used directly by EMS applications.

   Lotus 1-2-3 quickly took advantage of it and
hundreds of other applications have been written to
use it.  EMS can be installed in all PCs from XTs
on up, a major advantage when XTs were purchased
widely.  See EMS for details.


TASK SWITCHERS AND MULTITASKERS
Programs such as Software Carousel extend DOS's
capabilities by allowing the user to keep a variety
of programs open at the same time and switch back
and forth between them.  These "task switchers" use
EMS memory, extended memory and/or the hard disk to
swap applications in and out of conventional
memory.

   Combining multitasking with task switching,
Quarterdeck's popular DESQview was the first
control program to use expanded (EMS) memory to
allow programs to run in, not just reside in, the
background.


MEMORY MANAGERS
Memory managers were developed to store TSRs and
other memory-resident software (drivers) in the
384K upper memory area (UMA), thus freeing more
precious "conventional memory" in the 640K region.

   Memory managers manage both extended and EMS
memory, and products, such as QEMM-386, 386MAX and
DOS 6's EMM386.EXE, can allocate both types on
demand on 386s and up.  See DOS memory manager and
memory allocation.


EXTENDED MEMORY AND WINDOWS 3.X
By the late 1980s, the DOS extender was introduced,
which is software that allows DOS applications to
run in, not just reside in, extended memory in 286s
and up.  Paradox 386 and Lotus 1-2-3 Version 3.0
were some of the first programs to use it.

   Windows 3.x uses its own DOS extender to manage
up to 16MB of memory, which lets users launch, keep
active and switch between several Windows and DOS
applications.  Windows is making the PC more
cohesive, and its Macintosh-like desktop
environment is very popular.  See Windows.


DOS 5
DOS 5 added a task switching capability that runs
multiple DOS applications and swaps inactive ones
to disk.  It has improved memory management and can
load part of itself into the 1024-1088K HMA region.
It can also load TSRs and drivers into the upper
memory area (UMA).


DOS 6
DOS 6 has improved memory management and realtime
compression (doubles disk capacity).  New utility
programs are designed to make running DOS easier.


DR DOS
DR DOS is a DOS-compatible operating system with
advanced features that has always inspired
Microsoft to include similar functionality in
subsequent DOS releases.  DR DOS stores TSRs and
drivers in upper memory, and Version 6.0 includes
realtime compression that doubles hard disk
capacity.


THE NEXT GENERATION: OS/2 AND WINDOWS NT
The OS/2 operating system, initially developed by
IBM and Microsoft, was originally written for 286s
and up.  Joint development was disbanded, and in
1992, IBM introduced its own Version 2.0, which
runs on 386s and up and manages large amounts of
memory (see OS/2).  Its Workplace Shell graphical
user interface is similar to Windows, and this
version of OS/2 is highly regarded.

   Microsoft turned its development of OS/2 into
Windows NT (scheduled for 1993), a redesigned
operating system for 386s and up.  It runs current-
day DOS and Windows software as well as Windows NT
applications.  OS/2 compatibility is unclear.


                   THE BAD NEWS
The transition from DOS to Windows NT and OS/2 may
take years, just like it did to convert from the
old mainframe DOS to OS in the 1960s and 1970s.  In
the meantime, TSRs, EMS, memory managers, task
switchers, Windows, DESQview, DR DOS, DOS
extenders, DOS 5 and DOS 6 all compete to make the
PC more usable.  It's a nightmare for the micro
manager!


                   THE GOOD NEWS
If somebody already set up your PC, you may not
have to deal with any of the bad news!

   Also, DOS and Windows are entrenched.  You
should be able to buy DOS and Windows software
packages for years to come.  Any operating
environment that runs on the desktop must run these
programs.

   People are demanding Windows.  While this
environment is complicated to develop for, it
offers more consistency across all applications
than straight DOS programs.  Windows' multimedia
capabilities also bring a new level of enjoyment to
using computers.



                 INPUT AND OUTPUT
There are three ways of getting data into and out
of the PC.  The first is via the keyboard, which
plugs into a keyboard connector always built onto
the motherboard.  The keyboard plugs directly into
the 5-pin DIN receptacle.  The PS/2 uses a 6-pin
mini-DIN connector.

   The second is via the data bus, or expansion
bus, which is a set of slots on the motherboard.
Expansion boards, or cards, are plugged into the
slots and contain cables to their respective
devices.  These cards are control circuits for disk
drives, the video display, CD ROM reader and
network adapter for example.  See PC conflicts.

   The third way is through serial and parallel
ports which are input/output pathways built into
the motherboard or contained on a separate
expansion board.  On the back of the PC, there are
typically two serial ports (one 9-pin male and one
25-pin male).  In DOS, the first port is named
COM1, and the second is COM2.  Both ports provide
the same capability.  The parallel port (LPT1) uses
a 25-pin female connector on the PC.

   The serial ports are typically used for modems,
mice, scanners and digitizer tablets, and the
parallel port is used for the printer, although
some printers use a serial port.  Both serial and
parallel ports can be used for file transfer
between two computers cabled together.

   Mice can be purchased for either the serial port
(serial mouse) or for connection via an expansion
board (bus mouse).  Some scanners and printers
require an expansion board, which accompanies the
product when you buy it and must be plugged into
the PC.



            DATA BUS (EXPANSION SLOTS)
The original PC used an 8-bit bus (transfers 8 bits
simultaneously) known as the PC or XT bus.  With
the 286-based AT model, the bus was extended to 16-
bits.  Machines come with a mix of 8-bit and 16-bit
slots.  8-bit cards fit in both slots, but 16-bit
cards require 16-bit slots.

   When IBM introduced the PS/2 line, it switched
from the AT bus to the high-speed 32-bit Micro
Channel (MCA) bus.  The MCA also provides bus
mastering, which has yet to be exploited.  Later,
IBM introduced PS/2 models with the original AT-
bus, now known as the ISA ("i-suh") bus.  ISA and
MCA cards are not interchangeable.

   To counter the Micro Channel and extend the life
of the original bus, EISA ("e-suh") was conceived
by the compatible vendors in late 1988.  EISA
accepts new 32-bit EISA boards as well as the
original 8-bit and 16-bit boards.  See ISA, EISA
and Micro Channel.



                   VIDEO DISPLAY
Since 1981, IBM has introduced several display
standards, implemented by plugging a graphics
adapter into an expansion slot and connecting the
appropriate monitor to it.  Each new standard
incorporates the previous ones for compatibility;
however, vendors have to modify their programs to
handle the higher resolution graphics each time.

   Unlike the graphics-based Macintosh, PCs operate
in two software-selectable modes: text mode
(character mode) and graphics mode.  Prior to
Windows 3.x applications, which are graphics based
like the Mac, most business applications were text
based and text scrolled quickly on the earliest
PCs.  The graphics computations required to display
Windows applications on screen take longer than
text-based programs.  As a result, specialized
display adapters, known as graphics accelerators,
perform common graphics functions within their own
chips and improve on-screen Windows performance
dramatically, even on slow PCs.

   For demanding desktop publishing and CAD
requirements, there are many very-high-resolution
graphics systems (display adapter and monitor) from
third parties.  To use them, the user plugs in a
graphics adapter into the PC and installs driver
software that works with popular software packages,
such as AutoCAD and Windows.  However, once a
display system becomes widely used, it may be
supported by the software vendors.  The following
list shows the highest-resolution for each display
type.  For details, see PC display modes.


          COMMON PC DISPLAY STANDARDS

                IBM STANDARDS
MDA       720x350 text only, monochrome
Hercules  720x348 text/graphics (mono/non-IBM)
CGA       320x200 text/graphics (4 cols)*
EGA       640x350 text/graphics (16 cols)*
MCGA      640x400 text-320x200 graphics (256 cols)
VGA       720x400 text-640x480 graphics (16 cols)*
8514     1024x768 text/graphics (256 cols)
XGA      1024x768 text/graphics (256 cols)
*  More colors available from 3rd-party vendors.

                VESA STANDARDS
                 (Super VGA)
          640x480 ┐
          800x600 │ text/graphics in 16, 256,
         1024x768 │  32K, 64K and 16M colors
        1280x1024 ┘

   Note: High-end graphics systems provide
resolutions up to 2000x2000 pixels.



                     PRINTERS
There are hundreds of printer models that work with
PCs from dot matrix to ink jet to laser printers
and most of them plug into the PC's parallel port.
Printing text files directly from DOS works with
all printers, but in order to select fonts,
boldface, underline and other print attributes, the
application must support the printer.

   Word processing, desktop publishing, CAD and any
other package that offers full-featured printing,
provides drivers for the popular printers.  These
drivers are selected by the user when installing
the program, and fonts installed for one
application are often not sharable by another.

   One of the significant advantages of Windows is
that once the printer installation has been
performed for Windows, every Windows application
can use all the installed fonts.  All Windows
applications use the print services in Windows to
do their printing.  Once products such as
LaserMaster's WinJet system, which extends Windows'
printing capabilities, is hooked into Windows, then
all applications use it.  In either case, Windows
provides a single, central facility for managing
all the installed fonts and doing the printing.



                     KEYBOARDS
The original PC keyboard used an awkward return and
left shift key placement.  Finally corrected on the
AT keyboard, the backspace key was made harder to
reach.  Then came the Enhanced keyboard with a host
of relocated keys, making it impossible to assign
function keys intelligently.  What was easy to
reach on one is hard to reach on the other.  Only a
few keyboards, such as Northgate's Omnikey 102,
dare to be different and incorporate the best
features of both.

   Some laptop keyboards are worse than the first
PC keyboards, placing often-used Ctrl and Alt keys
in hard to reach locations and forcing users to
press the Fn key for commonly-used functions.
Touch typists beware!



                   FLOPPY DISKS
The most common floppy is the 360KB, 5.25" disk
introduced soon after the first IBM PC.  Later, the
AT model introduced the 1.2 megabyte floppy.  The
1.2MB drives can read and write the 360KB disks,
but earlier models of the drive cannot be used to
format 360KB disks.

   IBM introduced the 720KB, 3.5" microfloppy on
its Convertible laptop, then doubled the capacity
to 1.44MB with the PS/2 line.  Due to their greater
capacity and convenience, the 3.5" floppies have
been retrofitted to many machines and have become
the medium of choice.  1.44MB drives can read,
write and format 720KB disks.

   Newer IBM models include the extra-high density
2.88MB floppy drives, compatible with the 1.44MB
disks.

            FLOPPY DISK FORMATS

     360KB 5.25" Low density (Double Density)
     1.2MB 5.25" High density

     720KB  3.5" Low density (Double Density)
    1.44MB  3.5" High density
    2.88MB  3.5" Extra-high density



                    HARD DISKS
Non-removable, hard disks for PCs are available
with storage capacities from 40MB to 2GB and above,
although buying a system with less than an 80MB
hard disk may be shortsighted, considering the low
cost of today's drives.  Applications are getting
larger and are using more and more of the hard disk
all the time.

   There have been several hard disk interface
standards used for PCs, including MFM, RLL, ESDI,
IDE and SCSI (see hard disk).  Today, most hard
drives sold with PCs are IDE and SCSI.  It depends
on the controller (expansion board) whether or not
another hard disk interface type can co-exist in
the PC.  In some cases, IDE and SCSI drives can co-
exist, in others they cannot.

   The IDE host adapter (expansion board) that
plugs into a PC can generally control two IDE hard
disks.  Installing the second IDE hard disk on a
reasonably-new PC is not complicated (see IDE~).

   Since most hard disks are not removable, the
low-level physical format of one drive has no
bearing on that of another in a different machine.
For example, two computers can be cabled together
and files can be transferred from the IDE hard disk
of one PC to the SCSI disk of another.  The hard
disk controllers are reading and writing their
disks according to their own technology.

   Removable disk drives and Bernoulli disks
provide the convenience of transportability and
unlimited amounts of storage, although each drive
holds only one disk module at a time.  Cartridges
come in 40MB and higher capacities, and optical
disks hold up to 600MB and more.  Each cartridge is
of a proprietary design and can be inserted only
into the drive it is designed for.

   As storage capacity grows, so does performance.
Disk access times run from 9 milliseconds (fast) to
100 ms (slow).



                      SUMMARY
First attempts at cloning the IBM PC were not all
successful.  From 1982 to 1985, there were a lot of
"almost compatible" PCs.  However, as soon as the
part of the operation system known as the ROM BIOS
was successfully cloned and made commercially
available, true compatibles appeared in abundance.

   Today, you can replace floppies, hard disks and
video displays, add a scanner, CD ROM or other
device without too much difficulty.  In general, PC
components are interchangeable, especially if you
have a newer PC.  Expansion cards are easily taken
out and plugged in, and an entire motherboard can
be replaced with a faster one (from a different
vendor) in about a half hour.

   The problems come when you add a second or third
device and run into a conflict with an existing one
(see PC conflicts).  In addition, having to modify
DOS's infamous AUTOEXEC.BAT and CONFIG.SYS
configuration files causes every novice to flinch
in the beginning.

   Conflicts aside, the PC has become a commodity
item, winding its way onto the shelves of a wide
variety of retail outlets.  This is a testimonial
to the power of a standard.

   Today, most PCs run most software and work with
most plug-in boards, but there are always
exceptions.  With the myriads of adapters and
applications available for the PC, one device,
application, TSR or utility can always conflict
with another.  The way to guarantee that something
works is to try it.  However, this has been true
since day one in the computer business.

   Nevertheless, if all this hasn't confused the
life out of you...  Good Luck and Happy Computing!


PC-8
Symbol set that contains the extended ASCII
characters of the IBM PC.


PC board
See printed circuit board.


PC bus
Bus architecture used in first-generation IBM PCs
and XTs.  It refers to the original 8-bit bus,
which accepted only 8-bit expansion boards.  In
286s and up, it was superseded by the 16-bit AT
bus, later known as the ISA bus.  Contrast with
ISA, EISA and Micro Channel.


PC card
(1) Memory card, I/O card or memory and I/O card.
The "PC Card" logo refers to PCMCIA Version 2.0 and
JEIDA Version 4.1, compatible standards as of late
1991.

(2) Expansion board for a PC.


PC color codes
Following are the color numbers for the 16
foreground and eight background colors in text
mode.  Foreground and background numbers are added
together; for example, white text on a red
background is 79.  To blink the text, add 128.

   ┌ Number────────┐
   │     Color     │
  BACKGROUND  FOREGROUND
    0  Black       0
   16  Blue        1
   32  Green       2
   48  Cyan        3
   64  Red         4
   80  Magenta     5
   96  Brown       6
  112  Light gray  7

  FOREGROUND ONLY
   8  Dark gray
   9  Light blue
  10  Light green
  11  Light cyan
  12  Light red
  13  Light magenta
  14  Yellow
  15  White

  128  Blinking


PC conflicts
When adding new peripherals, such as a scanner, CD
ROM, sound card, etc., to your ISA-bus PC, the new
plug-in board may conflict with a setting of an
existing board.  If you're adding your first or
even second device to a basic system, you may have
no conflicts, but as you add more, the chances are
greater.

   The reason for conflicts is that PCs use the
three following ways to transfer signals to a
peripheral device, and the settings associated with
these methods are not entirely standardized.

        1. IRQ
        2. I/O address (port address)
        3. memory address

   Most peripherals use an IRQ and an I/O address.
Many use a memory address.  When you install a new
board in your PC, you MUST read the installation
manual in order to find out what the initial
settings are and how to change them if necessary.
If a new board uses the same setting as an existing
board, it won't work properly or at all.  Or, it
will work and the old one won't, or both won't
work.

   ┌───────────────────────────────────────┐
   │ Note: PCs that use the EISA and Micro │
   │ Channel buses avoid many of these     │
   │ conflicts, because the boards are     │
   │ self configuring.  A setup program is │
   │ run when installing an EISA or Micro  │
   │ Channel expansion board.              │
   └───────────────────────────────────────┘

                    Keep a List
If you plan on installing several peripherals, it's
a good idea to write down the status of each board
you install.  Utility programs, such as MSD.EXE,
which comes with Windows, and Quarterdeck's
Manifest, which comes with QEMM, will help you
identify most current settings, but not all of
them.

   Make a chart like the one below and keep it
handy:

      Device     IRQ  I/O  Memory address
   ┌────────────┬───┬─────┬────────────┐
   │ COM1       │   │     │            │
   │ COM2       │   │     │            │
   │ LPT1       │   │     │            │
   │ scanner    │   │     │            │
   │ CD ROM     │   │     │            │
   │ etc.       │   │     │            │


              IRQ (Interrupt Request)
An interrupt is a method of signalling the computer
for attention.  There are 16 IRQ lines in a PC.
Older XTs have only eight.  If the device uses an
interrupt, it must use a unique IRQ line.  IRQ
settings are changed by setting DIP switches or
changing jumpers on the board itself or by running
a setup program.

   Following are common IRQ settings as reported by
Microsoft's MSD.EXE utility:

    0 - System timer
    1 - Keyboard
    2 - Connects to IRQ 9
    3 - COM2, COM4
    4 - COM1, COM3
    5 - LPT2
    6 - Floppy disk
    7 - LPT1
    8 - Realtime clock
    9 - Redirected IRQ2
   10 -
   11 -
   12 -
   13 - Math coprocessor
   14 - Hard disk
   15 -

                    I/O Address
The I/O address, or port address, is one way a
peripheral device is identified, or addressed, from
another.  The addresses are numbered in hex; for
example:
                   280h
                   290h
                   2A0h

   Like IRQs, they are set with DIP switches or
jumpers on the board, or possibly by running a
setup program.  If you change settings, you may
have to identify that change elsewhere, such as by
changing a parameter in a device= line in the
CONFIG.SYS file.  Read the manual for your new
device.  There is no other source for that kind of
information.

   If you change I/O addresses and still have a
problem, try an address that is one or two numbers
apart on the list.  For example, if one board is
set to 280h and another at 290h, change 280h to
270h or 260h and try again.  For details on this
technology, see PC I/O addressing.


                  Memory Address
A peripheral device often requires a block of upper
memory (between 640K-1M) for transferring data,
which must be reserved for its exclusive use.  Some
common devices, such as VGA video, use fixed areas
in upper memory that are automatically reserved.
With other devices, you have to find an unused
block in this area (for a diagram, see PC memory
map).

   That's why you'll find a number of memory
addresses to select, typically in the C800h to
F000h range (800-960K) so that you can hopefully
find an unused block.  Addresses are usually given
as beginning and ending address in hex; for
example:
             C800-CFFF
             D000-D7FF
             D800-DFFF

   When a block is chosen, it is also necessary to
inform your memory manager not to load other
drivers or TSRs into it.  This may be done by a
setup program or you may have to do it yourself by
adding an "exclude" to the line in CONFIG.SYS that
loads the memory manager.  For example, EMM386.EXE
is the memory manager in DOS 5 and Windows.  To
exclude the E800-EFFF block, the x= parameter is
added to the device= line as follows:

     device=emm386.exe noems x=e800-efff

   See DOS EMM386.EXE for more on the above syntax.
For other memory managers, such as QEMM and 386MAX,
a similar "exclude" parameter is also used.

   If you use Windows, an "exclude" line is also
added to the [386Enh] section in the SYSTEM.INI
file; for example:

            EMMExclude=e800-efff

   If you later change the board to another memory
area, both CONFIG.SYS and SYSTEM.INI must be
updated.

                      Summary
You MUST read the installation manual that comes
with your peripheral.  Each type of board is
configured differently.  The first time you install
a new board, fill out the chart suggested above.
It will save you headaches later!


PC display modes
Following are the resolutions and mode numbers for
the IBM, VESA and Hercules display standards.

┌─ Mode number
│           colsXrows text Colors or
│ Resolution  or graphics  gray scale (gray)
└─┐
     CGA
  0  320x200  40x25 txt  16 gray
  1  320x200  40x25 txt  16
  2  640x200  80x25 txt  16 gray
  3  640x200  80x24 txt  16
  4  320x200  graphics    4
  5  320x200  graphics    4 gray
  6  640x200  graphics    2

     EGA
  0  320x350  40x25 txt  16 gray
  1  320x350  40x25 txt  16
  2  640x350  80x25 txt  16 gray
  3  640x350  80x25 txt  16
  7  720x350  80x25 txt  mono
 13  320x200  graphics   16
 14  640x200  graphics   16
 15  640x350  graphics    2
 16  640x350  graphics   16

     MCGA
  0  320x400  40x25 txt  16 gray
  1  320x400  40x25 txt  16
  2  640x400  80x25 txt  16 gray
  3  640x400  80x25 txt  16
 17  640x480  graphics   mono
 19  320x200  graphics   256

     VGA
  0  360x400  40x25 txt  16 gray
  1  360x400  40x25 txt  16
  2  720x400  80x25 txt  16 gray
  3  720x400  80x25 txt  16
  7  720x400  80x25 txt  mono
 18  640x480  graphics   16

     VESA VBE Standards (Super VGA)
                     Video
             Colors RAM used
256  640x400   256   250K
257  640x480   256   300K
258  800x600    16   234K
259  800x600   256   469K
260  1024x768   16   384K
261  1024x768  256   768K
262  1280x1024  16   640K
263  1280x1024 256  1280K
264   80x60 text     9.3K
265  132x25 text     6.4K
266  132x43 text    11.1K
267  132x50 text    12.9K
268  132x60 text    15.5K
269  320x200   32K   125K
270  320x200   64K   125K
271  320x200   16M   188K
272  640x480   32K   600K
273  640x480   64K   600K
274  640x480   16M   900K
275  800x600   32K   938K
276  800x600   64K   938K
277  800x600   16M  1406K
278  1024x768  32K  1536K
279  1024x768  64K  1536K
280  1024x768  16M  2304K
281  1280x1024 32K  2560K
282  1280x1024 64K  2560K
283  1280x1024 16M  3840K

    Number   Pixel Bits
  of colors   R  G  B
     32K      5  5  5
     64K      5  6  5
     16M      8  8  8

     XGA
  640x480  graphics   256 cols
  640x480  graphics   64K cols
  1024x768 graphics   256 cols

     Hercules
  720x348  txt/graphics  mono


PC-DOS
DOS operating system from Microsoft supplied by IBM
for its PCs.  Almost identical to MS-DOS for non-
IBM PCs, both versions are called DOS.


PC EXPO
Trade show for resellers and corporate PC buyers
held in the summer (New York) and fall (Chicago).
It started in New York in 1983 with 120 exhibitors
and drew 9,600 attendees.  In 1991, it had 728
exhibitors and 75,000 attendees.  Sponsored by
Bruno Blenheim Inc., 385 Sylvan Ave., Englewood
Cliffs, NJ 07632, 800/829-3976.  1993 schedule is
6/29-7/1 and 10/19-21.


PC I/O addressing
I/O addresses, or port addresses, on x86
architecture is a common method used to address the
controller boards of peripheral devices.  The other
method is memory-mapped peripherals, in which a
block of memory in the UMA is reserved for a
device, such as a video card.

   There is 64K of address space for I/O addresses,
although typically less than 1K is used.  Each
board that uses an I/O address contains a few bytes
of memory (16, 32, etc.) that have a default
address range and one or more alternate addresses
to resolve conflicts with other boards.  This
physically winds up as a bunch of tiny memory banks
scattered over different devices.  As long as each
one is set to a different address, the CPU can
signal one device from another.

   An I/O address operation takes place as follows.
If a program needs to send a byte to the serial
port, it issues an OUT instruction to the CPU with
the address of that serial port.  The CPU notifies
the address bus to activate the I/O space, not
regular memory, and the address bus signals the
appropriate byte location on the board.  The CPU
then sends the data character over the data bus to
that memory location.

   I/O and memory addressing are often used in
conjunction in which control instructions are
passed via the I/O space and the data is passed and
buffered via memory.


PC keyboard
Keyboard introduced with the IBM PC that provides a
dual-function keypad for numeric entry and cursor
movement.  It was severely criticized for its non-
standard shift key placement, which was corrected
with the AT keyboard.  Regardless of key placement,
users often praise the feel of IBM keyboards.


PC LAN
(1) Network of IBM or IBM-compatible PCs.

(2) Network of any variety of personal computers.


PC memory card
See memory card.


PC memory map
The following chart shows how the first megabyte of
RAM is used in a PC:

     Address    │                     │
11000:0000 1088K├─────────────────────┤ Extended
                │HMA(high memory area)│  Memory
10000:0000 1024K├───────────┬─────────┤------------
                │PC ROM BIOS│PS/2     │
 F000:0000  960K├───────────┤ROM BIOS │
                │           │& VGA ROM│
 E000:0000  896K│ Available └─────────┤ Top 384K
                │ for drivers and     │ of the
 D000:0000  832K│   EMS page frame    │ first
 C800:0000  800K├─────────────────────┤ megabyte
                │  EGA, VGA ROM BIOS  │ of RAM is
 C000:0000  768K├───────────┬─────────┤ called the
                │    Free   │         │ UMA (upper
 BC00:0000  752K├───────────┤         │ memory area
                │ CGA       │         │ made up
                │ Graphics  │Hercules │ of UMBs
                │ CGA, EGA, │Graphics │ (upper
                │ VGA Text  │         │ memory
 B800:0000  736K├───────────┤         │ blocks)
                │    Free   │         │
 B400:0000  720K├───────────┤         │
                │  MDA RAM  │         │
 B000:0000  704K├───────────┴─────────┤
                │EGA, VGA Graphics RAM│
 A000:0000  640K├─────────────────────┤------------
                │    Conventional     │
                │       Memory        │ Lower 640K
                │                     │ is used by
                │                     │ DOS and
                │                     │ user
                │                     │ programs.
                │                     │
                │                     │

                │ DOS and COMMAND.COM │
                │  Interrupt vectors  │
              0K└─────────────────────┘



PC-MOS/386
Mmultiuser PC operating system from The Software
Link, Inc., Norcross, GA.  It runs most standard
DOS applications as well as applications written
for the 386's Protected Mode.


PC network
(1) Network of IBM and/or IBM-compatible PCs.

(2) Network of any variety of personal computers.

(3) (PC Network)  First PC LAN from IBM introduced
in 1984.  It inaugurated the NetBIOS interface and
uses the CSMA/CD access method.  Token Ring support
was added later.  See MS-Net.


PC Paintbrush
PC paint program from ZSoft Corp., Marietta, GA,
that is widely used and has set an industry
standard graphics format.  Its PCX raster graphics
format is generated and accepted by many graphics,
word processing and desktop publishing programs.


PC Tools
Comprehensive package of PC utilities from Central
Point Software, Beaverton, OR, that includes a DOS
shell (PC Tools Desktop) as well as antivirus, file
management, communications, disk caching, backup,
data compression and data recovery utilities.


PCB
See printed circuit board.


PCI
(Peripheral Component Interconnect)  PC local bus
from Intel that connects up to 10 peripherals,
supports 32- and 64-bit data paths and allows bus
mastering.  Final specs are due in 1993.


PCjr
(PC junior)  IBM's first home computer introduced
in 1983.  Its original keyboard was unsuitable for
typing, but adequate keyboards were later added.
It was discontinued in 1985.


PCL
(Printer Control Language)  Command language for
the HP LaserJet printers.  It has become a de facto
standard used in many printers and typesetters.
PCL Level 5, introduced with the LaserJet III in
1990, also supports Compugraphic's Intellifont
scalable fonts.


PCM
(1) (Pulse Code Modulation)  Technique for
digitizing speech by sampling the sound waves and
converting each sample into a binary number.  It
uses waveform coding that samples a 4KHz bandwidth
8,000 times a second.  Each sample is an 8 bit
number, resulting in 64K bits of data per second.
See ADPCM.

(2) (Plug Compatible Manufacturer)  Organization
that makes a computer or electronic device that is
compatible with an existing machine.


PCMCIA
(Personal Computer Memory Card International
Association)  Organization of U.S. and Japanese
companies set up to standardize memory cards.  See
PC card.


PCradio
IBM laptop designed for mobile use.  It is a
ruggedized machine that provides cellular, wireless
data radio (Ardis) and modem communications.


PCTE
(Portable Common Tool Environment)  ECMA standard
for exchanging data between CASE tools.  See CDIF.


PCX
Widely-used raster graphics file format developed
by Zsoft Corp., Marietta, GA, that handles
monochrome, 2-bit, 4-bit, 8-bit and 24-bit color
and uses RLE to achieve compression ratios of
approximately 1.1:1 to 1.5:1.  Images with large
blocks of solid colors compress best under the RLE
method.


PD software
See public domain software.


PDA
(Personal Digital Assistant)  Handheld computer
that serves an an organizer, electronic book or
note taker and includes features such as pen-based
entry and wireless transmission to a cellular
service or desktop system.


PDES
(Product Data Exchange Specification)  Standard
format for exchanging data between advanced CAD and
CAM programs.  It describes a complete product,
including the geometric aspects of the images as
well as manufacturing features, tolerance
specifications, material properties and finish
specifications.  See IGES.


PDIP
(Plastic DIP)  Common type of DIP made of plastic.


PDL
See page description language.


PDP
(Programmed Data Processor)  Minicomputer family
from Digital that started with the 18-bit PDP-1 in
1959.  Its $120,000 price was much less than the
million dollar machines of the time and 50 units
were built.

   In 1965, Digital legitimized the minicomputer
industry with the PDP-8, which sold for about
$20,000.  By the late 1970s, the PDP-8 processor
was put on a single chip and used in DECmate
workstations.

   Other PDPs were built, including 12-, 18- and
36-bit machines, the larger ones evolving into
DECsystem models.

   In 1970, Digital introduced the 16-bit PDP-11,
which became the most widely used minicomputer with
over 50,000 systems sold.  The PDP series was
followed by the VAX series in 1977; however, PDP-
11s are still made.


PE
(1) (Phase Encoding)  Early magnetic encoding
method used on 1600bpi tapes in which a 1 is an up
transition and a 0 is a down transition in the
center of the bit cell.

(2) (Processing Element)  One of multiple CPUs in a
parallel processing system.

(3) (Professional Engineer)  Engineering degree.


PE format
(Portable Executable format)  Win32 file format for
executable programs (EXEs and DLLs) supported under
Windows 3.1 Enhanced Mode (Win32s) and Windows NT.


peek/poke
Instructions that view and alter a byte of memory
by referencing a specific memory address.  Peek
displays the contents; poke changes it.


peer
In communications, a functional unit that is on the
same protocol layer as another.


peer-to-peer communications
Communications in which both sides have equal
responsibility for initiating, maintaining and
terminating the session.  Contrast with master-
slave communications, in which the host controls
everything and determines which users can initiate
which sessions.  If the host were programmed to
allow all users to initiate all sessions, it would
look like a peer-to-peer system to the user.


peer-to-peer network
Network that allows users access to data on all
workstations or computers in the network.
Dedicated file servers may be used, but are not
required.  In today's environments, a peer-to-peer
network often implies peer-to-peer communications,
but peer-to-peer communications does not imply a
peer-to-peer network.  Downright confusing.


pel
Same as pixel.


pen-based computing
Using a stylus to enter hand writing and marks into
a computer.  See gesture recognition.


pen plotter
See plotter.


Pen Windows
Extension to Windows that allows pen-based
computing.


PenPoint
Operating system from Go Corp., Foster City, CA,
that provides a stylus (pen) interface for hand-
written input.  It uses a DOS-compatible file
system, but does not run DOS applications.  The
direction, speed and order of the user's pen
strokes is analyzed for recognition.  See NUI.


Pentium
Successor to the 486 from Intel.  Originally to be
called the 586 and code named P5, it refers to the
Pentium CPU chip or the PC that uses it.  It runs
about twice as fast as a 66MHz 486, and its
floating point operations are up to four times as
fast as a 486.  Although its integer performance
rivals major RISC-based CPUs (Alpha, HP-PA, MIPS,
SPARC, etc.), its floating point performance is
generally slower.

   Pentium PCs will be initially used as servers,
CAD workstations and for process-intensive
applications.  However, today's leading edge
technology always becomes tomorrow's entry level
machine.

   The P24T is the code name for a scaled-down
Pentium that will be used as a 486 upgrade on
motherboards that have the required socket.


            Pentium CPU Technical Specs
32-bit multitasking microprocessor in a 273-pin PGA
package.  Same registers and operational modes as
the 386 (see 386).  Uses RISC design techniques and
obtains its speed from a dual pipeline architecture
that executes several instructions in one clock
cycle.  It uses a 64-bit internal bus compared to
32-bits on the 486.  It contains 3.1 million
transistors.


PEP
High-speed modem protocol from Telebit Corp.,
Sunnyvale, CA, suited for cellular phone use.


PEPPER board
Family of high-resolution graphics display boards
for PCs from Number Nine Computer Corp., Lexington,
MA.


peripheral
Any hardware device connected to a computer, such
as a monitor, keyboard, printer, plotter, disk or
tape drive, graphics tablet, scanner, joy stick,
paddle and mouse.


peripheral controller
See control unit (2).


permanent font
(1) A soft font that is kept in the printer's
memory until the printer is turned off.

(2) Same as internal font.


permanent memory
Same as non-volatile memory.


permutation
One possible combination of items out of a larger
set of items.  For example, with the set of numbers
1, 2 and 3, there are six possible permutations:
12, 21, 13, 31, 23 and 32.


perpendicular recording
See vertical recording.


persistence
In a CRT, the time a phosphor dot remains
illuminated after being energized.  Long-
persistence phosphors reduce flicker, but generate
ghost-like images that linger on screen for a
fraction of a second.


persistent link
See hot link.


personal computer
Synonymous with microcomputer, a computer that
serves one user.  It is used at home and in the
office for almost all applications traditionally
performed on larger computers.

   With the addition of a modem, it becomes a
terminal, capable of retrieving information from
other computers and online services worldwide.

   There are a variety of personal computers on the
market, priced from $300 to over $10,000.  Size is
based on its memory and disk capacity.  Speed is
based on the CPU that runs it, and output quality
is based on the resolution of its display screen
and printer.


       MAJOR SUPPLIERS OF PERSONAL COMPUTERS
The personal computer world is overwhelmingly
dominated by IBM PCs and IBM-compatible PCs.  There
are hundreds of vendors and thousands of models,
although all models fall into a handful of
categories (see PC).

   The next largest supplier is Apple Computer,
with its Macintosh family and Apple IIe.  The Apple
II has been widely used in schools, but is rapidly
giving way to the Macs.  Macintoshes are popular
with individuals and are increasingly being
purchased by large corporations.

   Both Atari and Commodore continue to carve out a
niche and are popular as home and small business
computers.  Each of them has support from software
vendors providing a rounded supply of applications.


         THE HISTORY OF PERSONAL COMPUTERS
The industry began in 1977, when Apple, Radio Shack
and Commodore introduced the first off-the-shelf
computers as consumer products.

   The first machines used an 8-bit microprocessor
with a maximum of 64K of memory and floppy disks
for storage.  The Apple II, Atari 500, and
Commodore 64 became popular home computers, and
Apple was successful in companies after the
VisiCalc spreadsheet was introduced.  However, the
business world was soon dominated by the Z80
processor and CP/M operating system, used by
countless vendors in the early 1980s, such as
Vector Graphic, NorthStar, Osborne and Kaypro.  By
1983, hard disks began to show up on these
machines, but CP/M was soon to be history.

   In 1981, IBM introduced the PC, an Intel 8088-
based machine, slightly faster than the genre, but
with 10 times the memory.  It was floppy-based, and
its DOS operating system from Microsoft was also
available for the clone makers (MS-DOS).  The 8088
was cleverly chosen so that CP/M software vendors
could convert to it easily.  They did!

   dBASE II was introduced in 1981 bringing
mainframe database functions to the personal
computer level and launching an entire industry of
compatible products and add-ons.  Lotus 1-2-3 was
introduced in 1982, and its refined interface and
combined graphics helped spur sales of the new
standard.

   The IBM PC was successfully cloned by Compaq and
unsuccessfully by others.  However, by the time IBM
announced the AT in 1984, vendors were effectively
cloning the PC and, as a group, eventually grabbed
the majority of the PC market.

   In 1983, Apple introduced the Lisa, a graphics-
based machine that simulated the user's desktop.
Although ahead of its time, Lisa was abandoned for
the Macintosh in 1984.  The graphics-based desktop
environment caught on with the Mac, especially in
desktop publishing, and the graphical interface, or
"gooey," (GUI) worked its way to the PC world with
Microsoft Windows, and, eventually Ventura
Publisher with its GEM interface.

   In 1986, the Compaq 386 ushered in the first
Intel 386-based machine.  In 1987, IBM introduced
the PS/2, its next generation of personal
computers, which added improved graphics, 3.5"
floppy disks and an incompatible bus to help fend
off the cloners.  OS/2, jointly developed by IBM
and Microsoft, was also introduced to handle the
new machines, but the early versions didn't catch
on.

   In the same year, more powerful Macintoshes were
introduced, including the Mac SE and Mac II, which
opened new doors for Apple.

   In 1989, the PC makers introduced 486-based
computers, and Apple gave us faster Macs, which it
has continued to do each year since.

   In 1990, Microsoft's introduced Windows 3.0,
which is rapidly catching on as the graphical
environment for PCs.  Software publishers are
developing Windows versions of all their products.

   In 1991, Microsoft and IBM decided to go it
alone each working on their own version of the
future PC operating system (IBM's OS/2 2.0 and
Microsoft's Windows NT).  OS/2 2.0 has been
moderately successful and Windows NT is still to be
delivered.

   1992 was the year of PC price cuts with all
major suppliers slashing prices to keep in line
with mail-order vendors.  Prices keep getting
lower, machines keep getting faster.  In 1993,
Intel will introduce its Pentium CPU, successor to
the 486, with nearly 3,000,000 transistors.

   Inspired by Radio Shack's Model 100 in 1984 and
ignited by Toshiba and Zenith, the laptop market
provides a fascinating growth area in personal
computing.  More circuits are being stuffed into
less space, providing computing power on the go
that few would have imagined back in 1977.


                    THE FUTURE
The personal computer industry sprang up without
any planning.  All of a sudden, it was there.
Machines were bought to solve individual problems,
such as automating a budget or typing a letter.

   However, in large organizations, the real data
exists in the mainframe, and it doesn't make sense
to have an employee retype the mainframe reports
into the micro in order to analyze and manipulate
it.  Personal computers can serve as invaluable
tools for the user when they are designed into the
fabric of the organization.  The major issue of the
1990s is to tie them together in LANs and
interconnect them with the company's minis and
mainframes.

   Fast personal computers are changing the
marketplace.  Not only do they begin to compete
with minicomputer workstations, but, networks of
these machines are now being installed for
applications that were previously relegated to
minis and mainframes.

   These high-powered desktop computers will
encourage the development of more artificial
intelligence applications that are the backbone of
the next computing generation.  By the turn of the
century, you should be able to talk to your
computer as easily as typing on it.

   As stand-alone machines, personal computers have
placed creative capacity into the hands of an
individual that would have cost millions of dollars
less than 20 years ago.  It slowly but surely is
shifting the balance of power from the large
company to the small, from the elite to the masses,
from the wealthy to individuals of modest means.
The personal computer has truly revolutionized the
computer industry and the world.


personal workstation
Same as personal computer or workstation.


PET computer
(Personal Electronic Transaction computer)  CP/M
and floppy disk-based personal computer introduced
in 1977 by Commodore.  It was one of the three
first personal computers.


PFS:First Choice
Integrated software package for PCs from Spinnaker
Software Corp., Cambridge, MA, that provides word
processing, database, spreadsheet, graphics and
communications capabilities.


PFS:Write
See Professional Write.


PGA
(1) (Pin Grid Array)  Chip housing with high
density of pins (200 pins can fit in 1.5" square).
Used for large amounts of I/O, its underside looks
like a "bed of nails."

(2) (Programmable Gate Array)  Type of gate array
that is programmed by the customer.

(3) (Professional Graphics Adapter)  Early high-res
PC display standard (640x480, 256 cols.) with 3-D
processor that had minimal support.


PgUp/PgDn keys
Page Up and Page Down keys are typically used to
move text up and down one screenful, but they can
be programmed to do anything.


phase change recording
Optical recording technique that uses a laser to
create a bit by altering the crystalline structure
of a metallic surface.  The bit either reflects or
absorbs light when read.


phase encoding
See PE.


phase locked
Technique for maintaining synchronization in an
electronic circuit.  The circuit receives its
timing from input signals, but also provides a
feedback circuit for synchronization.


phase modulation
Transmission technique that blends a data signal
into a carrier by varying (modulating) the phase of
the carrier.  See modulate.


phase-shift keying
See DPSK.


PHIGS
(Programmer's Hierarchical Interactive Graphics
Standard)  Graphics system and language used to
create 2-D and 3-D images.  Like the GKS standard,
PHIGS is a device independent interface between the
application program and the graphics subsystem.

   It manages graphics objects in a hierarchical
manner so that a complete assembly can be specified
with all of its subassemblies.  It is a very
comprehensive standard requiring high-performance
workstations and host processing.


Phoenix BIOS
PC-compatible ROM BIOS from Phoenix Technolgies,
Ltd., Norwood, MA.  Phoenix was the first company
to successfully mass produce the ROM BIOS for the
PC.


phone connector
(1) Plug and socket for a two or three-wire coaxial
cable used to plug microphones and headphones into
amplifiers.  The plug is a single, nail-like ¼"
thick prong about 1¼" in length.  See phono
connector.

(2) Plug and socket for a telephone line, typically
the RJ-11 modular connector.


phone hawk
Slang for a person who calls up a computer via
modem and either copies or destroys data.


phoneme
Speech utterance, such as "k," "ch," and "sh," that
is used in synthetic speech systems to compose
words for audio output.


PhoneNET
Communications products from Farallon Computing,
Inc., Emeryville, CA, that extend LocalTalk
distances to 3,000 feet and use unshielded twisted
phone lines instead of shielded twisted pair.
Configurations include daisy chain, passive star as
well as active star topologies for both EtherTalk
and LocalTalk.  Optional Traffic Watch software
provides network management and administration.


Phong shading
In computer graphics, a technique developed by
Phong Bui Tuong that computes a shaded surface
based on the color and illumination at each pixel.
It is more accurate than Gouraud shading, but
requires much more extensive computation.


phono connector
Also called an RCA connector, a plug and socket for
a two-wire coaxial cable used to connect audio and
video components.  The Apple II has a video out
phono connector for a TV.  The plug is a 1/8" thick
prong that sticks out 5/16" from the middle of a
cylinder.  See phone connector.


phosphor
Rare earth material used to coat the inside face of
a CRT.  When struck by an electron beam, the
phosphor emits a visible light for a few
milliseconds.  In color displays, red, green and
blue phosphor dots are grouped as a cluster.


Photo CD
CD system from Kodak that records 35mm film images
on a CD.  Each image takes up 4.5MB of storage and
includes five resolutions, the highest known as
Base/16: 2048x3072x24.  The Photo CD is created by
photo finishers that have a Kodak Picture Imaging
Workstation.

   Additional formats include the Pro Photo CD
Master, which stores images from professional
format film (120, 4x5, etc.), the Photo CD
Portfolio, which holds up to 800 TV-quality images,
the Photo CD Catalog for use in catalog
distribution and the Photo CD Medical disk for
storing film-based images


photocomposition
Laying out a printed page using electrophotographic
machines, such as phototypesetters and laser
printers.  See page makeup and pagination.


photolithography
Lithographic technique used to transfer the design
of the circuit paths and electronic elements on a
chip onto a wafer's surface.  A photomask is
created with the design for each layer of the chip.
The wafer is coated with a light-sensitive film
(photoresist) and is exposed to light shining
through the photomask.  The light hardens the film,
and when the wafer is exposed to an acid bath (wet
processing) or hot ions (dry processing), the
unhardened areas are etched away.


photomask
Opaque image on a transluscent plate that is used
as a light filter to transfer an image from one
device to another.  See chip.


photomicrography
Photographing microscopic images.


photon
Unit of energy.  Elementary particle of
electromagnetic radiation (light, radio waves, X-
rays, etc.).


photonics
Science of building machine circuits that use light
instead of electricity.


photooptic memory
Storage device that uses a laser beam to record
data onto a photosensitive film.


photorealistic
Having the image quality of a photograph.


photorealistic image synthesis
In computer graphics, a format for describing a
picture that depicts the realism of the actual
image.  It includes such attributes as surface
texture, light sources, motion blur and
reflectivity.


photoresist
Film used in photolithography that temporarily
holds the pattern of a circuit path or microscopic
element of a chip.  When exposed to light, it
hardens and is resistant to the acid bath that
washes away the unexposed areas.


photosensor
Light-sensitive device that is used in optical
scanning machinery.


phototypesetter
Device that generates high-resolution text directly
onto a photo-sensitive material.  Input comes from
the keyboard, or via disk, tape or modem.  The
output is a paper-like or transparent film that is
processed into a camera-ready master for printing.

   Phototypesetters employ various light
technologies.  Older machines pass light through a
spinning font photomask, then through lenses that
create the point size and onto film.  Others create
images on CRTs and expose the film.  Modern
imagesetters use lasers to generate the image
directly onto the film.

   The phototypesetter was originally the only
machine that could handle multiple fonts and text
composition such as kerning.  Today, desktop laser
printers are used for many typesetting jobs and are
quickly advancing in resolution, although the 1270
and 2540 dpi resolutions of the phototypesetter
still provide the highest quality.

   Phototypesetters that handle both text and
graphics are called imagesetters.


physical
Refers to devices at the electronic, or machine,
level.  Contrast with logical.  See logical vs
physical.


physical address
Actual, machine address of an item or device.


physical format
See record layout and low-level format.


physical link
(1) Electronic connection between two devices.

(2) In data management, a pointer in an index or
record that refers to the physical location of data
in another file.


physical lock
Prevention of user access to data provided by a
locking on/off switch or file protection mechanism
such as on a floppy disk.  Contrast with logical
lock.


PIC
(1) (PICture)  File extension used for graphics
formats.  Lotus PIC is a vector format for 1-2-3
charts and graphs.  Videoshow PIC is a vector
format that is a subset of the NAPLPS standard.

(2) (Personal Intelligent Communicator)  Hand-held
computer that uses 3" CD ROMs and has a HyperCard-
like interface from General Magic, Inc. (Apple and
Sony) scheduled for 1992.  It will have cellular
phone capability.  Wireless communications for
networks, radio and TV is planned.

(3) (Programmable Interrupt Controller)  Intel 8259
chip that controls interrupts in PCs.


pica
(1) In word processing, a monospaced font that
prints 10 characters per inch.

(2) In typography, about 1/6th of an inch (0.166")
or 12 points.


Pick System
Multiuser operating environment from Pick Systems,
Inc., Irvine, CA, that runs in a variety of
computers and includes a virtual memory operating
system and relational database.  It is highly
praised for its ease of use and flexibility.

   It was originally developed by Richard Pick, who
created a system for the U.S. Army while working at
TRW Corp.  He later transformed it into the Reality
operating system for Microdata and then obtained
the right to license it to other vendors.


picosecond
One trillionth of a second.  Pronounced "pee-co-
second."


PICT
(PICTure)  Macintosh graphics file format that
stores images in the QuickDraw vector format.  When
PICT files are converted to the PC, they use the
.PCT file extension.


picture
In programming, a pattern that describes the type
of data allowed in a field or how it will print.
The pattern is made up of a character code for each
character in the field; for example, 9999 is a
picture for four numeric digits.  A picture for a
telephone number could be [phone].  XXX999
represents three alphanumerics followed by three
numerics.  Pictures are similar but not identical
in all programming languages.


picture element
See pixel.


Picturephone
Proposed video/telephone introduced by AT&T at the
1964 World's Fair (New York).   Many thought it
would flourish by the end of the 1980s.


PID
(1) (Process IDentifier)  Temporary number assigned
by the operating system to a process or service.

(2) (Proportional Integral Derivative)  Controller
used to regulate a continuous process such as
grinding or cooking.


pie chart
Graphical representation of information in which
each unit of data is represented as a pie-shaped
piece of a circle.  See business graphics.


piezoelectric
Generation of electricity from a crystal subjected
to pressure.  Certain crystal oscillators and
microphones are piezoelectric devices.


PIF
(Program Information File)  Windows data file used
to hold requirements for DOS applications running
under Windows.  Windows comes with a variety of
PIFs, but users can edit them and new ones can be
created with the PIF editor if a DOS application
doesn't work properly.  An application can be
launched by clicking on its PIF.


piggyback board
Small printed circuit board that plugs into another
circuit board in order to enhance its capabilities.
It does not plug into the motherboard, but would
plug into the boards that plug into the
motherboard.


PIL
(Publishing Interchange Language)  Standard for
document interchange that defines the placement of
text and graphics objects on the page.  It does not
address the content of the objects.


PILOT
(Programmed Inquiry Learning Or Teaching)  High-
level programming language used to generate
question-and-answer courseware.  A version that
incorporates turtle graphics runs on Atari personal
computers.


PIM
(Personal Information Manager)  Combination word
processor, database and desktop accessory program
that organizes a variety of information.  It allows
the user to tie together more loosely structured
information than traditional programs.

   PIMs vary widely, but all of them attempt to
provide methods for managing information the way
people use it in their jobs.


pin
(1) Male lead on a connecting plug (serial port,
monitor cable, keyboard connector, etc.) or the
spiderlike foot on a chip.  Each pin is plugged
into a socket to complete the circuit.

(2) (PIN) (Personal Identification Number)
Personal password used for identification purposes.


pin compatible
All connecting signal lines are compatible.


pin feed
Method for moving continuous paper forms.  Pins at
both ends of a rotating platen or tractor engage
the forms through pre-punched holes at both sides.


pinch roller
Small, freely-turning wheel in a tape drive that
pushes the tape against a motor-driven wheel in
order to move it.


pincushioning
Screen distortion in which the sides bow in.
Contrast with barrel distortion.


ping pong
(1) Half-duplex communications method in which data
is transmitted in one direction and acknowledgement
is returned at the same speed in the other.  The
line is alternately switched from transmit to
receive in each direction.  Contrast with
asymmetric modem.

(2) To go in one direction and then in the other.


ping-pong buffer
See double buffering.


Pink
Code name for Taligent's portable, object-oriented
operating system that will run on a variety of
computers.  Expected in 1994.  See Apple.


pinouts
Description and purpose of each pin in a multiline
connector.


PIP
(Peripheral Interchange Program)  CP/M utility
program used to copy files.


pipe
Shared space that accepts the output of one program
for input into another.  In DOS and OS/2, the pipe
command is a vertical line (|).  The statement, dir
| sort directs the output of the directory list to
the sort utility.  See DOS filters & pipes and DOS
redirection.


pipeline processing
Category of techniques that provide simultaneous,
or parallel, processing within the computer  It
refers to overlapping operations by moving data or
instructions into a conceptual pipe with all stages
of the pipe processing simultaneously.  For
example, while one instruction is being executed,
the computer is decoding the next instruction.  In
vector processors, several steps in a floating
point operation can be processed simultaneously.


piracy
Illegal copying of software for personal or
commercial use.


pitch
Number of printed characters per inch.  With
proportionally spaced characters, the pitch is
variable and must be measured as an average.  See
dot pitch.


pixel
(PIX [picture] ELement)  Smallest element on a
video display screen.  A screen is broken up into
thousands of tiny dots, and a pixel is one or more
dots that are treated as a unit.  A pixel can be
one dot on a monochrome screen, three dots (red,
green and blue) on color screens, or clusters of
these dots.

   For monochrome screens, the pixel, normally
dark, is energized to different light intensities,
creating a range from dark to light.  For color,
each red, green and blue dot is energized to
different intensities, creating a range of colors
perceived as the mixture of these dots.  Black is
all three dots off, white is all three dots on, and
grays are even intensities of each color.

   The number of bits assigned to each pixel in its
associated digital memory determines the number of
shades and colors that can be represented.  The
most economical system is monochrome in which one
bit is used per pixel (on or off).  In the most
elaborate color displays, which use up to four full
bytes for each of the red, green and blue dots,
each pixel can display billions of different
shades.  Considering that a high-resolution screen
may use a million pixels, many megabytes of memory
would have to be reserved to hold such an image.


pixel graphics
Same as raster graphics.


PixelPaint
Macintosh drawing program from SuperMac Technology,
Sunnyvale, CA, that is known for its extensive
paint palette and color mixing schemes.


PK software
Popular PC shareware compression programs from
PKWARE Inc., Brown Deer, WI (PK stands for Phil
Katz).  PKZIP compresses files into a ZIP file and
PKUNZIP decompresses them.  PKSFX compresses files
into a self-extracting EXE file that decompresses
when loaded and doesn't require the PKUNZIP
program.  ZIP2EXE creates the self-extracting file
from an existing ZIP file.

   PKLITE compresses only EXE and COM program
files.  Unlike ZIP'd files, which are compressed
for archiving or distribution and decompressed upon
installation, PKLITE'd files stay compressed all
the time and decompress automatically when loaded.

   PKARC and PKXARC were previous compression
programs no longer supported.


PL/I
(Programming Language 1)  High-level IBM
programming language introduced in 1964 with the
System/360 series.  It was designed to combine
features of and eventually supplant COBOL and
FORTRAN, which never happened.  A PL/I program is
made up of procedures (modules) that can be
compiled independently.  There is always a main
procedure and zero or more additional ones.
Functions, which pass arguments back and forth, are
also provided.


PL/M
(Programming Language for Microprocessors)  Dialect
of PL/I developed by Intel as a high-level language
for its microprocessors.  PL/M+ is an extended
version of PL/M, developed by National
Semiconductor for its microprocessors.


PLA
(Programmable Logic Array)  Programmable logic chip
(PLD) technology from Philips/Signetics.


plaintext
Normal text that has not been encrypted and is
readable by text editors and word processors.
Contrast with ciphertext.


planar
Technique developed by Fairchild Instruments that
creates transistor sublayers by forcing chemicals
under pressure into exposed areas.  Planar
superseded the mesa process and was a major step
toward creating the chip.


planar area
In computer graphics, an object that has
boundaries, such as a square or polygon.


planning system
See spreadsheet and financial planning system.


plasma display
Also called gas discharge, a flat-screen technology
that contains an inert ionized gas sandwiched
between x- and y-axis panels.  A pixel is selected
by charging one x- and one y-wire, causing the gas
in that vicinity to glow a bright orange.


platen
Long, thin cylinder in a typewriter or printer that
guides the paper through it and serves as a
backstop for the printing mechanism to bang into.


platform
Hardware architecture of a particular model or
computer family.  It is the standard to which
software developers write their programs.  The term
may also include the operating system.  See
environment.


PLATO
(Programmed Logic for Automatic Teaching
Operations)  Developed by Donald Bitzer and
originally marketed by CDC, it was the first CBT
system to combine graphics and touch-sensitive
screens for interactive training.


platter
One of the disks in a disk pack or hard disk drive.
Each platter provides a top and bottom recording
surface.  See magnetic disk.


PLB
(Picture Level Benchmark)  Graphics Performance
Characterization (GPC) committee's benchmark,
available through NCGA, for measuring graphics
workstation performance.  The Benchmark Interface
Format (BIF) defines the PLB format, the Benchmark
Timing Methodology (BTM) performs the test and the
Benchmark Reporting Format (BRF) generates results
in GPCmarks.  Image quality is not rated.


PLC
(Programmable Logic Controller)  Computer used in
process control applications.  PLC microprocessors
are typically RISC-based and are designed for high-
speed, realtime and rugged industrial environments.


PLCC
(Plastic LCC)  Widely-used type of leaded chip
carrier.  See LCC.


PLD
(Programmable Logic Device)  Logic chip that is
programmed at the customer's site.  There are a
wide variety of PLD techniques; however, most PLDs
are compatible with the PAL method from Advanced
Micro Devices.

   The PLD is not a storage chip like a PROM or
EPROM, although fuse-blowing techniques are used.
It contains different configurations of AND, OR and
NOR gates that are "blown" together.  Contrast with
gate array, which requires a manufacturing process
to complete the programming.


plot
To create an image by drawing a series of lines.
In programming, a plot statement creates a single
vector (line) or a complete circle or box that is
made up of several vectors.


plotter
Graphics printer that draws images with ink pens.
It requires data in vector graphics format, which
makes up an image as a series of point-to-point
lines.  See flatbed plotter and drum plotter.


Plotter in a Cartridge
HPGL emulation in a cartridge for laser printers
from Pacific Data Products, San Diego, CA.


PLP
(Presentation Level Protocol)  North American
standard protocol for videotex.


plug compatible
Hardware that is designed to perform exactly like
another vendor's product.  A plug compatible CPU
runs the same software as the machine it's
compatible with.  A plug compatible peripheral
works the same as the device it's replacing.


plugboard
Socket board with used to program early tabulating
machines and computers.  A wire is inserted into
one output and one input socket, closing a circuit
and activating a function.  Complicated programs
looked like "mounds of spaghetti."


plugs & sockets
Physical connectors used to link together all
variety of electronic devices.  See DB-9, RS-232,
and Centronics.


PM
See preventive maintenance, Presentation Manager
and phase modulation.


PMMU
(Paged Memory Management Unit)  Virtual memory chip
for the 68020 processor (it is built in on the
68030), which is required to run A/UX on the Mac or
any 68020 platform running hardware virtual memory.


PMOS
(Positive channel MOS)  Pronounced "P moss."  Type
of microelectronic circuit in which the base
material is positively charged.  PMOS transistors
were used in the first microprocessors and are
still used in CMOS.  They are also used in low-cost
products (calculators, watches, etc.).


PMS
(Pantone Matching System)  Color matching system
that has assigned a number to over 500 different
colors.


pocket computer
Hand-held, calculator-sized computer that runs on
batteries.  It can be plugged into a personal
computer for data transfer.


point
(1) To move the cursor onto a line or image on
screen by rolling a mouse across the desk or by
pressing the arrow keys.

(2) In typography, a unit equal to 1/72nd of an
inch, used to measure the vertical height of a
printed character.


point and shoot
To select a menu option or activate a function by
moving the cursor onto a line or object and
pressing the return key or mouse button.


point of sale
Capturing data at the time and place of sale.
Point of sale systems use personal computers or
specialized terminals that are combined with cash
registers, optical scanners for reading product
tags, and/or magnetic stripe readers for reading
credit cards.

   Point of sale systems may be online to a central
computer for credit checking and inventory
updating, or they may be stand-alone machines that
store the daily transactions until they can be
delivered or transmitted to the main computer for
processing.


pointer
(1) In database management, an address embedded
within the data that specifies the location of data
in another record or file.

(2) In programming, a variable that is used as a
reference to the current item in a table (array) or
to some other object, such as the current row or
column on screen.

(3) On-screen symbol used to identify menu
selections or the current screen location.  It is
moved by a mouse or other pointing device.


pointing device
Input device, such as a mouse or graphics tablet,
used to move the cursor on screen or to draw an
image.


Poisson distribution
Statistical method developed by the 18th century
French mathematician S. D. Poisson, which is used
for predicting the probable distribution of a
series of events.  For example, when the average
transaction volume in a communications system can
be estimated, Poisson distribution is used to
determine the probable minimum and maximum number
of transactions that can occur within a given time
period.


poke
See peek/poke.


polarity
(1) Direction of charged particles, which may
determine the binary status of a bit.

(2) In micrographics, the change in the light to
dark relationship of an image when copies are made.
Positive polarity is dark characters on a light
background; negative polarity is light characters
on a dark background.


polarized
One-way direction of a signal or the molecules
within a material pointing in one direction.


Polish notation
Method for expressing a sequence of calculations
developed by the Polish logician Jan Lukasiewicz in
1929.  For example, A(B+C) would be expressed as
* A + B C.  In reverse Polish notation, it would be
A B C + *.


polling
Communications technique that determines when a
terminal is ready to send data.  The computer
continually interrogates its connected terminals in
a round robin sequence.  If a terminal has data to
send, it sends back an acknowledgement and the
transmission begins.  Contrast with interrupt-
driven, in which the terminal generates a signal
when it has data to send.


polling cycle
One round in which each and every terminal
connected to the computer or controller has been
polled once.


polygon
In computer graphics, a multi-sided object that can
be filled with color or moved around as a single
entity.


polyhedron
Six- or more-sided object.  A group of connected
polygons.


polyline
In computer graphics, a single entity that is made
up of a series of connected lines.


polymorphic tweening
See tweening.


polymorphism
Meaning many shapes.  In object-oriented
programming, the ability of a generalized request
(message) to produce different results based on the
object that it is sent to.


Polyvision
Flat panel display from Alpine Polyvision Inc. that
uses a plastic film of metal ions sandwiched
between horizontal and vertical electrodes.  Where
current intersects, the metal ions turn black.

pop
See push/pop.


POP-11
(Package for Online Programming)  General-purpose
programming language with list processing and
compiler writing functionality from SD-Scicon PLC.


pop-down menu
See pull-down menu.


populate
To plug in chips or components into a printed
circuit board.  A fully populated board is one that
contains all the devices it can hold.


popup
(1) Type of menu called for and displayed on top of
the existing text or image.  When the item is
selected, the menu disappears and the screen is
restored.

(2) Same as TSR.


port
(1) Pathway into and out of the computer.    The
serial and parallel ports on a personal computer
are external sockets for plugging in communications
lines, modems and printers.  On a front end
processor, serial ports connect to communications
lines and modems.

(2) To convert software to run in a different
computer environment.


port address
Physical identification of an I/O port.  See PC
conflicts.


port expander
Device that connects several lines to one port in
the computer.  A line is given access to the port
either by a hardware switch or through software
selection.


portability
See portable.


portable
Refers to software that can be easily moved from
one type of machine to another.  It implies a
product that has a version for several hardware
platforms or has built-in capabilities for
switching between them.  However, a program that
can be easily converted from one machine type to
another is also considered portable.


portable computer
Personal computer that can be easily transported.
Compared to desktop models, it has limited
expansion slots and disk capacity.

   The first portable was the Osborne I, a CP/M
machine that was soon followed by many others, such
as the Kaypro and Otrona's Attache.  In late 1982,
Compaq introduced the first MS-DOS portable.  See
laptop computer, notebook computer and pocket
computer.


Portable NetWare
OEM version (C source code) of Novell's NetWare
operating system that can be compiled for a
specific vendor's machine.


porting
See port.


portrait
Orientation in which the data is printed across the
narrow side of the form.

      ┌────────┐
      │        │     ┌────────────┐
      │Portrait│     │ Landscape  │
      │        │     │            │
      │        │     └────────────┘
      └────────┘



POS
See point of sale.


positive logic
Use of low voltage for a 0 bit and high voltage for
a 1 bit.  Contrast with negative logic.


POSIX
(Portable Operating System Interface for UNIX)
IEEE standard that defines the language interface
between application programs and the UNIX operating
system.  Adherence to the standard ensures
compatibility when programs are moved from one UNIX
computer to another.


POST
(Power On Self Test)  Series of built-in
diagnostics that are performed when the computer is
first started.  Proprietary codes are generated
(POST codes) that indicate test results.  See
diagnostic board.


postfix notation
See reverse Polish notation.


postprocessor
Software that provides some final processing to
data, such as formatting it for display or
printing.


PostScript
Page description language from Adobe Systems, Inc.,
Mountain View, CA, used in a wide variety of
printers, imagesetters and display systems.

   PostScript commands do not drive the printer
directly.  They are language statements (ASCII
text) that are translated into the printer's
machine language by a PostScript interpreter built
into the printer.  Fonts are scaled to size by the
interpreter, thus eliminating the need to store a
variety of font sizes on disk.

   PostScript Level 2, downward compatible with
original PostScript, adds data compression and
enhancements, especially for color printing.

   PostScript fonts come in Type 1 and Type 3
formats, and Adobe makes only Type 1.  Type 1 fonts
are widely used and are made by other companies as
Adobe later made the format public.

   Type 1 fonts are encrypted and compressed and
also allow for hints, which improve the appearance
of text, especially at desktop laser printer
resolutions.  Type 1 fonts use a simpler, more
efficient command language than Type 3.  With Adobe
Type Manager, Type 1 fonts can also be used on non-
PostScript printers.

   Type 3 fonts do not use encryption or hints, but
can use the entire PostScript language to create
complex designs that include fills and patterns.
Type 3 fonts can also be bitmaps.  In order to
speed up printing small fonts on PostScript
printers, Windows 3.1 creates Type 3 bitmaps from
its TrueType outlines.

   Originally developed as a device-independent
imaging language, PostScript is used extensively on
Macs and PCs.  It has also migrated to
workstations, minis and mainframes.


pot
See potentiometer.


potentiometer
Device that controls the amount of current that
flows through a circuit, such as a volume switch on
a radio.


POTS
(Plain Old Telephone Service)  Traditional analog
telephone network.


power
See computer power.


power down
To turn off the computer in an orderly manner by
making sure all applications have been closed
normally and then shutting the power.


Power Platform
IBM 486 replacement processor boards for PS/2
models.


power supply
Electrical system that converts AC current from the
wall outlet into the DC currents required by the
computer circuitry.


power up
To turn the computer on in an orderly manner.


power user
Person who is very proficient with personal
computers.  It implies knowledge of a variety of
software packages.


PowerBook
Family of Macintosh portable computers from Apple
that include a trackball centered in a wrist rest.
See Macintosh for specifications.


PowerBuilder
Application generator for developing Windows
client/server applications from PowerSoft Corp.,
Burlington, MA.  Its programming language is a
superset of Visual BASIC.  Supports SQL and a
variety of databases including DB2 and Oracle.


PowerOpen
Version of UNIX from IBM/Apple's joint venture that
runs AIX and Mac applications on the PowerPC.


PowerPC
RISC chip from Motorola for IBM/Apple's joint
venture.


PowerPoint
Macintosh desktop presentation program from
Microsoft.  It was the first desktop presentation
program for the Mac and provides the ability to
create output for overheads, handouts, speaker
notes and film recorder.  Color palettes for
Genigraphics slides accompany the product.


PowerSCSI!
Software from Future Domain Corp. that accompanies
its SCSI host adapters for PCs allowing them to
control all SCSI peripherals.  It translates the
popular methods for accessing SCSI devices,
including DOS' int 13, Windows FastDisk, ASPI and
various CD ROM methods into industry standard CAM,
supported on its host adapter.  See CorelSCSI.


PPGA
(Plastic PGA)  See PGA.


pph
(Pages Per Hour)  Measures printing speed.


ppi
(Pixels Per Inch)  Measures display or print
elements.

(2) (Points Per Inch, Pulses Per Inch)  Measures
mouse movement.


ppm
(Pages Per Minute)  Measures printing speed.


PQFP
(Plastic Quad FlatPack)  Surface mount chip housing
with flat leads on all four sides.


PR/SM
(Processor Resource/Systems Manager)  IBM mainframe
feature that allows the CPU to run as multiple
logical processors, each capable of running a
different operating system and set of applications.
Standard on ES/9000 models, it is an upgrade to
3090 processors.


PRAM
(Parameter RAM)  Pronounced "P RAM."  Battery-
backed part of the Macintosh's memory that holds
Control Panel settings and the settings for the
hidden desktop file.  If the command and option
keys are held down at startup, the desktop settings
are cleared and a dialog to rebuild the desktop is
initiated.


precedence
Order in which an expression is processed.
Mathematical precedence is normally:

   1. unary + and - signs
   2. exponentiation
   3. multiplication and division
   4. addition and subtraction

   In the following two examples:

   fahrenheit-32*5/9 and (fahrenheit-32)*5/9

   the first one is incorrect, because
multiplication is evaluated before subtraction.

   Logical precedence is normally:

   1. NOT
   2. AND
   3. OR

   In the dbase query:

list for item = "TIE" .and. color = "GRAY"
   .or. color = "RED"

all gray ties and anything red will be selected,
since ANDs are evaluated before ORs.  Grouping the
colors in parentheses:

  (color="GRAY" .or. color="RED")

yields only gray and red ties.


precision
Number of digits used to express the fractional
part of a number.  The more digits, the more
precision.  See single precision and double
precision.


predicate
In programming, a statement that evaluates an
expression and provides a true or false answer
based on the condition of the data.


preemptive multitasking
Multitasking that shares processing time with all
running programs.  For example, background programs
can be given recurrent CPU time no matter how heavy
the foreground load.  Contrast with nonpreemtive
multitasking.


prefix notation
See Polish notation.


prepress
In typography and printing, the preparation of
camera-ready materials up to the actual printing
stage, which includes typesetting and page makeup.


preprocessor
Software that performs some preliminary processing
on the input before it is processed by the main
program.


presentation graphics
Business graphics, such as bar charts and graphs,
that are used as presentation material in meetings
and lectures.  It implies the ability to create
stylized graphics such as 3-D charts.


Presentation Manager
Graphical user interface included with OS/2, which
provides a desktop and windows environment similar
to Windows.


Prestel
Commercial videotex service of British Telecom
(formerly part of the British Post Office).


preventive maintenance
Routine checking of hardware that is performed by a
field engineer on a regularly scheduled basis.  See
remedial maintenance.


PRI
See ISDN.


primary index
The index that controls the current processing
order of a file.  See secondary index.


primary storage
The computer's internal memory (RAM).  Contrast
with secondary storage.


primitive
(1) In computer graphics, a graphics element that
is used as a building block for creating images,
such as a point, line, arc, cone or sphere.

(2) In programming, a fundamental instruction,
statement or operation.

(3) In microprogramming, a microinstruction, or
elementary machine operation.


print buffer
See printer buffer.


print column
Column of data on a printed report that may be
subtotalled or totalled.  Print columns are the
heart of a report writer's description.


print engine
See printer engine.


print head
Mechanism that deposits ink onto paper in a
character printer.


print image
Text or graphics document that has been prepared
for the printer.  Format codes for the required
printer have been embedded in the document at the
appropriate places.  With text files, headers,
footers and page numbers have been created and
inserted in every page.


print image format
See print image.


print queue
Disk space that holds output designated for the
printer until the printer can receive it.


print screen
Ability to print the current on-screen image.  See
screen dump.


print server
Computer in a network that controls one or more
printers.  It stores the print-image output from
all users of the system and feeds it to the printer
one job at a time.  This function may be part of
the network operating system or an add-on utility.


print spooler
Software that manages printing in the background.
When an application is made to print, it quickly
generates the output on disk and the spooler feeds
the print images to the printer at slower printing
speeds.  This second step can be run in the
background without appreciably interfering with
user interaction in the foreground.  See spooling.


print to disk
To redirect output from the printer to the disk.
The resulting file contains text and graphics with
all the codes required to direct the printer to
print it.  The file can be printed later or at a
remote location without requiring the word
processor, DTP or drawing program that was
originally used to create it.  This is actually the
first stage of a print spooling operation.  See
print spooler.


printed circuit board
Flat board that holds chips and other electronic
components.  The board is made of reinforced
fiberglass or plastic and interconnects components
via copper pathways.  The main printed circuit
board in a system is called a system board or
motherboard, while smaller ones that plug into the
slots in the main board are called boards or cards.

   The printed circuit board of the 1960s connected
discrete components together.  The circuit board of
the 1990s interconnects chips, each containing
hundreds of thousands and millions of elementary
components.

   The "printed" circuit is really an etched
circuit.  A copper foil is placed over the glass or
plastic base and covered with a photoresist.  Light
is shined through a negative image of the circuit
paths onto the photoresist, hardening the areas
that will remain after etching.  When passed
through an acid bath, the unhardened areas are
washed away.  A similar process creates the
microminiaturized circuits on a chip (see chip).


printer
Device that converts computer output into printed
images.  Following is an overview of printer types.

                  Serial Printers
Serial printers print a character at a time from
approximately 10 to 400 cps (about 6 to 240 lpm).
Serial printers use dot matrix and character
printer technologies.  Serial printers are referred
to as character printers regardless of the printing
technology employed.


                   Line Printers
Line printers print a line at a time from
approximately 100 to 5,000 lpm and are the standard
impact printers found in datacenters.  They employ
drum, chain, train, band, dot matrix and dot band
technologies.


                   Page Printers
Page printers, also called laser printers, print a
page at time from approximately 4 to 215 ppm (400
to 14,000 lpm), and generally use the copy machine
electrophotographic technique.  High-speed page
printers are used in large datacenters, and desktop
laser printers are now commonplace for personal
computers.


                 Graphics Printers
Graphics printers use impact serial dot matrix,
impact line dot matrix, impact line dot band and
all non-impact technologies.


                  Color Printers
Color printers use impact dot matrix with multiple
color ribbons, electrophotographic with multiple
color toners, electrostatic plotters with multiple
color toners, printers using Cycolor technology,
ink jet with multiple color inks and thermal-
transfer with multiple colors.


                  IMPACT PRINTERS

           Band, Chain & Train Printers
A continuous loop of several character sets
connected together spins horizontally around a set
of hammers.  When the desired character is in front
of the selected print location, that particular
hammer hits the paper forcing the shaped character
image on the band, chain, or train into the ribbon
and onto the paper.

   Since the chain, band, or train moves so fast,
it appears to print a line at a time.  A band is a
solid loop, while the chain is individual character
images (type slugs) chained together.  The train is
individual character images (type slugs) revolving
in a track, one pushing the other.  See band
printer and chain printer.


                   Drum Printer
A rotating drum (cylinder) contains the character
set carved around it for each print location, like
an odometer.  When the desired character for the
selected print location has rotated around to the
hammer line, the appropriate hammer hits the paper
from behind, forcing it against the ribbon that is
between the paper and the drum.  Since the drum
rotates so fast, it appears to print a line at a
time.  See drum printer.


                Character Printers
Character printers are similar to Selectric
typewriters, printing one character at a time.  A
daisy wheel or similar mechanism is moved serially
across the paper.  At the selected print location,
a hammer hits the shaped character image on the
wheel into the ribbon and onto the paper.


                 Serial Dot Matrix
A vertical set of printing wires moves serially
across the paper, formulating characters by
impacting a ribbon and transferring dots of ink
onto the paper.  The clarity of the character is
determined by how close the dots print together.


                  Line Dot Matrix
A stationary or oscillating line of printing wires
generates images by impacting a ribbon and
transferring dots of ink onto the paper a line at a
time.


                  Dot Band Matrix
A combination band and dot matrix configuration.  A
steel band is etched to create fingers (petals).
At the tip of each finger is an anvil with a steel
dot attached.  Print hammers impact the anvils,
which are larger than the dots, allowing the dots
to be printed in areas between the hammer faces.
Different size dots may be used on different bands
to change the speed of printing and the print
resolution.


                NON-IMPACT PRINTERS

                Electrophotographic
A drum is charged with a high voltage and an image
source paints a negative light copy of the image to
be printed onto the drum.  Where the light falls
onto the drum, the drum is discharged.  A toner
(ink) is allowed to adhere to the charged portion
of the drum.  The drum then fuses the image onto
the paper by pressure and heat.  See
electrophotographic.


                 Electrosensitive
Dots are charged onto specially coated silver-
colored paper, usually in a serial fashion.  The
charge removes the aluminum coating, leaving a
black image.


                   Electrostatic
Dots are charged onto specially coated paper,
usually a line at a time.  An ink adheres to the
charges that become embedded into the paper by
pressure or by heat.


                      Ink Jet
Continuous streams of ink are sprayed onto paper,
or droplets of ink generate a dot matrix image,
usually in a serial fashion.  Another technique
uses ink in a solid form, which is melted just
before it is ejected.


                    Ionographic
A technology that uses ion deposition and is
similar to direct electrostatic, except that in
this type of indirect electrostatic, the image is
formed on a dielectric surface and then transferred
to plain paper.


                  Magnetographic
A magnetic image is created by a set of recording
heads across a magnetic drum.  Monocomponent toner
is applied to the drum to develop the image.  It is
transferred to paper by light pressure and an
electrostatic field.  The toner is then fused by
heat.


                      Thermal
Dots are burned onto specially coated paper that
turns black or blue when heat is applied to it.  A
line of heat elements forms a dot matrix image as
the paper is passed across it, or a serial head
with heating elements is passed across the paper.


               Thermal Wax Transfer
Dots of ink are transferred from a mylar ribbon
onto paper by passing the ribbon and the paper
across a line of heat elements, or by passing a
serial head with heating element across the paper.
See thermal wax transfer.


printer buffer
Memory device that accepts printer output from one
or more computers and transmits it to the printer.
It lets the computer dispose of its printer output
at full speed without waiting for each page to
print.  Printer buffers with automatic switching
are connected to two or more computers and accept
their output on a first-come, first-served basis.


printer cable
Wire that connects a printer to a computer.  On a
PC, the cable has a 25-pin DB-25 male connector for
the computer and a 36-pin Centronics male connector
for the printer.


printer driver
Software routine that converts an application
program's printing request into the language the
printer understands.


printer engine
Unit within the printer that does the actual
printing.  For example, in a laser printer, it is
the "copy machine" unit, which transfers and fuses
the toner onto the paper.  It is specified by its
resolution and speed.


printer file
(1) Document in print image format ready to be
printed.  See print to disk.

(2) Same as printer driver.


printer font
Font used for printing.  Printer and screen
resolutions are not the same, thus fonts generated
for the printer will not display accurately on
screen.  Contrast with screen font.


printout
(PRINTer OUTput)  Same as hard copy.


privacy
Authorized distribution of information (who has a
right to know?).  Contrast with security, which
deals with unauthorized access to data.


Private Eye
Headband-mounted LED display system from Reflection
Technology, Waltham, MA, that plugs into a PC.  Its
1x1" screen gives the appearance of a 12" monitor
floating in space in front of the viewer.


private file
File made available only to the user that created
it.  Contrast with public file.


private line
(1) Dedicated line leased from a common carrier.

(2) Line owned and installed by the user.


PRMD
(PRivate Management Domain)  Inhouse e-mail
service.  See X.400.


PRN
(PRiNter)  DOS name for the first connected
parallel port.  See DOS device names.


problem-oriented language
Computer language designed to handle a particular
class of problem.  For example, COBOL was designed
for business, FORTRAN for scientific and GPSS for
simulation.


procedural language
Programming language that requires programming
discipline, such as COBOL, FORTRAN, BASIC, C,
Pascal and dBASE.  Programmers writing in such
languages must develop a proper order of actions in
order to solve the problem, based on a knowledge of
data processing and programming.  Contrast with
non-procedural language.

   The following dBASE example shows procedural and
non-procedural language to list a file.

  Procedural          Non-procedural (interactive)
USE FILEX                   USE FILEX
  DO WHILE .NOT. EOF        LIST NAME, AMOUNTDUE
    ? NAME, AMOUNTDUE
    SKIP
  ENDDO



procedure
(1) Manual procedures are human tasks.

(2) Machine procedures are lists of routines or
programs to be executed, such as described by the
job control language (JCL) in a mini or mainframe,
or the batch processing language in a personal
computer.

(3) In programming, another term for a subroutine
or function.


procedure oriented
Application that forces the user to follow a
predefined path from step A to step B.  Data entry
programs are typical examples.  Contrast with event
driven.


process
To manipulate data in the computer.  The computer
is said to be processing no matter what action is
taken upon the data.  It may be updated or simply
displayed on screen.

   In order to evaluate a computer system's
performance, the time it takes to process data
internally is analyzed separately from the time it
takes to get it in and out of the computer.  I/O is
usually more time consuming than processing.  See
computer (The 3 C's).


process bound
Excessive amount of processing causing an imbalance
between I/O and processing.  Process-bound
applications may slow down other users in a
multiuser system.

   A personal computer is process bound when it is
recalculating a spreadsheet, for example.


process control
Automated control of a process, such as a
manufacturing process or assembly line.  It is used
extensively in industrial operations, such as oil
refining, chemical processing and electrical
generation.  It uses analog devices to monitor
real-world signals and digital computers to do the
analysis and controlling.  It makes extensive use
of analog/digital, digital/analog conversion.


processing
Manipulating data within the computer.  The term is
used to define a variety of computer functions and
methods.  See centralized processing, distributed
processing, batch processing, transaction
processing, multiprocessing and computer (The 3
C's).


processor
(1) Same as CPU.

(2) May refer to software.  See language processor
and word processor.


processor unit
Same as computer.


Procomm
Popular PC shareware communications program from
Datastorm Technologies, Inc., Columbia, MO, that
supports a wide number of protocols and terminals.
Procomm Plus is the commercial version with more
features.


PRODIGY
Online information service (partnership of IBM and
Sears) that includes weather and stock market
reports, airline scheduling and at-home shopping.
Users receive a communications program that must be
installed in their personal computer, which
provides full-screen displays and simplifies the
logon.  See online services.


ProDOS
(PROfessional Disk Operating System)  Operating
system for the Apple II family that superseded
Apple's DOS 3.3.  It provides a hierarchical file
system with file names up to 15 characters in
length.


production database
Central database containing an organization's
master files and daily transaction files.


production system
Computer system used to process an organization's
daily work.  Contrast with a system used only for
development and testing or for ad hoc inquiries and
analysis.


Professional Write
Word processing program for DOS and Windows from
Software Publishing Corp., Mountain View, CA.  It
is easy to use and meets the needs of many who
write uncomplicated letters and memos.  Originally
called PFS:Write, it was one of the earliest PC
word processors.


Professional YAM
(Professional Yet Another Modem)  PC communications
program from Omen Technology, Inc., Portland, OR,
for the serious communications user.  It is a
flexible, full-featured program that supports a
wide variety of terminals and protocols.


PROFS
(PRofessional OFfice System)  IBM office automation
software for the VM mainframe environment.  It
provides an e-mail facility for text and graphics,
a library service for centrally storing text,
electronic calendars and appointment scheduling,
and it allows document interchange with DISOSS
users.


ProgMan
See Program Manager.


program
Collection of instructions that tell the computer
what to do.  A program is called software; hence,
program, software and instructions are synonymous.
A program is written in a programming language and
is converted into the computer's machine language
by software called assemblers, compilers and
interpreters.

   A program is made up of instructions, buffers
and constants.  Instructions are the directions
that the computer will follow (the program's
logic).  Buffers are reserved space in the program
that will accept and hold the data while it's being
processed.  Constants are fixed values within the
program used for processing.  See computer
(The 3 C's).

   The program calls for data in an input-process-
output sequence.  After data has been input into
one of the program's buffers from a peripheral
device (keyboard, disk, etc.), it is processed.
The results are then output to a peripheral device
(screen, printer, etc.).  If data has been updated,
it is output back onto the disk.

   The application program, which does the actual
data processing, does not instruct the computer to
do everything.  When it is ready for input or needs
to output data, it sends a request to the operating
system, which performs those services and then
turns control back to the application program.


program generator
See application generator.


program logic
Sequence of instructions in a program.  There are
many logical solutions to a problem.  If you give a
specification to ten programmers, each one may
create program logic that is slightly different
than all the rest, but the results can be the same.
The solution that runs the fastest is usually the
most desired, however.

   Program logic is written using three classes of
instructions: sequential processing, selection and
iteration.

   1. Sequential processing is the series of steps
that do the actual data processing.  Input, output,
calculate and move (copy) instructions are used in
sequential processing.

   2. Selection is the decision making within the
program and is performed by comparing two sets of
data and branching to a different part of the
program based on the results.  In assembly
languages, the compare and branch instructions are
used.  In high-level languages, IF THEN ELSE and
CASE statements are used.

   3. Iteration is the repetition of a series of
steps and is accomplished with DO LOOPS and FOR
LOOPS in high-level languages and GOTOs in assembly
languages.  See loop.


program maintenance
Updating programs to reflect changes in the
organization's business or to adapt to new
operating environments.


Program Manager
Control center for Windows 3.x operation.  It
provides the means to launch applications and
manage the desktop.


program state
Operating mode of the computer that executes
instructions in the application program.  Contrast
with supervisor state.


program statement
Phrase in a high-level programming language.  One
program statement may result in several machine
instructions when the program is compiled.


program step
Elementary instruction, such as a machine language
instruction or an assembly language instruction.
Contrast with program statement.


program-to-program communications
Communications between two programs.  Often
confused with peer-to-peer communications, it is a
set of protocols a program uses to interact with
another program.  Peer-to-peer establishment is the
network's responsibility.  You can have program-to-
program communications in a master-slave
environment without peer-to-peer capability.


programmable
Capable of following instructions.  What sets the
computer apart from all other electronic devices is
its programmability.


programmable calculator
Limited-function computer capable of working with
only numbers and not alphanumeric data.


programmatic interface
Same as API.


programmer
Person who designs the logic for and writes the
lines of codes of a computer program.  See
application programmer and systems programmer.


programmer analyst
Person who analyzes and designs information systems
and designs and writes the application programs for
the system.  A programmer analyst is both systems
analyst and applications programmer.


Programmer's Switch
Physical buttons included with the Macintosh (fkey
on the LC) that include a System Reset button and a
Debugging button that will invoke MacsBug if
present or switch to the built in monitor in ROM.


programming
Creating a computer program.  The steps are:

 1. Developing the program logic to solve the
    particular problem.

 2. Writing the program logic in a specific
    programming language (coding the program).

 3. Assembling or compiling the program to turn it
    into machine language.

 4. Testing and debugging the program.

 5. Preparing the necessary documentation.

   The logic is the most difficult part of
programming.  Writing the language statements is
comparatively easy once the solution has been
developed.  However, regardless of how difficult
the program may be, documenting it is considered
the most annoying activity by most programmers.


programming interface
See API.


programming language
Language used to write instructions for the
computer.  It lets the programmer express data
processing in a symbolic manner without regard to
machine-specific details.

   The statements that are written by the
programmer are called source language, and they are
translated into the computer's machine language by
programs called assemblers, compilers and
interpreters.  For example, when a programmer
writes MULTIPLY HOURS TIMES RATE, MULTIPLY must be
turned into a code that means multiply, and HOURS
and RATE must be turned into memory locations where
those items of data are actually located.

   Like human languages, each programming language
has its own grammar and syntax.  There are many
dialects of the same language, and each dialect
requires its own translating system.  Standards
have been set by ANSI for many programming
languages, and ANSI-standard languages are dialect
free.  However, it can take years for new features
to be included in ANSI standards, and new dialects
inevitably spring up as a result.

   Programming languages fall into two categories:
low-level assembly languages and high-level
languages.  Assembly languages are available for
each CPU family, and each assembly instruction is
translated into one machine instruction by the
assembler program.  With high-level languages, a
programming statement may be translated into one or
several machine instructions by the compiler.

   Following is a synopsis of the major high-level
languages.  Look up each one for more details.


Ada
Comprehensive, Pascal-based language used by the
Dept. of Defense.


ALGOL
International language for expressing algorithms.


APL
Used for statistics and mathematical matrices.
Requires special keyboard symbols.


BASIC
Developed as a timesharing language in the 1960s.
Widely used in microcomputer programming.


C
Developed in the 1980s at AT&T.  Widely used to
develop commercial applications.  UNIX is written
in C.


C++
Object-oriented version of C that is becoming very
popular.


COBOL
Developed in the 1960s.  Widely used for mini and
mainframe programming.  Also available for personal
computers.


dBASE
Widely used in business applications.  Offshoots of
dBASE ("Xbase" languages) are Clipper, Quicksilver,
FoxBase and FoxPro.


FORTH
Developed in the 1960s.  Used in process control
and game applications.


FORTRAN
Developed in 1954 by IBM.  First major scientific
programming language.  Some commercial applications
have been developed in it.


LISP
Developed in 1960.  Used for AI applications.  Its
syntax is very different than other languages.


Logo
Developed in the 1960s.  Noted for its ease of use,
it includes "turtle graphics" drawing functions.


Modula-2
Enhanced version of Pascal introduced in 1979.


MUMPS
Originally Massachusetts Utility MultiProgramming
System, it includes its own database.  Widely used
in medical applications.


Pascal
Originally an academic language developed in the
1970s.  Borland commercialized it with its Turbo
Pascal.


Prolog
Developed in France in 1973.  Used throughout
Europe and Japan for AI applications.


REXX
Runs on IBM mainframes.  Used as a general purpose
macro language.


progressive scan
Same as non-interlaced.


project manager
Software used to monitor the time and materials on
a project.  All tasks to complete the project are
entered into the database, and the program computes
the critical path, the series of tasks with the
least amount of slack time.  Any change in the
critical path slows down the entire project.


Prokey
Keyboard macro processor for PCs from RoseSoft,
Inc., Bellevue, WA, that allows users to eliminate
repetitive typing by setting up an occurrence of
text or a series of commands as a macro.


Prolog
(PROgramming in LOGic)  Programming language used
for developing AI applications (natural language
translation, expert systems, abstract problem
solving, etc.).  Developed in France in 1973, it is
used throughout Europe and Japan and is gaining
popularity in the U.S.

   Similar to LISP, it deals with symbolic
representations of objects.  The following example,
written in Univ. of Edinburgh Prolog, converts
Fahrenheit to Celsius:

  convert:- write('Enter Fahrenheit'),
   read(Fahr),
   write('Celsius is '),
   Cent is (5 * (Fahr - 32)) / 9,
   write(Cent),nl.



PROM
(Programmable Read Only Memory)  Permanent memory
chip that is programmed, or filled, by the customer
rather than by the chip manufacturer.  Contrast
with ROM, which is programmed at the time of
manufacture.  See PROM programmer.


PROM blower
Same as PROM programmer.


PROM programmer
Device that writes instructions and data into PROM
and/or EPROM chips.  The bits in a new PROM are all
1s (continuous lines).  The PROM programmer only
creates 0s, by "blowing" the middle out of the 1s.
The bits in EPROMs, which are not permanently
altered, can be erased under ultraviolet light and
reprogrammed.


prompt
Software message that requests action by the user;
for example, "Enter employee name."  Command-driven
systems issue a cryptic symbol when ready to accept
a command; for example, in dBASE it is simply a dot
(.), in UNIX, a $, and in DOS, the venerable C:\>.


propagation
Transmission (spreading) from one place to another.


propagation delay
Time it takes to transmit a signal from one place
to another.


property list
In a list processing language, an object that is
assigned a descriptive attribute (property) and a
value.  For example, in Logo, PUTPROP "KAREN
"LANGUAGE "PARADOX assigns the value PARADOX to the
property LANGUAGE for the person named KAREN.  To
find out what language Karen speaks, the Logo
statement PRINT GETPROP "KAREN "LANGUAGE will
generate PARADOX as the answer.


proportional spacing
Character spacing based on the width of each
character.  For example, an I takes up less space
than an M.  In monospacing (fixed), the I and M
each take up the same space.  See kerning.


proprietary software
Software owned by an organization or individual.
Contrast with public domain software.


Protected Mode
In Intel 286s and up, an operational state that
allows the computer to address all of memory.  It
also prevents an errant program from entering into
the memory boundary of another.  See Real Mode,
Virtual 8086 Mode and memory protection.


protocol
Rules governing transmitting and receiving of data.
See communications protocol and OSI.


protocol stack
Hierarchy of protocols used in a communications
network.  See OSI.


protocol suite
Same as protocol stack.


prototyping
Creating a demo of a new system.  Prototyping is
essential for clarifying information requirements.
The design of a system (functional specs) must be
finalized before the system can be built.  While
analytically-oriented people may have a clear
picture of requirements, others may not.

   Using fourth-generation languages, systems
analysts and users can develop the new system
together.  Databases can be created and manipulated
while the user monitors the progress.

   Once users see tangible output on screen or on
paper, they can figure out what's missing or what
the next question might be if this were a
production system.  If prototyping is carefully
done, the end result can be a working system.

   Even if the final system must be reprogrammed in
other languages for standardization or machine
efficiency, prototyping has served to provide
specifications for a working system rather than a
theoretical one.


Prt Sc
See print screen.


PS
(Personal Services)  IBM office automation software
for PCs, minis and mainframes, which includes word
processing, electronic mail and library services.


PS/1
IBM home computer series introduced in 1990 that
features an integrated monitor and easy-to-open
case.  Original models use the 286 CPU and PC bus.
See PC.


PS/2
IBM personal computer series introduced in 1987
that supersedes the original PC line.  It features
the 3.5" microfloppy disk, VGA graphics and Micro
Channel bus.  The 3.5" disks and VGA are now common
in all PCs and Micro Channel PCs are offered by
some non-IBM vendors.  Smaller PS/2 models use the
original PC bus.  See PC.


PS/2 bus
Same as Micro Channel.


pseudo compiler
Compiler that generates a pseudo language, or
intermediate language, which must be further
compiled or interpreted for execution.


pseudo-duplexing
Communications technique that simulates full-duplex
transmission in a half-duplex line by turning the
line around very quickly.


pseudo language
Intermediate language generated from a source
language, but not directly executable by a CPU.  It
must be interpreted or compiled into machine
language for execution.  It facilitates the use of
one source language for different types of
computers.  See "ANDF" in OSF definition.


PSK
See DPSK.


PSN
(1) (Packet-Switched Network)  Communications
network that uses packet switching technology.

(2) See Personal Server Network.


PSS
See EPSS.


PSTN
(Public Switched Telephone Network)  Worldwide
voice telephone network.


PSW
(Program Status Word)  Hardware register that
maintains the status of the program being executed.


PTOCA
(Presentation Text Object Content Architecture)
See MO:DCA.


PTT
(Postal, Telegraph & Telephone)  Governmental
agency responsible for combined postal, telegraph
and telephone services in many European countries.


PU
(Physical Unit)  In SNA, software responsible for
managing the resources of a node, such as data
links.  A PU supports a connection to the host
(SSCP) for gathering network management statistics.


PU 2.1
(Physical Unit 2.1)  In SNA, the original term for
Node Type 2.1, which is software that provides
peer-to-peer communications between intelligent
devices (PCs, workstations, minicomputers).  Only
LU 6.2 sessions are supported between Type 2.1
nodes (PU 2.1).


public domain software
Software in which ownership has been relinquished
to the public at large.  See freeware and
shareware.


public file
File made available to all other users connected to
the system or network.  Contrast with private file.


Publish and Subscribe
Macintosh System 7 capability that provides hot
links between files.  All or part of a file can be
published into an "edition file," which is imported
into a subscriber file.  When any of the published
files are updated, the subscriber file is also
updated.


puck
Puck-like tablet cursor used on a digitizer tablet.


pull-down menu
Also called a pop-down menu, a menu that is
displayed from the top of the screen downward when
its title is selected.  The menu remains displayed
while the mouse button is depressed.  To select a
menu option, the highlight bar is moved (with the
mouse) to the appropriate line and the mouse button
is let go.

   The drop-down menu is a variation that keeps the
menu open after its title is selected.  To select a
menu option, the highlight bar is moved to the line
and the mouse button is clicked.  Key commands may
also activate drop-down menus.


pulse code modulation
See PCM.


pulse level device
Disk drive or other device that inputs and outputs
raw voltages.  Data coding/decoding is in the
controller the device.  Contrast with bit level
device.


PUMA
(Programmable Universal Micro Accelerator)  Chips
and Technolgies' chip set that accelerates graphics
operations for the screen and printer.


punch block
Also called a quick-connect block, a device that
interconnects telephone lines from remote points.
The wires are pushed, or punched, down into metal
teeth that strip the insulation and make a tight
connection.


punched card
Early storage medium made of thin cardboard stock
that holds data as patterns of punched holes.  Each
of the 80 or 96 columns holds one character.  The
holes are punched by a keypunch machine or card
punch peripheral and are fed into the computer by a
card reader.

   Although still used as turnaround documents,
punched cards are practically obsolete.  However,
from 1890 until the 1970s, they were synonymous
with data processing.  Concepts were simple: the
database was the file cabinet; a record was a card.
Processing was performed on separate machines
called sorters, collators, reproducers, calculators
and accounting machines.


push/pop
Instructions that store and retrieve an item on a
stack.  Push enters an item on the stack, and pop
retrieves an item, moving the rest of the items in
the stack up one level.  See stack.


push/pull tractor
Printer tractor that can be switched from pushing
paper onto the platen to pulling it from the
platen.  Single-sheet continuous forms can be
pushed, but most multipart forms and labels must be
pulled to prevent jamming.


put
In programming, a request to store the current
record in an output file.  Contrast with get.


PVGA
(Paradise VGA)  VGA display board or VGA chips from
Paradise Division of Western Digital.


Px64
CCITT standard for transmitting audio and video in
64 Kbits/sec ISDN channels (P represents number of
channels used).  Although video conferencing can be
done in only one or two channels, more are required
for quality viewing of motion.



Q-bus
Bus architecture used in Digital's PDP-11 and
MicroVAX series.


Q&A
Integrated PC file manager and word processor from
Symantec Corp., Cupertino, CA, that includes mail
merge capability as well as a programming language
for customizing data entry forms and reports.  Its
Intelligent Assistant feature provides a query
language that can learn new words from the user.


QAM
(1) (Quadrature Amplitude Modulation)  Modulation
technique that generates four bits out of one baud.
For example, a 600 baud line (600 shifts in the
signal per second) can effectively transmit 2,400
bps using this method.  Both phase and amplitude
are shaped with each baud, resulting in four
possible patterns.

(2) (Quality Assessment Measurement)  System used
to measure and analyze voice transmission.


QBasic
BASIC interpreter from Microsoft that comes with
DOS starting with DOS 5.  It supersedes Microsoft's
GW-BASIC and includes REMLINE.BAS, a program that
helps convert GW-BASIC programs to QBasic.


QBE
(Query By Example)  Method for describing a query
originally developed by IBM for mainframes.  A
replica of an empty record is displayed and the
search conditions are typed in under their
respective columns.  The following query selects
all Pennsylvania records that have a balance due of
$5000 or more.

     City         State Balance due
    ┌────────────┬─────┬─────────────┐
    │            │PA   │>=5000       │

            A query by example



QCIF
(Quarter CIF)  Video format that transmits 9.115
Mbits/sec at 30 frames/sec, one quarter the speed
of CIF.  See H.261.


QEMM-386
(Quarterdeck EMM-386)  Popular DOS memory manager
for 386s and up from Quarterdeck Office Systems,
Santa Monica, CA.  Its Stealth feature in Version
6.0 remaps ROM BIOS routines into EMS to free up
high DOS memory.  It is also part of DESQview 386.
QEMM-50/60 is a version for PS/2 Models 50 and 60
(286s).


QIC
(Quarter Inch Cartridge Drive Standards, Inc.)
International trade association that develops
standards for 1/4" (6.35mm) magnetic tape drives
and cartridges.  QIC-compatible products use a
serpentine recording method.


 Recording     Media   Storage
  Format       Type      (MB)    Interfaces

 MINICARTRIDGE
 QIC-40      DC2000      40    QIC-107, 115, 117
 QIC-80      DC2080      80    QIC-107, 115, 117
             DC2080     120
 QIC-100     DC2000    20/40   QIC-103, 108
 QIC-128     DC2110      86    QIC-103, 108
             DC2165     128
 QIC-385M    QIC-143    385    Floppy, IDE
 QIC-410M    QIC-143    410    SCSI-2
 QIC-6GB(M)  QIC-138      6GB* SCSI-2

 CARTRIDGE
 QIC-24      DC600A      60    QIC-02, 36, SCSI
 QIC-120     DC6150     125    QIC-02, SCSI
 QIC-150     DC6150     150    QIC-02, SCSI
             DC6250     250    SCSI, SCSI-2
 QIC-525     DC6320     320    QIC-02, SCSI, SCSI-2
             DC6525     525
 QIC-1000C   QIC-136      1GB  SCSI, SCSI-2
 QIC-1350    QIC-137   1.35GB  SCSI-2
 QIC-2100C   QIC-137    2.1GB  SCSI-2
 QIC-20GB(C) QIC-139     20GB* SCSI-2

*With QIC-122 or QIC-130 built-in data compression.


QMF
(Query Management Facility)  IBM fourth-generation
language for end-user interaction with DB2.


QNX
Multiuser, multitasking, realtime operating system
for PCs from Quantum Software Systems, Kanata,
Ontario, noted for its low-memory requirement and
rapid response.  Similar to UNIX, it has been in
use since the early 1980s.


quadbit
Group of four bits used in QAM modulation.


quadrillion
One thousand times one billion.  See femtosecond.


quantize
To break into discrete values for sampling
purposes.


QuarkXpress
Desktop publishing program for the Macintosh and
Windows from Quark, Inc., Denver, CO.  Originally
developed for the Mac, it is noted for its precise
typographic control and advanced text and graphics
manipulation.


quartz crystal
Slice of quartz ground to a prescribed thickness
that vibrates at a steady frequency when stimulated
by electricity.  The tiny crystal, about 1/20th by
1/5th of an inch, creates the computer's heartbeat.


Quattro Pro
PC spreadsheet from Borland that provides advanced
graphics and presentation capabilities.  It has an
optional interface that is keystroke, macro and
file compatible with Lotus 1-2-3.  Version 2.0 adds
goal seeking, 3-D graphing and the ability to
create multi-layered slide shows.


query
To interrogate a database (count, sum and list
selected records).  Contrast with report, which is
usually a more elaborate printout with headings and
page numbers.  The report may also be a selective
list of items; hence, the two terms may refer to
programs that produce the same results.


query by example
See QBE.


query language
Generalized language that allows a user to select
records from a database.  It uses a command
language, menu-driven method or a query by example
(QBE) format for expressing the matching condition.

   Query languages are usually included in DBMSs,
and stand-alone packages are available for
interrogating files in non-DBMS applications.  See
query program.


query program
Software that counts, sums and retrieves selected
records from a database.  It may be part of a large
application and be limited to one or two kinds of
retrieval, such as pulling up a customer account on
screen, or it may refer to a query language that
allows any condition to be searched and selected.


queue
Pronounced "Q."  Temporary holding place for data.
See message queue and print queue.


Quick B
CompuServe's communications protocol for
downloading files.


QuickBASIC
Popular BASIC compiler from Microsoft that adds
advanced features to the BASIC language.


QuickC
C compiler from Microsoft that is compatible with
its larger C compiler and is used by the beginner
or occasional programmer.  QuickC for Windows is a
version that works entirely within Windows
environment for developing Windows applications.
It includes the QuickWin library.


Quickdraw
Graphics display system built into the Macintosh.
It accepts commands from the application and draws
the corresponding objects on the screen.  It
provides a consistent interface that software
developers can work with.


Quicken
Popular personal financial management program for
PCs and Macs from Intuit, Menlo Park, CA.  It
writes checks, organizes investments and produces a
variety of financial reports.


QuickPascal
Pascal compiler from Microsoft that is compatible
with Turbo Pascal and provides object oriented
capabilities.


Quicksilver
Family of dBASE III PLUS compilers originally
developed by WordTech Systems, Inc.  In 1992, the
technology was acquired by Borland.  See Arago.


QuickTime
Multimedia extensions to Macintosh's System 7 that
add sound and video capabilities.


QuickWin
Library of C and FORTRAN routines from Microsoft
that allows quick porting of DOS applications to
the Windows environment.  Character-based apps run
in resizable windows.


quit
To exit the current program.  It's a good habit to
quit a program before turning the computer off.
Some programs don't close all files properly until
quit is activated.

   To quit the DOS version of this Glossary, hold
down the Ctrl key and press Q.


qwerty keyboard
Standard English language typewriter keyboard.
Q, w, e, r, t and y are the letters on the top
left, alphabetic row.  It was originally designed
to slow typing to prevent the keys from jamming.
See Dvorak keyboard.



R3000, R4000
Families of 32-bit and 64-bit RISC processors from
MIPS.  MIPS licenses the design to other companies.


R:BASE
Relational DBMS for PCs from Microrim, Inc.,
Bellevue, WA, that provides interactive data
processing, a complete programming language and an
application generator.  It was the first DBMS to
compete with dBASE II in the early 1980s.


RACE
(Random Access Card Equipment)  Early RCA mass
storage device.  Magnetic cards were released from
a cartridge, passed down a raceway and wrapped
around a read/write head.  It often jammed!


RACF
(Resource Access Control Facility)  IBM mainframe
security software introduced in 1976 that verifies
user ID and password and controls access to
authorized files and resources.


rack
Frame or cabinet into which components are mounted.


rack mounted
Components that are built to fit in a metal frame.
Electronic devices, such as testing equipment and
tape drives, are often rack mounted units.


RAD
(Rapid Application Development)  Approach to
systems development that includes automated design
and development tools (CASE) and joint application
development (JAD).  Developed by industry guru,
James Martin, it focuses on human management and
user involvement as much as on technology.


radio
Transmission of electromagnetic energy (radiation)
over the air or through a hollow tube called a
waveguide.  Although radio is often thought of as
only AM or FM, all airborne transmission is radio,
including satellite and line-of-sight microwave.


radio buttons
Series of on-screen buttons that allow only one
selection.  If a button is currently selected, it
will de-select when another button is selected.


radio frequency
See RF.


radix
Base value in a numbering system.  For example, in
the decimal numbering system, the radix is 10.


radix point
Location in a number that separates the integral
part from the fractional part.  For example, in the
decimal system, it is the decimal point.


ragged right
In typography, non-uniform text at the right
margin, such as the text you're reading.


RAID
(Redundant Arrays of Inexpensive Disks)  Category
of disk arrays (two or more drives working
together) that provide increased performance and
various levels of error recovery and fault
tolerance.  The disk controller is designed to
perform these techniques.  In some cases, RAID can
be implemented in software using standard drives
and controllers.

 Level           Configuration

  0  Single disk only or multiple disks using
      disk striping only (essentially non-RAID).

  1  Uses disk mirroring to provide 100%
      duplication of data.

  2  Highest performance.  Uses extra drives to
      detect 2-bit errors and correct 1-bit errors
      on the fly.  Interleaves by bit or block.

  3  Highest performance.  Does parity checking but
      cannot guarantee on-the-fly recovery.
      Interleaves data by bit or block.

  4  Uses dedicated drive for parity.  Can be used
      with only two drives.  Interleaves data by
      sector and can handle multiple I/Os from
      sophisticated operating systems.

  5  Most popular RAID method.  Works with two or
      more drives.  Does not require dedicated
      parity drive.  Can be made fault tolerant.



RAM
(Random Access Memory)  Computer's primary
workspace.  Also true of most memory chips (ROMs,
PROMs, etc.), "random" means that the contents of
each byte can be directly accessed without regard
to the bytes before or after it.  RAM chips require
power to maintain their content.  See dynamic RAM,
static RAM and memory.


RAM cache
See cache.


RAM card
(1) Printed circuit board containing memory chips
that is plugged into a socket within the computer.

(2) Credit-card-sized module that contains memory
chips and battery.  See memory card.


RAM chip
(Random Access Memory chip)  Memory chip.  See
dynamic RAM, static RAM, RAM and memory.


RAM cram
Insufficient memory to run applications, especially
in DOS PCs with its 1MB memory limit.


RAM disk
Disk drive simulated in memory.  To use it, files
are copied from magnetic disk into the RAM disk.
Processing is faster, because there's no mechanical
disk action, only memory transfers.  Updated data
files must be copied back to disk before the power
is turned off, otherwise the updates are lost.
Same as E-disk and virtual disk.


RAM refresh
Recharging dynamic RAM chips many times per second
in order to keep the bit patterns valid.


RAM resident
Refers to programs that remain in memory in order
to interact with other programs or to be instantly
popped up when required by the user.  See TSR.


RAMAC
(Random Access Method of Accounting and Control)
First hard disk computer introduced by IBM in 1956.
All 50 of its 24" platters held a total of five
million characters!  It was half computer, half
tabulator.  It had a drum memory for program
storage, but I/O was wired by plugboard.


RAMDAC
(Random Access Memory Digital to Analog Converter)
The VGA controller chip that maintains the color
palette and converts data from memory into analog
signals for the monitor.


Ramdrive
See DOS RAM disks.


RAMIS II
IBM mainframe DMBS and DSS from On-Line Software
Int'l., Inc., Ft. Lee, NJ.  The earlier version of
RAMIS II was one of the first database packages
with a non-procedural language.


random access
Same as direct access.


random noise
Same as Gaussian noise.


random number generator
Program routine that produces a random number.
Random numbers are created easily in a computer,
since there are many random events that take place;
for example, the duration between keystrokes.  Only
a few milliseconds' difference is enough to seed a
random number generation routine with a different
number each time.  Once seeded, an algorithm
computes different numbers throughout the session.


range
(1) In data entry validation, a group of values
from a minimum to a maximum.

(2) In spreadsheets, a series of cells that are
worked on as a group.  It may refer to a row,
column or rectangular block defined by one corner
and its diagonally opposite corner.


RARP
See ARP.


RAS
(Reliability Availability Serviceability)
Originally an IBM term, it refers to a product's
quality, availability of optional features and ease
of diagnosis and repair.


raster display
Display terminal that generates dots line by line
on the screen.  TVs and almost all computer screens
use the raster method.  Contrast with vector
display.


raster graphics
In computer graphics, a technique for representing
a picture image as a matrix of dots.  It is the
digital counterpart of the analog method used in
TV.  However, unlike TV, which uses one standard,
there are many raster graphics standards.  See
graphics.  Contrast with vector graphics.


raster image processor
See RIP.  Remember...  use the acronym first!


raster scan
Displaying or recording a video image line by line.


rasterize
To perform the conversion of vector graphics
images, vector fonts or outline fonts into bitmaps
for display or printing.  Unless output is printed
on a plotter, which uses vectors directly, all non-
bitmapped images must be rasterized into bitmaps
for display or printing.  See font scaler.


raw data
Data that has not been processed.


ray tracing
In computer graphics, the creation of reflections,
refractions and shadows on a graphics image.  It
follows a series of rays from a specific light
source and computes each pixel in the image to
determine the effect of the light.  It is a very
process-intensive operation.


RBASE
See R:BASE.


RBHC
(Regional Bell Holding Company)  Same as RBOC.


RBOC
(Regional Bell Operating Company)  One seven
regional telephone companies created by
divestiture: Nynex, Bell Atlantic, BellSouth,
Southwestern Bell, US West, Pacific Telesis and
Ameritech.


RCA connector
Same as phono connector.


RCS
(1) (Remote Computer Service)  Remote timesharing
service.

(2) (Revision Control System)  UNIX utility that
provides version control.


Rdb
(Relational DataBase/VMS)  Relational DBMS from
Digital for its VAX series.


RDBMS
(Relational DataBase Management System)  See
relational database.


RDRAM
(Rambus DRAM)  Dynamic RAM chip from Rambus, Inc.,
that transfers data at 500MBytes/sec (3-10 times
faster than DRAM and VRAM chips).  It requires
modified motherboards, but eliminates the need for
memory caches.


read
To input into the computer from a peripheral device
(disk, tape, etc.).  Like reading a book or playing
an audio tape, reading does not destroy what is
read.

   A read is both an input and an output (I/O),
since data is being output from the peripheral
device and input into the computer.  Memory is also
said to be read when it is accessed to transfer
data out to a peripheral device or to somewhere
else in memory.  Every peripheral or internal
transfer of data is a read from somewhere and a
write to somewhere else.


read error
Failure to read the data on a storage or memory
device.  Although it is not a routine phenomenon,
magnetic and optical recording surfaces can become
contaminated with dust or dirt or be physically
damaged, and cells in memory chips can malfunction.

   When a read error occurs, the program will allow
you to bypass it and move on to the next set of
data, or it will end, depending on the operating
system.  However, if the damaged part of a disk
contains control information, the rest of the file
may be unreadable.  In such cases, a recovery
program must be used to retrieve the remaining data
if there is no backup.


read only
(1) Refers to storage media that permanently hold
their content; for example, ROM and CD ROM.

(2) File which can be read, but not updated or
erased.  See file attribute.


read-only attribute
File attribute that, when turned on, indicates that
a file can only be read, but not updated or erased.


read/write
(1) Refers to a device that can both input and
output or transmit and receive.

(2) Refers to a file that can be updated and
erased.


read/write channel
Same as I/O channel.


read/write head
Device that reads (senses) and writes (records)
data on a magnetic disk or tape.  For writing, the
surface of the disk or tape is moved past the
read/write head.  By discharging electrical
impulses at the appropriate times, bits are
recorded as tiny, magnetized spots of positive or
negative polarity.

   For reading, the surface is moved past the
read/write head, and the bits that are present
induce an electrical current across the gap.


read/write memory
Same as RAM.


reader
Machine that captures data for the computer, such
as an optical character reader, magnetic card
reader and punched card reader.  A microfiche or
microfilm reader is a self-contained machine that
reads film and displays its contents.


readme file
Text file copied onto software distribution disks
that contains last-minute updates or errata that
have not been printed in the documentation manual.


readout
(1) Small display device that typically shows only
a few digits or a couple of lines of data.

(2) Any display screen or panel.


real address
Same as absolute address.


Real Mode
Operational state in Intel 286s and up in which the
computer functions as an 8086/8088.  It is limited
to one megabyte of memory.  See Protected Mode and
Virtual 86 Mode.


real storage
Real physical memory in a virtual memory system.


Realizer
Windows development software from Computer
Associates that uses a structured superset of
BASIC, has its own forms design utilities and
includes a runtime module.


realtime
Immediate response.  It refers to process control
and embedded systems; for example, space flight
computers must respond instantly to changing
conditions.  It also refers to fast transaction
processing systems as well as any electronic
operation fast enough to keep up with its real-
world counterpart (animating complex images,
transmitting live video, etc.).


realtime clock
Electronic circuit that maintains the time of day.
It may also provide timing signals for timesharing
operations.


realtime compression
Quickly compressing and decompressing data.  PC
products such as Stacker and SuperStor let you
create a separate compressed drive on your hard
disk.  All data written to that drive is compressed
and decompressed when read back.  Realtime
compression is included with DOS 6 (see DOS
DoubleSpace).  See JPEG.


realtime conferencing
See teleconferencing (3).


realtime image
In computer graphics, a graphics image that can be
animated on screen in the same time frame as in
real life.


realtime information system
Computer system that responds to transactions by
immediately updating the appropriate master files
and/or generating a response in a time frame fast
enough to keep an operation moving at its required
speed.  See transaction processing.


realtime operating system
Master control program that can provide immediate
response to input signals and transactions.


realtime system
Computer system that responds to input signals fast
enough to keep an operation moving at its required
speed.


reasonable test
Type of test that determines if a value falls
within a range considered normal or logical.  It
can be made on electronic signals to detect
extraneous noise as well as on data to determine
possible input errors.


reboot
To reload the operating system and restart the
computer.  See boot.


receiver
Device that accepts signals.  Contrast with
transmitter.


record
(1) Group of related fields that store data about a
subject (master record) or activity (transaction
record).  A collection of records make up a file.

   Master records contain permanent data, such as
account number, and variable data, such as balance
due.  Transaction records contain only permanent
data, such as quantity and product code.

(2) In certain disk organization methods, a record
is a block of data read and written at one time
without any relationship to records in a file.


record format
Same as record layout.


record head
Device that writes a signal on tape.  Some tape
drives and all disk drives use a combination
read/write head.


record layout
Format of a data record, which includes the name,
type and size of each field in the record.


record locking
See file and record locking.


record mark
Symbol used to identify the end of a record.


record number
Sequential number assigned to each physical record
in a file.  Record numbers change when the file is
sorted or records are added and deleted.


records management
Creation, retention and scheduled destruction of an
organization's paper and film documents.  Computer-
generated reports and documents fall into the
records management domain, but traditional data
processing files do not.


recovery
See backup & recovery, checkpoint/restart and tape
backup.


rectifier
Electrical circuit that converts AC into DC current
with the use of diodes that act as one-way valves.
Contrast with inverter.


recursion
In programming, the ability of a subroutine or
program module to call itself.  It is helpful for
writing routines that solve problems by repeatedly
processing the output of the same process.


redirection
Diverting data from its normal destination to
another; for example, to a disk file instead of the
printer, or to a server's disk instead of the local
disk.  See DOS redirection and redirector.


redirector
In a LAN, software that routes workstation requests
for data to the server.


redundancy check
In communications, a method for detecting
transmission errors by appending a calculated
number onto the end of each segment of data.  See
CRC.


reentrant code
Programming routine that can be used by multiple
programs simultaneously.  It is used in operating
systems and other system software as well as in
multithreading, where concurrent events are taking
place.  It is written so that none of its code is
modifiable (no values are changed) and it does not
keep track of anything.  The calling programs keep
track of their own progress (variables, flags,
etc.), thus one copy of the reentrant routine can
be shared by an any number of users or processes.

   It is analogous to several people baking their
own cake by looking at a single recipe on the wall.
Everyone keeps track of their own progress on the
master recipe by jotting down the step number
they're at on their own sheet of paper so they can
pick up where they left off.


referential integrity
Database management safeguard that ensures every
foreign key matches a primary key.  For example,
customer numbers in a customer file are the primary
keys, and customer numbers in the order file are
the foreign keys.  If a customer record is deleted,
the order records must also be deleted otherwise
they are left without a primary reference.  If the
DBMS doesn't test for this, it must be programmed
into the applications.


reflection mapping
In computer graphics, a technique for simulating
reflections on an object.


reflective spot
Metallic foil placed on each end of a magnetic
tape.  It reflects light to a photosensor to signal
the end of tape.


reflective VGA
LCD screen that needs bright ambient light for
viewing.  Backlit and sidelit screens are much
easier to see.


reformat
(1) To change the record layout of a file or
database.

(2) To initialize a disk over again.


refraction
Bending of light, heat or sound as it passes
through different materials.


refresh
To continously charge a device that cannot hold its
content.  CRTs must be refreshed, because the
phosphors hold their glow for only a few
milliseconds.  Dynamic RAM chips require refreshing
to maintain their charged bit patterns.


refresh rate
(1) Number of times per second that a device is re-
energized, such as a CRT or dynamic RAM chip.  See
vertical scan frequency.

(2) In computer graphics, the time it takes to
redraw or redisplay an image on screen.


regenerator
(1) In communications, the same as a repeater.

(2) In electronics, a circuit that repeatedly
supplies current to a memory or display device that
continuously loses its charges or content.


ReGIS
(REmote Graphics InStruction)  Graphics language
from Digital used on graphics terminals and first
introduced on the PDP-11.


register
Small, high-speed computer circuit that holds
values of internal operations, such as the address
of the instruction being executed and the data
being processed.  When a program is debugged,
register contents may be analyzed to determine the
computer's status at the time of failure.

   In microcomputer assembly language programming,
programmers reference registers routinely.
Assembly languages in larger computers are often at
a higher level.


register level compatibility
Hardware component that is 100% compatible with
another device.  It implies that the same type,
size and names of registers are used.


regression analysis
Statistical technique for detecting relationships
among multiple properties of observations in a
sample.


related files
Two or more data files that can be matched on some
common condition, such as account number or name.


relational algebra
(1) Branch of mathematics that deals with
relations; for example, AND, OR, NOT, IS and
CONTAINS.

(2) In relational database, a collection of rules
for dealing with tables; for example, JOIN, UNION
and INTERSECT.


relational calculus
Rules for combining and manipulating relations; for
example De Morgan's law, "the complement of a union
is equal to the union of the complements."


relational database
Database organization method that links files
together as required.  In non-relational systems
(hierarchical, network), records in one file point
to the locations of records in another, such as
customers to orders and vendors to purchases.
These are fixed links set up ahead of time to speed
up daily processing.

   In a relational database, relationships between
files are created by comparing data, such as
account numbers and names.  A relational system has
the flexibility to take any two or more files and
generate a new file from the records that meet the
matching criteria.

   Routine queries often involve more than one data
file.  For example, a customer file and an order
file can be linked in order to ask a question that
relates to information in both files, such as the
names of the customers that purchased a particular
product.

   In practice, a pure relational query can be very
slow.  In order to speed up the process, indexes
are built and maintained on the key fields used for
matching.  Sometimes, indexes are created "on the
fly" when the data is requested.

   The term was coined in 1970 by Edgar Codd, whose
objective was to easily accomodate a user's ad hoc
request for selected data.

     Relational terms     Common terms
     table or relation    file
     tuple                record
     attribute            field


relational operator
A symbol that specifies a comparison between two
values.

      Relational Operator        Symbol
   EQ   Equal to                   =
   NE   Not equal to               <>  or #  or !=
   GT   Greater than               >
   GE   Greater than or equal to   >=
   LT   Less than                  <
   LE   Less than or equal to      <=


relational spreadsheet
See spreadsheet.


relative address
Memory address that represents some distance from a
starting point (base address), such as the first
byte of a program or table.  The absolute address
is derived by adding it to the base address.


relative vector
In computer graphics, a vector with end points
designated in coordinates relative to a base
address.  Contrast with absolute vector.


relay
Electrical switch that allows a low power to
control a higher one.  A small current energizes
the relay, which closes a gate, allowing a large
current to flow through.


Relay Gold
PC communications program from Microcom, Inc.,
Norwood, MA, that provides standard asynchronous
transmission as well as mainframe file transfer and
LAN support.


relocatable code
Machine language that can be run from any memory
location.  See base/displacement.


REM
(REMarks)  Programming language statement used to
document the program and contains no executable
code.


remedial maintenance
Repair service that is required due to a
malfunction of the product.  Contrast with
preventive maintenance.


remote access software
See remote control software.


remote batch
See RJE.


remote communications
(1) Communicating via long distances.

(2) See remote control software.


remote control software
Software, installed in both machines, that allows a
user at a local computer to have control of a
remote computer via modem.  Both users run the
remote computer.  It is used to teach remote
students as well as provide technical support.  See
door.


remote job entry
See RJE.


removable disk
Disk unit that is inserted into a disk drive for
reading and writing and removed when not required;
for example, floppy disks, disk cartridges and disk
packs.


render
To draw a real-world object as it actually appears.


rendering
In computer graphics, creating a 3-D image that
incorporates the simulation of lighting effects,
such as shadows and reflection.


Renderman interface
Graphics format from Pixar, Point Richmond, CA,
that uses photorealistic image synthesis.
Developer's Renderman (PCs and UNIX) and Mac
Renderman (Macintosh) are Pixar programs that apply
photorealistic looks and surfaces to 3-D objects.


repeater
In communications, a device that amplifies or
regenerates the data signal in order to extend the
transmission distance.  Available for both analog
and digital signals, it is used extensively in long
distance transmission.  It is also used to tie two
LANs of the same type together.  See bridge and
router.


report
Printed or microfilmed collection of facts and
figures with page numbers and page headings.  See
report writer and query.


report file
File that describes how a report is printed.


report format
Layout of a report showing page and column headers,
page numbers and totals.


report generator
Same as report writer.


report writer
Software that prints a report based on a
description of its layout.  As a stand-alone
program or part of a DBMS or file manager, it can
sort selected records into a new sequence for
printing.  It may also print standard mailing
labels.

   A report is described by entering text for the
page header and stating the position of the print
columns (data fields) and which ones are totalled
or subtotalled.  Once created, the description is
stored in a report file for future use.

   Developed in the early 1970s, report writers
(report generators) were the precursor to query
languages and were the first programs to generate
computer output without having to be programmed.


repository
Database of information about applications software
that includes author, data elements, inputs,
processes, outputs and interrelationships.  It may
be the central core of a CASE system; for example,
Repository Manager in IBM's AD/Cycle is designed to
integrate third-party CASE products.


reproducer
Early tabulating machine that duplicated punched
cards.


reprographics
Duplicating printed materials using various kinds
of printing presses and high-speed copiers.


ResEdit
(Resource Editor)  Macintosh system utility used to
edit the resource fork.


reserved word
Verb or noun in a programming or command language
that is part of the native language.


reset button
Computer button or key that reboots the computer.
All current activities are stopped cold, and any
data in memory is lost.  On a printer, the reset
button clears the printer's memory and readies it
to accept new data.


resident module
The part of a program that must remain in memory at
all times.  Instructions and data that stay in
memory can be accessed instantly.


resident program
Program that remains in memory at all times.  See
TSR.


resistor
Electronic component that resists the flow of
current in an electronic circuit.


resolution
Degree of sharpness of a displayed or printed
character or image.  On screen, resolution is
expressed as a matrix of dots.  VGA resolution of
640x480 means 640 dots across each of 480 lines.
Sometimes the number of colors are added to the
spec; for example, 640x480x16 or 640x480x256.  The
same resolution looks sharper on a small screen
than a large one.

   For printers, resolution is expressed as the
number of dots per linear inch.  300 dpi means
90,000 dots per square inch (300x300).  Laser
printers and plotters have resolutions from 300 to
1000 dpi and more, whereas most display screens
provide less than 100 dpi.  That means jagged lines
on screen may smooth out when they print.


resolve
To change, transform or solve a problem.  The
phrase "external references are resolved" refers to
determining the addresses that link modules
together; that is, solving the unknown links.


resource compiler
In a graphical interface (GUI), software that
converts and links a resource (menu, dialog box,
icon, font, etc.) into the executable program.


resource fork
Resource part of a Macintosh file.  For example, in
a text document, it contains format codes with
offsets into the text in the data fork.  In a
program, it contains executable code, menus,
windows, dialog boxes, buttons, fonts and icons.


response time
Time it takes for the computer to comply with a
user's request, such as looking up a customer
record.


restart
To resume computer opertion after a planned or
unplanned termination.  See boot, warm boot and
checkpoint/restart.


restricted function
Computer or operating system function that cannot
be used by an application program.


retrieve
To call up data that has been stored in a computer
system.  When a user queries a database, the data
is retrieved into the computer first and then
transmitted to the screen.


return key
Also called the enter key, the keyboard key used to
signal the end of a line of data or the end of a
command.  In word processing, return is pressed at
the end of a paragraph, and a return code is
inserted into the text at that point.  See CR.

       ┌───┐ ┌───┐ ┌──────┐
       │{ [│ │} ]│ │      │
       └───┘ └───┘ │      │
         ┌───┐ ┌───┘      │
         │" '│ │ ─┘ Enter│
         └───┘ └──────────┘

   Standard Return Key Placement



reusability
Ability to use all or the greater part of the same
programming code or system design in another
application.


reverse engineer
To isolate the components of a completed system.
When a chip is reverse engineered, all the separate
circuits that make up the chip are identified.


reverse polish notation
Mathematical expression in which the numbers
precede the operation.  For example, 2 + 2 would be
expressed as 2 2 +, and 10 - 3 * 4 would be 10 3 4
* -.  See FORTH.


reverse video
Display mode used to highlight characters on
screen.  For example, if the normal display mode is
black on white, reverse video would be white on
black.


revision level
See version number.


REXX
(REstructured EXtended eXecutor)  IBM mainframe
structured programming language that runs under
VM/CMS and MVS/TSO.  It can be used as a general-
purpose macro language that sends commands to
application programs and to the operating systems.
REXX is also included in OS/2 Version 2.0.

   The following REXX example converts Fahrenheit
to Celsius:

   Say "Enter Fahrenheit "
   Pull FAHR
   Say "Celsius is " (FAHR - 32) * (5 / 9)



RF
(Radio Frequency)  Range of electromagnetic
frequencies above the audio range and below visible
light.  All broadcast transmission, from AM radio
to satellites, falls into this range, which is
between 30KHz and 300GHz.  See RF modulation.


RF/ID
(Radio Frequency/IDentification)  Identification
system that uses tags that transmit a wireless
message.  The tag gets its power from a hand-held
gun/reading unit.


RF modulation
Transmission of a signal through a carrier
frequency.  In order to connect to a TV's antenna
input, some home computers and all VCRs provide RF
modulation of a TV channel, usually Channel 3 or 4.
See FCC class.


RF shielding
Material that prohibits electromagnetic radiation
from penetrating it.  Personal computers and
electronic devices used in the home must meet U.S.
government standards for electromagnetic
interference.


RFI
(Radio Frequency Interference)  High-frequency
electromagnetic waves that eminate from electronic
devices such as chips.


RFP
(Request For Proposal)  Document that invites a
vendor to submit a bid for hardware, software
and/or services.  It may provide a general or very
detailed specification of the system.


RFT
See DCA.


RGB
(Red Green Blue)  Video color generation method
that displays colors as varying intensities of red,
green and blue dots.  When all three are turned on
high, white is produced.  As intensities are
equally lowered, shades of gray are derived.  The
base color of the screen appears when all dots are
off.  See colors.


RGB monitor
(1) Video display screen that requires separate
red, green and blue signals from the computer.  It
generates a better image than composite signals
(TV) which merge the three colors together.  It
comes in both analog and digital varieties.

(2) Sometimes refers to a CGA monitor that accepts
digital RGB signals.


ribbon cable
Thin, flat, multiconductor cable that is widely
used in electronic systems; for example, to
interconnect peripheral devices to the computer
internally.


rich e-mail
E-mail annotated with voice messages.


RIFF
(Resource Interchange File Format)  Multimedia data
format jointly introduced by IBM and Microsoft.
See MCI.


right justify
Same as flush right.


rightsizing
Selecting a computer system, whether micro, mini or
mainframe, that best meets the needs of the
application.


rigid disk
Same as hard disk.


ring
One stage or level in a set of prioritized stages
or levels, typically involved with security and
password protection.


ring network
Communications network that connects terminals and
computers in a continuous loop.


RIP
(1) (Raster Image Processor)  In computer graphics,
the component (hardware, software or both) that
prepares data for a raster output device (screen or
printer).  RIPs are designed for a specific type of
input, such as vectors, PostScript as well as
different raster data.

(2) (Routing Information Protocol)  Early BSD UNIX
routing protocol used within a small network.


RISC
(Reduced Instruction Set Computer)  Computer
architecture that reduces chip complexity by using
simpler instructions.  RISC compilers have to
generate software routines to perform complex
instructions that were previously done in hardware
by CISC computers.  In RISC, the microcode layer
and associated overhead is eliminated.

   RISC keeps instruction size constant, bans the
indirect addressing mode and retains only those
instructions that can be overlapped and made to
execute in one machine cycle or less.  The RISC
chip is faster than its CISC counterpart and is
designed and built more economically.


RISC System/6000
See RS/6000.


RJ-11
Four or six-wire telephone connector.  The four-
wire plug and socket is the common connector for
telephone handsets and for plugging telephones and
modems into wall outlets.


RJE
(Remote Job Entry)  Transmitting batches of
transactions from a remote terminal or computer.
The receiving computer processes the data and may
transmit the results back to the RJE site for
printing.  RJE hardware at remote sites can employ
teleprinters with disk or tape storage or complete
computer systems.


RLE
See run length encoding.


RLL
(Run Length Limited)  Magnetic disk encoding method
that packs 50% more bits into the same space than
the earlier MFM method.  It is used with RLL, IDE,
ESDI, SCSI, SMD and IPI interfaces.

   The "run length" is the number of consecutive 0s
before a 1 bit is recorded.  MFM is actually a run
length of 1,3; not less than one or more than three
"no pulses" separating adjacent pulses.  RLL
increases the run length over MFM; for example, RLL
2,7 means not less than two or more than seven 0s
before a 1 is recorded.  ARLL (Advanced RLL) is RLL
3,9.  See hard disk.


RLL interface
See ST506 RLL.


RMS
(1) (Record Management Services)  File management
system used in VAXs.

(2) (Root Mean Square)  Method used to measure
electrical output in volts and watts.


RO terminal
(Receive Only terminal)  Printing device only (no
keyboard).


RoboCAD
PC CAD program from Robo Systems Int'l., Inc.,
Newtown, PA, that includes a wide variety of
features and text functions.  It provides up to 256
colors and layers, has two drawing pages and a
scratch pad, and can transfer data to its solid
modeling program.


robot
Stand-alone hybrid computer system that performs
physical and computational activities.  It is a
multiple-motion device with one or more arms and
joints that is capable of performing many different
tasks like a human.  It can be designed similar to
human form, although most industrial robots don't
resemble people at all.

   It is used extensively in manufacturing for
welding, riveting, scraping and painting.  Office
and consumer applications are also being developed.
Robots, designed with AI, can respond to
unstructured situations.  For example, specialized
robots can identify objects in a pile, select the
objects in the appropriate sequence and assemble
them into a unit.

   Robots use analog sensors for recognizing real-
world objects and digital computers for their
direction.  Analog to digital converters convert
temperature, motion, pressure, sound and images
into binary code for the robot's computer.  The
computer directs the physical actions of the arms
and joints by pulsing their motors.


robotics
Art and science of the creation and use of robots.


robust
Refers to a solid program that works properly under
all normal and most abnormal conditions.


roll in/roll out
Swapping technique for freeing up memory
temporarily in order to perform another task.  The
current program or program segment is stored
(rolled out) on disk, and another program is
brought into (rolled in) that memory space.


rollback
Database management system feature that reverses
the current transaction out of the database,
returning the database to its former state.  This
is done when some failure interrupts a half-
completed transaction.


rollover
See n-key rollover.


ROM
(Read Only Memory)  Memory chip that permanently
stores instructions and data.  Its contents are
created at the time of manufacture and cannot be
altered.  Used extensively to store control
routines in personal computers (ROM BIOS) and in
peripheral controllers, it is also used in plug-in
cartridges for printers, video games and other
systems.  See PROM, EPROM and EEPROM.


ROM BIOS
(ROM Basic Input Output System)  Instructions
contained in a ROM chip that activate peripheral
devices in a PC.  It includes routines for the
keyboard, screen, disk, parallel and serial port
and for internal services such as time and date.
It accepts requests from the device drivers in the
operating system as well as from application
programs.

   It also contains autostart functions that test
the system on startup and prepare the computer for
operation.  It searches for other BIOS's on the
plug-in boards and sets up pointers (interrupt
vectors) in memory to access BIOS routines.  It
loads the operating system and passes control to
it.

   BIOSs prior to 1990 may not be compatible with
new software and peripherals.  In order to use
devices such as 3.5" diskettes, 101-key keyboards,
IDE drives as well as provide compatibility with
Windows, NetWare and other applications, you can
upgrade an older PC with a new BIOS.  The following
firms specialize in ROM BIOS upgrades:

   UNICORE SOFTWARE    800/800-BIOS
   1538 Turnpike St.
   N. Andover, MA 01845

   UPGRADES, ETC.      800/955-3527
   2432-A Palma Drive
   Ventura, CA 93003


ROM BIOS swapping
Alternating areas in the UMA (640K-1M) between ROM
BIOSs and applications as needed.


ROM card
Credit-card-sized module that contains permanent
software or data.  See memory card.


ROMable
Machine language capable of being programmed into a
ROM chip.  Being "read only" the chip cannot be
updated and ROMable programs must use RAM or disk
for holding changing data.


root directory
In hierarchical file systems, the starting point in
the hierarchy.  When the computer is first started,
the root directory is the current directory.
Access to directories in the hierarchy requires
naming the directories that are in its path.  See
path and DOS abc's.


rotational delay
Amount of time it takes for the disk to rotate
until the required location on the disk reaches the
read/write head.


round robin
Continuously repeating sequence, such as the
polling of a series of terminals, one after the
other, over and over again.


router
Computer system that routes messages from one LAN
(local area network) to another.  It is used to
internetwork similar and dissimilar networks and
can select the most expedient route based on
traffic load, line speeds and costs and network
failures.  Routers maintain address tables for all
nodes in the network and work at OSI layer 3.  See
intermediate node routing.

   Routers are used to break apart the LAN into
smaller LANs for improved security, troubleshooting
and performance.  Routers with high-speed (gigabit)
buses may serve as an internet backbone, connecting
all networks in the enterprise.  See bridge,
brouter, gateway and hub.


routine
Set of instructions that perform a task.  Same as
subroutine, module, procedure and function.


routing
See intermediate node routing and router.


row
Horizontal set of data or components.  In a graph,
it is called the x-axis.  Contrast with column.


RPC
(Remote Procedure Call)  Type of interface that
allows one program to call another in a remote
location.  Using a standard RPC allows an
application to be used in a variety of networks
without change.


RPG
(Report Program Generator)  One of the first
program generators designed for business reports,
introduced in 1964 by IBM.  In 1970, RPG II added
enhancements that made it a mainstay programming
language for business applications on IBM's
System/3x midrange computers.  RPG III, which added
more programming structures, is widely used on the
AS/400.  RPG statements are written in columnar
format.

   The following RPG III System/38-AS/400 example
changes Fahrenheit to Celsius.  The A lines are
Data Description Specs (DDS) code.  They define a
display file and are compiled separately.  The F
line links RPG code (C lines) to the A lines:

A   R FHEITR
A                         6 18'Enter Fahrenheit: '
A     FRHEIT    3Y  0B    6 42DSPATR(PC)
A                             EDTCDE(J)
A                         9 18'Celsius is '
A     CGRADE    3Y  0B    9 42DSPATR(PC)
A                             EDTCDE(J)
FFHEITD   CF   E        WORKSTN
C               EXFMTFHEITR
C               Z-ADDO          CGRADE
C      FRHEIT   SUB    32       CGRADE
C      CGRADE   MULT   5        CGRADE
C      CGRADE   DIV    9        CGRADE    H
C               EXFMTFHEITR



rpm
(Revolutions Per Minute)  Used to measure the speed
of a disk drive.  Floppy disks rotate at 300 rpm,
while hard disks rotate at 2,400 to 3,600 rpm.


RPN
See reverse polish notation.


RPQ
(Request for Price Quotation)  Document that
requests a price for hardware, software or services
to solve a specific problem.  It is created by the
customer and delivered to the vendor.


RS-170
NTSC standard for composite video signals.


RS-232
(Recommended Standard-232)  EIA standard for serial
transmission between computers and peripheral
devices (modem, mouse, etc.).  It uses a 25-pin DB-
25 or 9-pin DB-9 connector.  Its normal cable
limitation of 50 feet can be extended to several
hundred feet with high-quality cable.

   RS-232 defines the purpose and signal timing for
each of the 25 lines; however, many applications
use less than a dozen.  RS-232 transmits positive
voltage for a 0 bit, negative voltage for a 1.

   In 1984, this interface was officially renamed
TIA/EIA-232-E standard (E is the current revision,
1991), although most people still call it RS-232.


              Pin Settings for Plug
           (Reverse order for socket.)
   ──────────────────────────────────────────
     1  2  3  4  5  6  7  8  9  10 11 12 13
      14 15 16 17 18 19 20 21 22 23 24 25
      ──────────────────────────────────

               ─────────────────
                 1  2  3  4  5
                   6  7  8  9
                   ─────────


  25 pin                            9 pin
    1 - PG   Protective ground
    2 - TD   Transmitted data         3
    3 - RD   Received data            2
    4 - RTS  Request to send          7
    5 - CTS  Clear to send            8
    6 - DSR  Data set ready           6
    7 - SG   Signal ground            5
    8 - CD   Carrier detect           1
    9 - + voltage (testing)
   10 - - voltage (testing)
   11 -
   12 - SCD  Secondary CD
   13 - SCS  Secondary CTS
   14 - STD  Secondary TD
   15 - TC   Transmit clock
   16 - SRD  Secondary RD
   17 - RC   Receiver clock
   18 -
   19 - SRS  Secondary RTS
   20 - DTR  Data terminal ready      4
   21 - SQD  Signal quality detector
   22 - RI   Ring indicator           9
   23 - DRS  Data rate select
   24 - XTC  External clock
   25 -



RS-422, 423, 449
EIA standards for serial interfaces that extend
distances and speeds beyond RS-232.  They often use
a DB-37 connector.  RS-422 is a balanced system
requiring more wire pairs than RS-423 and is
intended for use in multipoint lines.

   RS-449 specifies the pin definitions for 422 and
423.  RS-422/423 are subsets of RS-449, each
specifying electrical and timing characteristics of
the lines.


RS-485
EIA standard for multipoint communications lines.
It can be implemented with as little as a wire
block with four screws or with DB-9 or DB-37
connectors.  By using lower-impedance drivers and
receivers, RS-485 allows more nodes per line than
RS-422.


RS/6000
(RISC System/6000)  IBM family of RISC-based
workstations introduced in 1990.  It comes in
workstation (POWERstation) and server (POWERserver)
models and uses the Micro Channel bus.  It
introduced Version 3 of AIX and two graphical user
interfaces: AIXwindows Environment/6000 (enhanced X
Window system) and AIX NeXTStep Environment/6000
from NeXT Computer.


RSA
(Rivest-Shamir-Adleman)  Highly-secure encryption
method by RSA Data Security, Inc., Redwood City,
CA, that uses a two-part key.  The private key is
kept by the owner; the public key is published.

   You encrypt data by using the recipient's public
key, which can only be decrypted by the recipient's
private key.  RSA is very computation intensive,
thus it is often used to create a Digital Envelope,
which holds an RSA-encrypted DES key and DES-
encrypted data.

   You can create a digital signature as a means of
verifying who you are by encrypting with your
private key and letting others decrypt your message
with your public key.


RSCS
(Remote Spooling Communications Subsystem)
Software that provides batch communications for
IBM's VM operating system.  It accepts data from
remote batch terminals, executes them on a priority
basis and transmits the results back to the
terminals.  The RSCS counterpart in MVS is called
JES.  Contrast with CMS, which provides interactive
communications for VM.


RSI
(Repetitive Strain Injury)  Ailments of the hands,
neck, back and eyes due to computer use.  The
remedy for RSI is frequent breaks which should
include stretching or yoga postures.  See carpal
tunnel syndrome.


RSTS/E
PDP-11 operating system from Digital.


RSX-11
(Resource Sharing eXtension-PDP 11)  Multiuser,
multitasking operating system from Digital that
runs on its PDP-11 series.


RT
RISC-based workstation from IBM introduced in 1986
that has been superseded by the RS/6000 family.


RT-11
Single user, multitasking operating system from
Digital that runs on its PDP-11 series.


RTF
(Rich Text Format)  Microsoft standard for encoding
formatted text and graphics.  It was adapted from
IBM's DCA format and supports ANSI, IBM PC and
Macintosh character sets.


RTFM
(Read The Flaming Manual)  Last resort when having
a hardware or software problem!


RTS
(Request To Send)  RS-232 signal sent from the
transmitting station to the receiving station
requesting permission to transmit.  Contrast with
CTS.


rubber banding
In computer graphics, the moving of a line or
object where one end stays fixed in position.


rubout key
Keyboard key on a terminal that deletes the last
character that was entered.


rule-based expert system
Expert system based on a set of rules that a human
expert would follow in diagnosing a problem.
Contrast with model-based expert system.


ruler line
Graphic representation of a ruler on screen that is
used for laying out text and graphics.


rules
(1) Set of conditions or standards which have been
agreed upon.

(2) In printing, horizontal and vertical lines
between columns or at the top and bottom of a page
in order to enhance the appearance of the page.


run
(1) To execute a program.

(2) Single or multiple programs scheduled for
execution.


run around
In desktop publishing, the flowing of text around a
graphic image.


run length encoding
Simple data compression method that converts a run
of identical symbols as a symbol followed by a
count.  A rough example might be []36* where [] is
a code and 36* means 36 *'s follow.


run length limited
See RLL.


run on top of
To run as the control program to some other
program, which is subordinate to it.  Contrast with
run under.


run time
See runtime.


run under
To run within the control of a higher-level
program.  Contrast with run on top of.


runtime
Refers to the actual execution of a program.


runtime version
Software that enables another program to execute on
its own or with enhanced capabilities.  For
example, a runtime version of GEM comes with the
DOS version of Ventura Publisher.  It lets Ventura
use GEM's graphical interface, but won't run other
GEM programs.

   A DBMS often includes an interpreted programming
language for developing applications.  When running
the programs, the DBMS must be used to execute each
line of the program.  A runtime version of a DBMS
allows the programs to be run on computers that
don't have the DBMS installed.



S-100 bus
IEEE 696, 100-pin bus standard used extensively in
first-generation personal computers (8080, Z80,
6800, etc.).  It is still used in various systems.


S/360
See System/360.


S/370
See System/370.


S/3x
See System/3x.


S-RAM
See static RAM.


S3 chip
Refers to one of the graphics accelerator chips
(86C911, 86C928, etc.) from S3, Inc., San Jose, CA,
used in a variety of graphics accelerator boards.


SAA
(System Application Architecture)  Introduced in
1987, a set of IBM standards (user interfaces,
programming interfaces and communications
protocols) that provide consistency across all IBM
platforms.  Categories are Common User Access
(CUA), Common Programming Interface for
Communications (CPI-C) and Common Communications
Support (CCS).  See CUA, CPI-C and CCS.


sabermetrician
Slang for a statistician who uses computers to
predict future performance of sports teams and
players.


sag
Momentary drop in voltage from the power source.
Contrast with spike.


SAM
(1) (Symantec AntiVirus for Macintosh)  Popular
Macintosh antivirus program from Symantec Corp.,
Cupertino, CA.

(2) See sequential access method.


Samna
One of the first full-featured word processors for
PCs (1983) from Samna Corp., now part of Lotus.


sampling
(1) In statistics, the analysis of a group by
determining the characteristics of a significant
percentage of its members chosen at random.

(2) In digitizing operations, the conversion of
real-world signals or movements at regular
intervals into digital code.


sampling rate
In digitizing operations, the frequency with which
samples are taken and converted.  The higher the
sample rate, the closer real-world objects are
represented in digital form.


sans-serif
Typeface style without serifs, which are the short
horizontal lines added at the tops and bottoms of
the vertical member of the letter.  Helvetica is a
common sans-serif font.


SAP
(Secondary Audio Program)  NTSC audio channel used
for auxiliary transmission, such as foreign
language broadcasting or teletext.


SAS
(Statistical Analysis System)  Integrated software
from SAS Institute Inc., Cary, NC, that runs on IBM
mainframes, VAXs and other machines.  It includes
data management, spreadsheets, CBT, presentation
graphics, project management, operations research,
scheduling, linear programming, statistical quality
control, econometric and time series analysis,
mathematical, engineering and statistical
applications and full application development.


SASI
(Shugart Associates Systems Interface)  Peripheral
interface developed by Shugart and NCR in 1981 that
evolved into the ANSI SCSI standard in 1986.


satellite
See communications satellite


satellite channel
Carrier frequency used for satellite transmission.


satellite computer
Computer located remotely from the host computer or
under the control of the host.  It can function as
a slave to the master computer or perform offline
tasks.


satellite link
Signal that travels from the earth to a
communications satellite and back down again.
Contrast with terrestrial link.


saturation
(1) On magnetic media, occurs when the magnetizable
particles are completely aligned and a more
powerful writing signal will not improve the
reading back.

(2) In a bipolar transistor, occurs when the
current on the gate (the trigger) is equal to or
greater than what is necessary to close the switch.

(3) In a diode, occurs when the diode is fully
conducting.


save
To write the contents of memory to disk or tape.
Some applications save data automatically, others
do not.  Memory-based word processors, and most all
spreadsheets require that the user saves the data
before exiting the program.


SBS
(Satellite Business Systems)  Organization
developed to offer satellite communications
services to business, currently part of MCI.


Sbus
Originally a proprietary bus from Sun, it has been
released into the public domain.  The IEEE is
standardizing on a 64-bit version in 1993.


SCAI
(Switch-to-Computer Applications Interface)
Standard for integrating computers to a PBX.  See
switch-to-computer.


scalability
Ability to expand.  Implies minimal change in
current procedures in order to accomodate growth.


scalable
Capable of being changed in size and configuration.


scalable font
Font that is created in the required point size as
needed to display or print a document.  The dot
patterns (bitmaps) are generated from a set of
outline fonts, or base fonts, which contain a
mathematical representation of the typeface.
Although a bitmapped font designed from scratch for
a particular font size will always look the best,
scalable fonts eliminate storing dozens of
different font sizes on disk.  Contrast with
bitmapped font.

   The major scalable fonts are Adobe's Type 1
PostScript, Apple/Microsoft's TrueType, Agfa's
Intellifont and Bitstream's Speedo.  There are more
Type 1 typefaces available, although TrueType faces
are quickly appearing.


scalar
Single item or value.  Contrast with vector and
array, which are made up of multiple values.


scalar processor
Computer that performs arithmetic computations on
one number at a time.  Contrast with vector
processor.


scalar variable
In programming, a variable that contains only one
value.


scale
(1) In computer graphics and printing, to resize an
object, making it smaller or larger.

(2) To change the representation of a quantity in
order to bring it into prescribed limits of another
range.  For example, values such as 1249, 876, 523,
-101 and -234 might need to be scaled into a range
from -5 to +5.

(3) To designate the position of the decimal point
in a fixed or floating point number.


scan
(1) In optical technologies, to view a printed form
a line at a time in order to convert images into
bitmapped representations, or to convert characters
into ASCII text or some other data code.

(2) In video, to move across a picture frame a line
at a time, either to detect the image in an analog
or digital camera, or to refresh a CRT display.

(3) To sequentially search a file.


scan head
Optical sensing device in an scanner or fax machine
that is moved across the image to be scanned.


scan line
One of many horizontal lines in a graphics frame.


scan rate
Number of times per second a scanning device
samples its field of vision.  See horizontal scan
frequency.


ScanJet
Family of popular desktop scanners from HP.
Monochrome and color models are available.


scanner
Device that reads text, images and bar codes.  Text
and bar code scanners recognize printed fonts and
bar codes and convert them into a digital code
(ASCII or EBCDIC).  Graphics scanners convert a
printed image into a video image (raster graphics)
without recognizing the actual content of the text
or pictures.


scatter diagram
Graph plotted with dots or some other symbol at
each data point.  Also called a scatter plot or dot
chart.


scatter plot
Same as scatter diagram.


scatter read
Capability that allows data to be input into two or
more noncontiguous locations of memory with one
read operation.  See gather write.


SCERT II
(Systems and Computers Evaluation and Review
Technique)  Pronounced "skirt."  Software from
Pinnacle Software Corp., Washington, DC, that
measures the performance of a system by modeling
the computer environment and applications.


scheduler
The part of the operating system that initiates and
terminates jobs (programs) in the computer.  Also
called a dispatcher, it maintains a list of jobs to
be run and allocates computer resources as
required.


scheduling algorithm
Method used to schedule jobs for execution.
Priority, length of time in the job queue and
available resources are examples of criteria used.


schema
Definition of an entire database.  See subschema.


Scheme
LISP dialect developed at MIT and Indiana
University.  TI has a personal computer version of
Scheme called PC Scheme.


Schottky
Category of bipolar transistor known for its fast
switching speeds in the three-nanosecond range.
Schottky II devices have switching speeds in the
range of a single nanosecond.


scientific applications
Applications that simulate real-world activities
using mathematics.  Real-world objects are turned
into mathematical models and their actions are
simulated by executing the formulas.

   For example, some of an airplane's flight
characteristics can be simulated in the computer.
Rivers, lakes and mountains can be simulated.
Virtually any objects with known characteristics
can be modeled and simulated.

   Simulations use enormous calculations and often
require supercomputer speed.  As personal computers
become more powerful, more laboratory experiments
will be converted into computer models that can be
interactively examined by students without the risk
and cost of the actual experiments.


scientific computer
Computer specialized for high-speed mathematic
processing.  See array processor and floating point
processor.


scientific language
Programming language designed for mathematical
formulas and matrices, such as ALGOL, FORTRAN and
APL.  Although all programming languages allow for
this kind of processing, statements in a scientific
language make it easier to express these actions.


scientific notation
Display of numbers in floating point form.  The
number (mantissa) is always equal to or greater
than one and less than 10, and the base is 10.  For
example, 2.345E6 is equivalent to 2,345,000.  The
number following E (exponent) represents the power
to which the base should be raised (number of zeros
following the decimal point).


scissoring
In computer graphics, the deleting of any parts of
an image which fall outside of a window that has
been sized and laid over the original image.  Also
called clipping.


SCL
(1) (Switch-to-Computer Link)  Refers to
applications that integrate the computer through
the PBX.  See switch-to-computer.

(2) Extension used for ColoRIX raster graphics file
format (640x400 256 colors).


SCO
(The Santa Cruz Operation, Inc., Santa Cruz, CA)
System software company noted for its UNIX
operating systems.


SCO Open Desktop
Multiuser, virtual memory graphical operating
system for 386s and up from SCO that runs UNIX,
XENIX, DOS and X Window applications.  It includes
TCP/IP and NFS networking and database services
based on INGRES 6.2.


SCO UNIX System V
AT&T-licensed implementation of UNIX System V/386
3.2 for 386s and up from SCO.  It is a multiuser,
multitasking environment that runs both XENIX and
UNIX applications.  It has more security,
networking features and standards conformance than
SCO XENIX.  When used with SCO VP/ix or SCO Open
Desktop, it can also run DOS applications.


SCO VP/ix
System program for 386s and up from SCO that allows
DOS applications to run concurrently with SCO UNIX
or SCO XENIX in a virtual memory environment.  Each
application runs in its own secure virtual address
space.


SCO XENIX System V
AT&T-licensed, SVID-conforming implementation of
UNIX System V for 286 PCs and up from SCO.
Developed by Microsoft, it was the original UNIX
system for personal computers.  Faster and smaller
than SCO UNIX, it includes improved documentation
and easier installation.


scope
(1) CRT type of screen, such as used on an
oscilloscope or common display terminal.

(2) In programming, the visibility of variables
within a program; for example, whether one function
can use a variable created in another function.

(3) In dBASE, a range of records, such as the "next
50" or "current record to end of file."


scrambler
Device or software program that encodes data for
encryption.


scrambling
Encoding data to make it indecipherable.  See
encryption and DES.


Scrapbook
Macintosh disk file that holds frequently-used text
and graphics objects, such as a company letterhead.
Contrast with Clipboard, which holds data only for
the current session.


scratch tape
Magnetic tape that can be erased and reused.


scratchpad
Special register or a reserved section of memory or
disk used for temporary storage.


screen
Display area of a video terminal or monitor.  It is
either a CRT or one of the flat panel technologies.


screen angle
The angle at which a halftone screen is placed over
an image, typically 45°.


screen capture
Transfering the current on-screen image to a text
or graphics file.


screen dump
Printing the current on-screen image.  In PCs,
pressing Shift-PrtSc prints the screen.  If the
screen contains graphics, the DOS Graphics utility
must be loaded.  Third party screen capture
programs also dump graphic screens to the printer
or to disk.

   In the Macintosh, pressing Command-shift-3
creates a MacPaint file of the current screen.


screen font
Font used for on-screen display.  For true WYSIWYG
systems, screen fonts must be matched as close as
possible to the printer fonts.  Contrast with
printer font.


screen frequency
Resolution of a halftone.  It is the density of
dots (how far they're spaced apart from each other)
measured in lines per inch.


screen overlay
(1) Clear, fine-mesh screen that reduces the glare
on a video screen.

(2) Clear touch panel that allows the user to
command the computer by touching displayed buttons
on screen.

(3) Temporary data window displayed on screen.  The
part of the screen that was overlaid is saved and
restored when the screen overlay is removed.


screen saver
Utility that prevents a CRT from being etched by an
unchanging image.  After a specified duration
without keyboard or mouse input, it blanks the
screen or displays moving objects.  Pressing a key
or moving the mouse restores the screen.

   It would actually take many hours to burn in an
image on today's color monitors.  However, the
entertainment provided by these utilities (swimming
fish, flying toasters, etc.) has made them very
popular.


screen scraper
See frontware.


script
(1) Typeface that looks like handwriting or
calligraphy.

(2) Program written in a special-purpose
programming language such as used in a
communications program or word processor.  Same as
macro.


ScriptX
Multimedia technology from Kaleida Labs, Inc. that
includes data formats, a scripting language and a
runtime environment.  It is designed for creating
applications that can be played on a variety of
personal computers and consumer electronic devices.


scroll
To continuously move forward, backward or sideways
through the images on screen or within a window.
Scrolling implies continuous and smooth movement, a
line, character or pixel at a time, as if the data
were on a paper scroll being rolled behind the
screen.


scroll arrow
On-screen arrow that is clicked in order to scroll
the screen in the corresponding direction.  The
screen moves one line, or increment, with each
mouse click.


scroll back buffer
Reserved memory that holds a block of transmitted
data, allowing the user to browse back through it.


scroll bar
Horizontal or vertical bar that contains a box that
looks like an elevator in a shaft.  The bar is
clicked to scroll the screen in the corresponding
direction, or the box (elevator, thumb) is clicked
and then dragged to the desired direction.


scrollable
See scroll.


scrollable field
Short line on screen that can be scrolled to allow
editing or display of larger amounts of data in a
small display space.


SCSI
(Small Computer System Interface)  Pronounced
"scuzzy."  SCSI is a hardware interface that allows
for the connection of up to seven peripheral
devices, such as a disk, tape or CD ROM, to a
single SCSI expansion board, called a SCSI host
adapter (also called a SCSI controller), that plugs
into the computer.  The advantage of SCSI is that
seven different devices use up only one expansion
slot in the computer.

   However, the Macintosh, Sun and Digital
operating systems have supported SCSI directly, but
DOS has not, allowing various implementations of
SCSI drivers and host adapters to be developed for
the PC.  The SCSI host adapter and driver that
comes with a SCSI peripheral often works with only
that device or similar devices.  Thus when several
SCSI devices are used in a PC, multiple host
adapters are required, each taking up an expansion
slot.

   Attempts at standardizing SCSI have resulted in
Microsoft's LADDR, Adaptec's ASPI and ANSI's CAM
specifications (see CorelSCSI and PowerSCSI!).

  SCSI is a bus structure itself and functions like
a mini-LAN connecting eight devices, but the host
adapter counts as one device.  SCSI allows any two
devices to communicate at one time (host to
peripheral, peripheral to peripheral).

   Each SCSI device can actually be broken up into
eight logical units as logical unit numbers (LUNs)
0 to 7, theoretically allowing up to 56 peripherals
to connect to one SCSI host adapter.  For example,
a jukebox for five disks could be LUN 0 to 4.  SCSI
devices can be built to take advantage of this
capability, but to date, most function only as a
single device (LUN 0).

   SCSI, or SCSI-1, is an 8-bit interface that
provides up to five MBytes/sec data transfer and
uses a 50-pin ribbon cable for interconnection.

   SCSI-2 provides command queuing and a "fast
SCSI" option that provides 10MB data transfer.
With a secondary cable for 16- and 32-bit data,
"wide SCSI" provides up to 40MB transfer.  A new
68-conductor "P" cable is a single-cable solution
for 16 bits.

   SCSI-3 proposes enhanced features and the
ability to handle more than eight devices.  It also
supports serial transmission for small computers
such as palmtops.  See hard disk.


                 Parallel to SCSI
There are adapters that allow SCSI peripherals to
be connected via the parallel port.  Although the
parallel port's transfer rate is considerably less
than the SCSI host adapter, it does provide a means
to hook up SCSI devices that might be otherwise
impossible, such as to a laptop with no expansion
slots.


scuzzy
See SCSI.


SDBN
(Software-Defined Broadband Network)  Future high-
bandwidth service from AT&T for data, voice and
video.  It uses ATM cell relay technology with
speeds up to 600 Mbits/sec.


SDF
(Standard Data Format)  Simple file format that
uses fixed length fields.  It is commonly used to
transfer data between different programs.


                    SDF

  Pat Smith     5 E. 12 St.       Rye         NY
  Robert Jones  200 W. Main St.   Palo Alto   CA

               Comma delimited

  "Pat Smith","5 E. 12 St.","Rye","NY"
  "Robert Jones","200 W. Main St.","Palo Alto","CA"



SDI
(1) (Switched Digital Int'l.)  AT&T dial-up service
providing 54/64 Kbits/sec digital transmission to
international locations.

(2) (Standard Drive Interface)  Hard disk interface
for VAXs.

(3) (Single Document Interface)  In Windows, a
single window that is minimized or maximized
independently.  Contrast with MDI.

(4) (Serial Data Interface)  See serial interface.

(5) (Strategic Defense Initiative)  Proposed U.S.
high-tech defense system.


SDK
(Software Developer's Kit)  See developer's
toolkit.


SDLC
(Synchronous Data Link Control)  Primary data link
protocol used in IBM's SNA networks.  It is a bit-
oriented synchronous protocol that is a subset of
the HDLC protocol.


SDP
(Streaming Data Procedure)  Micro Channel mode that
increases data transfer from 20MB per second to
40MB per second.


SDRAM
(Synchronous DRAM)  New high-speed memory being
specified by JEDEC that can transfer bursts of non-
contiguous data at 100MBytes/sec.


SE
See systems engineer and Macintosh.


Seagate
(Seagate Technology, Inc., Scotts Valley, CA)
Largest independent manufacturer of disk drives.
Founded in 1979 by Alan Shugart, Tom Mitchell and
Doug Mahon, it was the first to offer a 5MByte
drive using 5.25" platters making it ideal for the
burgeoning desktop computer industry.  Seagate
became the first company to ship 10 million drives.
In 1989, it aquired Imprimis Technology, a CDC
subsidiary making workstation and mainframe drives,
nearly doubling Seagate's revenue to $2.5 billion.


SEAlink
Version of Xmodem that uses a sliding window
protocol, transmits file name, date and size and
provides batch file transfer.  Good for delay-
introduced transmissions (packet switching,
satellites).


seamless integration
Addition of a new application, routine or device
that works smoothly with the existing system.  It
implies that the new feature can be activated and
used without problems.  Contrast with transparent,
which implies that there is no discernible change
after installation.


search and replace
To look for an occurrence of data or text and
replace it with another set of data or text.


search key
In a search routine, the data entered and used to
match other data in the database.


second-generation computer
Computer made of discrete electronic components.
In the early 1960s, the IBM 1401 and Honeywell 400
were examples.


second source
Alternative supplier of an identical or compatible
product.  A second source manufacturer is one that
holds a license to produce a copy of the original
product from another manufacturer.


secondary channel
In communications, a subchannel that is derived
from the main channel.  It is used for diagnostic
or supervisory purposes, but does not carry data
messages.


secondary index
Index maintained for a data file, but is not used
to control the current processing order of the
file.  See primary index.


secondary storage
External storage, such as disk and tape.


sector
Smallest unit of storage read or written on a disk.
See magnetic disk.


sector interleave
Sector numbering on a hard disk.  A one to one
interleave (1:1) is sequential: 0,1,2,3, etc.  A
2:1 interleave staggers sectors every other one:
0,4,1,5,2,6,3,7.

   In 1:1, after data in sector 1 is read, the disk
controller must be fast enough to read sector 2,
otherwise the beginning of sector 2 will pass the
read/write head and must rotate around to come
under the head again.  If it isn't fast enough, a
2:1 or 3:1 interleave gives it time to read all
sectors in a single rotation, eliminating wasted
rotations.

   The best interleave depends on the disk and disk
controller.  It can be changed with a low-level
format program.


sector map
See sector interleave.


sector sparing
Maintaining a spare sector per track to be used if
another sector becomes defective.


security
Protection of data against unauthorized access.
Programs and data can be secured by issuing
identification numbers and passwords to authorized
users of a computer.  However, systems programmers,
or other technically competent individuals, will
ultimately have access to these codes.

   Passwords can be checked by the operating system
to prevent users from logging onto the system in
the first place, or they can be checked in
software, such as DBMSs, where each user can be
assigned an individual view (subschema) of the
database.  Any application program running in the
computer can also be designed to check for
passwords.

   Data transmitted over communications networks
can be secured by encryption to prevent
eavesdropping.

   Although precautions can be taken to detect an
unauthorized user, it is extremely difficult to
determine if a valid user is performing
unauthorized tasks.  Effective security measures
are a balance of technology and personnel
management.  See NCSC.


security kernel
The part of the operating system that grants access
to users of the computer system.


security levels
See NCSC.


sed
(Stream EDitor)  UNIX editing command that makes
changes a line at a time and is used to edit large
files that exceed buffer limitations of other
editors.


seed
(1) Starting value used by a random number
generation routine to create random numbers.

(2) (SEED)  (Self-Electro-optic-Effect Device)
Optical transistor developed by David Miller at
Bell Labs in 1986.


seek
(1) To move the access arm to the requested track
on a disk.

(2) Assembly language instruction that activates a
seek operation on disk.

(3) High-level programming language command used to
select a record by key field.


seek time
Time it takes to move the read/write head to a
particular track on a disk.


segment
(1) Any partition, reserved area, partial component
or piece of a larger structure.

(2) One of the bars that make up a single character
in an LED or LCD display.

(3) For DOS segment addressing, see paragraph.


segmented address space
Memory addressing in which each byte is referenced
by a segment, or base, number and an offset that is
added to it.  Contrast with flat address space.


Sel
(SELect)  Printer switch that takes the printer
alternately online and offline.


selection sort
Search for specific data starting at the beginning
of a file or list.  It copies each matching item to
a new file so that the selected items are in the
same sequence as the original data.


selective calling
In communications, the ability of the transmitting
station to indicate which station in the network is
to receive the message.


selector channel
High-speed computer channel that connects a
peripheral device (disk, tape, etc.) to the
computer's memory.


selector pen
Same as light pen.


Selectric typewriter
Introduced in 1961 by IBM, the first typewriter to
use a golf-ball-like print head that moved across
the paper, rather than moving the paper carriage
across the print mechanism.  It rapidly became one
of the world's most popular typewriters.  IBM has
always excelled in electromechanical devices.


self-booting
Refers to automatically loading the operating
system upon startup.


self-checking digit
See check digit.


self-clocking
Recording of digital data on a magnetic medium such
that the clock pulses are intrinsically part of the
recorded signal.  A separate timer clock is not
required.  Phase encoding is a commonly-used self-
clocking recording technique.


self-documenting code
Programming statements that can be easily
understood by the author or another programmer.
COBOL provides more self-documenting code than does
C, for example.


self-extracting file
One or more compressed files that have been
converted into an executable program which
decompresses its contents when run.


semantic error
In programming, writing a valid programming
structure with invalid logic.


semantic gap
Difference between a data or language structure and
the real world.  For example, in order processing,
a company can be both customer and supplier.  Since
there is no way to model this in a hierarchical
database, the semantic gap is said to be large.  A
network database could handle this condition,
resulting in a smaller semantic gap.


semantics
Study of the meaning of words.  Contrast with
syntax, which governs the structure of a language.


semaphore
(1) Hardware or software flag used to indicate the
status of some activity.

(2) Shared space for interprocess communications
(IPC) controlled by "wake up" and "sleep" commands.
The source process fills a queue and goes to sleep
until the destination process uses the data and
tells the source process to wake up.


semiconductor
Solid state substance that can be electrically
altered.  Certain elements in nature, such as
silicon, perform like semiconductors when
chemically combined with other elements.  A
semiconductor is halfway between a conductor and an
insulator.  When charged with electricity or light,
semiconductors change their state from
nonconductive to conductive or vice versa.

   The most significant semiconductor is the
transistor, which is simply an on/off switch.


semiconductor device
Elementary component, such as a transistor, or a
larger unit of electronic equipment comprised of
chips.


sensor
Device that measures or detects a real world
condition, such as motion, heat or light and
converts the condition into an analog or digital
representation.  An optical sensor detects the
intensity or brightness of light, or the intensity
of red, green and blue for color systems.


sequel
See SQL.


sequence check
Testing a list of items or file of records for
correct ascending or descending sequence based on
the item or key fields in the records.


sequential
One after the other in some consecutive order such
as by name or number.


sequential access method
Organizing data in a prescribed ascending or
descending sequence.  Searching sequential data
requires reading and comparing each record,
starting from the top or bottom of file.


serial
One after the other.


serial computer
Single-processor computer that executes one
instruction after the other.  Contrast with
parallel computer.


serial interface
Data channel that transfers digital data in a
serial fashion: one bit after the other.
Communications lines are generally serial, thus
modems are connected to the computer via a serial
port.  So are mice and scanners.  Serial interfaces
have multiple lines, but only one is used for data.
Contrast with parallel interface.  See RS-232.


serial mouse
See bus mouse.


serial number
Unique number assigned by the vendor to each unit
of hardware or software.  See signature.


serial port
I/O connector used to attach a modem, mouse,
scanner or other serial interface device to the
computer.  The typical serial port uses a DB-25 or
DB-9 connector, which on the back of a PC is a 25-
pin male or 9-pin male connector.  Contrast with
parallel port.  See RS-232.


serial printer
Type of printer that prints one character at a
time, in contrast to a line or page at a time.  In
this context, serial has no relationship to a
serial or parallel interface that is used to attach
the printer to the computer.  See printer.


serial transmission
Transmitting data one bit at a time.  Contrast with
parallel transmission.


serialize
To convert a parallel signal made up of one or more
bytes into a serial signal that transmits one bit
after the other.


Series/1
IBM minicomputer series introduced in 1976.  It was
used primarily as a communications processor and
for data collection in process control.


serif
Short horizontal lines added to the tops and
bottoms of traditional typefaces, such as Times
Roman.  Contrast with sans-serif.


serpentine recording
Tape recording format of parallel tracks in which
the data "snakes" back and forth from track to
track.


server
Computer in a network shared by multiple users.
See file server and print server.


server application
(1) Application designed to run in a server.  See
client/server.

(2) Any program that is run in the server, whether
designed as a client/server application or not.

(3) See OLE.


service
Functionality derived from a particular software
program.  For example, network services may refer
to programs that transmit data or provide
conversion of data in a network.  Database services
provides for the storage and retrieval of data in a
database.


service bureau
Organization that provides data processing and
timesharing services.  It may offer a variety of
software packages, batch processing services (data
entry, COM, etc.) as well as custom programming.

   Customers pay for storage of data on the system
and processing time used.  Connection is made to a
service bureau through dial-up terminals, private
lines, or other networks, such as Telenet or
Tymnet.


servo
Electromechanical device that uses feedback to
provide precise starts and stops for such functions
as the motors on a tape drive or the moving of an
access arm on a disk.


session
(1) In communications, the active connection
between a user and a computer or between two
computers.

(2) Using an application program (period between
starting up and quitting).


set theory
Branch of mathematics or logic that is concerned
with sets of objects and rules for their
manipulation.  UNION, INTERSECT and COMPLEMENT are
its three primary operations and they are used in
relational database as follows.

   Given a file of Americans and a file of Barbers,
UNION would create a file of all Americans and
Barbers.  INTERSECT would create a file of American
Barbers, and COMPLEMENT would create a file of
Barbers who are not Americans, or of Americans who
are not Barbers.


setup program
Software that configures a system for a particular
environment.  It is used to install a new
application and modify it when the hardware
changes.  When used with expansion boards, it may
change the hardware by altering on-board memory
chips (flash memory, EEPROMs, etc.).  See install
program.


setup string
Group of commands that initialize a device, such as
a printer.  See escape character.


seven dwarfs
IBM's early competitors in the mainframe business:
Burroughs, CDC, GE, Honeywell, NCR, RCA and Univac.


seven-segment display
Common display found on digital watches and
readouts that looks like a series of 8s.  Each
digit or letter is formed by selective illumination
of up to seven separately addressable bars.


sex changer
See gender changer.


SGML
(Standard Generalized Markup Language)  ISO-
standard metalanguage for defining ways of marking
up text content for purposes such as formatting and
hypertexting.


sh
(SHell)  UNIX command that invokes a different
shell.  It can be used like a batch file to execute
a series of commands saved as a shell.


shadow batch
Data collection system that simulates a transaction
processing environment.  Instead of updating master
files (customers, inventory, etc.) when orders or
shipments are initiated, the transactions are
stored in the computer.  When a user makes a query,
the master record from the previous update cycle is
retrieved; but before it's displayed, it's updated
in memory with any transactions that may affect it.
The up-to-date master record is then displayed for
the user.  At the end of the day or period, the
transactions are then actually batch processed
against the master file.


shadow mask
Screen full of holes that adheres to the back of a
color CRT's viewing glass.  The electron beam is
aimed through the holes onto the phosphor dots.


shadow RAM
In a PC, a copy of the operating system's BIOS
routines in RAM to improve performance.  RAM chips
are faster than ROM chips.


shared DASD
Disk system accessed by two or more computers
within a single datacenter.  Disks shared in
personal computer networks are called file servers
or database servers.


shared logic
Using a single computer to provide processing for
two or more terminals.  Contrast with shared
resource.


shared resource
Sharing a peripheral device (disk, printer, etc.)
among several users.  For example, a file server
and laser printer in a LAN are shared resources.
Contrast with shared logic.


shareware
Software distributed on a trial basis through
BBS's, online services, mail-order vendors and user
groups.  Shareware is software on the honor system.
If you use it regularly, you're required to
register and pay for it, for which you will receive
technical support and perhaps additional
documentation or the next upgrade.  Paid licenses
are required for commercial distribution.  See
freeware and public domain software.

   There are tens of thousands of shareware
programs, some fantastic, some awful.  Shareware
vendors compile catalogs with hundreds and
thousands of products and sell them by mail or at
shows for a small fee.  That fee is not the
registration fee, but the fee for distributing the
shareware to you.

   For a catalog of hand-picked shareware from
noted shareware expert, Alfred Glossbrenner, who
endorses one product from each category, contact:

        GLOSSBRENNER'S CHOICE
        699 River Road
        Yardley, PA 19067
        215/736-1213


sheet feeder
Mechanical device that feeds stacks of cut forms
(letterheads, legal paper, etc.) into a printer.


shelfware
Products that remain unsold on a dealer's shelf or
unused by the customer.


shell
Outer layer of a program that provides the user
interface, or way of commanding the computer.
Shells are typically add-on programs created for
command-driven operating systems, such as UNIX and
DOS.  It provides a menu-driven or graphical icon-
oriented interface to the system in order to make
it easier to use.  DOS 4.0 and 5.0 come with their
own shell (DOSshell).


shell out
To temporarily exit an application, go back to the
operating system, perform a function and then
return to the application.


shell script
File of executable UNIX commands created by a text
editor and made executable with the chmod command.


shift register
High-speed circuit that holds some number of bits
for the purpose of shifting them left or right.  It
is used internally within the processor for
multiplication and division, serial/parallel
conversion and various timing considerations.


short
In programming, an integer variable.  In C, a long
is two bytes and can be signed (-32K to +32K) or
unsigned (64K).  Contrast with long.


short card
In a PC, a plug-in printed circuit board that is
half the length of a full-size board.  Contrast
with long card.


short-haul modem
In communications, a device that transmits signals
up to about a mile.  Similar to a line driver that
can transmit up to several miles.


shrink-wrapped software
Refers to store-bought software, implying a
standard platform that is widely supported.


SI
See systems integration, Norton SI and Macintosh.


sideband
In communications, the upper or lower half of a
wave.  Since both sidebands are normally mirror
images of each other, one of the halves can be used
for a second channel to increase the data-carrying
capacity of the line or for diagnostic or control
purposes.


Sidekick
PC desktop utility program from Borland.
Introduced in 1984, it was the first popup (TSR)
program for the PC.  It includes a calculator,
WordStar-compatible notepad, appointment calendar,
phone dialer and ASCII table.  Sidekick Plus (1988)
adds more notepad commands, calendar alarms,
scientific and programming calculators, limited
file management and an outliner.


Sieve of Eratosthenes
Benchmark program used to test the mathematical
speed of a computer.  The program calculates prime
numbers based on Eratosthenes's algorithm.


SIG
(Special Interest Group)  Group of people that
meets and shares information about a particular
topic of interest.  It is usally a part of a larger
group or association.


SIGGRAPH
Special interest group on computer graphics that is
part of the ACM.


sign
Symbol that identifies a positive or negative
number.  In digital code, it is either a separate
character or part of the byte.  In ASCII, the sign
is kept in a separate character typically
transmitted in front of the number it represents
(+ and - is 2B and 2D in hex).

   In EBCDIC, the minus sign can be stored as a
separate byte (hex 60), or, more commonly, as half
a byte (+ and - is C and D in hex), which is stored
in the high-order bits of the least significant
byte.  For packed decimal, it is in the low-order
bits of the least significant byte.


sign on/sign off
Same as log-on/log-off.


signal
Physical form of transmitted data (pulses or
frequencies of electricity or light).


signal converter
Device that changes the electrical or light
characteristics of a signal.


signal processing
See digital signal processing.


signal to noise ratio
Ratio of the amplitude (power, volume) of a data
signal to the amount of noise (interference) in the
line.  Usually measured in decibels, it measures
the clarity or quality of a transmission channel or
electronic device.


signaling in/out of band
In communications, signaling "in band" refers to
sending control signals within the same frequency
range as the data signal.  Signaling "out of band"
refers to sending control signals outside of the
frequency range of the data signal.


signature
(1) Unique number built into hardware or software
for identification.

(2) (Signature)  Successor to XyWrite word
processor.  See XyWrite III Plus.


significant digits
Those digits in a number that add value to the
number.  For example, in the number 00006508, 6508
are the significant digits.


silica
Same as silicon dioxide.


silica gel
Highly absorbent form of silicon dioxide often
wrapped in small bags and packed with equipment to
absorb moisture during shipping and storage.


silicon
(Si)  Base material used in chips.  Next to oxygen,
it is the most abundant element in nature and is
found in a natural state in rocks and sand.  Its
atomic structure and abundance make it an ideal
semiconductor material.  In chip making, it is
mined from rocks and put through a chemical process
at high temperatures to purify it.  To alter its
electrical properties, it is mixed (doped) with
other chemicals in a molten state.


silicon compiler
Software that translates the electronic design of a
chip into the actual layout of the components.


silicon dioxide
(SiO2)  Hard, glassy mineral found in such
materials as rock, quartz, sand and opal.  In MOS
chip fabrication, it is used to create the
insulation layer between the metal gates of the top
layer and the silicon elements below.


silicon disk
Disk drive permanently simulated in memory.
Typically used in laptops for weight reduction, it
requires constant power from a battery to maintain
its contents.


silicon foundry
Organization that makes chips for other companies
that have only design, but not manufacturing
facilities.  It is typically a large chip maker
that uses excess manufacturing capacity in this
manner.


silicon nitride
(Si3N4)  Silicon compound capable of holding a
static electric charge and used as a gate element
on some MOS transistors.


silicon on sapphire
See SOS.


Silicon Valley
Area around San Jose (south of San Francisco) noted
for its large number of high-tech companies.


SIM
(Society for Information Management)  Organization
of MIS professionals founded as the Society for MIS
in 1968.  It is an exchange for technical
information and offers educational and research
programs, competitions and awards to its members.
Address: 111 East Wacker Dr., Suite 600, Chicago,
IL 60601.


SIMD
(Single Instruction stream Multiple Data stream)
Computer architecture that performs one operation
on multiple sets of data, for example, an array
processor.  One computer or processor is used for
the control logic and the remaining processors are
used as slaves, each executing the same
instruction.  Contrast with MIMD.


SIMM
(Single In-line Memory Module)  Narrow printed
circuit board about three inches long that holds
eight or nine memory chips.  It plugs into a SIMM
socket on the circuit board.

  SIMM specs    Capacity/configuration
    1x3       1MB, two 4Mb chips, one 1Mb chip
    1x9       1MB, nine 1Mb chips
    4x9       4MB, nine 4Mb chips
   16x9      16MB, nine 16Mb chips

   1x8, 4x8, etc., use eight chips (no parity).

   A number, typically from 50 to 80, following the
above designation is chip speed; for example,
1x9-60 means 60 nanosecond 1MB SIMMs.

   On PCs, SIMMs are installed in multiples of two
on 286s and 386SXs (16-bit data bus), and multiples
of four on 386DXs and up (32-bit).  In order to
increase memory in small increments, 256KB SIMMs
are used.  Adding two 256KB SIMMs on 286s and
386SXs adds 512KB, while four of them adds one
megabyte on 386DXs and up.


simplex
One way transmission.  Contrast with half-duplex
and full-duplex.


SIMSCRIPT
Programming language used for discrete simulations.


simulation
(1) Mathematical representation of the interaction
of real-world objects.  See scientific
applications.

(2) Execution of a machine language program
designed to run in a foreign computer.


sine wave
Uniform wave that is generated by a single
frequency.


single board computer
Printed circuit board that contains a complete
computer, including processor, memory, I/O and
clock.


single density disk
First-generation floppy disk.


single-ended configuration
Electrical signal paths that use a common ground,
which are more susceptible to noise than
differential configuration.


single mode fiber
Optical fiber with a core diameter of less than 10
microns used for high-speed transmission and long
distances.  Contrast with multi mode fiber.


single precision
Use of one computer word to hold a numeric value
for calculation.  Contrast with double precision.


single sided disk
Floppy disk that stores data on only one side.


single-system image
Operational view of multiple networks, distributed
databases or multiple computer systems as if they
were one system.


single threading
Processing one transaction to completion before
starting the next.


sink
Device or place that accepts something.  See heat
sink and data sink.


SIP
(Single In-line Package)  Type of chip module that
is similar to a SIMM, but uses pins rather than
edge connectors.  SIPs are sometimes called SIPPs
(Single In-Line Pin Package).


SISD
(Single Instruction stream Single Data stream)
Architecture of a serial computer.  Contrast with
SIMD and MIMD.


site license
License to use software within a facility.  It
provides authorization to make copies and
distribute them within a specific jurisdiction.


SIXEL
Graphics language from Digital that supersedes
ReGIS.  ReGIS to SIXEL conversion programs are
available.


skew
(1) Misalignment of a document or punched card in
the feed tray or hopper that prohibits it from
being scanned or read properly.

(2) In facsimile, the difference in rectangularity
between the received and transmitted page.

(3) In communications, a change of timing or phases
in a transmission signal.

(4) See cylinder skew and head skew.


sky wave
Radio signal transmitted into the sky and reflected
back down to earth from the ionosphere.


slave
Computer or peripheral device controlled by another
computer.  For example, a terminal or printer in a
remote location that only receives data is a slave.
When two personal computers are hooked up via their
serial or parallel ports for file exchange, the
file transfer program may make one computer the
master and the other the slave.


slave tube
Display monitor connected to another monitor in
order to provide an additional viewing station.


SLC
See 386SLC.


SLED
(Single Large Expensive Disk)  Traditional disk
drive.  Contrast with RAID.


sleep
(1) In programming, an inactive state due to an
endless loop or programmed delay.  A sleep
statement in a programming language creates a delay
for some specified amount of time.

(2) Inactive status of a terminal, device or
program that is awakened by sending a code to it.


slew rate
(1) How fast paper moves through a printer (ips).

(2) Speed of changing voltage.


sliding window
(1) Communications protocol that transmits multiple
packets before acknowledgement.  Both ends keep
track of packets sent and acknowledged (left of
window), those which have been sent and not
acknowledged (in window) and those not yet sent
(right of window).

(2) View of memory that can be instantly shifted to
another location.


slipstream
To fix a bug or add enhancements to software
without identifying such inclusions by creating a
new version number.


slot
(1) Receptacle for additional printed circuit
boards.

(2) Receptacle for inserting and removing a disk or
tape cartridge.

(3) In communications, a narrow band of
frequencies.  See time slot.

(4) May refer to reserved space for temporary or
permanent storage of instructions, data or codes.


slot mask
Sony Trinitron counterpart to the shadow mask.  It
uses vertical rectangular slots instead of holes.


slow scan TV
Transmission of still video frames over telephone
lines.  Not realtime transmission, it takes several
seconds to transmit one frame.  Also called
electronic still photography (ESP).


slug
Metal bar containing the carved image of a letter
or digit that is used in a printing mechanism.


SMA
(1) (Software Maintenance Assn.)  Non-profit
professional organization founded in 1985 and
dedicated to enhance understanding of software
maintenance and to advance those concerned with it.
Active chapters are in major cities worldwide.
Annual conference is held in the spring.  Address:
Ms. Robin Gross, Box 12004, Vallejo, CA 94590,
707/643-4423.

(2) (Systems Management Architecture)  IBM network
management repository.

(3) Type of fiber optic connector.

(4) (Spectrum Manufacturers Assn.)  DBMS standard
for application compatibility.


Smalltalk
Operating system and object-oriented programming
language that was developed at Xerox Corp.'s Palo
Alto Research Center.  As an integrated
environment, it eliminates the distinction between
programming language and operating system.  It also
allows the programmer to customize the user
interface and behavior of the system.

   Smalltalk was the first object-oriented
programming language and was used on Xerox's Alto
computer, which was designed for it.  It was
originally used to create prototypes of simpler
programming languages and the graphical interfaces
that are so popular today.


Smalltalk V
Version of Smalltalk for PCs from Digitalk, Inc.,
Los Angeles.  Versions for DOS, OS/2, Windows and
the Mac are also available.


smart cable
Connecting cable between two devices that has a
built-in microprocessor.  It analyzes incoming
signals and converts them from one protocol to
another.


smart card
Credit card with built-in microprocessor and memory
used for identification or financial transactions.
When inserted into a reader, it transfers data to
and from a central computer.  It is more secure
than a magnetic stripe card and can be programmed
to self-destruct if the wrong password is entered
too many times.  As a financial transaction card,
it can store transactions and maintain a bank
balance.


smart hub
See intelligent hub.


smart install program
Install program that configures itself
automatically based on the hardware environment.


smart terminal
Video terminal with built-in display
characteristics (blinking, reverse video,
underlines, etc.).  It may also contain a
communications protocol.  Sometimes refers to
intelligent terminal.  See intelligent terminal and
dumb terminal.


Smartcom
Family of communications programs for PCs and Macs
from Hayes Microcomputer Products, Inc., Atlanta,
GA.  Versions emulate a several terminals and
support a variety of protocols, including the Hayes
V-series.  Smartcom EZ is for the novice.


Smartdrive
Disk cache program that comes with DOS 4.0 and
Windows 3.0.  Driver is SMARTDRV.SYS.


SmartKey
PC keyboard macro processor from No Brainer
Software, Midvale, UT.  It was one of the first
macro processors that let users eliminate
repetitive typing by creating a macro for an
occurrence of text or a series of commands.


SmartWare
Integrated software package for PCs and various
UNIX-based systems from Informix Software, Inc.,
Menlo Park, CA, that includes a programming
language.


SMB
(Server Message Block)  Message format used in the
Microsoft/3Com file sharing protocol for PC
Network, MS-Net and LAN Manager.  Used to transfer
file requests between workstations and servers as
well as within the server for internal operations.
For network transfer, SMBs are carried within the
NetBIOS network control block (NCB) packet.


SMD
(1) (Storage Module Device)  High-performance hard
disk interface used with minis and mainframes that
transfers data in the 1-4 MBytes/sec range (SMD-E
provides highest rate).  See hard disk.

(2) (Surface Mount Device)  Surface mounted chip.


SMDS
(Switched Multimegabit Data Services)  High-speed
data services in the 45 Mbits/sec range proposed by
local telephone companies that will allow companies
to build private MANs.


SMF
(1) (Standard Messaging Format)  E-mail programming
interface from Novell.  NGM (NetWare Global
Messaging) is based on SMF-71, which supports long
addresses and synchronized directories.

(2) (Single Mode Fiber)  Class of optical fiber
used in FDDI that transmits through a single path
at 2Gbits/sec up to 50 miles.  See MMF.


smoke test
Test of new or repaired equipment by turning it on.
If there's smoke, it doesn't work!


smoothed data
Statistical data that has been averaged or
otherwise manipulated so that the curves on its
graph are smooth and free of irregularities.


smoothing circuit
Electronic filtering circuit in a DC power supply
that removes the ripples from AC power.


SMP
See symmetric multiprocessing.


SMPTE
(Society for Motion Picture and TV Engineers)
Organization that prepares standards and
documentation for TV production.  SMPTE time code
records hours, minutes, seconds and frames on audio
or videotape for synchronization purposes.
Address: 595 W. Hartsdale Ave., White Plains, NY
10607, 914/761-1100.


SMT
(1) See surface mount.

(2) (Station ManagemenT)  FDDI network management
protocol that provides direct management.  Only one
node requires the software.


SMTP
(Simple Mail Transfer Protocol)  E-mail protocol
used in TCP/IP networks.


SNA
(Systems Network Architecture)  IBM mainframe
network standards introduced in 1974.  Originally a
centralized architecture with a host computer
controlling many terminals, enhancements, such as
APPN and APPC (LU 6.2), have adapted SNA to today's
peer-to-peer communications and distributed
computing environment.  Following are some of SNA's
basic concepts.

               Nodes and Data Links
In SNA, nodes are end points or junctions, and data
links are the pathways between them.  Nodes are
defined as Type 5 (hosts), Type 4 (communications
controllers) and Type 2 (peripheral; terminals, PCs
and midrange computers).

   Type 2.0 nodes can communicate only with the
host, and Type 2.1 nodes can communicate with other
2.1 nodes (peer-to-peer) without going to the host.

   Data links include high-speed local channels,
the SDLC data link protocol and Token Ring.


                SSCPs, PUs and LUs
The heart of a mainframe-based SNA network is the
SSCP (System Services Control Point) software that
resides in the host.  It manages all resources in
its domain.

   Within all nodes of an SNA network, except for
Type 2.1, there is PU (Physical Unit) software that
manages node resources, such as data links, and
controls the transmission of network management
information.  In Node Type 2.1, Control Point
software performs these functions.

   In order to communicate user data, a session
path is created between two end points, or LUs
(Logical Units).  When a session takes place, an
LU-LU session is established between an LU in the
host (CICS, TSO, user appliction, etc.)  and an LU
in the terminal controller or PC.

   An LU 6.2 session provides peer-to-peer
communication and lets either side initiate the
session.


                   VTAM and NCP
VTAM (Virtual Telecommunications Access Method)
resides in the host and contains the SSCP, the PU
for the host, and establishes the LU sessions
within the host.

   NCP (Network Control Program) resides in the
communications controller (front end processor) and
manages the routing and data link protocols, such
as SDLC and Token Ring.


                    SNA Layers
SNA is implemented in functional layers with each
layer passing control to the next layer.  This
layering is called a protocol stack.


      User
        │
  ┌─────┴──────┐
  │Transaction │ Program to program communications
 7│  Services  │ for e-mail, file sharing, etc.
  │            │ (DIA, SNA/DS, DDM, etc.)
  ├────────────┤
 6│Presentation│ Formats data for terminal.
  │  Services  │ (3270 screens, APPC, etc.)
  │            │
  ├────────────┤
 5│ Data flow  │ Assigns sequence nos., controls
  │  Control   │ direction, groups related data.
  │            │ Provides end user acknowledgment.
  ├────────────┤
  │Transmission│ Logical end-to-end.  Checks packet
 4│  Control   │ sequence, handles encryption and
  │            │ paces transmission.
  ├────────────┤
  │   Path     │                 Path control ────┐
 3│  Control   │  Physical end-to-end (routing).  │
  │            │                                  │
  ├────────────┤                                  │
  │ Data link  │  Error detection and             │
 2│  Control   │  correction. (Local channel,     │
  │            │  SDLC, Token Ring, X.25, etc.)   │
  ├────────────┤                                  │
 1│  Physical  │  Wires, signals.                 │
  │  Control   │  (RS232, 802.5, etc.)          ──┘
  └────┬─┬─────┘
       │ │
       │ │
  ┌────┴─┴─────┐
 1│  Physical  │
        │

   Back up the
   hierarchy to
   the other user.


                    SNA vs OSI
SNA had major influence on the international OSI
model; however, OSI does not implement every layer
exactly the same.


               SNA              OSI
         ┌─────────────┐  ┌─────────────┐
         │ Transaction │  │ Application │
         ├─────────────┤  ├─────────────┤
         │Presentation │  │Presentation │
         ├─────────────┤  ├─────────────┤
         │  Data flow  │  │   Session   │
         ├─────────────┤  ├─────────────┤
         │Transmission │  │  Transport  │
         ├─────────────┤  ├─────────────┤
         │Path control │  │   Network   │
         ├─────────────┤  ├─────────────┤
         │ Data link   │  │  Data link  │
         ├─────────────┤  ├─────────────┤
         │  Physical   │  │  Physical   │
         └─────────────┘  └─────────────┘



SNADS
(SNA Distribution Services)  IBM e-mail system for
SNA networks.  It also provides store and forward
capabilities if a user's machine is unavailable to
receive a transmission.


snap to
Feature in a drawing program that moves a text or
graphic element to the closest grid line.


snapshot
Storing the contents of memory including all
hardware registers and status indicators.  It is
periodically taken in order to restore the system
in the event of failure.


snapshot dump
Memory dump of selected portions of memory.


snapshot program
Trace program that provides selected dumps of
memory when specific instructions are executed or
when certain conditions are met.


snd
(SouND resource)  Macintosh resource fork that
contains sound information, including compression
ratios if used and sampling rate.


sneakernet
Carrying floppy disks from one machine to another
to exchange information, when you don't have a
network.


sniffer
Software and/or hardware that analyzes traffic and
detects bottlenecks and problems in a network.


SNMP
(Simple Network Management Protocol)  Format used
for network management data.  Data is passed
between SNMP agents (processes that monitor
activity in hubs, routers, bridges, etc.) and the
workstation used to oversee the network.
Originating in the UNIX community, it has spread to
VMS, DOS and other environments.

   SNMP uses Management Information Bases (MIBs),
which are databases that define what information is
obtainable from a networked device and what can be
controlled (turned off, on, etc.).


SNOBOL
(StriNg Oriented symBOlic Language)  One of the
first list processing languages (Bell Labs; early
1960s).  It was used for text processing and
compiler development.


snow
Flickering snow-like spots on a video screen caused
by display electronics that are too slow to respond
to changing data.


socket
(1) Receptacle which receives a plug.

(2) BSD UNIX function that lets an application
access a communications protocol by "opening a
socket" and declaring a destination.


soft
Flexible and changeable.  Software can be
reprogrammed for different results.  The computer's
soft nature is its greatest virtue; however, the
reason it takes so long to get new systems
developed has little to do with the concept.  It is
based on how systems are developed (file systems vs
database management), the programming languages
used (assembly vs high-level), combined with the
skill level of the technical staff, compounded by
the organization's bureaucracy.


soft boot
Same as warm boot.


soft copy
Refers to data displayed on a video screen.
Contrast with hard copy.


soft error
Recoverable error, such as a garbled message that
can be retransmitted.  Contrast with hard error.


soft font
Set of characters for a particular typeface that is
stored on the computer's hard disk, or in some
cases the printer's hard disk, and downloaded to
the printer before printing.  Contrast with
internal font and font cartridge.


soft hyphen
Hyphen that prints if it winds up at the end of the
line, but does not print otherwise.  Contrast with
hard hyphen.  See discretionary hyphen.


soft key
Keyboard key simulated by an icon on screen.


soft patch
Quick fix to machine language currently in memory
that only lasts for the current session.


soft return
Code inserted by the software into a text document
to mark the end of the line.  When the document is
printed, the soft return is converted into the end-
of-line code required by the printer.  Soft returns
are determined by the right margin and change when
the margins are changed.

   In graphics-based environments, such as in the
Macintosh, soft returns are not used as the text
must be free to change within movable windows.

   With PCs, soft return codes differ; for example,
WordPerfect uses a return (ASCII 13) and WordStar
uses a line feed (ASCII 10).

   Contrast with hard return.


soft sectored
Common method of identifying sectors on a disk by
initially recording sector information on every
track with a format program.  Contrast with hard
sectored.


Soft-Switch
E-mail switching software and hardware from Soft-
Switch, Inc., Wayne, PA, that provides an e-mail
backbone for organizations with diverse e-mail
systems.  It directly supports X.400, SNADS and
SMTP and provides gateways to other e-mail systems.
Soft-Switch Central is software for IBM MVS and VM
mainframes, and its EMX 88000-based e-mail server
connects to Token Ring, Ethernet, X.25 and SDLC.


Softstrip
Optical scanner from Softstrip, Inc., Waterbury,
CT, that reads a unique, encoded pattern of 50 to
600 bytes of data per inch.


software
Instructions for the computer.  A series of
instructions that performs a particular task is
called a program or software program.  The two
major categories are system software and
application software.

   System software is made up of control programs,
including the operating system, communications
software and database manager.

   Application software is any program that
processes data for the user (inventory, payroll,
spreadsheet, word processor, etc.).


software architecture
Design of application or system software that
incorporates protocols and interfaces for
interacting with other programs and for future
flexibility and expandability.  A self-contained,
stand-alone program would have program logic, but
not a software architecture.


Software Carousel
Task switching program for PCs from SoftLogic
Solutions, Inc., Manchester, NH, that allows the
user to have up to a dozen applications open at the
same time and switch back and forth between them.


software engineering
Design, development and documentation of software.


software failure
Inability of a program to continue processing due
to erroneous logic.  Same as crash, bomb and abend.


software house
Organization that develops customized software for
a customer.  Contrast with software publisher,
which develops and markets software packages.


software IC
Object-oriented programming class packaged for
sale.  Term coined by The Stepstone Corp.


software interface
Same as API.


software interrupt
Interrupt caused by an instruction in the program.
See interrupt.


software package
Application program developed for sale to the
general public.


software program
Commonly used to refer to a computer application.
All computer software is made up of computer
programs.  All computer programs are software.


software programmer
Same as systems programmer.


software protection
See copy protection.


software publisher
Organization that develops and markets software.
It does market research, production and
distribution of software.  It may develop its own
software, contract for outside development or
obtain software that has already been written.


software stack
Stack implemented in memory.  See stack.


software tool
Program that aids in the development of other
software programs.  It may assist the programmer in
the design, coding, compiling, link editing or
debugging phases.


software vendors
Following is the calendar 1991 worldwide packaged
software ranking from the June 1992 Special Issue
of Software Magazine.  Consulting, custom services
and programming revenues are excluded.  Hardware
manufacturers are not included.  See vendors.

Reprinted with permission of Sentry Publishing Co.,
Inc., 1900 West Park Drive, Westborough, MA 01581.

       TOP 50 INDEPENDENT SOFTWARE VENDORS
              (* = privately held)

        Total number employees─┐  1991 Packaged
    COMPANY NAME               │  Software revenue
    HQ city (date founded)     │  ($ millions)

  1 MICROSOFT CORP.
    Redmond, WA (1975)       10000   1801
  2 COMPUTER ASSOCIATES INT'L., INC.
    Islandia, NY (1976)       7700   1438
  3 LOTUS DEVELOPMENT CORP.
    Cambridge, MA (1982)      4324    829
  4 ORACLE CORP.
    Redwood Shores, CA (1977) 7786    661

  5 WORDPERFECT CORP.*
    Orem, UT (1979)           2896    603
  6 NOVELL, INC.
    Provo, UT (1983)          3100    571
  7 DUN & BRADSTREET SOFTWARE
    Atlanta, GA (1990)        3400    549
  8 BORLAND INT'L. INC.
    Scotts Valley, CA (1983)  2000    502
  9 SAP AG (SAP AMERICA)
    Lester, PA (1972)         2685    375
 10 THE ASK COMPANIES
    Mountain View, CA (1972)  2200    315

 11 SOFTWARE AG*
    Reston, VA (1969)         4000    304
 12 SAS INSTITUTE, INC.*
    Cary, NC (1976)           2386    295
 13 LEGENT CORP.
    Vienna, VA (1989)         1300    215
 14 SYMANTEC CORP.
    Cupertino, CA (1982)       770    196
 15 INFORMATION BUILDERS INC.*
    New York, NY (1975)       1650    176

 16 BMC SOFTWARE, INC.
    Sugar Land, TX (1980)      738    170
 17 CANDLE CORP.
    Los Angeles, CA (1977)     950    169
 18 ALDUS CORP.
    Seattle, WA  (1984)        952    164
 19 CINCOM SYSTEMS, INC.*
    Cincinnati, OH (1968)     1355    158
 20 INFORMIX SOFTWARE, INC.
    Menlo Park, CA (1980)      941    149

 21 SOFTWARE PUBLISHING CORP.
    Mountain View, CA (1980)   750    141
 22 COMPUWARE CORP.*
    Farmington Hills, MI('73) 1379    137
 23 AMERICAN MANAGEMENT SYSTEMS
    Arlington, VA (1970)      3120    137
 24 THE CONTINUUM CO.
    Austin, TX (1968)         1100    129
 25 THE SANTA CRUZ OPERATION
    Santa Cruz, CA (1979)     1200    125

 26 STERLING SOFTWARE, INC.
    Dallas, TX (1983)         2000    123
 27 GOAL SYSTEMS INT'L. INC.
    Columbus, OH (1975)        900    121
 28 SYSTEMS CENTER, INC.
    Reston, VA (1981)          939    120
 29 SYSTEM SOFTWARE ASSOCIATES INC.
    Chicago, IL (1981)         800    119
 30 COMSHARE, INC.
    Ann Arbor, MI (1966)      1100    117

 31 SYBASE, INC.
    Emeryville, CA (1984)     1100    115
 32 COGNOS, INC.
    Ottawa, Ontario (1969)    1091    108
 33 CGI SYSTEMS, INC.
    Berwyn, PA (1951)         4050    104
 34 BOOLE & BABBAGE, INC.
    Sunnyvale, CA (1967)       640     99
 35 MICRO FOCUS GROUP PLC.
    Palo Alto, CA (1976)       548     98

 36 KNOWLEDGEWARE, INC.
    Atlanta, GA (1979)         775     97
 37 J.D. EDWARDS & CO.*
    Denver, CO (1977)          934     91
 38 INTERLEAF, INC.
    Waltham, MA (1981)         820     81
 39 UNIX SYSTEM LABS, INC.*
    Summit, NJ (1991)          700     80
 40 CENTRAL POINT SOFTWARE, INC.
    Beaverton, OR (1981)       310     75

 41 POLICY MANAGEMENT SYSTEMS CORP.
    Columbia, SC (1974)       4309     73
 42 AMERICAN SOFTWARE
    Atlanta, GA (1970)         854     72
 43 SOFTWARE ENGINEERING OF AMERICA, INC.*
    Lake Success, NY (1982)    250     67
 44 INFORMATION RESOURCES, INC.
    Waltham, MA (1982)         528     66
 45 LUCAS MANAGEMENT SYSTEMS
    Fairfax, VA (1977)         697     66

 46 ANDERSEN CONSULTING*
    Chicago, IL (1954)       25100     65
 47 ATTACHMATE CORP.
    Bellevue, WA (1984)        500     65
 48 BANYAN SYSTEMS, INC.
    Westborough, MA (1983)     625     62
 49 SOFTLAB, INC.
    San Francisco, CA (1971)   800     54
 50 INTERSOLV, INC.
    Rockville, MD (1991)       530     53


SOG
(Small Outline Gullwing)  Same as SOIC.


SOIC
(Small Outline IC)  Small-dimension, surface mount
DIP that uses gullwing-shaped pins extending
outward.


SOJ
(Small Outline J lead)  Small-dimension, surface
mount DIP that uses J-shaped pins extending inward.


Solaris 2.0
Multitasking, multiprocessing distributed computing
environment from SunSoft for SPARC computers and
386s and up.  Solaris 2.0 for SPARC machines is
backward compatible with Solaris 1.0, and includes
the SunOS 5.0 operating system (based on UNIX
SVR4), Sun's ONC networking products (NFS, NIS,
etc.), OpenWindows (Sun's version of X Windows) and
Sun's Open Look graphical interface with DeskSet
utilities that provide multimedia mail and drag &
drop capability.

   Solaris 2.0 for x86 machines will run
applications written for Solaris, Sun's INTERACTIVE
UNIX for x86 machines, as well as DOS and Windows
applications.


solder mask
Insulating pattern applied to a printed circuit
board that exposes only the areas to be soldered.


solenoid
Magnetic switch that closes a circuit, often used
as a relay.


solid logic
Same as solid state.


solid modeling
Mathematical technique for representing solid
objects.  It is the least abstract form of CAD.
Unlike wireframe and surface modeling, solid
modeling systems ensure that all surfaces meet
properly and that the object is geometrically
correct.  A solid model can also be sectioned (cut
open) to reveal its internal features.  Solids
allow interference checking, which tests to see if
two or more objects occupy the same space.


solid state
Electronic component or circuit made of solid
materials, such as transistors, chips and bubble
memory.  There is no mechanical action in a solid
state device, although an unbelievable amount of
electromagnetic action takes place within.

   For data storage, solid state devices are much
faster and more reliable than mechanical disks and
tapes, but are more expensive.  Although solid
state costs continually drop, disks, tapes and
optical disks also continue to improve their
cost/performance ratio.

  The first solid state device was the "cat's
whisker" of the 1930s.  A whisker-like wire was
moved around on a solid crystal in order to detect
a radio signal.


solid state disk
Disk drive made of memory chips used for high-speed
data access or in adverse environments.  Dynamic
RAM solid state disks are used in battery-powered,
hand-held devices as well as in desktop units with
hundreds of megabytes of storage that contain their
own UPS systems.


solid state memory
Any transistorized, semiconductor or thin film
memory that contains no mechanical parts.


solid state relay
Relay that contains no mechanical parts.  All
switching mechanisms are semiconductor or thin film
components.


solver
Mathematical mechanisms that allow spreadsheets to
perform goal seeking.


SONET
(Synchronous Optical NETetwork)  International
standard for broadband transmission through fiber
optic cables in the 50 megabit to 13 gigabit per
second range.  It is included in the Broadband ISDN
(BISDN) specification.


sort
To reorder data into a new sequence.  The operating
system can typically sort file names and text
lists.

   In word processors, sorting allows for all the
text in the document or a marked block of text to
be resequenced into either an ascending (normal) or
descending sequence.

   In database programs, sorting resequences all
the records in the file by one or more fields and
often generates an entirely new copy of the file.


sort algorithm
Formula used to reorder data into a new sequence.
Like all complicated problems, there are many
solutions that can achieve the same results.  One
sort algorithm can resequence data faster than
another.  In the early 1960s, when tape was "the"
storage medium, the sale of a computer system may
have hinged on the sort algorithm, since without
direct access capability, every transaction had to
be sorted into the sequence of the master file.


sort field
Same as sort key.


sort key
Field or fields in a record that dictate the
sequence of the file.  For example, the sort keys
STATE and NAME arrange the file alphabetically by
name within state.  STATE is the major sort key,
and NAME is the minor key.


sorter
(1) Sort program.

(2) Person who manually puts data into a specific
sequence.

(3) Early tabulating machine that routed punched
cards into separate stackers based on the content
of a card column.  The complete operation required
passing the cards through the machine once for each
column sorted.


SOS
(1) (Silicon On Sapphire)  MOS chip-fabrication
method that places a thin layer of silicon over a
sapphire substrate (base).

(2) (Sophisticated Operating System)  Operating
system used on the Apple III.


sound bandwidth
Range of sound frequencies.  The human ear can
perceive approximately from 20 to 20,000Hz, but
human voice is confined to within 3,000Hz.


sound board
Same as sound card.


sound card
Personal computer expansion board that generates
sound and provides outputs for external
amplification and speakers.  Unshielded speakers
located too close to CRT screens will cause visible
interference.  Shielded speakers are commonly
available for computer use.  See MPC.


source
(1) Source of current in a MOS transistor.  Same as
emitter in a bipolar transistor.

(2) (The Source)  Online information service in
McLean, VA, launched in 1979 and purchased by
CompuServe in 1989.


source code
Program in its original form as written by the
programmer.  It is not executable by the computer
directly.  It must be converted into machine
language by compilers, assemblers and interpreters.

   In some cases, source code can be converted into
another dialect or a different language by a
conversion program.


source computer
Computer in which a program is being assembled or
compiled.  Contrast with object computer.


source data
Original data that is handwritten or printed on a
source document or typed into the computer system
from a keyboard or terminal.


source data acquisition
Same as source data capture.


source data capture
Capturing data electronically when a transaction
occurs; for example, at the time of sale.


source directory
Directory from which data is obtained.


source disk
Disk from which data is obtained.  Contrast with
target disk.


source document
Paper form onto which data is written.  Order forms
and employment applications are examples.


source drive
Disk or tape drive from which data is obtained.
Contrast with target drive.


source language
Language used in a source program.


source program
Program in its original form, as written by the
programmer.


source routing
Communications protocol in which stations are aware
of bridges in the network and route messages via
the bridges.  Contrast with transparent bridging.
See SRT.


source statement
Instructional phrase in a programming language
(source language).


SPA
(Software Publishers Assn.)  Trade organization of
the personal computer software industry that
supports legislation for copyright enforcement.  It
conducts raids on organizations suspected of
illegal copying and files lawsuits against
violators.

   To blow the whistle on a company that has a
policy of making illegal copies, call 800/388-PIR8.
Address: 1730 M St., N.W., Washington, DC 20036,
202/452-1600.


space
In digital electronics, a 0 bit.  Contrast with
mark.


space/time
The following units of measure are used to define
storage and transmission capacities.

S P A C E                           Bits or bytes
Kilo (K)  Thousand                          1,024
Mega (M)  Million                       1,048,576
Giga (G)  Billion                   1,073,741,824
Tera (T)  Trillion              1,099,511,627,776
Peta (P)  Quadrillion       1,125,899,906,842,624


T I M E                        Fraction of second
Millisecond (ms)  Thousandth              1/1,000
Microsecond (µs)  Millionth           1/1,000,000
Nanosecond  (ns)  Billionth       1/1,000,000,000
Picosecond  (ps)  Trillionth  1/1,000,000,000,000
Femtosecond (fs)  Quadrillionth
                            1/100,000,000,000,000


Storage/channel capacity measured in:
CPU word size           Bits
Bus size                Bits
Disk, tape              Bytes
MEMORY
 Overall capacity       Bytes
 SIMM or SIP module     Bytes
 Individual chip        Bits

Transmission speed measured in:
Network line/channel       Bits per second
Disk transfer rate         Bits or bytes per second
Disk access time           Milliseconds
Memory access time         Nanoseconds
Machine cycle              Microseconds/Nanoseconds
Instruction execution      Microseconds/Nanoseconds
Transistor switching       Nanoseconds, Picoseconds
                            and Femtoseconds

spaghetti code
Program code written without a coherent structure.
The logic moves from routine to routine without
returning to a base point, making it hard to
follow.  It implies excessive use of the GOTO
instruction, which directs the computer to branch
to another part of the program without a guarantee
of returning.

   In structured programming, functions are used,
which are subroutines that guarantee a return to
the instruction following the one that called it.


SPARC
(Scalable Performance ARChitecture)  32-bit RISC
CPU developed by Sun and licensed by SPARC Int'l.,
Menlo Park, CA.


spatial data
Data represented as 2-D or 3-D images.


spawn
To launch another program from the current program.
The DOS TSR version of this Glossary is called
POPGLOSS.EXE.  It resides in RAM and "spawns"
GLOSS.EXE when the hotkey is pressed.


spec
See specs and specification.


spec sheet
Detail listing of the components of a system.


special character
Non-alpha or non-numeric character, such as @, #,
$, %, &, * and +.


special-purpose computer
Computer designed from scratch to perform a
specific function.  Contrast with general-purpose
computer.


special-purpose language
Programming language designed to solve a specific
problem or class of problems.  For example, LISP
and Prolog are designed for and used extensively in
AI applications.  Even more specific are languages
such as COGO, for civil engineering problems, and
APT for directing machine tools.  Contrast with
general-purpose language.


specification
Definition (layout, blueprint, design) of hardware
or software.  See specs and functional
specification.


SPECmark
(Systems Performance Evaluation Cooperative MARK)
Suite of 10 benchmarks that test integer (SPECint)
and floating point (SPECfp) performance of a
computer.  SPEC reporting requires all 10 numbers
as users may only need subsets.  A VAX-11\780 is a
one-SPECmark machine, and SPECmarks closely track
VUPs ratings from Digital's internal benchmarks.


specs
(SPECificationS)  Details of the components built
into a device.  See specification.


spectral color
In computer graphics, the color of a single
wavelength of light, starting with violet at the
low end and proceeding through indigo, blue, green,
yellow and orange and ending with red.


spectral response
Variable output of a light-sensitive device that is
based on the color of the light it perceives.


spectrum
Range of electromagnetic frequencies.


speech recognition
Same as voice recognition.


speech synthesis
Generating machine voice by arranging phonemes (k,
ch, sh, etc.) into words.  It is used to turn text
input into spoken words for the blind.  Speech
synthesis performs realtime conversion without a
pre-defined vocabulary, but does not create human-
sounding speech.  Although individual spoken words
can be digitized into the computer, digitized voice
takes a lot of storage, and resulting phrases still
lack inflection.


speed buffering
Technique that compensates for speed differences
between input and output.  Data is accepted into
the buffer at high speed and transferred out at low
speed, or vice versa.


Speed Doubler
See 486.


speed of electricity/light
Approximately 186,000 miles per second.
Electricity and light travel around the equator
over seven times per second.  This inherent speed
of Mother Nature is why computers are so fast.
Within the tiny chip, electricity has to flow only
a couple of millimeters, and, within an entire
computer, only a few feet.

   As fast as that is, it's never fast enough.
There is resistance in the lines, and even though
transistors switch in billionths of a second, CAD,
image processing and scientific applications are
always exhausting the fastest computers.


spelling checker
Separate program or word processing function that
tests for correctly spelled words.  It can test the
spelling of a marked block, an entire document or
group of documents.  Advanced systems check for
spelling as the user types and can correct common
typos and misspellings on the fly.

   Spelling checkers simply compare words to a
dictionary of words, and the wrong use of a
correctly-spelled word cannot be detected.  See
grammar checker.


spherization
In computer graphics, turning an image into a
sphere.


SPI
(Service Provider Interface)  Programming interface
for developing Windows drivers under WOSA.  In
order to provide common access to services, the
application is written to a particular interface,
such as ODBC and MAPI, and the developer of the
service software (DBMS, e-mail, etc.) writes to the
SPI for that class of service.


spike
Also called a transient, a burst of extra voltage
in a power line that lasts only a fraction of a
second.  Contrast with sag.  See surge.


spindle
Rotating shaft in a disk drive.  In a fixed disk,
the platters are attached to the spindle.  In a
removable disk, the spindle remains in the drive.


SpinRite
Popular low-level formatting program for PCs from
Gibson Research, Aliso Viejo, CA, that reformats
without erasing data.  It rewrites only sector ID,
which may have drifted over time.  Version 3.0 can
low-level format IDE drives, which have typically
required proprietary format programs.


SPL
(1) (Systems Programming Language)  HP 3000
assembly language.  See assembly language for an
SPL program example.

(2) (Structured Programming Language)  See
structured programming.


spline
In computer graphics, a smooth curve that runs
through a series of given points.  The term is
often used to refer to any curve.  See Bezier and
B-spline.


split screen
Display of two or more sets of data on screen at
the same time.  It implies that one set of data can
be manipulated independently of the other.  Split
screens, or windows, are usually created by the
operating system or application software, rather
than the hardware.


spooling
(Simultaneous Peripheral Operations OnLine)
Overlapping of low-speed operations with normal
processing.  It originated with mainframes in order
to optimize slow operations such as reading cards
and printing.  Card input was read onto disk and
printer output was stored on disk.  In that way,
the actual business data processing was done at
high speed, since all I/O was on disk.

   Today, spooling is used to buffer data for the
printer as well as remote batch terminals.  See
print spooler.


spread spectrum
Radio transmission that continuously changes
carrier frequency according to a unique pattern in
both sending and receiving devices.  It is used for
security as well as to allow multiple wireless
transmissions in the same space.


spreadsheet
Software that simulates a paper spreadsheet, or
worksheet, in which columns of numbers are summed
for budgets and plans.  It appears on screen as a
matrix of rows and columns, the intersections of
which are identified as cells.  Spreadsheets can
have thousands of cells and can be scrolled
horizontally and vertically in order to view them.

   The cells are filled with:

             1. labels
             2. numeric values
             3. formulas

   The labels, can be any descriptive text, for
example, RENT, PHONE or GROSS SALES.

   The values are the actual numeric data used in
the budget or plan, and the formulas command the
spreadsheet to do the calculations; for example,
SUM CELLS A5 TO A10.

   Formulas are easy to create, since spreadsheets
allow the user to point to each cell and type in
the arithmetic operation that affects it.  Roughly
speaking, a formula is created by saying "this cell
PLUS that cell TIMES that cell."

   The formulas are the spreadsheet's magic.  After
numbers are added or changed, the formulas will
recalculate the data either automatically or with
the press of a key.  Since the contents of any cell
can be calculated with or copied to any other cell,
a total of one column can be used as a detail item
in another column.  For example, the total from a
column of expense items can be carried over to a
summary column showing all expenses.  If data in
the detail column changes, its column total
changes, which is then copied to the summary
column, and the summary total changes.

   Done manually, each change would require
recalculating, erasing and changing the totals of
each column.  The automatic ripple effect allows
users to create a plan, plug in different
assumptions and immediately see the impact on the
bottom line.  This "what if?" capability makes the
spreadsheet indispensable for budgets, plans and
other equation-based tasks.

   The spreadsheet originated with VisiCalc in 1978
for the Apple II, and was followed by SuperCalc,
Multiplan, Lotus 1-2-3 and a host of others.


              CLASSES OF SPREADSHEETS

                     Standard
Every spreadsheet creates a two-dimensional matrix
of rows and columns.  In order to summarize data,
totals from various parts of the spreadsheet can be
summed to another part of the spreadsheet.


                  Dynamic Linking
Allows data in one spreadsheet to automatically
update another spreadsheet.  Although often
referred to as 3-D spreadsheets, dynamic linking
creates the effect of a third dimension in a
separate file.  For example, several detail files
can be summarized into one summary file.  Excessive
linking is difficult to manage, since the
relationships span several physical files.


                   3-Dimensional
Each cell in the spreadsheet has an X, Y and Z
reference.  For example, a spreadsheet of expense
items by month uses two dimensions, but expense
items by month by department requires three
dimensions.

   While this method is superior for consolidating
and summarizing data, it lacks some of the
flexibility inherent in the dynamic linking
approach, since all pages must have essentially the
same structure.  In addition, all data must reside
in one file as with a standard 2-D spreadsheet.


              Relational Spreadsheet
This method stores the data separate and apart from
the formulas.  Data is stored in a central database
and the formulas are stored in the spreadsheet.
When the spreadsheet is called up, the data from
the database is copied into it, thus ensuring that
everyone's spreadsheet contains current data.

   Relational spreadsheets reference data by name
rather than by row and column number.  With name
references, data can be used in multiple
spreadsheets with greater accuracy, and new
spreadsheets can be created more easily.  A
spreadsheet that analyzes the budget for one
department can analyze the budget for any
department simply by changing the department name
and recalculating.

   Name references make it possible to analyze data
from multiple perspectives.  Since data isn't tied
to cell references as with 3-D spreadsheets, more
than three dimensions can be created.  For example,
in a corporate budget, numbers are kept for every
combination of accounts, time periods and
departments in both forecast and actual versions.
A view of accounts by department by period can be
automatically switched to a view of accounts by
period by version.  Instead of complicated
spreadsheet programming, the relational spreadsheet
prepares the views automatically.


spreadsheet compiler
Software that translates spreadsheets into stand-
alone programs that run without the spreadsheet
package that created them.


sprite
Independent graphic object controlled by its own
bit plane (area of memory).  Commonly used in video
games, sprites move freely across the screen,
passing by, through and colliding with each other
with much less programming.


sprocket feed
Same as pin feed.


SPS
(Standby Power System)  UPS system that switches to
battery backup upon detection of power failure.


SPS Association
Nonprofit organization dedicated to an open
PostScript standard.  Address: 7 Stuart Road,
Chelmsford, MA 01824.


SPSS
Statistical package from SPSS, Inc., Chicago, that
runs on PCs, most mainframes and minis and is used
extensively in marketing research.  It provides
over 50 statistical processes, including regression
analysis, correlation and analysis of variance.
Originally named Statistical Package for the Social
Sciences, it was written by Norman Nie, a professor
at Stanford.  In 1976, he formed SPSS, Inc.


spt
(Sectors Per Track)  Number of sectors in one
track.


SPX
(Sequenced Packet EXchange)  NetWare communications
protocol used for interprocess communications
(IPC).  It guarantees that an entire message
arrives intact and uses the NetWare IPX protocol as
its delivery mechanism.


SQL
(Structured Query Language)  Pronounced "SQL" or
"see qwill," a language used to interrogate and
process data in a relational database.  Originally
developed by IBM for its mainframes, there have
been many implementations created for mini and
micro database applications.  SQL commands can be
used to interactively work with a database or can
be embedded within a programming language to
interface to a database.

   The following SQL query selects customers with
credit limits of at least $5,000 and puts them into
sequence from highest credit limit to lowest.


       SELECT NAME, CITY, STATE, ZIPCODE
       FROM CUSTOMER
       WHERE CREDITLIMIT > 4999
       ORDER BY CREDITLIMIT DESC



SQL/DS
(SQL/Data System)  Full-featured relational DBMS
from IBM for VSE and VM environments that has
integrated query and report writing facilities.


SQL engine
Program that accepts SQL commands and accesses the
database to obtain the requested data.  Users'
requests in a query language or database language
must be translated into an SQL request before the
SQL engine can process it.


SQL Server
Relational DBMS from Sybase, Inc., Emeryville, CA,
that runs on OS/2-based PCs, VAXs and UNIX
workstations.  It is designed for network use and
is accessed by applications using SQL or via
Sybase's own QBE and decision support utilities.
It is also available from Microsoft as Microsoft
SQL Server for OS/2.


square wave
Graphic image of a digital pulse as visualized on
an oscilloscope.  It appears square because it
rises quickly to a particular amplitude, stays
constant for the duration of the pulse and drops
fast at the end of it.


SQUID
(Superconducting Quantum Interference Device)
Electronic detection system that uses Josephson
junctions circuits.  It is capable of detecting
extremely weak signals.


SRAM
See static RAM.


SRPI
(Server Requester Programming Interface)  IBM
programming interface that allows a PC to interact
with a mainframe.  See ECF.


SRT
(Source Routing Transparent)  IEEE-standard
technology that allows bridging between Ethernet
and token ring networks (Token Ring, FDDI).
Existing token ring bridges are not compatible with
SRT bridges, but Proteon's (Westborough, MA)
Adaptive SRT bridges are compatibile with the
installed base.  See source routing.


SS/DD
(Single Sided/Double Density)  Refers to earlier
floppy disk formats that store data on only one
side of the disk.


SSCP
(System Services Control Point)  Controlling
program in an SNA domain.  It resides in the host
and is a component within VTAM.


SSD
See solid state disk.


SSE
Protected Mode full-screen editor in OS/2.


SSI
(Small Scale Integration)  Up to 100 transistors on
a chip.  See MSI, LSI, VLSI and ULSI.


SSP
(System Support Program)  Multiuser, multitasking
operating system from IBM that is the primary
control program for System/34 and System/36.


ST
(1) Personal computer series from Atari that uses a
Motorola 68000 CPU and includes the GEM interface,
ROM-based TOS operating system, a MIDI interface
and a three-voice sound chip.  The 520ST has 512K
RAM; the 1040ST has 1MB.  Display is 640x200, 16
colors.  The current model is the 1040STE.

(2) Type of fiber optic connector.


ST412
Enhancement to ST506 standard that buffers track-
to-track commands for a continuous seek to the
required track.  All new ST506 drives/controllers
incorporate this, thus ST412, ST506/412 and current
ST506 units are the same.


ST506
Hard disk interface commonly used in drives 40MB
and less.  It transfers data at 625 KBytes/sec and
uses the MFM encoding method.  See ST412 and hard
disk.


ST506 RLL
(ST506 Run-Length Limited)  Hard disk interface
(also called RLL interface) that increases capacity
and speed by 50% over ST506 MFM drives and
transfers data at 937 KBytes/sec.  With MFM drives
certified for increased capacity, the ST506 MFM
controller can be replaced with an ST506 RLL
controller and the drive can be reformatted.  See
hard disk.


stack
(1) Set of hardware registers or a reserved amount
of memory used for arithmetic calculations or to
keep track of internal operations.  Stacks keep
track of the sequence of routines called in a
program.  For example, one routine calls another,
which calls another and so on.  As each routine is
completed, the computer returns control to the
calling routine all the way back to the first one
that started the sequence.  Stacks used in this way
are LIFO based: the last item, or address, placed
(pushed) onto the stack is the first item removed
(popped) from the stack.

   Stacks are also used to hold interrupts until
they can be serviced.  Used in this manner, they
are FIFO stacks, in which the first item onto the
stack is the first one out of the stack.  See DOS
Stacks.

   An "internal stack failure" is a fatal error
which means that the operating system has lost
track of its next operation.  Restarting the
computer usually corrects this, otherwise the
operating system may have to be re-installed.

(2) See HyperCard.


stack overflow
Error condition that occurs when there is no room
in the stack for a new item.  A stack underflow
occurs when an item is called for, but the stack is
empty.


stack pointer
Address that identifies the location of the most
recent item placed on the stack.


stacker
(1) Output bin in a document feeding or punched
card machine.  Contrast with hopper.

(2) (Stacker)  Realtime compression program from
Stac Electronics, Carlsbad, CA, that doubles
(approximately) the disk capacity of a PC and is
transparent to the user.  A coprocessor board is
optionally available.


stackware
HyperCard application that is made up of a
HyperCard stack (data) and HyperTalk programming.


STAIRS
(STorage And Information Retrieval System)  IBM
text document management system for mainframes.  It
allows users to search for documents based on key
words or word combinations.


standard cell
Finished design of an electronic function ready for
chip fabrication.  It can be as small as a clock
circuit or as large as a microprocessor.  It is
used to make custom-designed chips.


standard deviation
In statistics, the average amount a number varies
from the average number in a series of numbers.


Standard Mode
Windows operation mode.  See Windows.


standards & compatibility
  Machine Languages
  Data Codes
  Hardware Interfaces
  Storage Media
  Operating Systems
  Communications

Standards is the most important issue in the
computer field.  As an unregulated industry, we
have wound up with thousands of data formats and
languages, but very few standards that are
universally used.  This subject is as heated as
politics and religion to vendors and industry
planners.

   No matter how much the industry talks about
compatibility, new formats and languages appear
routinely.  The standards makers are always trying
to cast a standard in concrete, while the
innovators are trying to create a new one.  Even
when standards are created, they are violated as
soon as a new feature is added by the vendor.

   If a format or language is used extensively and
others copy it, it becomes a de facto standard and
may become as widely used as official standards
from ANSI and IEEE.  When de facto standards are
sanctioned by these organizations, they become
stable, at least, for a while.

   In order to truly understand this industry, it
is essential to understand the categories for which
standards are created.



                 MACHINE LANGUAGES
Machine language is the fundamental standard for
hardware compatibility.  Vendors often have several
families of computers, each with different machine
languages.  For example, although all IBM
mainframes use the same machine language, IBM's
AS/400, RS/6000 and PC series are each different.

   After a program is written, it must be
translated (assembled, compiled or interpreted)
into the machine language that the computer
understands.  In order to run in a different
machine, the program must be reassembled or
recompiled into a different machine language,
providing there are appropriate translators.

   Since the late 1960s, companies seeking a chunk
of the IBM market have designed computers that run
the same machine language as the IBM computers.
RCA's Spectra 70 was the first IBM-compatible
mainframe, and companies, such as Amdahl, Itel,
National Advanced Systems, Hitachi and Fujitsu have
introduced IBM-compatible mainframes at one time or
another.

   IBM PC machine language compatibility is
achieved by using a processor from Intel's 8086
family of microprocessors.

   Machine language compatibility can also be
achieved by simulation or emulation.  A simulator
is software that translates and executes a program
in a foreign machine language.  An emulator is
hardware that executes the machine language of
another computer and is used to encourage customers
to buy a new series of computers.  For example, in
the 1960s, IBM provided an optional emulator in its
System/360 series that executed most of its
customer's existing 1401 programs.  The terms
simulator and emulator are used interchangeably.



                    DATA CODES
The data code is built into the computer and
determines how each character (letter, digit or
special character) is represented in binary code.
Fortunately, there are only two major data codes in
wide use today, EBCDIC and ASCII.  That means
alphabetic data and numbers stored in one code can
easily be converted to the other.  IBM mainframes
and minicomputers and other mainframes use EBCDIC.
ASCII is used by all personal computers, most
minicomputers and some mainframes.

   However, ASCII is only a 7-bit code with 128
character combinations, and the 8th bit (which
derives another 128 values) is used differently.
In the PC, it is used for foreign language
characters and line drawing symbols.  In the
Macintosh, it can be defined by the programmer.

   Other codes are used in various different
machines, but all data codes can be converted from
one to another with one possible exception.  If
numbers are stored in floating point and the new
machine can't handle as many digits as the old
machine, a loss of precision may occur.

   When data is moved to a different computer, data
code conversion is often only one small part of the
conversion process.  Data, text and graphics file
formats must also be converted if different
programs are going to process them.

   The following is a sample of ASCII and EBCDIC
code.  See ASCII chart, hex chart and EBCDIC chart.

        Character  ASCII    EBCDIC
         space   01000000  00100000
         period  01001011  00101110
         < sign  01001100  00111100
         + sign  01001110  00101011
         $ sign  01011011  00100100
         A       11000001  01000001
         B       11000010  01000010



                HARDWARE INTERFACES
The hardware interface specifies the plugs,
sockets, cables and electrical signals that pass
through each line between the CPU and a peripheral
device or communications network.

   Common hardware interfaces for personal
computers are the Centronics parallel interface
used for printers and the RS-232 interface,
typically used for modems, graphics tablets, mice
and printers.  In addition, the ST506, RLL, ESDI
and SCSI interfaces are used for disks and tapes,
and the GPIB IEEE 488 standard is used for process
control instruments.

   The bus in a computer's motherboard, into which
additional printed circuit boards are inserted, is
a hardware interface.  For example, the Micro
Channel in IBM's PS/2 series accepts a physically
different board than the original PC bus.

   LANs, such as ARCNET and Ethernet, also dictate
the hardware interface as part of their
specifications.



                   STORAGE MEDIA
There are many varieties of disk packs, disk
cartridges, floppy disks, reel-to-reel tapes, tape
cartridges and tape cassettes.  Each one has its
own unique shape and size and can be used only in
drives designed to accommodate them.

   With removable media, the physical standard is
half the compatibility issue.  The other half is
the recording pattern, which is invisible to the
human eye.  Magnetic tapes and disks fresh out of
the box are blank.  The recording tracks are placed
onto the surface by the read/write head of the
storage drive.  Thus, the same floppy disk that
stores 720K bytes in one disk drive, can hold 800K
if formatted for another.  If the computer reads an
incompatible tape or reads and writes and
incompatible disk, it will signal a read/write
error.

   For minicomputers and mainframes, the half-inch
magnetic tape reel is a common interchangeable
medium.  For personal computers, the 5.25"
minifloppy and the 3.5" microfloppy disks are used.



                 OPERATING SYSTEMS
An operating system is a master control program
that manages the running of the computer system.
In all environments, except for specialized
scientific and process control applications, the
operating system interacts with the application
programs.  The application programs must "talk" to
the operating system.

   If application programs are moved to a different
computing environment, they have to be converted to
interface with a different operating system.  If a
new operating system is installed that is not
compatible with the old one, the application
programs have to be converted to the new operating
system.



                  COMMUNICATIONS
Transmitting between two personal computers or
between a personal computer and a timesharing or
information service is relatively simple.  All
that's required is a modem for each computer, a
telephone line and a communications program in each
computer that uses the same error checking protocol
to ensure that data has not been lost.  Most
communications programs support several protocols.
If data is not critical, an ASCII protocol without
error checking can be used, which is found in every
communications program.

   Transmitting in a network is another story.
Traditional minicomputer and mainframe networks
allow multiple users to have access to central
databases via terminals.  The control is typically
in the main, or host, computer.  Personal computer
LANs have evolved to share information within a
small work group.  The major problem most large
organizations have is to tie independent networks
together so that each user's workstation can
communicate with any other user's workstation
within the company.

   Since each type of network uses different
protocols, conversion from one protocol to another
is required.  In today's multivendor environment,
protocol conversion can be performed by gateways,
black boxes, digital PBXs or via interconnection to
value added communication services.

   The OSI is a seven-layer reference model for
worldwide communications that has been defined by
ISO (Int'l. Standards Organization).  Although most
vendors have committed to support OSI in one form
or another, it will take a long time before
universal communications is achieved.

   Computers were originally developed for
computations, not communications.  In the early
days, nobody realized the implications or computer
communications might have been standardized as was
the telephone industry.

   See next definition for more standards.


standards (continued)
  Programming Languages
  File Management Systems
  Database Management Systems
  Text Systems
  Graphics Systems
  Standards Organizations


               PROGRAMMING LANGUAGES
Every software program is written in a programming
language, and there is at least one programming
language for every major CPU series.  There is
typically an assembly language and a number of
high-level languages for each series or family.
Assembly languages are machine specific, and the
machine language they generate runs on only one CPU
family.  Unless the machine languages are very
similar, it is difficult to translate an assembly
language program from one CPU series into another.

   The high-level programming language was created
to eliminate this machine dependency.  Programming
languages, such as COBOL, FORTRAN and BASIC are
supposed to be able to run on many different
computers.  However, due to many dialects of each
language, compatibility is still an issue.  Each
compiler vendor keeps adding new features to its
language thereby making it incompatible with
previous or other versions.

   By the time a new feature becomes a standard, a
dozen new features have been already implemented.
For example, dBASE has become a de facto standard
business programming language.  Since 1981, dBASE
has spawned competitive products, such as Clipper,
QuickSilver, Force III, dbXL and Foxbase, all of
which are incomplete versions of dBASE.  None of
them provides every command in dBASE, and they all
provide features not found in dBASE.

   There's no rule of thumb for translating one
dialect of a programming language into another.
The job may be difficult or easy.  At times,
software is written to translate one dialect into
another, as well as one programming language into
another.  If the translation program cannot
translate the program entirely, then manual
tailoring is necessary.  In these cases, it is
often easier to rewrite the program from scratch.

   Compatibility can be achieved when a programming
language conforms to the ANSI (American National
Standards Institute) standard for that language.
If the same version of an ANSI COBOL compiler is
available for two different CPUs, a program written
in ANSI COBOL will run on both machines.



              FILE MANAGEMENT SYSTEMS
In its simplest form, a data file uses fields of
the same length for each item of data, for example,
a plain EBCDIC or ASCII file would look like:

Chris Smith   34 Main St.     Bangor      ME18567
Pat Jones     10 W. 45 St.    New York    NY10002


A common format created by BASIC programming
languages is an ASCII comma delimited file; for
example, the data above would look as follows:

"Chris Smith","34 Main St.","Bangor","ME","18567"
"Pat Jones","10 W. 45 St.","New York","NY","10002"


Both file formats above are simple, contain only
data (except for quotes and commas) and can be
easily manipulated by a word processor.  However,
data files may also contain special codes that
identify the way the data is structured within the
file.  For example, variable length records require
a code in each field indicating the size of the
field.

   Whether fixed or variable length fields, the
data in non-DBMS systems is linked directly to the
processing.  The program must know the layout of
the fields in each record that it processes, and it
cannot accept records in a different format.  In
order to process a different file format, the
program must be changed.

   Incompatible file formats often exist within the
same organization when developed separately.  The
following fixed-length records are incompatible
even though they contain the same data.  The
program that processes the first file structure
would have to be changed to process the second.

┌─────────────┬───────────────┬──────────┬──┬─────┐
│ Name        │ Address       │ City     │St│Zip  │
└─────────────┴───────────────┴──────────┴──┴─────┘
┌──────────┬─────────────┬──────────┬──┬─────┐
│ Name     │ Address     │ City     │St│Zip  │
└──────────┴─────────────┴──────────┴──┴─────┘



        DBMSs (DATABASE MANAGEMENT SYSTEMS)
DBMSs have their own proprietary formats for
storing data.  For example, a header record with a
unique format that contains identification data is
typically placed at the beginning of each file.
Codes may also be embedded in each record.

   Most DBMSs have an import and export capability
that converts popular database formats into their
proprietary format.  If not, the program usually
can import and export a plain EBCDIC or ASCII file,
which is stripped of all proprietary codes and can
be used as a common denominator between both
systems.  If conversion facilities cannot be found,
a custom program can be written to convert one
database format into another if documentation
describing the old format is available.

   The application program interface (API), or
language used by the application program to "talk"
to the database, is typically a proprietary
language in every DBMS.  SQL has become popular as
a standard language and has been implemented in
many DBMSs.  Theoretically, that means any
application program requesting data in the SQL
language would work with any DBMS that supports
SQL.  Like everything else however, there are
dialects of SQL.



                   TEXT SYSTEMS
Although the basic structure of an English-language
text file is standard throughout the world: word,
sentence, paragraph, page; every word processing,
desktop publishing and typesetting program uses its
own codes to set up the layout within a document.
For example, the code that turns on boldface in
WordPerfect Version 5.0 is [BOLD]; in WordStar,
it's ^PB.

   The codes that define a header, footer,
footnote, page number, margin, tab setting, indent
and font change are unique to the word processing
program in which the document was created or the
desktop publishing program into which the text file
is converted.  Even the codes to end a line or
paragraph are not the same.

   Document conversion is accomplished with special
conversion programs or black boxes.  Although every
word processing program has a search and replace
capability, it may not be effective for converting
embedded layout codes from one format to another.
In some programs, the search & replace simply does
not handle layout codes.  In addition, while some
systems use one code to turn a function on and
another code to turn it off, other systems use the
same code for on and off, requiring manual
verification and tailoring when using the search &
replace function.



                 GRAPHICS SYSTEMS
There are many formats for storing a picture in a
computer; but, unlike text and data files, which
are primarily made up of alphanumeric characters,
graphics formats are more complex.

   To begin with, there are the two major
categories of graphics: vector graphics (objects
made up of lines) and raster graphics (TV-like
dots).  Images stored in vector format can be moved
to another vector system typically without loss of
resolution.  There are 2-D vector formats as well
as 3-D vector formats.

   In transferring raster images among different
devices, resolution is a major concern.  Such
transfers can occur without loss of resolution as
long as the new format has the same or higher
resolution as the older one.

   Standard graphics formats allow graphics data to
be moved from machine to machine, while standard
graphics languages let graphics programs be moved
from machine to machine.  For example, GKS and
PHIGS are major graphics languages that have been
adopted by many high-performance workstation and
CAD vendors.  Apple's consistent use of its
QuickDraw language has helped the Macintosh become
very popular in graphics-oriented applications.

   High-resolution graphics has typically been
expensive to implement due to its large storage and
fast processing requirements.  However, as personal
computers become more powerful, graphics are
becoming widely used in business applications.  The
ability to see a person's face or a product's
appearance on screen will eventually become as
commonplace as text and data.


                De Facto Standards
When a vendor's product is widely used, it becomes
a de facto standard.  Apple, Digital, HP, IBM,
Intel, Lotus, Microsoft, Motorola and many others
have set de facto standards.

   For a list of standards bodies, see Lessons
Associations.

                    THE FUTURE
The problem of standards and compatibility is a
never ending dilemma.  However, the fact is that
standards could be created that would embrace the
future and allow for expandability far more than
they currently do.  Ironically, the field that is
the very forefront of the future, has a very myopic
view of it.

   Some day, a standard for defining the standard
will have to be implemented in order that one
program can ask another what language it speaks.  A
program could also interrogate a data file and
quickly determine its format.  If the program can't
understand the other program's language or the
file's format, the interfacing problem would still
exist.  However, as programs become more multi-
lingual, a standard identification protocol would
go a long way to establishing an AI link between
all computers in the future.


standards bodies
See Lessons Associations.


Star
Xerox workstation that formally introduced the
graphical user interface and desktop metaphor in
1981.  Although unsuccessful, it was inspiration
for Xerox's subsequent computers and for Apple's
Lisa and Macintosh.  See Alto.


star network
Communications network in which all terminals are
connected to a central computer or central hub.
PBXs are prime examples as well as IBM's Token Ring
and AT&T's Starlan LANs.


Starlan
AT&T LAN that uses twisted pair wire, the CSMA/CD
access method, transmits at 1Mbps and uses a star
or bus topology.  In 1988, Starlan was renamed
Starlan 1, and Starlan 10 was introduced, a 10Mbps
Ethernet version that uses twisted pair or optical
fibers.


start bit
In asynchronous communications, the bit transmitted
before each character.


start/stop transmission
Same as asynchronous transmission.


startup routine
Routine that is executed when the computer is
booted or when an application is loaded.  It is
used to customize the environment for its
associated software.


STARTUP.CMD
(STARTUP.CoMmanD)  OS/2 file executed immediately
upon startup.  It contains instructions that can
initialize operating system settings and call in a
specific application program.  The DOS counterpart
is AUTOEXEC.BAT.


stat mux
(STATistical MUltipleXor)  See statistical
multiplexor.


state-of-the-art
Most current technique or method applied to
designing and developing hardware and software.


statement
In a high-level programming language, a descriptive
phrase that generates one or more machine language
instructions in the computer.  In a low-level
assembly language, programmers write instructions
rather than statements, since each source language
instruction is translated into one machine language
instruction.


static binding
Same as early binding.


static column memory
A type of page mode memory that requires less
electronic pulsing in order to access the memory
bits.


static electricity
Stationary electrical charge that is the result of
intentional charging or of friction in low-humidity
environments.


static RAM
Memory chip that requires power to hold its
content.  Static RAM chips have access times in the
10 to 30-nanosecond range.  Dynamic RAMs are
usually above 30, and Bipolar and ECL memories are
under 10.

     A static RAM bit is made up of a pretzel-like
flip-flop circuit that lets current flow through
one side or the other based on which one of two
transistors is activated.  Static RAMs do not
require refresh circuitry as do dynamic RAMs, but
they take up more space and use more power.


static SQL
See embedded SQL.


station
Computer, workstation or terminal in a network.
Same as node.


statistical multiplexor
In communications, a device that combines several
low-speed channels into a single high-speed channel
and vice versa.  A standard multiplexor is set to a
fixed interleaving pattern, but the statistical
multiplexor can analyze the traffic load and
dynamically switch to different channel patterns to
speed up transmission.


status line
Information line displayed on screen that shows
current activity.


STD bus
Bus architecture used in medical and industrial
equipment due to its small size and rugged design.
Originally an 8-bit bus, extensions have increased
it to 16 and 32 bits.


stepper motor
Motor that rotates in small, fixed increments and
is used to control the movement of the access arm
on a disk drive.  Contrast with voice coil.


stereophonic
Sound reproduction using two or more channels.
Contrast with monophonic.


stick font
Same as vector font.


stick model
Picture made of lines, or vectors.  For example, in
biomedical applications, the limbs of a person or
animal are converted into lines so that the motion
can be visually observed and graphically plotted
and analyzed.


stiction
(STatic frICTION)  Type of hard disk failure in
which the read/write heads stick to the platters.
The lubricant used on certain drives heats up and
liquifies.  When the disk is turned off, it cools
down and can become like a glue.


STN
See LCD.


stop bit
In asynchronous communications, a bit transmitted
after each character.


storage device
Hardware unit that holds data.  In this Glossary,
it refers only to external peripheral equipment,
such as disk and tape, in contrast with memory
(RAM).


storage hierarchy
Range of memory and storage devices within the
computer system.  The following list runs from
lowest to highest speed.

  Low     Punched cards
 Speed    Punched paper tape
   │      Removable cartridge mass storage
   │       devices (non-disk)
   │      Magnetic tape
   │      Floppy disks
   │      CD ROM and optical disks
   │      Magnetic disks (movable heads)
   │      Magnetic disks (fixed heads)
   │      Bubble memory
   │      Low-speed bulk memory
   │      Main memory
         Cache memory
 High     Microcode
 Speed    Registers


storage media
Refers to disks, tapes and bubble memory
cartridges.


store and forward
In communications, the temporary storage of a
message for transmission to its destination at a
later time.  Store and forward techniques allow for
routing over networks that are not accessible at
all times; for example, messages headed for
different time zones can be stored and forwarded
when daytime arrives at the destination location.
Messages can be stored and forwarded at night in
order to obtain off-peak rates.


stored program concept
Fundamental computer architecture in which it acts
upon (executes) internally-stored instructions.
See von Neumann architecture.


STP
(Shielded Twisted Pair)  Telephone wire wrapped in
a metal sheath to eliminate external interference.
See twisted pair.


Strand88
Parallel processing programming language developed
by AI Ltd., England.


stream
(1) Contiguous group of data.

(2) I/O management in the C programming language.
A stream is a channel through which data flows
to/from a disk, keyboard, printer, etc.


stream-oriented file
Type of file, such as a text document or digital
voice file, that is more openly structured than a
data file.  Text and voice are continuous streams
of characters, whereas database records are
repeating structures with a fixed or reasonably
uniform format.


streaming tape
High-speed magnetic tape drive that is frequently
used to make a backup copy of an entire hard disk.


Streamline
Macintosh tracing program from Adobe Systems Inc.,
Mountain View, CA.  It converts scanned or MacPaint
images into PostScript files, which can be modified
in Illustrator 88.


STREAMS
Architecture in the UNIX System V operating system
used for creating layered communications protocols.
Each layer is comprised of a STREAMS module, which
passes messages to other modules.  AT&T's TLI
transport protocol is a STREAMS module.  See OSI.


string
(1) In programming, a contiguous set of
alphanumeric characters that does not contain
numbers used for calculations.  Names, addresses,
words and sentences are strings.  Contrast with
numeric data.

(2) Any connected set of structures, such as a
string of bits, fields or records.


string handling
Abilty to manipulate alphanumeric data (names,
addresses, text, etc.).  Typical functions include
the ability to handle arrays of strings, to left
and right align and center strings and to search
for an occurrence of text within a string.


Stringy Floppy
Continuous loop cartridge of 1/16" tape from
Exatron, Inc., available for early personal
computers.


striping
Interleaving or multiplexing data to increase
speed.  See disk striping.


stroke
(1) In printing, the weight, or thickness, of a
character.  For example, in the LaserJet, one of
the specifications of the font description is the
stroke weight from -3 to +3.

(2) In computer graphics, a pen or brush stroke or
to a vector in a vector graphics image.


stroke font
Same as vector font.


stroke weight
Thickness of lines in a font character.  The HP
LaserJet III manual defines stroke weights from
Ultra Thin (-7) to Ultra Black (+7), with Medium,
or Text, as normal (0).


stroke writer
Same as vector display.


structured analysis
Techniques developed in the late 1970s by Yourdon,
DeMarco, Gane and Sarson for applying a systematic
approach to systems analysis.  It included the use
of data flow diagrams and data modeling and
fostered the use of implementation-independent
graphical notation for documentation.


structured design
Systematic approach to program design developed in
the mid 1970s by Constantine, Yourdon, et al, that
included the use of graphical notation for
effective documentation and communication, design
guidelines and recipes to help programmers get
started.


structured programming
Techniques that impose a logical structure on the
writing of a program.  Large routines are broken
down into smaller, modular routines.  The use of
the GOTO statement is discouraged (see spaghetti
code).

   Certain programming statements are indented in
order to make loops and other program logic easier
to follow.  Structured walkthroughs, which invite
criticism from peer programmers, are also used.

   Structured languages, such as Pascal, Ada and
dBASE, force the programmer to write a structured
program.  However, unstructured languages such as
FORTRAN, COBOL and BASIC require discipline on the
part of the programmer.


Stuffit
Macintosh shareware program from Aladdin Systems,
Aptos, CA, that compresses files onto multiple
floppies.  A commercial version adds a scripting
language, file viewing and supports multiple
compression techniques.  It was originally
developed by Raymond Lau at age 16.


style sheet
In word processing and desktop publishing, a file
that contains layout settings for a particular
category of document.  Style sheets include such
settings as margins, tabs, headers and footers,
columns and fonts.


stylus
Pen-shaped instrument that is used to "draw" images
or point to menus.  See light pen and digitizer
tablet.


sub-notebook
Lightweight notebook computer.  As computers get
lighter, the sub-notebook (if term persists) should
weigh two to three pounds, the notebook four to
five.


subarea node
In an SNA network, a system that contains network
controlling functions.  It refers to a host
computer or a communications controller and its
associated terminals.


subdirectory
Disk directory that is subordinate to (below)
another directory.  In order to gain access to a
subdirectory, the path must include all directories
above it.


submarining
Temporary visual loss of the moving cursor on a
slow display screen such as found on a laptop
computer.  See active matrix LCD.


submenu
Additional list of options within a menu selection.
There can many levels of submenus.


subroutine
Group of instructions that perform a specific task.
A large subroutine is usually called a module or
procedure; a small one, a function or macro, but
all terms are used interchangeably.


subschema
Pronounced "sub-skeema."  In database management,
an individual user's partial view of the database.
The schema is the entire database.


subscript
(1) In word processing and mathematical notation, a
digit or symbol that appears below the line.
Contrast with superscript.

(2) In programming, a method for referencing data
in a table.  For example, in the table PRICETABLE,
the statement to reference a specific price in the
table might be PRICETABLE (ITEM), ITEM being the
subscript variable.  In a two-dimensional table
that includes price and discount, the statement
PRICETABLE (ITEM,DISCOUNT) could reference a
discounted price.  The relative locations of the
current ITEM and DISCOUNT are kept in two index
registers.


substrate
Base material upon which integrated circuits are
built.  Silicon is the most widely used substrate
for chips.


substring
Subset of an alphanumeric field or variable.  A
programming language substring function extracts
the subset; for example, substr(prodcode,4,3)
extracts characters 4, 5 and 6 out of a product
code field or variable.


subtract
In relational database, an operation that generates
a third file from all the records in one file that
are not in a second file.


SUM II
(Symantec Utilities for Macintosh)  Set of
Macintosh utilities from Symantec Corp., Cupertino,
CA, that provides hard disk optimization, analysis
and repair and security capabilities.


Summit
Code name for IBM's ES/9000 models.  Since water
cooled models below the 820 are re-architected 3090
J models, the term may stay in usage to refer to
the top-end models (820, 860, 900).


Sun
(Sun Microsystems, Inc., Mountain View, CA)
Manufacturer of network-based, high-performance
workstations founded in 1982.  Product lines
include stand-alone and networked systems, diskless
workstations and file servers that feature its
SPARC microprocessor architecture.

   Sun supports an open systems model of computing
throughout its product line that allows it to
interact in networks of computer systems from other
vendors.  Its ONC (Open Network Computing) software
is supported by over 300 vendors, and its NFS
(Network File System) software, which allows data
sharing across the network, has become an industry
standard.

   In 1991, Sun split its business into the
following wholly-owned subsidiaries:

     Sun Microsystems - Systems
     SunSoft - System software
     SunPro  - Programmer productivity tools
     SunPics - Printing and imaging
     SunConnect - Network integration
     SunExpress - Distribution


SunSoft
See Sun.


super floppy
(1) PC 3.5" floppy disk that holds 2.88MB and is
compatible with the 1.44MB and 720KB formats.

(2) Very-high-capacity floppy disk in the 20MB
range.  See Floptical.


Super VGA
See VGA and PC display modes.


SuperCalc
PC spreadsheet from Computer Associates.  It was
one of the first spreadsheets following in
VisiCalc's footsteps in the early 1980s.
SuperCalc5 (1988) provides 3-D capability, enhanced
graphics and can link up to 256 spreadsheets.


supercomputer
Fastest computer available.  It is typically used
for simulations in petroleum exploration and
production, structural analysis, computational
fluid dynamics, physics and chemistry, electronic
design, nuclear energy research and meteorology.
It is also used for realtime animated graphics.


superconductor
Material that has little resistance to the flow of
electricity.  Traditional superconductors operate
at -459 Fahrenheit (absolute zero).

   Thus far, the major use for superconductors,
made of alloys of niobium, is for high-powered
magnets in medical imaging machines that use
magnetic fields instead of x-rays.

   Using experimental materials, such as copper
oxides, barium, lanthanum and yttrium, IBM's Zurich
research lab in 1986 and the Univ. of Houston in
1987 raised the temperature of superconductivity to
-59 degrees Fahrenheit.  If superconductors can
work at reasonable temperatures, they will have a
dramatic impact on the future.  See Josephson
junction.


SuperDrive
Macintosh floppy disk drive that stores 1.44MB of
data in its highest density format.  It also reads
and writes earlier Mac 400 and 800KB disks, as well
as Apple II ProDOS, MS-DOS and OS/2 formats.


SuperFloppy
Superdrive-compatible floppy disk for older
Macintoshes from Peripheral Land, Inc., Fremont,
CA.  See super floppy.


superframe
T1 transmission formats made up of 12 T1 frames
(superframe) and 24 frames (extended superframe).
See D4.


SuperKermit
See Kermit.


SuperKey
PC keyboard macro processor from Borland that lets
users create keyboard macros, rearrange the
keyboard and encrypt data and programs.


supermini
Large-scale minicomputer that overlaps in
processing capability with a small-scale mainframe.
The difference in terminology is point of view.  If
you're a mini maker, your largest machine is
"super."  If you're a mainframe maker, your
smallest machine isn't worth talking about!

   Note: Supermini is not the same as mini-
supercomputer.


superscript
Any letter, digit or symbol that appears above the
line.  Contrast with subscript.


superserver
Network server with very large RAM and disk
capacity, multiple processors and high-speed
multiprocessing (Micro Channel, EISA, etc.) buses.


supertwist
LCD technology that twists liquid molecules greater
than 90° in order to improve contrast and viewing
angle.  See LCD.


supervisor
Same as operating system.


supervisor call
Instruction in an application program that switches
the computer to supervisor state.


supervisor control program
The part of the operation system that always
resides in memory.  Same as kernel.


supervisor state
Typically associated with mainframes, it is a
hardware mode in which the operating system
executes instructions unavailable to an application
program; for example, I/O instructions.  Contrast
with program state.


support
(1) Assistance provided by a hardware or software
vendor in installing and maintaining its product.

(2) Software or hardware designed to work with some
other software or hardware product.  For example,
if a word processor "supports the LaserJet," it can
activate special features of that printer.


SUPRA
Relational DBMS from Cincom Systems, Inc.,
Cincinnati, OH, that runs on IBM mainframes and
VAXs.  It includes a query language and a program
that automates the database design process.


surface
(1) In CAD, the external geometry of an object.
Surfaces are generally required for NC (numerical
control) modeling rather than wireframe or solids.

(2) Coined by Wayne Ratliff, creator of dBASE, a
language that interfaces to a database engine.


surface modeling
In CAD, a mathematical technique for representing
solid-appearing objects.  Surface modeling is a
more complex method for representing objects than
wireframe modeling, but not as sophisticated as
solid modeling.

   Although surface and solid models can appear the
same on screen, they are quite different.  Surface
models cannot be sliced open as can solid models.
In addition, in surface modeling, the object can be
geometrically incorrect; whereas, in solid
modeling, it must be correct.


surface mount
Circuit board packaging technique in which the
leads (pins) on the chips and components are
soldered on top of the board, not through it.
Boards can be smaller and built faster.


surge
Oversupply of voltage from the power company that
can last up to several seconds.  See spike.


surge protector
Device that protects a computer from excessive
voltage (spikes and surges) in the power line.  See
voltage regulator and UPS.


surge suppressor
Same as surge protector.


suspend and resume
To stop an operation and restart where you left
off.  In portable computers, the hard disk is
turned off, and the CPU is made to idle at its
slowest speed.  All open applications are retained
in memory.


SV
(Scientific Visualization)  See visualization.


SVGA
(Super VGA)  See VGA.


SVID
(System V Interface Definition)  AT&T specification
for the UNIX System V operating system.  SVID
Release 3 specifies the interface for UNIX System V
Release 4.


SVR4
See System V Release 4.0.


swap file
Disk file used to temporarily save a program or
part of a program running in memory.  See Windows
swap file.


swapping
Replacing one segment of a program in memory with
another and restoring it back to the original when
required.  In virtual memory systems, it is called
paging.


switch
(1) Mechanical or electronic device that directs
the flow of electrical or optical signals.
Remember!  Open is "off."  Closed is "on."
See data switch and transistor.

(2) In programming, a bit or byte used to keep
track of something.  Sometimes refers to a branch
in a program.

(3) Command modifier.  See DOS switch.


switch-to-computer
To integrate voice telephone and database access.
For example, in customer service applications,
using telephone services, such as automatic number
identification (ANI) and automatic call
distribution (ACD), an incoming call can retrieve
and route the customer's file to the next available
human agent.


switched line
In communications, a link that was established in a
switched network.


switched network
(1) International dial-up telephone system.

(2) Network in which a temporary connection is
established from one point to another for each
transmission session.


SX
See 386SX, 486SX and LaserJet.


SYBASE System
Family of SQL development tools from Sybase, Inc.,
that includes SQL Server, SQL Toolset (design,
development and control) and Client/Services
Interfaces (distributed database architecture).
See SQL Server.


SYLK file
(SYmbolic LinK file)  Spreadsheet file format
originating with Multiplan that is used by a number
of spreadsheet programs.


symbol
In data compression, a unit of data (byte, floating
point number, spoken word, etc.) that is treated
independently.


symbol set
In printing, a group of symbols that are extensions
to standard characters for use in a particular
country or specific application.  Symbol sets
provide codes for the non-standard upper half of
the ASCII character set.


symbolic language
(1) Programming language that uses symbols, or
mnemonics, for expressing operations and operands.
All modern programming languages are symbolic
languages.

(2) Language that manipulates symbols rather than
numbers.  See list processing.


symmetric multiprocessing
Multiprocessing design in which any CPU can be
assigned any application task.  One CPU acts as a
control processor, or scheduler, which boots the
system, distributes work to the next available CPU
and manages I/O requests.  Contrast with asymmetric
multiprocessing.


Symphony
Integrated software package for PCs from Lotus that
includes word processing, database management,
speadsheet, business graphics, communications and a
macro language.


sync character
In synchronous communications systems, a special
character transmitted to synchronize timing.


sync generator
Device that supplies synchronization signals to a
series of cameras to keep them all in phase.


synchronous
(1) Sequence of fixed or concurrent events.  See
synchronous transmission.

(2) Completing the current I/O operation before the
next one is started.

(3) In SCSI, the transfer of data without immediate
acknowledgment of each byte.

(4) Contrast with asynchronous.


synchronous protocol
Communications protocol that controls a synchronous
transmission, such as bisync, SDLC and HDLC.
Contrast with asynchronous protocol.


synchronous transmission
Transmission of data in which both stations are
synchronized.  Codes are sent from the transmitting
station to the receiving station to establish the
synchronization, and data is then transmitted in
continuous streams.

   Modems that transmit at 1200 bps and higher
often convert the asynchronous signals from a
computer's serial port into synchronous
transmission over the transmission line.  Contrast
with asynchronous transmission.


syntax
Rules governing the structure of a language
statement.  It specifies how words and symbols are
put together to form a phrase.


syntax error
Error that occurs when a program cannot understand
the command that has been entered.  See parse.


sysgen
(SYStem GENeration)  Installation of a new or
revised operating system.  It includes selecting
the appropriate utility programs and identifying
the peripheral devices and storage capacities of
the system the operating system will be
controlling.


sysop
(SYStem OPerator) Pronounced "siss-op."  Person who
runs an online communications system or bulletin
board.  The sysop may also act as mediator for
system conferences.


Sysplex
IBM System/390 multiprocessing.  The Sysplex Timer
external clock is used to synchronize time-of-day
clocks in multiple processors.  If failure occurs
in a multiprocessor complex, precise transaction
time stamps are required for accurate rollback and
recovery.


SysReq key
(SYStem REQuest key)  Keyboard key on a terminal
keyboard that is used to get the attention of the
central computer.  The key exists on PC keyboards,
but is rarely used by applications.


system
(1) Group of related components that interact to
perform a task.

(2) A computer system is made up of the CPU,
operating system and peripheral devices.

(3) An information system is made up of the
database, all the data entry, update, query and
report programs and manual and machine procedures.

(4) "The system" often refers to the operating
system.


System 2000
(1) Hierarchical, network and relational DBMS from
the SAS Institute, Cary, NC, that runs on IBM, CDC
and Unisys computers.  It has been integrated into
the SAS System.

(2) See FTS 2000.


System/3
Batch-oriented minicomputer from IBM.  Introduced
in 1969, it introduced a new punched card about
half the size of previous ones.  With the addition
of the Communications Control Program (CCP), it
could handle interactive terminals.


System/32
Batch-oriented minicomputer from IBM.  Introduced
in 1975, it provided a single terminal for operator
use.  It was superseded by the System/34, which
could run System/32 applications in a special mode.


System/34
Multiuser, multitasking minicomputer from IBM,
introduced in 1977.  The typical system had from a
handful to a dozen terminals and could run
System/32 programs in a special mode.  Most large
System/34 users migrated to the System/38, while
small users migrated to the System/36.


System/36
Multiuser, multitasking minicomputer from IBM that
was introduced in 1983.  It superseded the
System/34 and is mostly compatible with it.
System/34 programs run in the System/36 after
recompilation.  The typical system supports from a
handful to a couple of dozen terminals.  It has
been superseded by the AS/400.


System/360
IBM's first family of computer systems introduced
in 1964.  It was the first time in history that a
complete line of computers was announced at one
time.  Although considerable enhancements have been
made, much of the 360 architecture is still carried
over in current-day IBM mainframes.  See IBM
mainframes.


System/370
Mainframe product line introduced in 1970 by IBM
(superseding System/360), which added virtual
memory and other enhancements.  Subsequent series
include the 303x, 43xx, 308x, 309x and 9370, all
370-architecture machines.  The 370 architecture
was brought down to the PC level in 1983 with the
PC XT/370, and then again in 1989 with the VM/SP
Technical Workstation.  See IBM mainframes.


System/38
Minicomputer from IBM that includes an operating
system with an integrated relational database
management system.  Introduced in 1978, it was an
advanced departure from previous System/3x
computers.  The typical system handles from a dozen
to several dozen terminals.  It has been superseded
by the AS/400.


System/390
Mainframe product line introduced in 1990 by IBM
(superseding System/370) that features ESA/390
architecture and operating systems, ES/9000
hardware (18 models introduced), ESCON fiber optic
channels, Sysplex multiprocessing and SystemView.


System/3x
IBM System/34, System/36 and System/38 midrange
computers.


System 7
(1) Major upgrade of the Macintosh operating system
(1991).  It includes virtual memory, increased
memory addressing, hot links (Publish & Subscribe),
multitasking (MultiFinder no longer optional),
TrueType fonts and a variety of enhancements to the
user interface.

(2) (System/7) Sensor-based minicomputer from IBM
introduced in 1970 and used for process control.
It was superseded by the Series/1.


System/88
Family of fault-tolerant midrange computers from
IBM used for online transaction processing.  Uses
the System/88 virtual memory and System/88 FTX
(Fault Tolerant UNIX) operating systems.  Includes
4579 and 4576 multiprocessor series and 4593 entry-
level models.


system board
Printed circuit board that contains the primary
CPU.  In a personal computer, it is also called the
motherboard.


system development cycle
Sequence of events in the development of an
information system (application), which requires
mutual effort on the part of user and technical
staff.

   1. SYSTEMS ANALYSIS & DESIGN
       feasibility study
       general design
       prototyping
       detail design
       functional specifications

   2. USER SIGN OFF

   3. PROGRAMMING
       design
       coding
       testing

   4. IMPLEMENTATION
       training
       conversion
       installation

   5. USER ACCEPTANCE


system development methodology
Formal documentation for the phases of the system
development cycle.  It defines the precise
objectives for each phase and the results required
from a phase before the next one can begin.  It may
include specialized forms for preparing the
documentation describing each phase.


system disk
Hard or floppy disk that contains part or all of
the operating system or other control program.


system failure
Hardware or software malfunction.  May refer to a
problem with the operating system.


system file
Machine language file that is part of the operating
system or other control program.  It may also refer
to a configuration file used by such programs.


system folder
Operating system folder in the Macintosh that
contains the System, Finder and MultiFinder,
printer drivers, fonts, desk accessories, INITs and
cdevs.


system image
Memory view of current operating environment,
including the operating system and running
programs.


system level
Operation that is performed by the operating system
or some other control program.


system life cycle
Useful life of an information system.  Its length
depends on the nature and volatility of the
business, as well as the software development tools
used to generate the databases and applications.
Eventually, an information system that is patched
over and over no longer is structurally sound
enough to be expanded.

   Tools like DBMSs allow for changes more readily,
but increased transaction volumes can negate the
effectiveness of the original software later on.


system management
See systems management.


system memory
Memory used by the operating system.


system program
Component of system software.


system prompt
On-screen symbol that indicates the operating
system is ready for a command.  See DOS prompt.


system software
Programs used to control the computer and run
application programs.  It includes operating
systems, TP monitors, network control programs,
network operating systems and database managers.
Contrast with application program.


system test
Running a complete system for testing purposes.


system time/date
Running time of day in the computer, which is
maintained by a battery when the computer is turned
off.  It is used to time stamp all newly-created
files and activate time-dependent processes.


System V Release 4.0
Unified version of UNIX released in 1989.  See
UNIX.


System V.4
See System V Release 4.0.


SYSTEM.INI
See WIN.INI.


Systemantics
Insightful book on the systems process by John Gall
(1977).  The following is copied with permission
from Random House.


         A Concise Summary of the Field of
               General Systemantics
Systems are seductive.  They promise to do a hard
job faster, better, and more easily than you could
do it by yourself.  But if you set up a system, you
are likely to find your time and effort now being
consumed in the care and feeding of the system
itself.  New problems are created by its very
presence.  Once set up, it won't go away, it grows
and encroaches.  It begins to do strange and
wonderful things.  Breaks down in ways you never
thought possible.  It kicks back, gets in the way,
and opposes its own proper function.  Your own
perspective becomes distorted by being in the
system.  You become anxious and push on it to make
it work.  Eventually you come to believe that the
misbegotten product it so grudgingly delivers is
what you really wanted all the time.  At that point
encroachment has become complete...

    you have become absorbed...

      you are now a systems person!


systems
General term for the department, people or work
involved in systems analysis & design activities.


systems analysis & design
Examination of a problem and the creation of its
solution.  Systems analysis is effective when all
sides of the problem are reviewed.  Systems design
is most effective when more than one solution can
be proposed.  The plans for the care and feeding of
a new system are as important as the problems they
solve.  See system development cycle and
Systemantics.


systems analyst
Person responsible for the development of an
information system.  They design and modify systems
by turning user requirements into a set of
functional specifications, which are the blueprint
of the system.  They design the database or help
design it if data administrators are available.
They develop the manual and machine procedures and
the detailed processing specs for each data entry,
update, query and report program in the system.

   Systems analysts are the architects, as well as
the project leaders, of an information system.  It
is their job to develop solutions to user's
problems, determine the technical and operational
feasibility of their solutions, as well as estimate
the costs to develop and implement them.

   They develop prototypes of the system along with
the users, so that the final specifications are
examples of screens and reports that have been
carefully reviewed.  Experienced analysts leave no
doubt in users' minds as to what is being
developed, and they insist that all responsible
users review and sign off on every detail.

   Systems analysts require a balanced mix of
business and technical knowledge, interviewing and
analytical skills, as well as a good understanding
of human behavior.  See Systemantics.


systems disk
Disk pack or disk drive reserved only for system
software, which includes the operating system,
assemblers, compilers and other utility and control
programs.


systems engineer
Often a vendor title for persons involved in
consulting and pre-sales activities related to
computers.  See systems analyst, systems
programmer, programmer analyst and application
programmer.


systems house
Organization that develops customized software
and/or turnkey systems for customers.  Contrast
with software house, which develops software
packages for sale to the general public.  Both
terms are used synonymously.


systems integration
Making diverse components work together.  See NASI.


systems integrator
Individual or organization that builds systems from
a variety of diverse components.  With increasing
complexity of technology, more customers want
complete solutions to information problems,
requiring hardware, software and networking
expertise in a multivendor environment.  See OEM,
VAR and NASI.


systems management
(1) Management of systems development, which
includes systems analysis & design, application
development and implementation.  See system
development cycle.

(2) Software that manages computer systems in an
enterprise, which may include any and all of the
following functions: software distribution, version
control, backup & recovery, printer spooling, job
scheduling and performance and capacity planning.
Network management may be an integrated component
of systems management.


systems program
See system program and system software.


systems programmer
(1) In the IS department of a large organization, a
technical expert on some or all of the computer's
system software (operating systems, networks,
DBMSs, etc.).  They are responsible for the
efficient performance of the computer systems.

   They usually don't write programs, but perform a
lot of technical tasks that integrate vendors'
software.  They also act as technical advisors to
systems analysts, application programmers and
operations personnel.  For example, they would know
whether additional tasks could be added to the
computer and would recommend conversion to a new
operating or database system in order to optimize
performance.

   In mainframe environments, there is one systems
programmer for about 10 or more application
programmers.  In smaller environments, users rely
on vendors or consultants for systems programming
assistance.

(2) In a computer hardware or software
organization, a person who designs and writes
system software.


SystemView
IBM architecture for computer systems management
introduced with System/390 that provides an
enterprise-wide approach for controlling multiple
systems and networks.  It will be implemented in
stages through the 1990s.  NetView is a major
component.


systolic array
Array of processing elements (typically multiplier-
accumulator chips) in a pipeline structure that is
used for applications such as image and signal
processing and fluid dynamics.  The "systolic,"
coined by H. T. Kung of Carnegie-Mellon, refers to
the rhythmic transfer of data through the pipeline
like blood flowing through the vascular system.


SYZYGY
Pronounced "SIZE-uh-gee."  PC workgroup software
from Information Research Corp., Charlottesville,
VA.  Used for coordinating schedules, resources and
budgets for group projects and includes e-mail and
a calendar with to-do and activity lists.



T
See tera.


T-byte
See terabyte.


T-carrier
Digital transmission service from a common carrier.
Introduced by AT&T in 1983 as a voice service, its
use for data has grown steadily.

   T-carrier service requires multiplexors at both
ends that merge the various signals together for
transmission and split them at the destination.
Multiplexors analyze the traffic load and vary
channel speeds for optimum transmission.


T1
1.544 megabit T-carrier channel that can handle 24
voice or data channels at 64 Kbits/sec.  The
standard T1 frame is 193 bits long, which holds 24
8-bit voice samples and one synchronization bit.
8,000 frames are transmitted per second.  See D4
and ESF.


T2
6.312 megabit T-carrier channel that can handle 96
voice or data channels at 64 Kbits/sec.


T3
44.736 megabit T-carrier channel that can handle
672 voice or data channels at 64 Kbits/sec.  T3
requires fiber optic cable.


tab character
Control character in a document that represents
movement to the next tab stop.  See ASCII chart (9
and 11).


tab delimited
Text format that uses tab characters as separators
between fields.  Unlike comma delimited files,
alphanumeric data is not surrounded by quotes.


tab key
Keyboard key that moves the cursor to the next tab
stop.


tabbing
Moving the cursor on a video display screen or the
print head on a printer to a specified column.


table
(1) In programming, a collection of adjacent
fields.  Also called an array, a table contains
data that is either constant within the program or
is called in when the program is run.  See decision
table.

(2) In a relational database, the same as a file; a
collection of records.


table lookup
Searching for data in a table, commonly used in
data entry validation and any operation that must
match an item of data with a known set of values.


table view
Screen display of several items or records in rows
and columns.  Contrast with form view.


tablet
See digitizer tablet.


tabular form
Same as table view with respect to printed output.


tabulate
(1) To arrange data into a columnar format.

(2) To sum and print totals.


tabulating equipment
Punched card machines, including keypunches,
sorters, collators, interpreters, reproducers,
calculators and tabulators.


tabulator
Punched card accounting machine that prints and
calculates totals.


tag
(1) Set of bits or characters that identifies
various conditions about data in a file and is
often found in the header records of such files.

(2) Name (label, mnemonic) assigned to a data
structure, such as a field, file, paragraph or
other object.

(3) Key field in a record.

(4) Brass pin on a terminal block that is connected
to a wire by soldering or wire wrapping.


tag sort
Sorting procedure in which the key fields are
sorted first to create the correct order, and then
the actual data records are placed into that order.


Taligent
(Taligent, Inc., Cupertino, CA)  Joint venture of
IBM and Apple that is developing the next-
generation, object-oriented operating system.  See
Apple and Pink.


talk-off
Unintentional command activation when a human voice
generates the same tone as a control signal.


Tandem
(Tandem Computers Inc., Cupertino, CA)
Manufacturer of fault tolerant computers founded in
1974 by James Treybig to address the transaction
processing market (reservations, financial
transfers, etc.).  It introduced the first
commercial computer based on a fault tolerant,
multiprocessor architecture.

   Its NonStop series is built around multiple
parallel processors, thousands of which can be tied
together.  If a processor fails, the system
distributes the workload to the remaining
processors.  The system can be expanded while
running.


tandem processors
Two processors hooked together in a multiprocessor
environment.


Tandy
(Tandy Corp., Ft. Worth, TX)  Manufacturer of PCs
and electronics that started as a family leather
business in 1919.  In 1963, it acquired the nine
Radio Shack stores in Boston.  Today, it has over
7,000 company-owned stores and franchises.

   In 1977, it introduced one of the first personal
computers, the TRS-80 Model I.  Tandy's Model 100
and 200 lightweight portables were also inspiration
to the laptop generation.  Its first computers were
proprietary, and its initial PCs were non-standard.
However, starting with the Model 1000 in 1984,
Tandy offers a full line of IBM-compatible PCs.


tap
In communications, a connection onto the main
transmission medium of a local area network.  See
transceiver.


tape
See magnetic disk & tape.


tape backup
Use of magnetic tape for storing duplicate copies
of hard disk files.  QIC drives are the most widely
used, but DAT and 8mm (Exabyte) formats are gaining
ground.  See QIC, DDS (3), DATA/DAT, D/CAS and
Exabyte.


tape drive
Physical unit that holds, reads and writes the
magnetic tape.  See magnetic tape & disk.


tape dump
Printout of tape contents without any report
formatting.


tape mark
Control code used to indicate the end of a tape
file.


tape transport
Mechanical part of a tape drive.


tar
UNIX utility for archiving files, often used in
conjunction with "compress."


Targa
Raster graphics file format (.TGA extension)
developed by Truevision, Inc., Indianapolis, IN,
that handles 16-, 24- and 32-bit color.  It is also
the trade name of a line of video graphics boards
used in high-resolution imaging.


target computer
Computer into which a program is loaded and run.
Contrast with source computer.  See cross
assembler/compiler.


target directory
Directory into which data is being sent.


target disk
Disk onto which data is recorded.  Contrast with
source disk.


target drive
Drive containing the disk or tape onto which data
is recorded.  Contrast with source drive.


target language
Language resulting from a translation process
(assembler, compiler, etc.).


tariff
Schedule of rates for common carrier services.


task
Independent running program.  See multitasking.


task management
The part of the operating system that controls the
running of one or more programs (tasks) within the
computer at the same time.


task swapping
Switching between two applications by copying the
current running program to disk or other high-speed
storage device (auxiliary memory, EMS, etc.) and
loading another program into that program space.


task switching
Switching between active applications.  See context
switching.


TB, Tb
See terabyte and terabit.


Tbit
See terabit.


Tbits/sec
(TeraBITS per SECond)  Trillion bits per second.


TBps, Tbps
(TeraBytes Per Second, TeraBits Per Second)
Trillion bytes per second.  Trillion bits per
second.


TByte
See terabyte.


Tbytes/sec
(TeraBYTES per SECond)  Trillion bytes per second.


TC
See true color.


TCAM
(TeleCommunications Access Method)  IBM
communications program widely used to transfer data
between mainframes and 3270 terminals.  See access
method.


TCM
(1) (Trellis-Coded Modulation/Viterbi Decoding)
Technique that adds forward error correction to a
modulation scheme by adding an additional bit to
each baud.  TCM is used with QAM modulation, for
example.

(2) (Thermal Conduction Module)  IBM circuit
packaging technique that seals chips, boards and
components into a module that serves as a heat
sink.  TCMs are mostly water cooled, although some
are air cooled.


TCO
Stringent low-radiation standards set by the
Swedish Confederation of Professional Employees.
See MPR II.


TCP/IP
(Transmission Control Protocol/Internet Protocol)
Communications protocols developed under contract
from the Dept. of Defense (DOD) to internetwork
dissimilar systems.  It is a de facto UNIX
standard, but is supported on almost all systems.
It is used by many corporations and most
universities and federal agencies.

   File Transfer Protocol (FTP) and Simple Mail
Transfer Protocol (SMTP) provide file transfer and
e-mail.  The TELNET protocol provides terminal
emulation for all types of computers in the
network.  TCP controls data transfer.  IP provides
the routing.  Protocol comparisons follow:


   TCP/IP          DOD            OSI
┌───────────┐ ┌────────────┐ ┌────────────┐
│Application│ │            │ │Application │
│           │ │            │ ├────────────┤
│(FTP, SMTP │ │  Process   │ │Presentation│
│  TELNET)  │ │            │ ├────────────┤
│           │ │            │ │  Session   │
├───────────┤ ├────────────┤ ├────────────┤
│ Transport │ │Host to Host│ │ Transport  │
│   (TCP)   │ │            │ │            │
├───────────┤ ├────────────┤ ├────────────┤
│ Internet  │ │  Internet  │ │  Network   │
│   (IP)    │ │            │ │            │
├───────────┤ ├────────────┤ ├────────────┤
│  Network  │ │            │ │ Data link  │
│ Interface │ │  Network   │ ├────────────┤
│ (IEEE 802 │ │   Access   │ │  Physical  │
│   X.25)   │ │            │ │            │
└───────────┘ └────────────┘ └────────────┘



TCSEC
See NCSC.


TCU
(Transmission Control Unit)  Communications control
unit controlled by the computer that does not
execute internally stored programs.  Contrast with
front end processor, which executes its own
instructions.


TDM
(Time Division Multiplexing)  Technique that
interleaves several low-speed signals into one
high-speed transmission.  For example, if A, B & C
are three digital signals of 1,000 bps each, they
can be mixed into one 3,000 bps as follows:
AABBCCAABBCCAABBCC.  The receiving end divides the
single stream back into its original signals.
Contrast with FDM.  See baseband.


tear-off menu
On-screen menu or palette that can be moved off of
its primary position and relocated to any part of
the screen.


tech support
Technical assistance.


tech writer
Person who is responsible for writing documentation
for a hardware or software product.


telco
(TELephone COmpany)  Company that provides
telephone services.


tele
Operations performed remotely or by telephone.


telecom
See telecommunications.


telecommunications
Communicating information, including data, text,
pictures, voice and video.  See communications.


telecommunity
Society in which information can be transmitted or
received freely between all members without
technical incompatibilities.


telecommuting
Working at home and communicating with the office.


teleconferencing
(1) Video teleconferencing.  Video conference among
several users provided by video cameras and
monitors set up inhouse or in a public conferencing
center.  It requires a high-bandwidth (TV capacity)
network that uses coaxial cable, optical fibers,
microwave or satellite transmission.  Conventional
computer networks can't handle video.

   Video conferencing is slowly being integrated
into data networks.  In time, all data networks
will provide this capability.

(2) Audio teleconferencing.  Telephone conference
among several users provided internally by an
organization's PBX and externally by the telephone
companies.

(3) Computer teleconferencing.  Keyboard conference
among several users at terminals or personal
computers provided by specialized software in a
host computer or BBS.


telecopying
(long distance copying)  Formal term for fax.


telegraph
Low-speed communications device that transmits up
to approximately 150 bps.  Telegraph grade lines,
stemming from the days of Morse code, can't
transmit a voice conversation.


telemanagement
Management of an organization's telephone systems.


telemarketing
Selling over the telephone.


Telematics
Convergence of telecommunications and information
processing.


telemetry
Transmitting data captured by instrumentation and
measuring devices to a remote station where it is
recorded and analyzed.  For example, data from a
weather satellite is telemetered to earth.


Telenet
Value-added, packet switching network that enables
many varieties of terminals and computers to
exchange data.  It is a subsidiary of US Sprint.


telephone wiring
See twisted pair.


telephony
Science of converting sound into electrical
signals, transmitting it within cables or via radio
and reconverting it back into sound.


teleprinter
Typewriter-like terminal with a keyboard and built-
in printer, often a portable unit.  Contrast with
video terminal.


teleprocessing
(long distance processing)  Early IBM term for data
communications.


teleprocessing monitor
See TP monitor.


Telescript
Programming language and software for
communications from General Magic.  It embeds
intelligence in e-mail and other applications
allowing them to cooperate with one another and
allows messages to move intelligently through
diverse public and private networks.  Telescript
can be added to existing and future operating
systems.  See Magic Cap.


Teletex
See Telex.


teletext
Broadcasting service that transmits text to a TV
set that has a teletext decoder.  It uses the
vertical blanking interval of the TV signal (black
line between frames when vertical hold is not
adjusted) to transmit about a hundred frames.  See
videotex.


Teletype
Trade name of Teletype Corp. and refers to a
variety of teleprinters used for communications.
The Teletype was one of the first communications
terminals in the U.S.


teletype interface
See teletype mode.


teletype mode
Line-at-a-time output like a typewriter.  Contrast
with full-screen mode.


teletypewriter
Low-speed teleprinter, often abbreviated "TTY."


televaulting
Continuous transmitting of data to vaults for
backup purposes.  The term was coined by TeleVault
Technology Inc.


Telex
International dial-up communications service that
uses teleprinters and transmits Baudot code at 50
bps (66 words/minute).  In the U.S., it is
administered by Western Union, which in 1971
purchased the Bell System's TWX service and
connected it to the Telex network.

   In the early 1980s, a new service called Teletex
was initiated that provides higher speeds and upper
and lowercase text to subscribers using intelligent
terminals and personal computers.

   Group 3 fax machines quickly supplanted Telex
transmission.


TeLink
Xmodem protocol with batch file transfer designed
for the Fido BBS.  It sends file name, date and
size in the first block.


TELNET
Terminal emulation protocol originally developed
for ARPAnet.  See TCP/IP.


Telon
Application generator from Computer Associates that
generates COBOL and PL/I code for IBM mainframes
and COBOL code for AS/400s.  Development can be
performed on mainframes or PCs.  It was developed
by Pansophic Systems (acquired by CA).


template
(1) Plastic or stiff paper form that is placed over
the function keys on a keyboard to identify their
use.

(2) Programmatic and descriptive part of a
programmable application; for example, a
spreadsheet that contains only descriptions and
formulas or a HyperCard stack that contains only
programming and backgrounds.  When the template is
filled with data, it becomes a working application.


temporary font
Soft font that remains in the printer's memory
until the printer is reset manually or by software.
Contrast with permanent font.


ter
Third version.


tera
Trillion.  Abbreviated "T."  It often refers to the
precise value 1,099,511,627,776 since computer
specifications are usually binary numbers.  See
binary values and space/time.


terabit
One trillion bits.  Also Tb, Tbit and T-bit.  See
tera and space/time.


terabyte
One trillion bytes.  Also TB, Tbyte and T-byte.
See tera and space/time.


teraflops
(tera FLoating point OPerations per Second)  One
trillion floating point operations per second.


terminal
(1) I/O device for a computer that usually has a
keyboard for input and a video screen or printer
for output.

(2) Input device, such as a scanner, video camera
or punched card reader.

(3) Output device in a network, such as a monitor,
printer or card punch.

(4) Connector used to attach a wire.


terminal emulation
Using a computer to simulate the type of terminal
required to gain access to another computer.  See
virtual terminal.


terminal mode
Operating mode that causes the computer to act like
a terminal; ready to transmit typed-in keystrokes
and ready to receive transmitted data.


terminal server
Computer or controller used to connect multiple
terminals to a network or host computer.


terminal session
Time in which a user is working at a terminal.


terminal strip
Insulated bar that contains a set of screws to
which wires are attached.


terminate and stay resident
See TSR.


terminator
(1) Character that ends a string of alphanumeric
characters.

(2) Hardware component that is connected to the
last peripheral device in a series or the last node
in a network.


terrestrial link
Communications line that travels on, near or below
ground.  Contrast with satellite link.


test automation software
Software used to test new revisions of software by
automatically entering a predefined set of commands
and inputs.


test data
Set of data created for testing new or revised
programs.  It should be developed by the user as
well as the programmer and must contain a sample of
every category of valid data as well as many
invalid conditions.


testing
Running new or revised programs to determine if
they process all data properly.  See test data.


TeX
Typesetting language used in a variety of
typesetting environments.  It uses embedded codes
within the text of the document to initiate changes
in layout including the ability to describe
elaborate scientific formulas.


text
Words, sentences and paragraphs.  Contrast with
data, which are defined units, such as name and
amount due.  Text may also refer to alphanumeric
data, such as name and address, to distinguish it
from numeric data, such as quantity and dollar
amounts.  A page of text takes about 2,000 to 4,000
bytes.  See text field.


text based
Also called character based, the display of text
and graphics as a fixed set of predefined
characters.  For example, 25 rows of 80 columns.
Contrast with graphics based.


text editing
Ability to change text by adding, deleting and
rearranging letters, words, sentences and
paragraphs.


text editor
Software used to create and edit files that contain
only text (batch files, address lists, source
language programs, etc.).  Unlike a word processor,
it usually does not provide word wrap or formatting
features such as underline, boldface or font
changes.  Editors designed for programming may
provide automatic indention and multiple windows.
See DOS Edlin and DOS Editor.


text field
Data structure that holds alphanumeric data, such
as name and address.  If a text field holds large,
or unlimited, amounts of text, it may be called a
memo field.  Contrast with numeric field.


text file
File that contains only text characters.  Contrast
with graphics file and binary file.


text management
Creation, storage and retrieval of text.  It
implies flexible retrieval capabilities that can
search for text based on a variety of criteria.
Although a word processor manages text, it usually
has limited retrieval capabilities.


text mode
(1) Screen display mode that displays only text and
not graphics.

(2) Program mode that allows text to be entered and
edited.


text to speech
Converting text into voice output using speech
synthesis techniques.


texture mapping
In computer graphics, the creation of a special
surface.  With algorithms, all kinds of textures
can be produced: the rough skin of an orange, the
metallic surface of a can and the irregularity of a
brick.  It can also be done by electronically
wrapping a secondary image around an object.


TFT
(Thin Film Transistor)  See thin film.


TFT LCD
(Thin Film Transistor LCD)  See LCD.


TFTP
(Trivial File Transfer Protocol)  Version of the
TCP/IP FTP protocol that has no directory or
password capability.


TGA
See Targa.


thermal dye diffusion
Printing process similar to thermal wax transfer
except that a dye is used instead of ink.  The
printhead heats the ribbon causing the dye to turn
from a solid to a gas and condense on special
paper.  The more heat, the denser the image.
Continuous color can be produced that approaches
photographic quality.


thermal printer
Low-cost, low- to medium-resolution non-impact
printer that uses heat-sensitive paper.  Where the
heated pins of the print head touch the paper, the
paper darkens.  See printer.


thermal wax transfer
Printing process that transfers a waxlike ink onto
paper.  For example, in a color printer, a mylar
ribbon is used that contains several hundred
repeating sets of full pages of black, cyan,
magenta and yellow ink.  A sheet of paper is
pressed against each color and passed by a line of
heating elements that transfers the dots, or
pixels, of ink onto the paper.


thick film
Layer of magnetic, semiconductor or metallic
material that is thicker than the microscopic
layers of the transistors on a chip.  For example,
metallic thick films are silk screened onto the
ceramic base of hybrid microcircuits.  Contrast
with thin film.


thimble printer
Letter quality printer similar to a daisy wheel
printer.  Instead of a wheel, characters are formed
facing out and around the rim of a thimble-shaped
cup.  For example, the NEC Spinwriters are thimble
printers.


thin Ethernet
See Ethernet.


thin film
Microscopically thin layer of semiconductor or
magnetic material that is deposited onto a metal,
ceramic or semiconductor base.  For example, the
layers that make up a chip and the surface coating
on high-density magnetic disks are called thin
films.


thin film head
Read/write head for high-density disks that is made
from thin layers of a conducting film deposited
onto a nickel-iron core.


ThinNet
See Ethernet.


third-generation computer
Computer that uses integrated circuits, disk
storage and online terminals.  The third generation
started roughly in 1964 with the IBM System/360.


third-generation language
Traditional high-level programming language such as
FORTRAN, COBOL, BASIC, Pascal and C.


third normal form
See normalization.


THOR
(Tandy High-intensity Optical Recorder)  Erasable
CD recorder from Tandy scheduled for introduction
in the early 1990s.  It records audio on a special
disc that can be erased and reused and also played
on a standard CD player.  Models for recording data
are projected.


thrashing
Excessive paging in a virtual memory computer.  If
programs are not written to run in a virtual memory
environment, the operating system may spend
excessive amounts of time swapping program pages in
and out of the disk.


thread
One transaction or message in a multithreaded
system.


threading
See multithreading.


three-state logic element
Electronic component that provides three possible
outputs: off, low voltage and high voltage.


throughput
Speed with which a computer processes data.  It is
a combination of internal processing speed,
peripheral speeds (I/O) and the efficiency of the
operating system and other system software all
working together.


thunk
In PCs, to execute the instructions required to
switch between segmented addressing of memory and
flat addressing.


THz
(TeraHertZ)  One trillion cycles per second.


TI
(Texas Instruments, Inc., Dallas, TX)  Leading
semiconductor manufacturer founded in 1930 as
Geophysical Service, Inc., to provide services to
the petroleum industry.  During the war, GSI
manufactured electronics for the Navy and later
added them to its product line.

   In 1951, GSI was renamed Texas Instruments and
soon after entered the semiconductor business.  TI
was the first to commercialize the silicon
transistor, pocket radio, integrated circuit, hand-
held calculator, single-chip computer and the LISP
chip.

   In the early 1980s, TI sold a large number of
its low-priced 99/4a home computers.  It later
introduced desktop PCs, but today offers only a
line of notebook PCs.

   With 1991 revenues of nearly seven billion, TI's
strength is integrated circuits, but, it also
creates computer systems for AI applications,
composite metals, electrical control products and
consumer electronics, including its well-known line
of calculators and educational math and reading
machines.


TI-RPC
(Transport-Independent-Remote Procedure Call)
Operating system and network-independent library of
functions from Sun for executing procedures on
remote computers.  Allows development of
distributed applications in multivendor
environments.


TIA
See EIA.


TIA/EIA-232
See RS-232.


TIES
(Time-Independent Escape Sequence)  Modem escape
sequence that uses three pluses like the Hayes
sequence, but does not require a pause before and
after them.  If a valid AT command code and a
return follows the +++, it is considered a
legitimate command.  See Hayes Smartmodem.


TIFF
(Tagged Image File Format)  Widely-used raster
graphics file format developed by Aldus and
Microsoft that handles monochrome, gray scale, 8-
and 24-bit color.  Since 1986, there have been six
versions of TIFF.  It uses several compression
methods: LZW provides ratios of about 1.5:1 to 2:1.
Ratios of 10:1 to 20:1 are possible for documents
with lots of white space using CCITT Group III & IV
compression methods (fax).  See JPEG.


TIGA
(Texas Instruments Graphics Architecture)  Graphics
standard that provides a resolution-independent
interface between a program and the graphics
processor.  See 34010.


tightly coupled
Refers to two or more computers linked together and
dependent on each other.  One computer may control
the other, or both computers may monitor each
other.  For example, a database machine is tightly
coupled to the main processor.  Two computers tied
together for multiprocessing are tightly coupled.
Contrast with loosely coupled, such as personal
computers in a LAN.


tiled
Display of objects side by side; for example, tiled
windows cannot be overlapped on top of each other.


time base generator
Electronic clock that creates its own timing
signals for synchronization and measurement
purposes.


time-division multiplexing
See TDM.


time slice
Fixed interval of time allotted to each user or
program in a multitasking or timesharing system.


time slot
Continuously repeating interval of time or a time
period in which two devices are able to
interconnect.


timer interrupt
Interrupt generated by an internal clock.  See
interrupt.


timesharing
Multiuser computer environment that lets users
initiate their own sessions and access selected
databases as required, such as when using online
services.  A system that serves many users, but for
only one application, is technically not
timesharing.


timing clock
See clock.


timing signals
Electrical pulses generated in the processor or in
external devices in order to synchronize computer
operations.  The main timing signal comes from the
computer's clock, which provides a frequency that
can be divided into many slower cycles.  Other
timing signals may come from a timesharing or
realtime clock.

   In disk drives, timing signals for reading and
writing are generated by holes or marks on one of
the platters, or by the way the digital data is
actually recorded.


Tiny BASIC
Subset of BASIC that has been used in first
generation personal computers with limited memory.


TIRIS
(Texas Instruments Registration and Identification
System)  RF/ID system from TI that uses a 3.6x29mm
cylindrical tag.  Reading can be done from as far
as 40 inches away.


TLA
(Three Letter Acronym)  The epitome of acronyms!


TLI
(Transport Level Interface)  AT&T UNIX System V
transport layer protocol (OSI layer 4).  It is a
STREAMS module that can serve as a programming
interface between an application and OSI or TCP/IP
protocols.


TM/1
(Tables Manager/1)  Relational spreadsheet for PCs
from Sinper Corp., Warren,  NJ, that allows data to
be viewed in up to eight dimensions.  An option
allows Lotus users to access a TM/1 database
directly from a 1-2-3 spreadsheet.


TN
(Twisted Nematic)  First LCD technology, which
twists liquid crystal molecules 90° between
polarizers.  Requires bright ambient light and
still used for low-cost applications.  See LCD.


TOF
(Top Of Form)  Beginning of a physical paper form.
To position paper in many printers, the printer is
turned offline, the forms are aligned properly and
the TOF button is pressed.


toggle
To alternate back and forth between two states.


token passing
Communications network access method that uses a
continuously repeating frame (the token) that is
transmitted onto the network by the controlling
computer.  When a terminal or computer wants to
send a message, it waits for an empty token.  When
it finds one, it fills it with the address of the
destination station and some or all of its message.

   Every computer and terminal on the network
constantly monitors the passing tokens to determine
if it is a recipient of a message, in which case it
"grabs" the message and resets the token status to
empty.  Token passing uses bus and ring topologies.


token ring network
(1) Communications network that uses the token
passing technology in a sequential manner.  Each
station in the network passes the token on to the
station next to it.

(2) (Token Ring Network)  IBM local area network
(LAN) that conforms to the IEEE 802.5 standard.
All stations connect to a central wiring hub (star
topology) through special twisted wire cable.  The
central hub makes it easier to troubleshoot failed
units.  It uses the token passing access method
transmitting at 4 or 16 Mbits/sec and passes tokens
to up to 255 nodes in a ring-like sequence.


TokenTalk
Software for the Macintosh from Apple that
accompanies its TokenTalk NB board and adapts the
Mac to Token Ring Networks.


toner
Electrically charged ink used in copy machines and
laser printers.  It adheres to an invisible image
that has been charged with the opposite polarity
onto a plate or drum or onto the paper itself.


tool
(1) On-screen function in an interactive program;
for example, a line draw, circle draw or paintbrush
option in a graphics program.

(2) Program used for software development or system
maintenance.  Utility programs, editors, debuggers
and graphics routines are examples.  A program that
helps a user customize, adapt or work with a
computer may be called a tool.


tool palette
Collection of on-screen functions, typically
graphics related, that are grouped in a menu
structure for interactive selection.


ToolBook
Application development system for Windows from
Asymetrix Corp., Bellevue, WA, that uses a "page
and book" metaphor analogous to HyperCard's "card
and stack."  Its OpenScript language is similar to
HyperTalk.


toolbox
Same as toolkit.


toolkit
Set of software routines that allow a program to be
written for and work in a particular environment.
The routines are called by the application program
to perform various functions, for example, to
display a menu or draw a graphic element.


TOP
(Technical Office Protocol)  Communications
protocol for office systems from Boeing Computer
Services.  It uses the Ethernet access method and
is often used in conjunction with MAP, the factory
automation protocol developed by GM.  TOP is used
in the front office, and MAP is used on the factory
floor.


top of file
Beginning of a file.  In a word processing file, it
is the first character in the document.  In a data
file, it is either the first record in the file or
the first record in the index.  For example, in a
dBASE file that is indexed on name, goto top might
go to physical record #608 if record #608 is
AARDVARK.


topdown design
Design technique that starts with the highest level
of an idea and works its way down to the lowest
level of detail.


topdown programming
Programming design and documentation technique that
imposes a hierarchical structure on the design of
the program.  See structured programming.


topology
(1) In a communications network, the pattern of
interconnection between nodes; for example, a bus,
ring or star configuration.

(2) In a parallel processing architecture, the
interconnection between processors; for example, a
bus, grid, hypercube or Butterfly Switch
configuration.


TOPS
(1) Multiuser, multitasking, timesharing, virtual
memory operating system from Digital that runs on
its PDP-6, DECsystem 10 and DECsystem 20 series.

(2) (Transparent OPerating System)  Peer-to-peer
LAN from Sitka Corp., Alameda, CA, that uses the
LocalTalk access method and connects Apple
computers, PCs and Sun workstations.  Its Flashcard
plugs LocalTalk capability into PCs.


TOPVIEW
IBM's first PC windowing environment.  It never
caught on.


TOTAL
Early network DBMS from Cincom Systems that ran on
a variety of minis and mainframes.


total bypass
Bypassing local and long distance telephone lines
by using satellite communications.


touch screen
Touch-sensitive display screen that uses a clear
panel over on the screen surface.  The panel is a
matrix of cells that transmit pressure information
to the software.


tower
(1) Floor-standing cabinet taller than it is wide.
Desktop computers can be made into towers by
turning them on their side and inserting them into
a floor-mounted base.

(2) Tower. Series of UNIX-based single and
multiprocessor computer systems from NCR that use
the Motorola 68000 family of CPUs.


TP monitor
(TeleProcessing monitor or Transaction Processing
monitor)  Communications control program that
manages the transfer of data between multiple local
and remote terminals and the application programs
that serve them.  It may also include programs that
format the terminal screens and validate the data
entered.  See CICS and Tuxedo.


TP0-TP4
(Transport Protocol Class 0 to Class 4)  Grades of
OSI transport layers from least to most complete
and specific.  TP4 is a full connection-oriented
transport protocol.


TPA
(Transient Program Area)  See transient area.


tpi
(Tracks Per Inch)  Used to measure the density of
tracks recorded on a disk or drum.


TPS
(1) (Transactions Per Second)  Number of
transactions processed within one second.

(2) (Transaction Processing System)  Originally
used as an acronym for such a system, it now refers
to the measurement of the system (#1 above).


track
Storage channel on disk or tape.  On disks, tracks
are concentric circles (hard and floppy disks) or
spirals (CDs and videodiscs).  On tapes, they are
parallel lines.  Their format is determined by the
specific drive they are used in.  On magnetic
devices, bits are recorded as reversals of polarity
in the magnetic surface.  On CDs, bits are recorded
as physical pits under a clear, protective layer.
See magnetic disk.


trackball
Input device used in video games and as a mouse
alternative.  It is a stationary unit that contains
a movable ball rotated with the fingers or palm
and, correspondingly, moves the cursor on screen.


tractor feed
Mechanism that provides fast movement of paper
forms through a printer.  It contains pins on
tractors that engage the paper through perforated
holes in its left and right borders.  Contrast with
sheet feeder.


Tradacoms
European EDI standard developed by the Article
Numbering Assn.  See X12 and EDIFACT.


trade shows
See PC EXPO and COMDEX.


trailer
In communications, a code or set of codes that make
up the last part of a transmitted message.  See
trailer label.


trailer label
Last record in a tape file.  May contain number of
records, hash totals and other ID.


train printer
Line printer mechanism similar to a chain printer,
but uses unconnected type slugs that ride in a
track rather than a connected chain of type.  The
slugs are pushed around the track by engaging with
a drive gear at one end.  Slugs and track come as a
replaceable cartridge.


training
(1) Teaching the details of a subject.  With regard
to software, training provides instruction for each
command and function in an application.  Contrast
with education.

(2) In communications, the process by which two
modems determine the correct protocols and
transmission speeds to use.

(3) In voice recognition systems, the recording of
the user's voice in order to provide samples and
patterns for recognizing that voice.


transaction
Activity or request.  Orders, purchases, changes,
additions and deletions are typical business
transactions stored in the computer.  Queries and
other requests are also transactions, but are
usually just acted upon and not saved.  Transaction
volume is a major factor in figuring computer
system size and speed.


transaction file
Collection of transaction records.  The data in
transaction files is used to update the master
files, which contain the subjects of the
organization.  Transaction files also serve as
audit trails and are usually transferred from
online disks to the data library after some period
of time.

   As optical disks become more economical,
transaction files will remain online in the
computer so that an organization's history will be
immediately available for ad hoc queries.  See
information system.


transaction processing
Processing transactions as they are received by the
computer.  Also called online or realtime systems,
master files are updated as soon as transactions
are entered at terminals or arrive over
communications lines.

   If you save receipts in a shoebox and add them
up at the end of the year for taxes, that's batch
processing.  However, if you buy something and
immediately add the amount to a running total,
that's transaction processing.


transceiver
Transmitter and receiver of analog or digital
signals. It comes in many forms; for example, a
transponder or network adapter.


transcribe
To copy data from one medium to another; for
example, from one source document to another, or
from a source document to the computer.  It often
implies a change of format or codes.


transducer
Device that converts one energy into another; for
example, a read/write head converts magnetic energy
into electrical energy and vice versa.  In process
control applications, it is used to convert
pressure into an electrical reading.


transfer
To send data over a computer channel or bus.
"Transfer" generally applies to transmission within
the computer system, and "transmit" refers to
transmission outside the computer over a line or
network.

   Transfers are actually copies, since the data is
in both locations at the end of the transfer.
Input, output and move instructions activate data
transfers in the computer.


transfer protocol
See file transfer protocol.


transfer rate
Also called data rate, the transmission speed of a
communications or computer channel.  Transfer rates
are measured in bits or bytes per second.


transfer time
Time it takes to transmit or move data from one
place to another.  It is the time interval between
starting the transfer and the completion of the
transfer.


transformer
Device that changes AC voltage.  It is made of
steel laminations wrapped with two coils of wire.
The coil ratio derives the voltage change.  For
example, if the input coil has 1,000 windings, and
the output has 100, 120 volts is changed to 12.  In
order to create direct current (DC), the output is
passed through a rectifier.


transient
Malfunction that occurs at random intervals; for
example, a rapid fluctuation of voltage in a power
line or a memory cell that intermittently fails.


transient area
Area in memory used to hold application programs
for processing.  The bulk of a computer's main
memory is used as a transient area.


transient state
Exact point at which a device changes modes, for
example, from transmit to receive or from 0 to 1.


transistor
Semiconductor device used to amplify a signal or
open and close a circuit.  In a computer, it
functions as an electronic switch.  In its normal
state, it is non-conductive.  When voltage is
applied at the gate, it becomes conductive and
current flows from source to drain.

   Transistors, resistors, capacitors and diodes,
make up logic gates.  Logic gates make up circuits,
and circuits make up electronic systems.

            Source  Gate  Drain
              │ │   │ │   │ │
              ││   ││   ││
              │ └──┬┴─┴┬──┘ │
              └────┴───┴────┘
                     │
                  Switch

      Conceptual View of A Transistor



translate
(1) To change one language into another; for
example, assemblers, compilers and interpreters
translate source language into machine language.

(2) In computer graphics, to move an image on
screen without rotating it.

(3) In telecommunictions, to change the frequencies
of a band of signals.


TransLISP PLUS
Version of LISP for PCs from Solution Systems,
Inc., Wellesley, MA.  It provides an interface to
Microsoft C that allows a C routine to be added to
the LISP library as a function.


transmission
Transfer of data over a communications channel.


transmission channel
Path between two nodes in a network.  It may refer
to the physical cable, the signal transmitted
within the cable or to a subchannel within a
carrier frequency.  In radio and TV, it refers to
the assigned carrier frequency.


transmission control unit
See TCU.


transmit
To send data over a communications line.  See
transfer.


transmitter
Device that generates signals.  Contrast with
receiver.


transparent
Refers to a change in hardware or software that,
after installation, causes no noticeable change in
operation.


transparent bridging
Communications protocol in which the stations are
unaware of bridges in the network.  Ethernet uses
this method.  Contrast with source routing.


transponder
Receiver/transmitter on a communications satellite.
It receives a microwave signal from earth (uplink),
amplifies it and retransmits it back to earth at a
different frequency (downlink).  A satellite has
several transponders.


transport protocol
Communications protocol responsible for
establishing a connection and ensuring that all
data has arrived safely.  It is defined in layer 4
of the OSI model.


transport services
Collective functions of layers 1 through 4 of the
OSI model.


transputer
(TRANSistor comPUTER)  Computer that contains a
CPU, memory and communications capability on a
single chip.  Chips are strung together in
hypercube or grid-like patterns to create large
parallel processing machines, used in scientific,
realtime control and AI applications.


trap
To test for a particular condition in a running
program; for example, to "trap an interrupt" means
to wait for a particular interrupt to occur and
then execute a corresponding routine.  An error
trap tests for an error condition and provides a
recovery routine.  A debugging trap waits for the
execution of a particular instruction in order to
stop the program and analyze the status of the
system at that moment.


trapdoor
Alternate way of gaining access to an interactive
program.  It implies a special entrance or exit
that can be used if necessary.


trash can
Macintosh icon used for deleting files, folders and
applications and ejecting a floppy disk.


trashware
Software that is so poorly designed that it winds
up in the garbage can.


tree
Hierarchical structure.  See directory tree.


trichromatic
In computer graphics, the use of red, green and
blue to create all the colors in the spectrum.


trillion
One thousand times one billion.  See tera and
picosecond.


Trilogy
Company founded in 1979 by Gene Amdahl to
commercialize wafer scale integration and build
supercomputers.  It raised a quarter of a billion
dollars, the largest startup funding in history,
but could not create its 2.5" superchip.  In 1984,
it abandoned supercomputer development and later
the superchip project.  In 1985, Trilogy acquired
Elxsi Corp., a manufacturer of VAX-compatible
systems, and eventually merged itself into Elxsi.


triple precision
Use of three computer words to hold a number used
for calculation, providing an enormous amount of
arithmetic precision.


triple twist
Supertwist variation that twists crystals to 260°
for improved clarity.  See LCD.


troff
(Typesetting RunOFF)  UNIX utility that formats
documents for typesetters and laser printers.
Using a text editor, troff codes are embedded into
the text and the troff command converts the
document into the required output.  See nroff.


Trojan horse
Program routine that invades a computer system by
being secretly attached to a valid program that
will be downloaded into the computer.  It may be
used to locate password information, or it may
alter an existing program to make it easier to gain
access to it.  A virus is a Trojan horse that
continues to infect programs over and over.


TRON
(The Realtime Operating System Nucleus)  Advanced
realtime computer architecture and operating system
under development by Japanese universities and
corporations.  Its goal is a common architecture
and user interface from the smallest consumer
appliance to the largest supercomputer.  TRON-based
intelligent cars and houses are under research.

   CTRON (Central TRON) is an OSI-compliant
communications system for network file servers;
BTRON (Business TRON) for accounting applications;
ITRON (Industrial TRON) for intelligent machinery;
MTRON (Macro TRON) for intelligent objects and
networks (housing and urban development); µITRON
(Micro ITRON) runs on 8-bit computers for home
appliances.  Address: P.O.Box 23990, Tempe, AZ
85285.


TRS
(Tandy Radio Shack)  Early Tandy trade name.  In
1977, the TRS-80 was one of the three first
personal computers.  TRS-DOS was its operating
system.  See personal computer.


True BASIC
ANSI-standard structured-programming version of
BASIC for the PC, Mac and Amiga from True BASIC,
Inc., West Lebanon, NH.  Developed in 1984 by
BASIC's creators, John Kemeny and Thomas Kurtz, it
includes many enhancements over original BASIC.  It
comes in both interpreter and compiler form.


true color
(1) Ability to generate 16,777,216 colors (24-bit
color).  See high color.

(2) Ability to generate photo-realistic color
images (requires 24-bit color minimum).


TrueImage
Enhanced PostScript interpreter from Microsoft that
prints PostScript Type 1 and TrueType fonts.


TrueType
Scalable font technology from Apple (enhanced
jointly by Apple and Microsoft) that renders
printer and screen fonts.  It is used in Windows
3.1 and Mac System 7.  Unlike PostScript, in which
the algorithms are maintained in the rasterizing
engine, each TrueType font contains its own
algorithms for converting the outline into bitmaps.
The lower-level language embedded within the
TrueType font allows unlimited flexibility in the
design.  See TrueImage.


truncate
To cut off leading or trailing digits or characters
from an item of data without regard to the accuracy
of the remaining characters.  Truncation occurs
when data is converted into a new record with
smaller field lengths than the original.


trunk
Communications channel between two points.  It
often refers to large-bandwidth telephone channels
between major switching centers, capable of
transmitting many simultaneous voice and data
signals.


truth table
Chart of a logical operation's inputs and outputs.
The following example is a Boolean AND truth table:

         Inputs  Output
        ┌───────┬─────┐
        │ 0   0 │  0  │
        │ 0   1 │  0  │
        │ 1   0 │  0  │
        │ 1   1 │  1  │
        └───────┴─────┘



TSAT
See VSAT.


TSO
(Time Sharing Option)  Software that provides
interactive communications for IBM's MVS operating
system.  It allows a user or programmer to launch
an application from a terminal and interactively
work with it.  The TSO counterpart in VM is called
CMS.  Contrast with JES, which provides batch
communications for MVS.


TSOP
(Thin Small Outline Package)  One-millimeter-thick
package used to house dynamic RAM chips.


TSR
(Terminate and Stay Resident)  Refers to programs
that remain in memory so they can be instantly
popped up over the current application by pressing
a hotkey.  The program is displayed either as a
small window on top of the existing text or image,
or it takes the full screen.  When the program is
exited, previous screen contents are restored.

   On DOS PCs, TSRs provide quick access to a
calculator, calendar or dictionary; however,
conflicts may arise when multiple TSRs are loaded.
Older ones may not always work with newer ones.

   Task switching environments such as Windows and
DESQview, provide the ability to switch back and
forth between applications, thus making all
programs function as a TSR.

   The term refers to loading a program,
terminating its action but not removing it from
memory.


TTL
(Transistor Transistor Logic)  Digital circuit in
which the output is derived from two transistors.
Although TTL is a specific design method, it often
refers generically to digital connections in
contrast with analog connections.  For example, a
TTL input on a monitor requires digital output from
the display board rather than analog output.


TTY
(TeleTYpewriter)  See teletypewriter.


TTY protocol
Low-speed asynchronous communications protocol with
limited or no error checking.


tube
See CRT and vacuum tube.


tuner
Electronic part of a radio or TV that locks on to a
selected carrier frequency (station, channel) and
filters out the audio and video signals for
amplification and display.


tuple
In relational database management, a record, or
row.  See relational database.


Turbo C
C compiler from Borland used to create a wide
variety of commercial products.  It is known for
its exceptionally well-designed debugger.  The PC
version of this Glossary was written in Turbo C.


Turbo Mouse
Macintosh trackball from Kensington Microware,
Ltd., San Mateo, CA.  If the ball is moved slowly,
the cursor moves slowly, but if moved quickly, the
same spatial movement moves the cursor a greater
distance on the screen.  Its PC counterpart is
called the Expert Mouse.


Turbo Pascal
Pascal compiler for DOS from Borland used in a wide
variety of applications from accounting to complex
commercial products.  Turbo Pascal for Windows
provides an object-oriented programming environment
for Windows development.  Borland is responsible
for moving the Pascal language from the academic
halls to the commercial world.


TURBOchannel
32-bit data bus from Digital introduced in 1990.
It has a peak transfer rate of 100 MBytes/sec.


turnaround document
Paper document or punched card prepared for re-
entry into the computer system.  Paper documents
are printed with OCR fonts for scanning  Invoices
and inventory stock cards are examples.


turnaround time
(1) In batch processing, the time it takes to
receive finished reports after submission of
documents or files for processing.  In an online
environment, turnaround time is the same as
response time.

(2) In half-duplex transmission, the time it takes
to change from transmit to receive and vice versa.


turnkey system
Complete system of hardware and software delivered
to the customer ready-to-run.


turnpike effect
In communications, a lock up due to increased
traffic conditions and bottlenecks in the system.


turtle graphics
Method for creating graphic images in Logo.  The
turtle is an imaginary pen that is given drawing
commands, such as go forward and turn right.  On
screen, the turtle is shaped like a triangle.


tutorial
Instructional book or program that takes the user
through a prescribed sequence of steps in order to
learn a product.  Contrast with documentation,
which, although instructional, tends to group
features and functions by category.


Tuxedo
TP monitor from USL that runs on a variety of UNIX-
based computers.


TWAIN
Programming interface that lets a graphics
application, such as a desktop publishing program,
activate a scanner, frame grabber or other image-
capturing device.


tweak
To make minor adjustments in an electronic system
or in a software program in order to improve
performance.


tweening
Animation technique that, based on starting and
ending shapes, creates the necessary "in-between"
frames.  See morphing.


TwinAxcess
IBM midrange terminal emulation system for the
Macintosh from Andrew/KMW, Austin, TX.  It includes
a controller card and software that emulates the
5250 terminal used on System/3x and AS/400s.  It
allows the user to have seven concurrent sessions
broadcast over LocalTalk, EtherTalk or TokenTalk
networks.


twinaxial
Type of cable similar to coax, but with two inner
conductors instead of one.  It is used in IBM
midrange communications environments.


TWIP
(TWentIeth of a Point)  Equal to 1/1440th of an
inch.


twisted pair
Abbreviated "UTP" (Unshielded Twisted Pair), a pair
of thin-diameter (22 to 26 gauge) insulated wires
commonly used in telephone wiring.  The wires are
twisted around each other to minimize interference
from other twisted pairs in the cable.  Twisted
pairs have less bandwidth than coaxial cable or
optical fiber.


two-out-of-five code
Numeric code that stores one decimal digit in five
binary digits in which two of the bits are always 0
or 1 and the other three are always in the opposite
state.


two-phase commit
Technique for ensuring that a transaction
successfully updates all appropriate files in a
distributed database environment.  All DBMSs
involved in the transaction first confirm that the
transaction has been received and is recoverable
(stored on disk).  Then each DBMS is told to commit
the transaction (do the actual updating).


two-wire lines
Transmission channel made up of only two wires,
such as used in the common dial-up telephone
network.


TWX
(TeletypeWriter eXchange Service)  U.S. and
Canadian dial-up communications service that uses
teleprinters and transmits 5-bit Murray code or 7-
bit ASCII code at up to 150 bps.  Originally part
of the Bell System, it was sold to Western Union in
1971 and interconnected with Telex.


Tymnet
(BTC Tymnet) Value-added, packet switching network
that enables many varieties of terminals and
computers to exchange data.  It is a subsidiary of
British Telecom Corp.


type
(1) In data or text entry, to press the keys on the
keyboard.

(2) In programming, a category of variable that is
determined by the kind of data stored in it.  For
example, integer, floating point, string, logical,
date and binary are common data types.

(3) In DOS and OS/2, a command that displays the
contents of a text file.


Type 1 font
See PostScript.


Type 3 font
See PostScript.


type ball
Golf ball-sized element used in typewriters and
low-speed teleprinters that contains all the print
characters on its outside surface.  It was
introduced with IBM's Selectric typewriter.


type family
See typeface family.


type font
Set of print characters of a particular design
(typeface), size (point size) and weight (light,
medium, heavy).  See font.


type scaler
See font scaler.


typeahead buffer
See keyboard buffer.


typeface
Design of a set of printed characters, such as
Courier, Helvetica and Times Roman.  The following
chart shows common typeface measurements.

 ══════ ▄▄▄▄▄▄▄ ═▄ ═══════════════════════════════
   │    ██       █       ▄          Ascender area
   │    ██ ──────█▄▄▄▄▄─ ▄ ─▄▄▄▄▄▄ ───────────────
 Point  ██       █▀▀▀▀█  █  █    █     │
  size  ██       █    █  █  █    █   x-height
   │    ███████  █    █  █  ██████     │
   │ ── ▀▀▀▀▀▀▀ ─▀ ── ▀ ─▀ ─█▀▀▀▀▀ ───────BASELINE
   │  │                     █       Descender area
 ═════│════════════════════ ▀ ════════════════════
      │
 ═════│═══════════════════════════════════════════
      │
  Leading (in points, from baseline to baseline)
      │
      │
      │
      │
 ─────────────────────────────────────────BASELINE



typeface family
Group of typefaces that include the normal, bold,
italic and bold-italic variations of the same
design.


typeover mode
In word processing and data entry, a state in which
each character typed on the keyboard replaces the
character at the current cursor location.  Contrast
with insert mode.


typesetter
See phototypesetter and imagesetter.



UAE
(Uninterruptible Application Error)  Application
program abend in Windows 3.0.  See GPF.


UART
(Universal Asynchronous Receiver Transmitter)
Electronic circuit that transmits and receives data
on the serial port.  It converts bytes into serial
bits for transmission, and vice versa, and
generates and strips the start and stop bits
appended to each character.

   8250A and 16450 UART chips provide a one-byte
buffer for storing data.  The 16550 provides two
16-byte buffers and is better for high-speed lines.
See UART overrun.


UART overrun
Condition in which a UART cannot process the
current byte fast enough before the next byte comes
in.


UCR
(Under Color Removal)  Method for reducing amount
of printing ink used.  It substitutes black for
gray color (equal amounts of cyan, magenta and
yellow).  Thus black ink is used instead of the
three CMY inks.  See GCR and dot gain.


UCSD p-System
(Univ. of California at San Diego p-System)
Software development system designed for
portability.  Source programs (BASIC, Pascal, etc.)
are compiled into an interim "p-code," which is
executed by an interpreter in the target machine.


UDP
(User Datagram Protocol)  TCP/IP protocol that
allows an application to send a message to one of
several applications running in the destination
machine.  The application is responsible for
reliable delivery.


UHF
(Ultra High Frequency)  Range of electromagnetic
frequencies from 300MHz to 3GHz.


UI
See UNIX International and user interface.


UIMX
(User Interface Management System for X Window)
Software from Visual Edge Software, Ltd., St.
Laurent, Quebec, that allows a user to design and
modify Open Look and Motif interfaces.


ULSI
(Ultra Large Scale Integration)  More than one
million transistors on a chip.  See SSI, MSI, LSI
and VLSI.


ultrafiche
Pronounced "ultra feesh."  Microfiche that holds up
to 1,000 document pages per 4x6" sheet of film.
Normal microfiche stores around 270 pages.


ultraviolet
Invisible band of radiation at the high-frequency
end of the light spectrum.  It takes about 10
minutes of ultraviolet light to erase an EPROM
chip.


ULTRIX
Digital's version of UNIX for its PDP-11 and VAX
series.


UMA
(Upper Memory Area)  PC memory between 640K and
1024K.  See PC memory map and PC conflicts.


UMB
(Upper Memory Block)  Unused blocks in the UMA
(640K-1M).  A UMB provider is software that can
load drivers and TSRs into this area.


unary
Meaning one; a single entity or operation, or an
expression that requires only one operand.


unbundle
To sell components in a system separately.
Contrast with bundle.


UNC
(Universal Naming Service)  Standard for
identifying servers, printers and other resources
in a network.


unconditional branch
In programming, a GOTO, BRANCH or JUMP instruction
that passes control to a different part of the
program.  Constrast with conditional branch.


undelete
To restore the last delete operation that has taken
place.  There may be more than one level of
undelete, allowing several or all previous
deletions to be restored.  See DOS Undelete.


underflow
(1) Error condition that occurs when the result of
a computation is smaller than the smallest quantity
the computer can store.

(2) Error condition that occurs when an item is
called from an empty stack.


underscan
Area within the normal rectangular viewing are on a
display screen.  Contrast with overscan.


undo
To restore the last editing operation that has
taken place.  For example, if a segment of text has
been deleted or changed, performing an undo will
restore the original text.  Programs may have
several levels of undo, including being able to
reconstruct the original data for all edits
performed in the current session.


Unibus
Bus architecture from Digital that was introduced
in 1970 with its PDP-11 series.  Unibus peripherals
can be connected to a VAX through Unibus
attachments on the VAXs.


unidirectional
Transfer or transmission of data in a channel in
one direction only.


union
In relational database, the joining of two files.
See set theory.


Unisys
(Unisys Corp., Blue Bell, PA)  Computer
manufacturer formed in 1986 as a merger of
Burroughs and Sperry corporations.  This was the
largest computer merger in history.

   Sperry started in 1933 in navigational guidance
and control equipment.  In 1955, it merged with
Remington Rand, creator of the UNIVAC I, and became
Sperry Rand.  Sperry became known for its large-
scale mainframes and for providing communications
and realtime systems to the military and NASA.  In
1971, it absorbed RCA's Spectra 70 computer line
and supported it until it phased out.

   Burroughs started as a maker of calculating
machines and cash registers in 1886.  It was first
involved with computers by supplying memory for the
ENIAC in 1952.  A decade later, it introduced the
B5000 computer, which was known for its advanced
operating system.  Burroughs computers became well
established in the banking and finance industries.

   Today, Unisys still provides versions of
products originating from both companies.  It also
offers UNIX systems, a full line of PCs, and
continues to provide integrated solutions to
vertical markets.


unit record equipment
See tabulating equipment.


UNIVAC I
(UNIVersal Automatic Computer) First commercially-
successful computer, introduced in 1951 by
Remington Rand.  Over 40 systems were sold.  Its
memory was made of mercury-filled acoustic delay
lines that held 1,000 12-digit numbers.  It used
magnetic tapes that stored 1MB of data at a density
of 128 cpi.  In 1952, it predicted Eisenhower's
victory over Stevenson, and UNIVAC became
synonymous with computer (for a while).


UNIX
Multiuser, multitasking operating system from
Novell, Inc., Provo, UT, that runs on computers
from micro to mainframe.  UNIX was developed at
AT&T and is written in C (also developed at AT&T),
which can be compiled into many different machine
languages, causing UNIX to run in a wider variety
of hardware than any other control program.  UNIX
has thus become synonymous with "open systems."

   UNIX is made up of the kernel (fundamental
tasks), the file system (hierarchical directory for
organizing the disk) and the shell (interface that
processes user commands).  The major command-line
interfaces are the Bourne shell, C shell and Korn
shell.  The UNIX vocabulary is exhaustive with over
600 commands that manipulate data and text every
way conceivable.  Many commands are cryptic (see
comparison below), but just as Windows hides the
DOS prompt, graphical user interfaces, such as
OSF/Motif and Open Look, are presenting a
friendlier image to UNIX users.

      Command         UNIX   DOS
    List directory     ls    dir
    Copy a file        cp    copy
    Delete a file      rm    del
    Rename a file      mv    rename
    Display contents   cat   type
    Print a file       lpr   print
    Check disk space   df    chkdsk



                The History of UNIX
UNIX was developed in 1969 by Ken Thompson at AT&T,
who scaled down the sophisticated MULTICS operating
system for the PDP-7.  The named was coined for a
single-user version (un) of MULT "ICS" (ix).  More
work was done by Dennis Ritchie, and, by 1974, UNIX
had matured into a state-of-the-art operating
system primarily on PDPs.  UNIX became very popular
in scientific and academic environments.

   Considerable enhancements were made to UNIX at
the Univ. of California at Berkeley, and versions
of UNIX with the Berkeley extensions became widely
used.  By the late 1970s, commercial versions of
UNIX, such as IS/1 and XENIX, became available.

   In the early 1980s, AT&T began to consolidate
the many UNIX versions into standards which evolved
into System III and eventually System V.  Before
divestiture (1984), AT&T licensed UNIX to
universities and other organizations, but was
prohibited from outright marketing of the product.
After divestiture, it began to market UNIX
aggressively.

   In 1989, UNIX Software Operation (USO) was
formed as an AT&T division.  USO introduced System
V Release 4.0 (SVR4), which incorporated XENIX,
SunOS, Berkeley 4.3BSD and System V into one UNIX
standard.  System V Interface Definition (SVID) was
introduced, which defines UNIX compatibility.  In
1990, USO was turned into UNIX System Laboratories,
Inc., (USL) an AT&T subsidiary.  In 1993, USL was
acquired by Novell.

   Although every major hardware vendor has a
version of UNIX, UNIX International (UI) and the
Open Software Foundation (OSF) each promote
software for universal adoption.  X/Open and POSIX
also govern UNIX standards.

   UNIX has evolved into the archetype environment
for distributed processing and interoperability.
TCP/IP communications protocols are used in the
Internet, the world's largest network.  SMTP
provides e-mail, NFS allows files to be distributed
across the network, NIS provides a "Yellow Pages"
directory, Kerberos provides network security, and
X Windows allows a user to run applications on
other machines in the network simultaneously.


UNIX International
Independent, non-profit industry association funded
by its members to promote and provide future
direction of the UNIX System V operating system.
It has over 130 members and works closely with
X/Open.  Address: 20 Waterview Blvd., Parsippany,
NJ 07054, 201/263-8400.


UnixWare
Operating system for PCs from Univel, Inc. that is
based on UNIX System V Release 4.2.  Univel was
originally a joint venture of Novell and USL;
however, in 1993, Novell acquired USL.

   The UnixWare Personal Edition single user
version provides client access to NetWare and runs
UNIX, DOS and Windows applications.  DR DOS is also
included.  The Application Server version
integrates NetWare and supports X Window, TCP/IP
and NFS.


unload
To remove a program from memory or take a tape or
disk out of its drive.


UNMA
(Unified Network Management Archicture)  Network
strategy from AT&T for managing multi-vendor
networks.


unmark
(1) In word processing, to deselect a block of
text, which usually removes its highlight.

(2) To deselect an item that has been tagged for a
particular purpose.


unpack
See pack.


unzip
To decompress a file with PKUNZIP.  See PK
software.


up
Refers to a device that is working.


UPC
(Universal Product Code)  Standard bar code printed
on retail merchandise.  It contains the vendor's
identification number and the product number, which
is read by passing the bar code over a scanner.


update
To change data in a file or database.  The terms
update and edit are often used synonymously.


uplink
Communications channel from an earth station to a
satellite.  Contrast with downlink.


upload
See download.


upper CASE
See front-end CASE.


UPS
(Uninterruptible Power Supply)  Backup power used
when the electrical power fails or drops to an
unacceptable voltage level.  Small UPS systems
provide battery power for a few minutes; enough to
power down the computer in an orderly manner.
Sophisticated systems are tied to electrical
generators that can provide power for days.

   A UPS system can be connected to a file server
so that, in the event of a problem, all network
users can be alerted to save files and shut down
immediately.

   An online UPS provides a constant source of
electrical power from the battery, while the
batteries are being recharged from AC power.  An
offline UPS, also known as a standby power system
(SPS), switches to battery within a few
milliseconds after detecting a power failure.

   A surge protector filters out surges and spikes,
and a voltage regulator maintains uniform voltage
during a brownout, but a UPS keeps a computer
running when there is no electrical power.  UPS
systems typically provide surge suppression and may
also provide voltage regulation.


uptime
Time during which a system is working without
failure.  Contrast with downtime.


upward compatible
Also called forward compatible.  Refers to hardware
or software that is compatible with succeeding
versions.  Contrast with downward compatible.


used computers
See computer exchange.


USENET
(USEr NETwork)  Public access network on the
Internet that provides user news and e-mail.  It is
a giant, dispersed bulletin board that is
maintained by volunteers willing to provide news
and mail feeds to other nodes.  It began in 1979 as
a bulletin board between two universities in North
Carolina.


user
Any individual who interacts with the computer at
an application level.  Programmers, operators and
other technical personnel are not considered users
when working in a professional capacity on the
computer.


user area
Reserved part of a disk or memory for user data.


user defined
Any format, layout, structure or language that is
developed by the user.


user friendly
System that is easy to learn and easy to use.  This
term has been so abused that many vendors are
reluctant to use it.


user group
Organization of users of a particular hardware or
software product.  Members share experiences and
ideas to improve their understanding and use of a
particular product.  User groups are often
responsible for influencing vendors to change or
enhance their products.


user interface
Combination of menus, screen design, keyboard
commands, command language and help screens, which
create the way a user interacts with a computer.
Mice, touch screens and other input hardware is
also included.  A well-designed user interface is
vital to the success of a software package.  In
time, interactive video, voice recognition and
natural language understanding will be included.


USL
(UNIX System Laboratories, Inc.)  AT&T subsidiary
formed in 1990, responsible for developing and
marketing UNIX.  In 1993, USL was acquired by
Novell, Inc., Provo, UT.


USO
(UNIX Software Operation)  AT&T's UNIX division
before it turned into USL.


USRT
(Universal Synchronous Receiver Transmitter)
Electronic circuit that transmits and receives data
on the serial port.  It converts bytes into serial
bits for transmission, and vice versa, and
generates the necessary signals for synchronous
transmission.


utility program
Program that supports using the computer.  Utility
programs, or "utilities," provide file management
capabilities, such as sorting, copying, comparing,
listing and searching, as well as diagnostic and
measurement routines that check the health and
performance of the system.


UTP
See twisted pair.


UTP Ethernet
(1) Same as twisted pair Ethernet.  See Ethernet.

(2) May refer to pre-IEEE standard twisted pair
Ethernet networks.


UTS
(Universal Timesharing System)  Amdahl's version of
UNIX System V.  Release 4.0 is POSIX compliant.


UUCP
(UNIX to UNIX CoPy)  UNIX utility that copies a
file from one UNIX system to another.  It is
commonly used as a mail transfer.


UUNET
(UNIX to UNIX NETwork)  Information and
communications network from UUNET Technologies,
Inc., Falls Church, VA, that provides news, mail
service and an extensive library of UNIX software.
Custom networking for companies is available
through its AlterNet service.



V Series
Series of of small to medium-scale mainframes from
Unisys that were the Burroughs B2500 and B3500
product lines, originally introduced in 1966.


V.110
CCITT standard (1984) that specifies how data
terminal equipment (DTE) with asynchronous or
synchronous serial interfaces can be supported on
an ISDN network.  It uses rate adaption, which
involves a bit-by-bit alignment between the DTE and
the ISDN B channel.


V.120
CCITT standard (1988) that specifies how DTEs with
asynchronous or synchronous serial interfaces can
be supported on an ISDN network using a protocol
(similar to LAP-D) to encapsulate the data to be
transmitted.  It includes the capability of using
statistical multiplexing to share a B channel
connection between multiple DTEs.


V.17
CCITT fax standard (1991) that uses TCM modulation
at 12000 and 14400 bps for Group 3.  It adds TCM to
the V.29 standard at 7200 and 9600 bps to allow
transmission over noisier lines.  It also defines
special functions (echo protection, turn-off
sequences, etc.) for half-duplex operation.
Modulation use is a half-duplex version of V.32bis.


V.21
CCITT standard (1964) for asynchronous 0-300 bps
full-duplex modems for use on dial-up lines.  It
uses FSK modulation.


V.22
CCITT standard (1980) for asynchronous and
synchronous 600 and 1200 bps full-duplex modems for
use on dial-up lines.  It uses DPSK modulation.


V.22bis
CCITT standard (1984) for asynchronous and
synchronous 2400 bps full-duplex modems for use on
dial-up lines and two-wire leased lines, with
fallback to V.22 1200 bps operation.  It uses QAM
modulation.


V.23
CCITT standard (1964) for asynchronous and
synchronous 0-600 and 0-1200 bps half-duplex modems
for use on dial-up lines.  It has an optional
split-speed transmission method with a reverse
channel of 0-75 bps (1200/75, 75/1200). It uses FSK
modulation.


V.24
CCITT standard (1964) that defines the functions of
all circuits for the RS-232 interface.  It does not
describe the connectors or pin assignments; those
are defined in ISO 2110.  In the U.S., EIA-232
incorporates the control signal definition of V.24,
the electrical characteristics of V.28 and the
connector and pin assignments defined in ISO 2110.


V.25
CCITT standard (1968) for automatic calling and/or
answering equipment on dial-up lines.  It uses
parallel circuits and is similar in function to RS-
366 and Bell 801 autodialers used in the U.S.  The
answer tone defined in V.25 is the first thing
heard when calling a modem.  It serves a dual
function of identifying the answering equipment as
being a modem and also disabling the echo
suppression and echo cancellation equipment in the
network so that a full-duplex modem will operate
properly.


V.25bis
CCITT standard (1968) for automatic calling and/or
answering equipment on dial-up lines.  It has three
modes: asynchronous (rarely used), character-
oriented synchronous (bisync) and bit-oriented
synchronous (HDLC/SDLC).  Both synchronous versions
are used in IBM AS/400 and other small-to-medium
sized computers that do automatic dialing for
remote job entry.

   Due to the popularity of the Hayes AT Command
Set, V.25bis is not used as widely in North
America.  It does not perform modem configuration
functions and is limited to dialing and answering
calls.


V.26
CCITT standard (1968) for synchronous 2400 bps
full-duplex modems for use on four-wire leased
lines.  It uses DPSK modulation and includes an
optional 75 bps back channel.


V.26bis
CCITT standard (1972) for synchronous 1200 and 2400
bps full-duplex modems for use on dial-up lines.
It uses DPSK modulation and includes an optional 75
bps back channel.


V.26ter
CCITT standard (1984) for asynchronous and
synchronous 2400 bps full-duplex modems using DPSK
modulation over dial-up and two-wire leased lines.
It includes a 1200 bps fallback speed and uses echo
cancellation, permitting a full-duplex modem to
send and receive on the same frequency.


V.27
CCITT standard (1972) for synchronous 4800 bps
full-duplex modems for use on four-wire leased
lines.  It uses DPSK modulation.


V.27bis
CCITT standard (1976) for synchronous 2400 and 4800
bps full-duplex modems using DPSK modulation for
use on four-wire leased lines.  The primary
difference between V.27 and V.27bis is the addition
of an automatic adaptive equalizer.


V.27ter
CCITT standard (1976) for synchronous 2400 and 4800
bps half-duplex modems using DPSK modulation on
dial-up lines.  It includes an optional 75 bps back
channel.  V.27ter is used in Group 3 fax
transmission without the back channel.


V.28
CCITT standard (1972) that defines the functions of
all circuits for the RS-232 interface.  In the
U.S., EIA-232 incorporates the electrical signal
definitions of V.28, the control signals of V.25
and the connector and pin assignments defined in
ISO 2110.


V.29
CCITT standard (1976) for synchronous 4800, 7200
and 9600 bps full-duplex modems using QAM
modulation on four-wire leased lines.  It has been
adapted for Group 3 fax transmission over dial-up
lines at 9600 and 7200 bps.


V.32
CCITT standard (1984) for asynchronous and
synchronous 4800 and 9600 bps full-duplex modems
using TCM modulation over dial-up or two-wire
leased lines.  TCM encoding may be optionally
added.  V.32 uses echo cancellation to achieve
full-duplex transmission.


V.32bis
CCITT standard (1991) for asynchronous and
synchronous 4800, 7200, 9600, 12000 and 14400 bps
full-duplex modems using TCM and echo cancellation.
Supports rate renegotiation, which allows modems to
change speeds as required.


V.33
CCITT standard (1988) for synchronous 12000 and
14400 bps full-duplex modems for use on four-wire
leased lines using QAM modulation.  It includes an
optional time-division multiplexor for sharing the
transmission line among multiple terminals.


V.35
CCITT standard (1968) for group band modems that
combine the bandwidth of several telephone circuits
to achieve high data rates.  V.35 has become known
as a high-speed RS-232 interface rather than a type
of modem.  The large, rectangular V.35 connector
was never specified in V.35, but has become a de
facto standard for a high-speed interface.


V.42
CCITT standard (1989) for modem error checking that
uses LAP-M as the primary protocol and provides MNP
Classes 2 through 4 as an alternative protocol for
compatibility.


V.42bis
CCITT standard (1989) for modem data compression.
It uses the British Telecom Lempel Ziv technique to
achieve up to a 4:1 ratio.  V.42bis implies the
V.42 error checking protocol.


V.54
CCITT standard (1976) for various loopback tests
that can be incorporated into modems for testing
the telephone circuit and isolating transmission
problems.  Operating modes include local and remote
digital loopback and local and remote analog
loopback.


V.56
CCITT standard (1972) for a method of testing
modems to compare their performance.  Newer
procedures are currently under study.


V.fast
Future CCITT standard for 19200 bps modems to be
approved in 1993.


V20, V30
8088- and 8086-compatible processors from NEC.
Versions running at 16MHz were introduced in 1991.


VAC
(Volts Alternating Current)  See volt and AC.


vacuum tube
Electronic device that controls the flow of
electrons in a vacuum, used as a switch, amplifier
or display screen.  Used as on/off switches, they
allowed the first computers to perform digital
computations.  Today, it is primarily the CRT in
monitors and TVs.


VAD
(Value Added Dealer)  Same as VAR (value added
reseller).


validity checking
Routines in a data entry program that tests the
input for correct and reasonable conditions, such
as numbers falling within a range and correct
spelling, if possible.  See check digit.


value
(1) Content of a field or variable.  It can refer
to alphabetic as well as numeric data.  For
example, in the expression, state = "PA", PA is a
value.

(2) In spreadsheets, the numeric data within the
cell.


value-added network
Communications network that provides services
beyond normal transmission, such as automatic error
detection and correction, protocol conversion and
message storing and forwarding.  Telenet and Tymnet
are examples of value-added networks.


VAN
See value-added network.


VAP
(Value Added Process)  Software that enhances or
provides additional server functions in a NetWare
286 server.  Support for different kinds of
workstations, database engines, fax and print
servers are examples.  The NetWare 386 counterpart
is the NLM.


vaporware
Software that has been advertised but not
delivered.


VAR
(Value Added Reseller)  Organization that adds
value to a system and resells it.  For example, it
could purchase a CPU and peripherals from different
vendors and graphics software from another and
package it together as a specialized CAD system.
See OEM.


variable
In programming, a structure that holds data and is
uniquely named by the programmer.  It holds the
data assigned to it until a new value is assigned
or the program is finished.

   Variables are used to hold control values.  For
example, the C statement for (x=0; x<5; x++)
performs the instructions following it five times.
X is a variable set to zero (x=0), incremented
(x++) and tested to reach five (x<5).  Variables
also hold data temporarily that is being processed.

   Variables are usually assigned with an equal
sign; for example, counter = 1, places a 1 in
COUNTER.  Numeric data is unquoted: counter = 1,
character data requires quotes: product="abc4344".
In some languages, the type of data must be
declared before it is assigned; for example, in C,
the statement, int counter; creates a variable that
will only hold whole numbers.

   A local variable is one that is referenced only
within the subprogram, function or procedure it was
defined in.  A global variable can be used by the
entire program.


variable length field
Record structure that holds fields of varying
lengths.  For example, PAT SMITH takes nine bytes
and GEORGINA WILSON BARTHOLOMEW takes 27.  A couple
of bytes of control information would also be
added.  If fixed length fields were used, 27 bytes
would have to be reserved for both names.

   There's more programming with variable length
fields, because every record has to be separated
into fixed length fields after it is brought into
memory.  Conversely, each record has to be coded
into the variable length format before it is
written to disk.

   The same storage savings can be achieved by
compressing data stored on disk and decompressing
it when retrieved.  All blank spaces in fixed
length fields would be filtered out.  For
acceptable performance, this method must be well
integrated into the operating system.  See realtime
compression.


variable length record
Data record that contains one or more variable
length fields.


varname
(VARiable NAME)  Abbreviation for specifying the
name of a variable.


VAX
(Virtual Address eXtension)  Family of 32-bit
computers from Digital introduced in 1977 with the
VAX-11/780 model.  VAXes range from desktop
personal computers to mainframes all running the
same VMS operating system.  Large models can be
clustered in a multiprocessing environment to serve
thousands of users.  Software compatibility between
models caused the VAX family to achieve outstanding
success during the 1980s.  VAXes also provide PDP
emulation.


VAXcluster
Group of VAXs coupled together in a multiprocessing
environment.


VAXELN
Realtime operating environment for VAXs from
Digital.  It runs under VMS and provides
application development in Pascal and other
languages.  Resulting programs are downloaded into
the target systems.


VAXmate
Partially IBM-compatible PC from Digital introduced
in 1986, which has been superseded by the
DECstation 200 and 300 series in 1989.


VAXstation
Single-user VAX computer that runs under VMS
introduced in 1988.


VBE
(VGA BIOS Extension)  VESA VGA standard for
interrogating the capabilities of a graphics
adapter.  It allows the software developer to write
a universal driver for all VBE-compliant VGA cards.
See PC display modes for VBE specs.


Vbox
(video box)  Hardware interface from Sony that
attaches up to seven VCRs, videodiscs and
camcorders to the serial port.  Devices must have
the Control-L (LANC) connector.


VCPI
(Virtual Control Program Interface)  DOS extender
specification for 386s and up that allows DOS
extended programs to run with Real Mode programs.
VCPI allows for example, Paradox 386, a DOS-
extended program, to run cooperatively with
DESQview, which runs multiple Real Mode programs in
Virtual 8086 mode.  Developed by Quarterdeck, Phar
Lap Software, et al, it was the first DOS extender
standard.  See DPMI.


VCR
(Video Cassette Recorder)  Videotape recording and
playback machine that comes in the following
formats:

   One inch tape is used for mastering video
recordings.  Sony Umatic 3/4" tape was widely used
in commercial training.  VHS 1/2" tape, first used
only in the home, has mostly replaced the 3/4"
tape.  Sony's 1/2" Beta tape, the first home VCR
format, is defunct.

   Although VCRs are analog recording machines,
adapters allow them to store digital data for
computer backup.


VDE
(1) (Video Display Editor)  WordStar and
WordPerfect-compatible shareware word processor
written by Eric Meyer.

(2) (Verband Deutscher Elektrotechniker)  German
counterpart of the U.S. Underwriters Lab.


Vdeck
(video deck)  Frame-accurate, Super 8mm tape drive
from Sony for serial-port connection to a personal
computer.  It contains an internal Vbox, is
controlled by the ViSCA language and has no
external play buttons.


VDI
(Virtual Device Interface)  ANSI standard format
for creating device drivers.  For example, if a
vendor sells a screen display and adapter board
with a proprietary resolution, and also includes a
driver written in the VDI format, software packages
that support VDI will be able to use the new
monitor.

   The VDI standard has been incorporated into the
CGI standard.  When CGI is officially endorsed by
ANSI, it may supersede VDI.


Vdisk
See DOS RAM disks.


VDM
See CGM.


VDS
(Virtual DMA Services)  Programming interface that
lets bus mastering devices cooperatively manage DMA
channels.


VDT
(Video Display Terminal)  Terminal with a keyboard
and display screen.


VDT radiation
Electromagnetic radiation emitted from a computer
display screen.  Exhaustive testing so far seems
inconclusive, but vendors recommend keeping the
face at least 18 to 20 inches from the screen.


VDU
(Video Display Unit)  Same as VDT.


vector
(1) In computer graphics, a line designated by its
end points (x-y or x-y-z coordinates).  When a
circle is drawn, it is made up of many small
vectors.

(2) In matrix algebra, a one-row or one-column
matrix.


vector display
Display terminal that draws vectors on the screen.
Contrast with raster display.


vector font
Scalable font made of vectors (point-to-point line
segments).  It is easily scaled as are all vector-
based images, but lacks the hints and
mathematically-defined curves of outline fonts,
such as Adobe Type 1 and TrueType.


vector graphics
In computer graphics, a technique for representing
a picture as points, lines and other geometric
entities.  See graphics.  Contrast with raster
graphics.


vector processor
Computer with built-in instructions that perform
multiple calculations on vectors (one-dimensional
arrays) simultaneously.  It is used to solve the
same or similar problems as an array processor;
however, a vector processor passes a vector to a
functional unit, whereas an array processor passes
each element of a vector to a different arithmetic
unit.  See pipeline processing and array processor.


Vectra
PC series from HP.  Vectras are noted for their
ruggedness and reliability.


vendors
There are thousands of companies comprising the
computer industry.  The following hardware,
software, consulting and service vendors represent
all the majors and some of the more widely known.
Many are individual entries in the Glossary.  See
software vendors and Fortune 500.

ACER AMERICA CORP., San Jose, CA, 800/SEE-ACER
  Complete line of PCs under Acer and Acros brands.


ADOBE SYSTEMS, INC., Mtn. View, CA, 800/833-6687
  PostScript language and Type 1 and Type 3 font
  technologies.


ADVANCED LOGIC RESEARCH, Irvine, CA, 800/257-1230
  Complete line of PCs.  "ALR" pioneered upgradable
  CPU architecture.


ADVANCED MICRO DEVICES, Sunnyvale, CA, 800/2929-AMD
  Intel-compatible CPU chips.


ALDUS CORP., Seattle, WA, 800/332-5387
  Pioneered desktop publishing with PageMaker,
  originally on the Mac.


AMDAHL CORP., Sunnyvale, CA, 800/538-8460
  First successful IBM-compatible mainframe
  manufacturer.


AMERICAN MEGATRENDS, INC., Norcross, GA
  800/828-9264  "AMI" PC motherboards, ROM BIOS.


APPLE COMPUTER, Cupertino, CA, 800/776-2333
  Macintosh series and Apple IIe. Largest non-IBM
  compatible personal computer manufacturer.
  Pioneered the microcomputer revolution.


ARTISTOFT, INC., Tucson, AZ, 800/TINYRAM
  Lantastic network operating system. Major
  success in peer-to-peer networking.


AST RESEARCH, INC., Irvine, CA, 714/727-4141
  Complete line of PCs. Known for high-end.


ATARI, INC., Sunnyvale, CA, 408/745-2000
  ST personal computer line.  Founded in 1972
  by Nolan Bushnell.  Known for its video games.


AUTODESK, INC., Sausalito, CA, 800/964-6432
   AutoCAD software, one of the first major
   CAD programs for personal computers.


BOLT, BARANEK & NEWMAN, Cambridge, MA, 800/422-2359
  Consulting, software, research.  "BBN"
  has been at the forefront of major projects.


BORLAND INT'L. INC., Scotts Valley, CA
  800/331-0877  Programming languages, dBASE,
  Paradox, Quattro Pro, Sidekick.  First to
  commercialize Pascal (Turbo Pascal).


BULL HN, Billerica, MA, 800/999-2181
  Mini and mainframe manufacturer originally
  started as Honeywell's computer division, later
  merged with Groupe Bull of France and NEC of
  Japan.


CLARIS CORP., Santa Clara, CA, 800/325-2747
  Software subsidiary of Apple Computer
  MacDraw, MacWrite, FileMaker Pro, HyperCard, etc.


COMMODORE BUSINESS MACHINES, Inc., West Chester, PA
  800/66-AMIGA  Amiga personal computer line.
  Founded in 1977 and introduced the PET, one of
  the first personal computers.


COMPAQ COMPUTER CORP., Houston, TX, 800/345-1518
  Complete line of PCs.  First to successfuly clone
  IBM PC. First portable PC. First American
  company to reach $111 million sales in a year.


COMPUSERVE, INC., Columbus, OH, 800/848-8990
  Widely-used online information service.
  Provides many technical forums for users and
  developers.


COMPUTER ASSOCIATES INT'L, INC., Islindia, NY
  800/CALL-CAI  Software from micro to mainframe.
  Founded in 1976 by Charles Wang.


CONNER PERIPHERALS, INC., San Jose, CA
  408/456-4500  Manufacturer of disk drives.


CONTROL DATA SYSTEMS, INC., Minneapolis, MN
  612/893-4120  Workstations to supercomputers. One
  of the first computer companies. Founded in 1957
  under Bill Norris.


CRAY RESEARCH, INC., Egan, MN, 800/284-2729
  Supercomputers originally designed by Seymour
  Cray, leading architect at Control Data.


D&B SOFTWARE, Atlanta, GA, 800/234-3867
  1990 merger of MSA and McCormack & Dodge
  mainframe software companies. Under leadership of
  John Imlay, CEO of MSA.


DATA GENERAL CORP., Westboro, MA, 800/328-2436
  One of the pioneers in minicomputers. Founded
  in 1968 by Edson De Castro.


DELL COMPUTER CORP., Austin, TX, 800/289-3355
  Complete line of mail-order PCs.  Originally
  "PCs Limited" brand. First to legitimize mail-
  order PCs with quality telephone support.


DIALOG INFORMATION SERVICES, Palo Alto, CA
  800/334-2564  Online service. Largest collection
  of databases in the world.


DIGITAL EQUIPMENT CORP., Maynard, MA, 800/344-4825
  "DEC" pioneered the minicomputer industry under
  leadership of Ken Olsen who retired in 1992.
  Complete line of PCs, minis and mainframes.
  Founded in 1957.


DIGITAL RESEARCH, INC., Monterey, CA, 800/274-4DRI
  Creator of CP/M, first common operating system
  for personal computers. Later DOS-compatible DR
  DOS. Founded in 1976 by Gary Kildall. Acquired
  by Novell in 1991.


ELECTRONIC DATA SYSTEMS CORP., Maryland Hgts, MO
  314/344-5900  Pioneered facilities management.
  Founded in 1962 by Ross Perot. Acquired by GM.


EVEREX SYSTEMS, INC., Fremont, CA, 800/356-8486
  Complete line of PCs, high-end servers.


GATEWAY 2000, N. Sioux City, SD, 800/523-2000
  Complete line of mail-order PCs. Became very
  successful in early 1990s.


GENIE, Rockville, MD, 800/638-9636
  Online service.  Wide variety of databases.


HAYES MICROCOMPUTER PRODUCTS, INC., Atlanta, GA
  404/840-9200  Pioneered the personal computer
  modem. Hayes AT command set is de facto standard
  modem language.


HEWLETT-PACKARD CO., Palo Alto, CA, 800/752-0900
  "HP" was one of the first minicomputer companies.
  Complete line of PCs, workstations and minis plus
  10,000 electronic products. Founded in 1939 by
  Wm. Hewlett & David Packard.


HITACHI AMERICA (various locations in U.S.)
  Monitors, CD ROM players, computers.


INTERNATIONAL BUSINESS MACHINES, Armonk, NY
  800/426-2468  "IBM" is the world's largest
  computer company. Complete line of mainframes,
  minis and PCs. Founded in 1911.  Renamed IBM in
  1924 under leadership of T. J. Watson, Sr.


INTEL CORP., Santa Clara, CA, 800/538-3373
  Maker of x86 CPU chips used in PCs.


LOTUS DEVELOPMENT CORP., Cambridge, MA
  800/343-5414  First spreadsheet (Lotus 1-2-3)
  for the PC, Ami Pro, Lotus Notes, etc. Founded in
  1981 by Mitch Kapor.


MAXTOR CORP., San Jose, CA, 800/262-9867
  Disk drives manufacturer.


MICRONICS COMPUTERS, INC., Fremont, CA
  510/651-2300  PC motherboards, electronics,
  laptops.


MICROSOFT CORP., Redmond, WA, 800/227-4679
  DOS, Windows, programming langauges and
  applications.  Founded in 1975 by Bill Gates and
  Paul Allen.


MOTOROLA, INC., Schaumburg, IL, 708/576-5000
  Maker of 68xxx CPU chips used in Macintoshes
  and various workstations.


NCR CORP., Dayton, OH, 800/CALL-NCR
  One of the first computer companies. Leading
  cash register company dating back to 1884 under
  John Henry Patterson. Acquired by AT&T in 1991.


NEC TECHNOLOGIES, INC., Boxborough, MA
  800/343-4418  Pioneered multifrequency monitor
  with its MultiSync line.


NEXT COMPUTER, INC., Redwood City, CA, 800/848-NEXT
  Family of UNIX-based workstations and the
  NeXTstep operating environment.  Founded by Steve
  Jobs, co-founder of Apple.


NORTHGATE COMPUTER SYSTEMS, INC., Minneapolis, MN
  800/548-1993  Complete line of mail-order PCs.
  Known for its Omnikey keyboards. Founded in 1987.


NOVELL, INC., Provo, UT, 800/453-1267
  NetWare operating systems. Most widely-used
  networking software. Founded in 1983 by Ray
  Noorda.


OPEN SOFTWARE FOUNDATION, Cambridge, MA
  617/621-8700  UNIX-based open systems
  software for distributed computing.


ORACLE CORP., Redwood Shores, CA, 800/ORACLE-1
  Oracle database system runs on more platforms
  than any other DBMS. Founded in 1977.


PACKARD BELL, INC., Chatsworth, CA, 818/886-4600
  Complete line of PCs and peripherals. Founded
  in 1986.


PHOENIX TECHNOLOGIES, INC., Norwood, MA
  800/344-7200  PC ROM BIOS chips, electronics.


PRODIGY, White Plains, NY, 800/776-3449
  Online service for home and office computing.
  Shopping, news, databases.


QUARK, INC., Denver, CO., 800/788-7835
  QuarkXpress desktop publishing for
  Mac and Windows.


SANTA CRUZ OPERATION (THE), Santa Cruz, CA
  800/SCO-9694  UNIX and XENIX operating systems.


SEAGATE TECHNOLOGY, INC., Scotts Valley, CA
  800/468-3472  Largest independent
  manufacturer of disk drives.


SOFTWARE PUBLISHING CORP., Santa Clara, CA
  800/447-7991  Harvard Graphics, Superbase
  and other applications.


SONY CORP. OF AMERICA, San Jose, CA, 800/352-7669
  Monitors, CR ROM players, disk drives and
  diskettes.


SUN MICROSYSTEMS, INC., Mtn. View, CA, 800/821-4643
  Complete line of workstations using Sun's SPARC
  CPU. Largest supplier of UNIX-based systems.
  Founded in 1982 by Bill Joy.


SYMANTEC CORP., Cupertino, CA, 800/441-7234
  Q&A, Norton Utilities and other applications.


TANDEM COMPUTERS, INC., Cupertino, CA
  800/538-3107  First to make fault-tolerant
  computer systems. Founded in 1974 by James
  Treybig.


TANDON CORP., Moorpark, CA, 800/800-8850
  Complete line of PCs, peripherals.


TANDY CORP., Ft. Worth, TX, 817/390-3011
  Complete line of PCs and electronics through
  Radio Shack chain originally acquired in 1963.
  TRS-80 was one of the first personal computers.


TEXAS INSTRUMENTS, INC., Dallas, TX, 800/527-3500
  Chips, electronics, computer systems. Founded in
  1930 as Geophysical Service. Renamed TI in 1951.


TOSHIBA AMERICA INFO. SYSTEMS, INC., Irvine, CA
  800/334-3445  Complete line of high-end, quality
  portable PCs. Pioneered laptop revolution.


UNISYS CORP., Blue Bell, PA, 800-448-1424
  1986 merger of Sperry and Burroughs, two of the
  oldest computer companies. Complete line of PCs,
  minis and mainframes.


UNIX SYSTEMS LABORATORIES, INC., Summit, NJ
  800/828-8649  AT&T subsidiary responsible for
  developing and marketing UNIX System V.


WANG LABORATORIES, INC., Lowell, MA, 800/835-9264
  Early minicomputer company and leader in WP in
  the 1970s. Founded by Dr. An Wang in 1951.


WESTERN DIGITAL CORP., Irvine, CA, 800/832-4778
  Manufacturer of disk drives, controllers and
  electronics. "Paradise" display boards.


WORDPERFECT CORP., Orem, UT, 800/321-5906
  WordPerfect is the most widely-used word
  processing software. Founded in 1979.


WORDSTAR INT'L. INC., Novato, CA, 800/227-5609
  WordStar was the first full-featured word
  processor for personal computers. Founded in
  1978.


XEROX CORP., Palo Alto, CA, 800/626-6775
  Pioneered the graphical user interface at its
  PARC (Palo Alto Research Ctr.) on the Alto
  computer. Introduced concept on the Star
  workstation in 1981. Sells personal computer
  applications such as Ventura Publisher.


ZENITH DATA SYSTEMS CORP., Buffalo Grove, IL
  800/227-3360  Complete line of PCs, monitors.
  Pioneered laptop revolution.



Venn diagram
Graphic technique for visualizing set theory
concepts using overlapping circles and shading to
indicate intersection, union and complement.


Ventura Publisher
Desktop publishing program for PCs and the
Macintosh from Ventura Software, Inc. (a Xerox
company), that provides full-scale pagination for
large documents.  It is designed to import data
created in other graphics and word processing
programs, although it does have rudimentary text
and graphics capabilities.

   Ventura is available for DOS, Windows, OS/2 and
the Mac.  The DOS version comes with a runtime
version of the GEM interface.


verify
In data entry operations, to compare the keystrokes
of a second operator with the files created by the
first operator.


VersaCAD
Family of CAD systems for PCs and the Macintosh
from Computervision, Bedford, MA, that features 2-D
geometric and construction drafting and 3-D
modeling with 16 viewports.  It features complete
programmability and universal CAD communications.
The Mac version includes CAD-oriented HyperCard
stacks.


version control
Management of source code in a large software
project.  Version-control software provides a
database that keeps track of the revisions made to
a program by all the programmers involved in it.


version number
Identification of a release of software.  The
difference between Version 2.2 and 2.3 can be night
and day, since new releases not only add features,
but often correct bugs.  What's been driving you
crazy may have been fixed!

   Numbers, such as 3.1a or 3.11, often indicate a
follow-up release only to fix a bug in the previous
version, whereas 3.1 and 3.2 usually mean routine
enhancements.  Version "1.0" drives terror into the
hearts of experienced users.  The program has just
been released, and bugs are still to be uncovered.


vertical bandwidth
See vertical scan frequency.


vertical recording
Magnetic recording method that records the bits
vertically instead of horizontally, taking up less
space and providing greater storage capacity.  The
vertical recording method uses a specialized
material for the construction of the disk.


vertical redundancy checking
See VRC.


vertical refresh
See vertical scan frequency.


vertical resolution
Number of lines (rows in a matrix).  Contrast with
horizontal resolution.


vertical scan frequency
Number of times an entire display screen is
refreshed, or redrawn, per second.  Measured in
Hertz, display systems range from 45 to over 100Hz.
For example, VGA in the U.S. is generally 56 to
60Hz; in Europe, 70Hz and above.  TV is refreshed
60 half-frames/sec (interlaced) resulting in 30
full frames/sec.  Contrast with horizontal scan
frequency.


VESA
(Video Electronics Standards Assn.)  Organization
of major PC graphics vendors dedicated to improving
video and multimedia standards.  It has defined a
local bus standard that is becoming very popular
(see VL-bus).  Address: 2150 N. 1st St., Suite 360,
San Jose, CA 95131, 408/435-0333.


vesicular film
Film used to make copies of microforms.  It
contains its own developer and creates a pink
negative or positive copy when exposed to a
negative master through ultraviolet light.


VGA
(Video Graphics Array)  IBM video display standard
built into most PS/1 and PS/2 models that provides
medium-resolution text and graphics.  It has become
the minimum standard for all PCs.

   VGA supports previous CGA and EGA modes and
requires an analog monitor.  Its highest-resolution
mode is 640x480 with 16 colors, but VESA and third
parties have boosted colors and resolution.  See PC
display modes.


VGA HC
(VGA HiColor)  VGA board that provides 32K or 64K
colors using Tseng Labs' ET4000 chip or equivalent.


VGA pass through
Feature of a high-resolution display adapter that
couples internally with a VGA display adapter and
passes its signals through to the monitor.


VHD
(Very High Density)  Floppy disk technologies that
place 20MB and more of data on a 3.5" disk.  See
Floptical.


VHF
(Very High Frequency)  Range of electromagnetic
frequencies from 30MHz to 300MHz.


VHS
VCR format introduced by JVC in 1976 (to compete
with Sony's Beta format) that has become the
standard for home and industry.  SVHS (Super VHS)
is a subsequent format that improves resolution.


VHSIC
(Very High Speed Integrated Circuit)  Pronounced
"vizik."  Ultra-high-speed chips employing LSI and
VLSI technologies.


vi
(Visual Interface)  UNIX full-screen text editor
that can be run from a terminal or the system
console.  It is a fast, programmer-oriented
utility.


video
Audio/visual playback and recording technology used
in TV.  It also refers to computer screens and
terminals.  However, there is only one TV/video
standard in the U.S., but there are dozens of
computer/video display standards.


video adapter
Same as video display board.


video bandwidth
Maximum display resolution, measured in MHz, and
calculated by horizontal x vertical resolution x
refreshes/sec.  For example, 800x600x60 = 28.8MHz.
TV studio recording is limited to 5MHz; TV
broadcasting is limited to 3.58Mhz.


video board
Same as video display board.


video camera
Camera that takes continuous pictures and generates
a signal for display or recording.  It captures
images by breaking down the image into a series of
lines.  The U.S. and Canadian standard (NTSC) is
525 scan lines.  Each line is scanned one at a
time, and the continuously varying intensities of
red, green and blue light across the line are
filtered out and converted into a variable signal.
Most video cameras are analog, but digital video
cameras are also available.  See digital camera.


video card
Same as video display board.


video codec
Circuit that converts NTSC video into digital code
and vice versa.  It incorporates a compression
technique to reduce the data and may or may not
provide full-motion video.


video conferencing
See teleconferencing.


video controller
(1) Device that controls some kind of video
function.

(2) Same as video display board.


video digitizer
Same as frame grabber.


video display board
Expansion board that plugs into a personal computer
and generates the text and graphics images for the
monitor's screen.  Also called a display adapter,
graphics adapter, graphics card, video adapter,
video card or video controller, it determines the
resolution and number of colors on screen.

   It converts the characters or graphic patterns
(bitmaps) within a reserved segment of the
computer's memory into signals used to refresh the
display screen.  In digital systems (CGA, EGA,
etc.), the display board generates digital signals
for the monitor.  The monitor then does the
conversion from digital to analog.  In analog
systems (VGA, Macintosh, etc.), the display board
creates the analog signals sent to the monitor.

   The monitor must be capable of handling the
frequency range of the display board (number of
lines per second).  Multisync monitors accept a
range of frequencies and work with several display
standards.


video display card
Same as video display board.


video display terminal/unit
Same as video terminal.


video editor
Dedicated computer that controls two or more
videotape machines.  It keeps track of frame
numbers in its own database and switches the
recording machine from playback to record.  The
video editor does accept video signals; only SMPTE
time codes provided on professional tape formats.


Video for Windows
Software from Microsoft that supplements Windows
3.1 multimedia.  It supports the AVI format and
lets you capture, edit and play full-motion video.
It includes Media Player 2.0.


video graphics board
Video display board that generates text and
graphics and accepts video from a camera or VCR.
Truevision's Targa board and Vision Technologies
Vision board are examples.

   The terms video graphics board and video display
board sound alike, but video display boards
(display adapters) do not handle NTSC video.


video overlay card
Graphics controller that allows NTSC video and
computer images to be mixed.


video RAM
Specially-designed memory circuits on a video
display board that are used to hold the image that
appears on the video screen.  Often uses dual-
ported RAM, which allows simultaneous reads and
writes.


video teleconferencing
See teleconferencing.


video terminal
Data entry device that uses a keyboard for input
and a display screen for output.  Although the
display screen resembles a TV, it usually does not
accept TV/video signals.


video window
Display of NTSC video (TV) in an independent window
on a computer screen.


videodisc
Read-only optical disc that holds up to two hours
of video data.  Like a phonograph record and CD
player, most videodisc players provide direct
access to any location on the disc.  Videodiscs are
recorded in an analog format like videotape.

   Various videodisc systems were introduced during
the 1970s, but only the LaserVision optical disc
technology survived.  As of 1990, videodiscs have
barely made a dent in the home market, where VCRs
are commonplace.  It appears that videotapes will
continue to be the major video recording and
playback medium until such time as an erasable
optical system can be economically mass produced.
Videodiscs are used for interactive instructional
training courses, however.

   Videodiscs used for movies use a constant linear
velocity (CLV) format that records the signal on a
continuous, spiraling track, as does a phonograph
record.  In addition, the signal density is
uniform, and the player increases or decreases the
speed of rotation depending on which part of the
disc is being played.

   Videodiscs used for interactive purposes use a
constant angular velocity (CAV) format like that of
a magnetic disk, in which the tracks are concentric
circles, each one containing one frame of video.
Each side of a CAV videodisc holds 54,000 frames,
which is 30 minutes of continuous video at 30
frames per second.


videotex
Interactive information technology that includes
shopping, banking, news, weather and e-mail
services.  Experiments have been tried in the U.S.,
but it has yet to catch on.

   It is delivered over a telephone line to a
subscriber's TV through a decoder box and attached
keyboard.  Information is broadcast to and stored
in the decoder as predefined screens (frames) which
can be retrieved by menu.  Videotex delivers simple
graphics and limited animation.


view
(1) To display and look at data on screen.

(2) In relational database management, a special
display of data, created as needed.  A view
temporarily ties two or more files together so that
the combined files can be displayed, printed or
queried; for example, customers and orders or
vendors and purchases.  Fields to be included are
specified by the user.  The original files are not
permanently linked or altered; however, if the
system allows editing, the data in the original
files will be changed.


Viewdata
British term for videotex.


viewer
See file viewer.


viewport
(1) In the Macintosh, the entire scrollable region
of data that is viewed through a window.

(2) Same as window.


VIM
(Vendor Independent Messaging Interface)  E-mail
protocol developed by Lotus, Apple, Novell and
Borland that supersedes OMI.  See MAPI.


VINES
(VIrtual NEtworking System)  UNIX System V-based
network operating system from Banyan Systems Inc.,
that runs on DOS and OS/2-based servers.  It
provides internetworking of PCs, minis, mainframes
and other computer resources providing information
sharing across organizations of unlimited size.

   Incorporating mainframe-like security with a
global directory service, VINES allows access to
all network users and resources.  Options include
printer sharing, e-mail, remote PC dial-in, bridges
and gateways.


virtual
Simulated, conceptual or extended environment,
which, as a result, may refer to virtually
anything.


Virtual 8086 Mode
Operational mode in Intel 386s and up that allows
it to perform as multiple 8086 CPUs.  Under
direction of a control program, each virtual
machine runs as a stand-alone 8086 running its own
operating system and applications, thus DOS, UNIX
and other operating systems can be running
simultaneously.  All virtual machines are
multitasked together.

   This mode divides up the computer into multiple
address spaces and maintains virtual registers for
each virtual machine.  This is not the same as the
386's virtual memory mode, which extends main
memory to disk.


virtual circuit
Resulting pathway created between two devices
communicating with each other in a packet switching
system.  A message from NY to LA may actually start
in New York and go through Atlanta, St. Louis,
Denver and Phoenix before it winds up in Los
Angeles.


virtual desktop
Desktop beyond the borders of the viewing screen.
Rather than overlapping windows or reducing them to
an icon, a virtual desktop simulates a giant
desktop that lets you browse several full-size
documents using a virtual screen or other
navigation method, such as the "rooms" and "doors"
metaphor in Xsoft's Rooms for Windows.


virtual device
See virtual peripheral and VxD.


virtual disk
Same as RAM disk.


virtual image
In graphics, the complete graphic image stored in
memory, not just the part of it that is displayed
at the current time.


virtual machine
(1) Computer that runs multiple operating systems
with each operating system running its own
programs; for example, an IBM mainframe running
under VM or a 386 PC running multiple DOS
applications in Virtual 8086 Mode.

(2) One virtual machine (operating system and
associated applications) running in a virtual
machine environment.

(3) Virtual memory computer.


virtual memory
Technique that simulates more memory than actually
exists and allows the computer to run multiple
programs concurrently regardless of size.

   Virtual memory breaks up a program into
segments, called pages.  Instead of bringing the
entire program into memory, it brings as many pages
as it can fit based on the current program mix and
leaves the remaining pages on disk.  When
instructions are called for that are not in memory,
the appropriate disk page is called in, overlaying
a page in memory.

   If a memory page contains variables or other
data that are altered by the running of the
program, the page is temporarily stored on disk
when room is needed for new pages.  The input and
output of program pages is called paging or
swapping.

   If a program contains spaghetti code, in which
its logic points back and forth to opposite ends of
the program, thrashing may result (excessive disk
accesses).  Disk access should be reserved for
retrieving data, not the same instructions over and
over again.

   Although virtual memory can be implemented in
software, efficient operation requires virtual
memory hardware.

   Programs sometimes claim virtual memory
capability, but only swap code into memory as
needed.  True virtual memory is a hardware
implementation that works with any application.


virtual monitor
In the Macintosh, the ability to dynamically
configure to any monitor type and to use multiple
monitors of different types including displaying
the same object across two or more screens.


virtual networking
As defined by Banyan Systems, the ability for users
to transparently communicate locally and remotely
across similar and dissimilar networks through a
simple and consistent user interface.


virtual peripheral
Peripheral device simulated by the operating
system.


virtual printer
Simulated printer.  If a program is ready to print,
but all printers are busy, the operating system
will transfer the printer output to disk and keep
it there until a printer becomes available.


virtual processing
Parallel processing technique that simulates a
processor for applications that require a processor
for each data element.  It creates virtual
processors for data elements above and beyond the
number of processors available.


virtual processor
Simulated processor in a virtual processing system.


virtual reality
Artificial reality that projects the user into a
3-D space generated by computer.  Implementations
by AutoDesk and others include the use of a data
glove and head-mounted stereoscopic display, which
allow users to point to and manipulate illusory
objects in their view.  See cyberspace.


virtual route
Same as virtual circuit.


virtual screen
Screen area beyond the borders of the viewing
screen.  The viewing screen serves as a scrollable
window that navigates around the larger screen.
Video display boards may offer this capability; for
example, you could browse a 1280x1024 viewing area
with an 800x600 screen resolution.  See virtual
desktop.


virtual storage
Same as virtual memory.


virtual terminal
Terminal emulation that allows access to a foreign
system.  Often refers to a personal computer
gaining access to a mini or mainframe.


virtual toolkit
Development software that creates programs for
several computer environments.  Its output may
require additional conversions or translations to
produce executable programs.


virtualize
(1) To activate a program in virtual memory.

(2) To create a virtual screen.


virus
Software used to infect a computer.  After the
virus code is written, it is buried within an
existing program.  Once that program is executed,
the virus code is activated and attaches copies of
itself to other programs in the system.  Infected
programs copy the virus to other programs.

   The effect of the virus may be a simple prank
that pops up a message on screen out of the blue or
the actual destruction of programs and data.

   A virus cannot be attached to data.  It must be
attached to a runnable program that is downloaded
into or installed in the computer.  The virus-
attached program must be executed in order to
activate the virus.  See worm.


               Be Careful Out There
Before you run a shareware, public domain or
freeware program, check it with a virus detection
program first!


virus signature
Binary pattern of the actual machine code of a
particular virus.  Antivirus programs use virus
signatures for fast detection of known viruses.


VIS
(Voice Information Service)  Variety of voice
processing service applications.


Visa
See VESA.


ViSCA
(VIdeo System Control Architecture)  Platform-
independent protocol from Sony for synchronized
control of multiple video peripherals.  ViSCA is
the software interface.  Control-L is the hardware
interface.


VisiCalc
First electronic spreadsheet.  It was introduced in
1978 for the Apple II.  Conceived by Dan Bricklin,
a Harvard student, and programmed by a friend, Bob
Frankston, it became a major success.  It launched
an industry and was almost entirely responsible for
the Apple II being used in business.  Thousands of
$3,000 Apples were bought to run the $150 VisiCalc.

   VisiCalc was a command-driven program that was
followed by SuperCalc, MultiPlan, Lotus 1-2-3 and a
host of others, each improving the user interface.
Spreadsheets have also been implemented on minis
and mainframes.  It all started with VisiCalc.


Visual BASIC
Version of Microsoft QuickBASIC for developing
Windows applications (not 100% compatible with
QuickBASIC).  User interfaces are developed by
dragging objects from the Visual BASIC Toolbox onto
the application form.


visual programming
Developing programs with tools that allow menus,
buttons and other graphics elements to be selected
from a palette and drawn and built on screen.  It
may include developing source code by visually
interacting with flow charts that graphically
display the logic paths and associated code.


visualization
In computer graphics, the converting of numeric
data into picture form to allow humans to recognize
patterns that are difficult to identify in numeric
form.  It is used especially in research
situations, both theoretical and practical.


VL-bus
(VESA Local-BUS)  Local bus for PCs standardized by
VESA that provides a high-speed data path between
the CPU and peripherals (video, disk, network,
etc.).  Up to three VL-bus slots can be placed onto
the motherboard.  See local bus.

   The VL-bus runs at speeds up to 40MHz or up to
66MHz for controllers built directly on the
motherboard.  It is currently a 32-bit bus with 64-
bit capability forthcoming to handle the Pentium
CPU.  The VL-bus expansion slot uses one 32-bit
Micro Channel slot placed adjacent to the standard
ISA, EISA or Micro Channel slot, allowing vendors
to design boards that use only the local bus or
both buses at the same time.  VL-bus also supports
bus mastering.


VLF
(Very Low Frequency)  See low radiation.


VLSI
(1) (Very Large Scale Integration)  Between 100,000
and one million transistors on a chip.  See SSI,
MSI, LSI and ULSI.

(2) (VLSI Technology, Inc., Tempe, AZ)  Designer
and manufacturer of custom chips.


VM
(Virtual Machine)  IBM mainframe operating system,
originally developed by its customers and
eventually adopted as an IBM system product
(VM/SP).  It can run multiple operating systems
within the computer at the same time, each one
running its own programs.  CMS (Conversational
Monitor System) provides VM's interactive
capability.


VM/386
(Virtual Machine/386)  Multiuser operating system
for 386s and up from IGC Corp., San Jose, CA.  Each
user at a terminal runs an application within a
virtual machine of the 386 (Virtual 8086 Mode).


VM/SP
See VM.


VMEbus
(VersaModule Eurocard bus)  32-bit bus developed by
Motorola, Signetics, Mostek and Thompson CSF.  It
is widely used in industrial, commercial and
military applications with over 300 manufacturers
of VMEbus products worldwide.  VME64 is an expanded
version that provides 64-bit data transfer and
addressing.


VMS
(1) (Virtual Memory System)  Multiuser,
multitasking, virtual memory operating system for
the VAX series from Digital.  VMS applications will
run on any VAX from the MicroVAX to the largest
VAX.

(2) (Voice Messaging System)  See voice mail.


VMTP
(Virtual Message Transaction Protocol)  Datagram
communications protocol that provides efficient and
reliable transmission across networks.


voice channel
Transmission channel or subchannel that carries
human voice.


voice coil
Type of motor used to move the access arm of a disk
drive in very small increments.  Like the voice
coil of a speaker, the amount of current determines
the amount of movement.  Contrast with stepper
motor, which works in fixed increments.


voice grade
Refers to the bandwidth required to transmit human
voice, which is usually about 4,000Hz.


voice mail
Computerized telephone answering system that
digitizes incoming voice messages and stores them
on disk.  It usually provides auto attendant
capability, which uses prerecorded messages to
route the caller to the appropriate person,
department or mail box.


voice messaging
Using voice mail as an alternative to electronic
mail, in which voice messages are intentionally
recorded, not because the recipient was not
available.


voice processing
Computerized handling of voice, which includes
voice store and forward, voice response, voice
recognition and text to speech technologies.


voice recognition
Conversion of spoken words into computer text.
Speech is first digitized and then matched against
a dictionary of coded waveforms.  The matches are
converted into text as if the words were typed on
the keyboard.

   Speaker-dependent systems must be trained before
using, by taking samples of actual words from the
person who will use it.  Speaker-independent
systems can recognize limited vocabularies such as
numeric digits and a handful of words.  In the
telephone companies, these systems will begin to
replace the human operator for services, such as
collect and credit card calls, for example.

   In the future, voice recognition systems will be
able to understand large vocabularies from just
about anybody; however, it could be well past the
turn of the century before voice recognition is
part of every computer system.


voice response
Generation of voice output by computer.  It
provides pre-recorded information either with or
without selection by the caller.  Interactive voice
response allows interactive manipulation of a
database.  See audiotex.


voice store and forward
Technology behind voice mail and messaging systems.
Human voice is digitized, stored in the computer,
possibly forwarded to another mail box, and
retrieved by the called party.


volatile memory
Memory that does not hold its contents without
power.  A computer's main memory, made up of
dynamic RAM or static RAM chips, loses its content
immediately upon loss of power.


volt
Unit of measurement of force, or pressure, in an
electrical circuit.  The common voltage of an AC
power line is 120 volts of alternating current
(alternating directions).  Common voltages within a
computer are from 5 to 12 volts of direct current
(one direction only).


volt-amps
Measurement of electrical usage that is computed by
multiplying volts times amps.  See watt.


voltage regulator
Device used to maintain a level amount of voltage
in the electrical line.  Contrast with surge
suppressor, which filters out excessive amounts of
current, and contrast with UPS, which provides
backup power in the event of a power failure.


volume
(1) Physical storage unit, such as a hard disk,
floppy disk, disk cartridge or reel of tape.

(2) Logical storage unit that spans some number of
physical drives.


volume label
(1) Name assigned to a disk (usually optional).

(2) Identifying stick-on label attached to the
outside of a tape reel or disk cartridge.

(3) See header label.


von Neumann architecture
Sequential nature of computers: an instruction is
analyzed, data is processed, the next instruction
is analyzed, and so on.  Hungarian-born John von
Neumann (1903-1957), an internationally renowned
mathematician, promoted the stored program concept
in the 1940s.


VOS
Operating system used in Stratus computers.  FTX is
Stratus' UNIX operating system.


VP/ix
See SCO VP/ix.


VP Planner
Lotus-compatible relational spreadsheet from
Paperback Software.  In 1991, it was taken off the
market due to settlement of Lotus' copyright
lawsuit.


VP ratio
(Virtual Processor ratio)  Number of virtual
processors that a physical processor is simulating.


VPC
(Virtual Processor Complex)  IBM mainframe
multiprocessing that uses several computers under
tight central control.


VPS
(Vectors Per Second)  Used to measure the speed of
a vector or array processor.


VRAM
See video RAM.


VRC
(Vertical Redundancy Check)  Error checking method
that generates and tests a parity bit for each byte
of data that is moved or transmitted.


VS
(1) (Virtual Storage)  Same as virtual memory.

(2) (Virtual Storage)  Family of minicomputers from
Wang introduced in 1977, which use virtual memory
techniques.


VSAM
(Virtual Storage Access Method)  IBM access method
for storing data, widely used in IBM mainframes. 
It uses the B+tree method for organizing data.


VSAT
(Very Small Aperture satellite Terminal)  Small
earth station for satellite transmission that
handles up to 56 Kbits/sec of digital transmission.
VSATs that handle the T1 data rate (up to 1.544
Mbits/sec) are called TSATs.


VSE
(Disk Operating System/Virtual Storage Extended)
IBM multiuser, multitasking operating system that
typically runs on IBM's 43xx series.  It used to be
called DOS, but due to the abundance of DOS PCs, it
is now referred to as VSE.


VSX
(Verification Suite for X/Open)  Testing procedure
from X/Open that verifies compliance with their
endorsed standards.  VSX3 has over 5,500 tests for
compliance with XPG3.


VT100, 200, 300
Series of asynchronous display terminals from
Digital for its PDP and VAX computers.  Available
in text and graphics models in both monochrome and
color.


VTAM
(Virtual Telecommunications Access Method)  Also
called ACF/VTAM (Advanced Communications
Function/VTAM), software that controls
communications in an IBM SNA environment.  It
usually resides in the mainframe under MVS or VM,
but may be offloaded into a front end processor
that is tightly coupled to the mainframe.  It
supports a wide variety of network protocols,
including SDLC and Token Ring.  VTAM can be thought
of as the network operating system of SNA.


VTR
(VideoTape Recorder)  Video recording and playback
machine that uses reels of magnetic tape.  Contrast
with VCR, which uses tape cassettes.


VUP
(VAX Unit of Performance)  Unit of measurement
equal to the performance of the VAX 11/780, the
first VAX machine.


VxD
(Virtual Device Driver)  Special type of Windows
driver for 386 Enhanced Mode.  WIN386.EXE, the 386
Enhanced Mode kernel of Windows, is itself made up
of VxDs.  VxDs run at the most priviledged CPU mode
(ring 0) and allows low-level interaction with DOS
and Windows programs running under Windows.



 W5086
Weitek chip set that accelerates graphics
performance.


WABI
(Windows ABI)  Software emulator from Sun that runs
Windows applications under UNIX at higher
performance levels than typical Windows emulation
products.


wafer
(1) Base material in chip making.  It is a slice,
approx. 1/30" thick, from a salami-like silicon
crystal from 3 to 6" in diameter.  The wafer goes
through a series of photomasking, etching and
implantation steps.  See chip.

(2) Small, continuous-loop magnetic tape cartridge
that is used for the storage of data.


wafer scale integration
Next evolution in semiconductor technology.  It
builds a gigantic circuit on an entire wafer.  Just
as the integrated circuit eliminated cutting apart
thousands of transistors from the wafer only to
wire them back again on circuit boards, wafer scale
integration eliminates cutting apart the chips.
This next step is difficult (see Trilogy).


wait state
Time spent waiting for an operation to take place.
It may refer to a variable length of time a program
has to wait before it can be processed, or to a
fixed duration of time, such as a machine cycle.

   When memory is too slow to respond to the CPU's
request for it, wait states are introduced until
the memory can catch up.


WAN
(Wide Area Network)  Communications network that
covers wide geographic areas, such as states and
countries.  See MAN and LAN.


wand
Hand-held optical reader used to read typewritten
fonts, printed fonts, OCR fonts and bar codes.  The
wand is waved over each line of characters or codes
in a single pass.


Wang
(Wang Laboratories, Inc., Lowell, MA)  Computer
manufacturer and applications developer.  Founded
in 1951 by Dr. An Wang, the company specialized in
electronic devices.  Its desktop calculator became
a standard in the late 1960s.

   In the 1970s, Wang introduced word processing
systems and computers, which evolved into the WPS
and VS series.  By 1978, it was North America's
largest supplier of small business computers and
the world's largest supplier of CRT-based word
processors.  Throughout the 1980s, Wang developed
integrated voice and data networks and imaging
systems.  It chose industry-standard platforms for
the 1990s.

    Dr. Wang came from China in 1945 to study
applied physics at Harvard.  Six years later, he
started Wang Labs.  In 1988, two years before he
died, he was inducted into the National Inventors
Hall of Fame for his 1948 invention of a pulse
transfer device that let magnetic cores be used for
computer memory.  The Hall of Fame has recognized
an elite group including Edison, Pasteur and Bell.


Wangnet
Broadband LAN from Wang that handles data, voice
and video.


warm boot
Restarting the computer by performing a reset
operation (pressing reset, Ctrl-Alt-Del, etc.).
See cold boot and boot.


warm start
Same as warm boot.


Warnier-Orr diagram
Graphic charting technique used in software
engineering for system analysis and design.


WARP
Parallel processor developed at Carnegie-Mellon
Univ. that was the predecessor of iWARP.


WATCOM compilers
C and FORTRAN compilers for PCs from WATCOM,
Waterloo, Ontario, noted for generating fast,
compact code.  WATCOM C/386 is the first 32-bit
compiler for extended DOS, Windows, OS/2 2.0 and
AutoCAD ADS and ADI applications.  Corporate
mission is to provide advanced compilers for most
x86 environments.


watt
A measurement of electrical power.  One watt is one
ampere of current flowing at one volt.  Watts are
typically rated as AMPS x VOLTS; however, AMPS x
VOLTS, or VOLT-AMP (V-A) ratings and watts are only
equivalent when powering devices that absorb all
the energy such as electric heating coils or
incandescent light bulbs.  With computer power
supplies, the actual watt rating is only 60 to 70%
of the VOLT-AMP rating.


WAV
Windows sound file.  .WAV files use lots of disk
space; for example, one audio minute takes about
2.5MB.


wave
Shape of radiated energy.  All radio signals, light
rays, x-rays, and cosmic rays radiate an energy
that looks likes rippling waves.  To visualize
waves, take a piece of paper and start drawing an
up and down line very fast while pulling the paper
perpendicular to the line.


waveform
Pattern of a particular sound wave or other
electronic signal in analog form.


waveguide
Rectangular, circular or elliptical tube through
which radio waves are transmitted.


wavelength
Distance between crests of a wave, computed by
speed divided by frequency (speed / Hz).
Wavelength in meters of electromagnetic waves
equals 300,000,000 / Hz.  Wavelength in meters for
sound travelling through the air equals 335 / Hz.


WDM
(Wavelength-Division Multiplexing)  High-speed
optical fiber transmission technique that carries
multiple signals, each within its own wavelength
(color) of light.


weak typing
Programming languages that allow different types of
data to be moved freely among data structures, as
is found in Smalltalk and other earlier object-
oriented languages.


Weitek coprocessor
High-performance math coprocessor from Weitek Corp.
Since 1981, Weitek has been making coprocessors for
CAD and graphics workstations.  In order to use a
coprocessor, the software must be written to
activate it.


well behaved
Refers to programs that do not deviate from a
standard.


well mannered
Same as well behaved.


wetware
Biological system.  Typically refers to the human
brain and nervous system.


WFW
See Windows for Workgroups.


what if?
Using a spreadsheet as a planning tool.  When new
data is entered, results are calculated based upon
the formulas.  Assumptions can be plugged in that
ripple through to the bottom line.  For example,
"what if hourly pay is increased $2?"  "What if
interest rates are lowered .5%?"


Whetstones
Benchmark program that tests floating point
operations.  Results are expressed in Whetstones
per second.  Whetstone I tests 32-bit, and
Whetstone II tests 64-bit operations.  See
Dhrystones.


white noise
Same as Gaussian noise.


wide area network
See WAN.


widget set
Group of screen structures (menu, button, scroll
bar, etc.) provided in a graphical interface.


widow & orphan
A widow is the last line of a paragraph that
appears alone at the top of the next page, and an
orphan is the first line of a paragraph that
appears alone at the bottom of a page.  Widow and
orphan settings are usually set for a minimum of
two lines.


width table
List of horizontal measurements for each character
in a font, used by word processing and desktop
publishing programs.


wild cards
Symbols used to represent any value when naming
files.  See DOS wild cards.


wimp interface
(Windows, Icons, Menus and a Pointing device)  Same
as GUI.


WIN.INI
(WINdows INItialization)  File read by Windows on
startup that contains data about the current
environment (desktop, fonts, sounds, etc.) and
individual applications.  It is often updated by an
install program to provide information for the
application when it runs.  SYSTEM.INI, another
startup file, contains data about the hardware
(drivers, 386 Enhanced Mode settings, etc.).


Win32
Programming specification (API) for the 386's 32-
bit mode fully supported in Windows NT.  Many
functions are also supported in Windows 3.1, and
applications can be written to this Win32 subset
(Win32s) to gain improved performance on a 386 or
up running Windows 3.1 or Windows NT.


Winbench
Series of tests that analyze computer performance
from Ziff-Davis' PC Labs.  See Winmark.


Winchester disk
Removable disk from IBM that put the access arm,
read/write heads and disk platters into a sealed
unit.  By keeping heads and disks intact, greater
speed and capacity was achieved.  It was designed
as a dual 30MB module, and got its name from its
"Winchester rifle" 30-30 specification.  Although
originally a removable disk, the term later
referred to any fixed hard disk.


WinDisk
Driver from Future Domain Corp. that converts
Windows 3.1 FastDisk accesses into the SCSI CAM
standard supported on its SCSI host adapters.


window
(1) Rectangular, scrollable viewing area.  May
refer to a scrollable list such as this Glossary
index or to a re-sizable window that contains the
entire application.  See GUI and windows
environment.

(2) Reserved area of memory.

(3) Time period.


window manager
Software incorporated into all popular GUIs, which
displays a window with accompanying menus, buttons
and scroll bars.  It allows the windows to be
relocated, overlapped, resized, minimized and
maximized.  See desktop manager.


windowing software
Same as windows program.


Windows
Graphics-based windows environment from Microsoft
that integrates with and interacts with DOS.  It
provides a desktop environment similar to the
Macintosh, in which applications are displayed in
re-sizable, movable windows on screen.

   In order to use all the features of Windows,
applications must be written for it.  However,
Windows also runs DOS applications and is
increasingly being used as the primary operating
environment from which all programs are launched.


            Windows 3.x Operating Modes

 REAL MODE (Windows 3.0 only)
   For computers with less than 1MB memory.
   Provides compatibility with earlier Windows
   applications (Windows 1.x, 2.x).

 STANDARD MODE  (286 and up)
   Used when running on a 286.  Also used in
   Windows 3.0 on 386s because it runs faster.
   Provides access to extended memory and allows
   users to run full-screen DOS applications.

 386 ENHANCED MODE  (386 and up)
   Uses the 386's virtual machine and virtual
   memory capabilities and is the common mode
   for 386s under Windows 3.1.  Can multitask DOS
   applications (program continues running in the
   background), and DOS applications can be run
   within a movable window, and text can be copied
   between DOS applications.

               Windows 3.1 Evolution
Windows 1.x, Windows 286 (2.x) and Windows/386 were
the first attempts at Windows.  But, it wasn't
until 1990 and Windows 3.0 that it took off and
created an industry due to its enhanced user
interface and ability to break DOS' infamous 1MB
memory barrier.   Windows contains its own DOS
extender, which allows it to manage 16MB of
extended memory.

   Windows 3.1 (1992) is more stable and faster,
supports multimedia, TrueType fonts and drag & drop
commands.  Compound documents (OLE) are added and
Real Mode is eliminated.

   Windows applications are 16-bit programs that
run on all x86 CPUs.  Windows applications can also
be written that exploit the 386's native 32-bit
instructions.  These "Win32s" applications require
Windows 3.1 and will also run under Windows NT.


               WIN.INI & SYSTEM.INI
WIN.INI and SYSTEM.INI are text files used to
configure Windows.  WIN.INI contains environment
information (desktop, fonts, sounds, etc.) as well
as individual applications.  SYSTEM.INI contains
hardware information.

   Install programs and Windows' own SETUP.EXE
program modify these files, but they can be edited
manually in Notepad or any text editor.  When an
application is installed, it often adds text to
WIN.INI, which it may modify from time to time.  If
the application is deleted by the user, the lines
of text remain, but have no purpose.

   A useful utilty, called SYSEDIT.EXE, resides in
the \WINDOWS\SYSTEM directory and opens all four
files: WIN.INI, SYSTEM.INI, AUTOEXEC.BAT and
CONFIG.SYS, for editing.


               Advantages of Windows
Windows' windowing capability is its major feature.
The ability to keep multiple applications active is
more productive than closing out one application
and opening another.  In addition, data can be
copied from one application to another via Windows'
clipboard.

   Applications written for Windows provide a
measure of consistency, although not as unvarying
as in the Macintosh.  Users know how to open,
close, copy, move and paste data in all Windows
applications.  The operation of the drop-down menus
is the same and Windows' online help system
functions similarly in every Windows application.
The help window can be left on screen so that a
user can read instructions while performing the
operation.

   Centralized device and font management is a
significant advantage.  In DOS, each application is
responsible for interacting with all the possible
peripheral devices on the market, and the DOS
installation program must set up its own
application with the appropriate drivers.  If a
user changes to a different printer for example,
each DOS application has to be notified of the
change.  Many DOS applications use proprietary
fonts, and the same typefaces may be duplicated
with different applications, wasting disk space.

   When a new device is installed for Windows, that
information is made available to all Windows
applications that use it.  The same goes for fonts.
Once users have installed a new font, it becomes
available to all Windows applications.

   Windows dynamic data exchange (DDE) and object
linking and embedding (OLE) allow for information
in one database to automatically update information
in another.  Windows multimedia, built into Windows
3.1, allow graphics, video and sound to be added to
traditional text-only databases.  These
capabilities allow for enterprise-wide integration
of information and are just being exploited.



             Disadvantages of Windows
Windows is a complicated operating environment that
has its roots in DOS, which was developed for the
first PCs.  Fine tuning Windows on a fully-loaded
PC that is running a mix of DOS and Windows
applications can be a daunting task, requiring
knowledge of the CONFIG.SYS, AUTOEXEC.BAT, WIN.INI
and SYSTEM.INI configuration files.

   Windows applications can be just as intimidating
as DOS.  The graphics-based environment of Windows
allows for enormous creativity in the design of the
user interface.  Too often however, the myriad of
cute little icons with imaginative, but cryptic
symbols, are more difficult to remember than simple
menus with straightforward explanations.

   In addition, Windows doesn't enforce enough
ridigity for common tasks.  In one application, you
use the Character menu to change fonts, on another,
you use the Paragraph menu.  Windows popularity is
so high that developers can't get their new
applications out fast enough.  The graphical
interface does not obviate the need for a well-
designed and well-thought-out interaction between
the user and the computer.


Windows accelerator
See graphics accelerator.


windows environment
Any operating system, operating system extension or
application program that provides multiple windows
on screen.  DESQview, Windows, PM, MultiFinder and
X Window are examples.


Windows for Workgroups
Version of Windows 3.1 that incorporates peer-to-
peer networking and includes e-mail.


Windows Metafile
Windows file format that holds vector graphics,
bitmaps and text.  It is used as a common vector
graphics format.  It is also used by programs to
hold data between sessions.  Sometimes Windows uses
it for temporary storage.

   The Aldus Placeable Metafile is a PageMaker
variation that contains a header indicating into
what size rectangle the object will be rendered.


Windows NT
(Windows New Technology)  Advanced 32-bit operating
system from Microsoft for 386s and up, MIPS and
Alpha CPUs scheduled for 1993.  It runs NT-specific
applications as well as those written for DOS,
Windows 3.x (16-bit and 32-bit), OS/2 character-
mode (non-graphical) and POSIX.  NT does not use
DOS, it is a self-contained operating system.

   Features include peer-to-peer networking,
preemptive multitasking, symmetric multiprocessing,
multithreading, security and fault tolerance.  It
supports 2GB of virtual memory for applications and
2GB for Windows NT.


windows program
(1) Software that adds a windows capability to an
existing operating system.

(2) Application program written to run under
Windows.


Windows SNA APIs
Programming interfaces that allow Windows
applications to communicate with SNA protocols and
functions, such as HLLAPI and APPC.


Windows swap file
Disk file used to store applications temporarily
when there isn't enough memory to hold all active
applications.  On setup, Windows creates a
permanent swap file for running in 386 Enhanced
Mode (SPART.PAR file and 386SPART.PAR hidden file).
If these files are not present, or if Windows is in
Standard Mode, Windows creates temporary swap files
as needed.

   To free up disk space, you can delete or reduce
the size of the permanent swap file.  In Windows
3.0, load Windows in Real Mode (win /r) and run the
SWAPFILE program.  In Windows 3.1, select Control
Panel/386 Enhanced/Virtual Memory/Change.


WINGZ
Presentation-oriented Macintosh spreadsheet from
Informix Software., Menlo Park, CA.  Text, graphs
and charts, scanned images, freehand illustration
and spreadsheet data can be combined.  When data is
updated, related graphics and numerical references
within the text are changed.


WinJet
High-speed PostScript emulation system for Windows
and LaserJet printers from LaserMaster Corp., Eden
Prarie, MN.  It generates PostScript output,
including Type 1 and TrueType fonts, on a PC
expansion board cabled directly to the LaserJet
video input.  WinJet 300 and 800 provide 300 and
800 dpi for LaserJet II/III models.  WinJet 1200
provides 1200 dpi for the LaserJet 4.


Winmark
Unit of performance based on Ziff-Davis' PC Labs
Winbench tests.  Graphics Winmarks rate Windows
video performance as a weighted average of 12
benchmarks.  Common VGA adapters are rated around
two million Winmarks.  Fast graphics accelerators
can achieve 20 million and more.

   Winbench Version 3.1 provides more accurate
Winmark tests and avoids slanted results from
"benchmark-aware" drivers used in some graphics
accelerator boards.

   Disk Winmarks rate the speed of disks and disk
caching.  See DOSmark.


WinWord
See Microsoft Word.


wire wrap
Early method of wiring circuit boards.  A tool
strips the end of the wire and coils it.  The coil
is pressed onto a metal prong on the board.


wireframe modeling
In CAD, a technique for representing 3-D objects,
in which all surfaces are visibly outlined in
lines, including the opposite sides and all
internal components that are normally hidden from
view.  Compared to surface and solid modeling,
wireframe modeling is the least complex method for
representing 3-D images.


wireless
Same as radio.


wiring closet
Central distribution or servicing point for cables
in a network.


wizzy wig
See WYSIWYG.


WK1
Lotus 1-2-3 Version 2.0 file extension.


WKS
Lotus 1-2-3, Version 1A file extension.


WMF
See Windows Metafile.


word
(1) Computer's internal storage unit.  Refers to
the amount of data it can hold in its registers and
process at one time.  A word is often 16 bits, in
which case 32 bits is called a double word.  Given
the same clock rate, a 32-bit computer processes
four bytes in the same time it takes a 16-bit
machine to process two.

(2) Primary text element, identified by a word
separator (blank space, comma, etc.) before and
after a group of contiguous characters.

(3) See Microsoft Word.


word addressable
Computer that can address memory only on word
boundaries.  Contrast with byte addressable.


Word for Windows
See Microsoft Word.


word processing
Creation of text documents.  Except for labels and
envelopes, it has replaced the electric typewriter
in most offices, because of the ease in which
documents can be edited, searched and reprinted.

   Advanced word processors function as elementary
desktop publishing systems and support graphics and
multiple fonts.  Although there are still machines
dedicated only to word processing, most word
processing is performed on general-purpose
computers using word processing software.

    Functions of a Full-featured Word Processor

TEXT EDITING
Text can be changed by deleting it, typing over it
or by inserting additional text within it.

WORD WRAP AND CENTERING
Words that extend beyond the right margin are
wrapped around to the next line.  Text can be
centered between left and right margins.

SEARCH & REPLACE, MOVE AND COPY
Any occurrence of text can be replaced with another
block of text.  You can mark a block of text and
move it elsewhere in the document or copy it
throughout the document.

LAYOUT SETTINGS
Margins, tabs, line spacing, indents, font changes,
underlining, boldface and italics can be set and
reset anywhere within the document.

HEADERS, FOOTERS AND PAGE NUMBERING
Headers and footers are common text printed on the
top and bottom of every page.  Headers, footers and
page numbering can be set and reset anywhere within
the doucment.  Page numbering in optional Roman
numerals or alphabetic letters is common.

STYLE SHEETS
After designing a document, its format can be used
again.  Layout codes (margins, tabs, fonts, etc.)
can be stored in a style sheet file and applied to
a new document.

MAIL MERGE
Creates customized letters from a form letter and a
list of names and addresses.  The list can be
created as a document or can be imported from
popular database formats.

MATH AND SORTING
Columns of numbers can be summed and simple
arithmetic expressions can be computed.  Lines of
text can be reordered into ascending (A-Z) or
descending (Z-A) sequence.

PREVIEW, PRINT AND GROUP PRINT
A document can be previewed before it is printed to
show any layout change that may not normally show
on screen (page breaks, headers, footers, etc.).
Documents can be printed individually or as a group
with page numbers consecutively numbered from the
first to the last document.

FOOTNOTES
Footnote entries can be made at any place in the
document, and the footnotes printed at the end of a
page or document.

SPELLING CHECKER AND THESAURUS
Spelling for an individual word, marked block of
text or an entire document can be checked.  When
words are in doubt, possible corrections are
suggested.  Advanced systems can correct the
misspellings automatically the next time.  A
thesaurus displays synonyms for the word at the
current cursor location.

FILE MANAGEMENT
Documents can be copied, renamed and deleted, and
directories, or folders, can be created and deleted
from within the program.  Advanced systems set up a
purge list of names or glimpses of document
contents in order to allow a user to easily rid the
disk of unwanted files.


                Advanced Functions

WINDOWS
Allows two or more documents to be worked on at the
same time.  Text can be moved or copied from one
document to the other.

COLUMNS
Columns can be created in all word processors by
tabbing to a tab stop.  However, true column
capability wraps words to the next line within each
column.  Columns are required for writing resumes
with employer information on the left and work
history on the right.  Script writing also requires
column capability.  Magazine-style columns flow
words from the bottom of one column to the top of
the next.

TABLES OF CONTENTS AND INDEXES
Tables of contents and indexes can be generated
from entries typed throughout the document.

DESKTOP PUBLISHING
Graphics can be merged into the text and either
displayed on screen with the text or in a preview
mode before printing.  A graphic object can be
resized (scaled), rotated and anchored so that it
remains with a particular segment of text.  Rules
and borders can also be created within the text.


           Graphics-based Vs Text-based
Graphics-based programs (Windows, Macintosh, etc.)
show a close facsimile on screen of the typefaces
that will be printed.  Text-based programs always
show the same type size on screen.

   Graphics-based systems are far superior for
preparing newsletters and brochures that contain a
variety of font sizes.  Text-based screens are fine
for office typing or for documents with a simple
format.  They are also very responsive and good for
creative writing.


                 Format Standards
Every major word processing program generates its
own proprietary codes for layout settings.  For
example, in WordStar, ^PB turns on and off
boldface.  In WordPerfect 5.x, [BOLD] turns
boldface on, and [bold] turns it off.

   Conversion programs are used to translate
documents from one format to another.  If a
conversion program doesn't exist for the two
required formats, multiple search & replace
commands can be performed on the original document.
However, if the same code turns a mode on as well
as off, as in the WordStar example above, the codes
have to be changed manually one at a time.


                The User Interface
Word processing programs run from the ridiculous to
the sublime.  Some of the most awkward programs
have sold well.  As a novice, it's difficult to
tell a good one from a bad one.  It takes time to
explore the nuances.  Also, what's acceptable for
the slow typist can be horrendous for the fast
typist.

   Repetitive functions such as centering and
changing display attributes (boldface, italics,
etc.) should be a snap.  Changing margins, tabs,
indents and fonts should also be easy.

   The most important components in word processing
hardware are the keyboard and screen.  The feel of
a keyboard is personal, but proper key placement is
critical.  Display screens should have the highest
resolution possible, and color screens are better
than monochrome as long as the program allows the
user to change colors.


word processing machine
Computer that is specialized for only word
processing functions.


word processor
(1) Software that provides word processing
functions on a computer.

(2) Computer specialized for word processing.
Until the late 1970s, word processors were always
dedicated machines.  Today, personal computers have
mostly replaced the dedicated word processor.


word separator
Character that separates a word, such as a blank
space, comma, period, -, ? and !.


word wrap
Word processing feature that moves words to the
next line automatically as you type based on the
current right margin setting.  Some word processing
programs allow word wrap to be turned off for
writing source code.


WordBASIC
Subset of Microsoft QuickBASIC with added word
processing functions used to customize Microsoft
Word word processors.


WordPerfect
Full-featured word processing program from
WordPerfect Corp., Orem, UT.  Introduced in 1980,
it runs on most all personal computers and some
workstations, and is the most widely used word
processor in the world.  Version 5.0 introduced
significant improvements that included desktop
publishing features and a WYSIWYG preview mode.
Version 5.1 added menus.


WordStar
Full-featured PC word processing program from
WordStar Int'l., Novato, CA.  Introduced in 1978
for CP/M machines, it was the first program to give
sophisticated word processing capabilities to
personal computer users at far less cost than the
dedicated word processors of the time.  Many
WordStar keyboard commands have become de facto
standards.


workflow automation
Automatically routing data and documents over the
network to the users responsible for working with
them.


workgroup
Two or more individuals who share files and
databases.  LANs designed around workgroups provide
electronic sharing of required data.


working directory
See current directory.


Workplace Shell
Graphical user interface (GUI) in OS/2 Versions
2.x.  See OS/2.


worksheet
Same as spreadsheet.


worksheet compiler
Same as spreadsheet compiler.


workstation
(1) High-performance, single-user microcomputer or
minicomputer that has been specialized for
graphics, CAD, CAE or scientific applications.

(2) Personal computer in a network.  Contrast with
server and host.  See client.

(3) Any terminal or personal computer.


worm
(1) Destructive program that replicates itself
throughout disk and memory, using up the computers
resources and eventually putting the system down.
See virus and logic bomb.

(2) Program that moves through a network and
deposits information at each node for diagnostic
purposes or causes idle computers to share some of
the processing workload.

(3) (WORM) (Write Once Read Many)  Optical disk
that can be recorded only once.  Updating requires
destroying the existing data (all 0s made 1s), and
writing new data to an unused part of the disk.


WOSA
(Windows Open System Architecture)  Extensions to
Windows programming that allow Windows applications
to access services on the network from any software
provider (e-mail, databases, network services,
etc.) that supports the WOSA interface.  It
provides a single standard between Windows clients
and servers.  See SPI and ODBC.


WP
See word processing.


WPS
See Workplace Shell.


Wrist Pro
Wrist support from Wrist Pro, St. Louis, MO, that
provides a multi-level platform that keeps the
wrist in a neutral wrist position.


wrist rest
Platform used to raise the wrist to keyboard level
for typing.


wrist support
Product that prevents and provides a therapy for
carpal tunnel syndrome by keeping the hands in a
neutral wrist position.


write
To store data in memory or record data onto a
storage medium, such as disk and tape.  Read and
write is analogous to play and record on an audio
tape recorder.


write back cache
Disk or memory cache that handles writing.  Data
written into the high-speed cache memory from the
CPU is written onto disk or into real memory during
idle machine cycles.


write error
Inability to store into memory or record onto disk
or tape.  Malfunctioning memory cells or damaged
portions of the disk or tape's surface will cause
those areas to be unusable.


write only code
Jokingly refers to source code that is difficult to
understand.


write protect
Prohibits erasing or editing a disk file.  See file
protection.


write protect notch
Small, square cutout on the side of a floppy disk
used to prevent it from being written and erased.
On 5.25" floppies, the notch must be covered for
protection.  To protect a 3.5" diskette, press the
slide lever toward the edge of the disk uncovering
a hole (upper left side viewed from the back).

   You "cover" the notch on 5.25" disks; you
"uncover" the hole on 3.5" disks.  The two common
formats use exact opposite methods!


WSI
See wafer scale integration.


WUGNET
(Windows Users Group NETwork)  Organization of
Windows users and developers founded in 1988.  It
provides technical information, software resources
and tools, CompuServe forums and newsletters.
Address: 107 S. Monroe St., Media, PA 19063,
215/565-1861.


WXmodem
(Window Xmodem)  Faster version of the Xmodem
protocol that allows the sending system to transmit
data without waiting for the receiving system to
acknowledge the transfer.


WYSIWYG
(What You See Is What You Get)  Pronounced "wizzy-
wig."  Refers to text and graphics appearing on
screen the same as they print.  To have WYSIWYG
text, a screen font must be installed that matches
each printer font.  Otherwise, a 24-point font may
display in correct size relationship to a 10-point
font, but it won't look like the printed typeface.

   It is almost impossible to get 100% identical
representation, because screen and printer
resolutions rarely match.  Even a 300 dpi printer
has a higher resolution than almost every monitor.


WYSIWYG MOL
(WYSIWYG More Or Less)  Quite often what you get,
when what you want is WYSIWYG!



x
(1) In programming, symbol used to identify a
hexadecimal number.  For example, 0x0A and \x0A
specify the hex number 0A.

(2) See X Window.


x-axis
See x-y matrix.


X-based
See X Window and Xbase.


x-height
In typography, the height of the letter x in lower
case.  Point size includes the x-height, the height
of the ascender and the height of the descender.
See typeface.


X/Open
Consortium of international computer vendors
founded in 1984 to resolve standards issues.
Incorporated in 1987 and based in London, North
American offices are in San Francisco.  Its purpose
is to integrate evolving de facto and international
standards in order to achieve an open environment,
or CAE (Common Application Environent).  XPG
defines X/Open's specification, and VSX defines its
testing and verification procedure.  Telephones:
U.S. 415/323-7992, U.K. 44-734-508311.


X protocol
Message format of the X Window System.


X terminal
Terminal with built-in X Window server capability.


X toolkit
Development software for building X Window
applications.  Typically includes a widget set, X
Toolkit Intrinsics (Xt) libraries for managing the
widget set and the X Library (Xlib).


X Window
Formally "X Window System," also called "X Windows"
and "X," it is a windowing system developed at MIT,
which runs under UNIX and all major operating
systems.  X lets users run applications on other
computers in the network and view the output on
their own screen.

   X generates a rudimentary window that can be
enhanced with GUIs, such as Open Look and
OSF/Motif, but does not require applications to
conform to a GUI standard.  The window manager
component of the GUI allows multiple resizable,
relocatable X windows to be viewed on screen at the
same time.

   X terminology seems backward to LAN concepts.
The X client resides in the computer that generates
the output, and the X server resides in the
computer that displays it.  The server draws the
image from the client.  The X client and X server
can also be in the same machine.


x-y matrix
Group of rows and columns.  The x-axis is the
horizontal row, and the y-axis is the vertical
column.  An x-y matrix is the reference framework
for two-dimensional structures, such as
mathematical tables, display screens, digitizer
tablets, dot matrix printers and 2-D graphics
images.


x-y monitor
In graphics, the display screen of a vector display
terminal.  The entire vector display comprises the
monitor and vector graphics controller.


x-y plotter
Same as plotter.


x-y-z matrix
Three-dimensional structure.  The x and y axes
represent the first two dimensions; the z axis, the
third dimension.  In a graphic image, the x and y
denote width and height; the z denotes depth.


X.12
See X12.


X.21
CCITT standard protocol for a circuit switching
network.


X.25
CCITT standard (1976) for the protocols and message
formats that define the interface between a
terminal and a packet switching network.


X.28
CCITT standard (1977) for exchange of information
between a DTE and a PAD; commonly known as PAD
commands.


X.29
CCITT standard (1977) for exchange of information
between a local PAD and a remote PAD; procedures
for interworking between PADs.


X.3
CCITT standard (1977) for a PAD (packet
assembler/disassembler), which divides a data
message into packets for transmission over a
packet-switched network and reassembles them at the
receiving side.


X.32
CCITT standard (1984) for connecting to an X.25
network by dial up.  It defines how the network
identifies the terminal for billing and security
purposes and how default parameters are negotiated
for the connection.


X.400
OSI-compliant, CCITT standard mail and messaging
protocol.  The format of an X.400 address is:

     c=  /admd=  /prmd=  /o=  /s=  /g=

     c - country
  admd - administrative management domain
           (public e-mail service)
  prmd - private management domain
           (inhouse e-mail)
     o - organization
     s - surname
     g - given name

See XAPIA.


X.500
OSI-compliant, CCITT standard protocol for
maintaining online address directories.


X.75
CCITT standard for connecting X.25 networks.


X.PC
Communications protocol developed by McDonnell
Douglas for connecting a PC to its Tymnet packet-
switched public data network.


X11
Current version of the X Window System.  X11R5
(Version 11, Release 5, Sept. 1991) provides a
stable and feature-rich environment.


X12
ANSI standard protocol for EDI.  See Tradacoms and
EDIFACT.


x86
Refers to the Intel 8086 CPU family (8086, 8088,
80186, 80286, 386, 486, Pentium).  Starting with
the 386, Intel has dropped the "80" prefix in its
reference manuals.  Same as 80x86.


              x86 CPU SPECIFICATIONS

               Bus size (bits)       Typical
CPU#    Clock          │  Max Floppy Hard Disk
(Word   Speed          │  RAM  Disk   (MB)
 Size)  (MHz)   MIPS   │ (------Bytes------)  OS
───────┬──────┬───────┬──┬───┬───────┬─────┬───────
 8088  │  5   │ .33   │ 8│ 1M│5.25"  │10-20│ DOS
 (16)  │      │       │  │   │  360K │     │
       │      │       │  │   │3.5"   │     │DR DOS
       │      │       │  │   │  720K │     │
 8086  │ 5-10 │.33-.66│16│ 1M│  1.44M│10-40│
 (16)  │      │       │  │   │       │     │
       │      │       │  │   ├───────┤     ├───────
 286   │ 6-12 │1.2-2.4│16│16M│5.25"  │20-80│ DOS
 (16)  │      │       │  │   │  360K │     │DR DOS
       │      │       │  │   │  1.3M │     │ OS/2
       │      │       │  │   │       │     │Ver 1.x
       │      │       │  │   │3.5"   │     ├───────
 386DX │16-40 │6-15   │32│ 4G│  720K │80-  │
 (32)  │      │       │  │   │  1.44M│  200│ DOS
       │      │       │  │   │  2.88M│     │
 386SX │16-33 │2.5-5  │16│16M│       │60-  │DR DOS
 (32)  │      │       │  │   │       │  100│
       │      │       │  │   │       │     │ OS/2
 386SL │20-25 │3.2-4  │16│32M│       │60-  │Ver 1.x
 (32)  │      │       │  │   │       │  100│Ver 2.x
       │      │       │  │   │       │     │
 486DX │25-66 │20-54  │32│ 4G│       │100- │ UNIX
 (32)  │      │       │  │   │       │ 2000│
       │      │       │  │   │       │     │Windows
 486SX │20-25 │16.5-20│32│ 4G│       │80-  │  NT
 (32)  │      │       │  │   │       │  500│
       │      │       │  │   │       │     │
Pentium│60-100│100-168│64│ 4G│       │400- │
 (32)  │      │       │  │   │       │ 5000│


XA
See CD ROM XA and 370/XA.


XAPIA
(X.400 API Assn.)  Consortium dedicated to
standardizing X.400 specifications.


Xbase
dBASE-like languages such as Clipper and FoxPro.
Originally almost identical to dBASE, new commands
and features over the years have made them only
partially dBASE compatible.


XCMD
(eXternal CoMmanD)  User-developed HyperCard
command written in a language such as C or Pascal.
See XFCN.


Xcopy
DOS and OS/2 utility that copies files and
subdirectories.  See DOS Xcopy.


XDOS
Software from Hunter Systems, Inc., Mountain View,
CA, that converts Intel 80x86 executable code into
Motorola 68020 code ready to run under UNIX.  A PC
program can be translated into a running program on
a UNIX-based 68020 computer.


XDR
(EXternal Data Representation)  Data format
developed by Sun that is part of its networking
standards.  It deals with integer size, byte
ordering, data representation, etc. and is used as
an interchange format.  Different systems convert
to XDR for sending and from XDR upon receipt.


XENIX
See SCO XENIX.


xerography
See electrophotographic.


XFCN
(eXternal FunCtioN)  User-developed HyperCard
function that is written in a language, such as C
or Pascal.  XFCNs usually return a value.  See
XCMD.


XGA
(EXtended Graphics Array)  IBM video display
standard (1990) optimized for graphical user
interfaces.  It adds 132 column text to VGA, plus
additional resolutions up to 1024x768 with 256
colors interlaced.  XGA-2 (1992) provides non-
interlaced 1024x768x64K.


XGML
Family of text manipulation software for PCs, Macs,
IBM mainframes, UNIX and others from Software
Exoterica Corp., Ottawa, Ontario.  With strong
support for SGML, it includes XTRAN, a language
that translates, matches and links text.


XIP
(Execute In Place)  Ability to execute a program
directly from a memory card.


Xlib
(X LIBrary)  Functions in the X Window System.  See
X toolkit.


XLISP
Microcomputer version of the LISP programming
language that has been in the public domain for a
number of years.


XMI
High-speed bus from Digital used in large VAX
machines.


Xmodem
First widely-used file transfer protocol for
personal computers, developed by Ward Christensen
for CP/M machines.  Early versions used a checksum
to detect errors.  Later versions use the more
effective CRC method (Xmodem-CRC).  Programs
typically include both methods and drop back to
checksum if CRC is not present at the other end.

   Xmodem transmits 128-byte blocks.  Xmodem-1K
improves speed by transmitting 1,024-byte blocks.
Xmodem-1K-G transmits without acknowledgment (for
error-free channels or when modems are self
correcting), but transmission is cancelled upon any
error.


XMS
(eXtended Memory Specification)  Interface that
allows DOS programs to use extended memory in 286s
and up.  It provides a set of functions for
reserving, releasing and transferring data to and
from extended memory without conflict, including
the high memory area (HMA).  See HIMEM.SYS and DOS
extender.


XMT
In communications, an abbreviation for transmit.


XNS
(Xerox Network Services)  Early Ethernet protocol
suite from Xerox.

        XNS layers       OSI layers
  0 - Transmission media   1 & 2
  1 - Internet               3
  2 - Transport              4
  3 - Control              5 & 6
  4 - Application            7


xon-xoff
In communications, a simple asynchronous protocol
that keeps the receiving device in synchronization
with the sender.  When the buffer in the receiving
device is full, it sends an x-off signal (transmit
off) to the sending device, telling it to stop
transmitting.  When the receiving device is ready
to accept more, it sends the sending device an x-on
signal (transmit on) to start again.


XPG
(X/Open Portability Guide)  Standards that specify
compliance with X/Open's Common Application
Environment (CAE).  XPG3 (Release 3), introduced in
early 1989, specifies standards for UNIX System V
Release 4.0.


XT
(1) (EXtended Technology)  First IBM PC with a hard
disk, introduced in 1983.  See PC.

(2) (Xt)  See X toolkit.


XT bus
See PC bus.


XT class
Refers to PCs that use the 8088/8086 CPU and the
8-bit bus.


XT interface
See XT bus.


XTRAN
See XGML.


XTree
PC disk management program and DOS shell from XTree
Co., San Luis Obispo, CA.  Introduced in 1985, it
was the first program to help users manage hard
disks by providing a hierarchical display of
directories.  XTreePro added a built-in text
editor, and XTreePro Gold added application
launching, split windows and file viewers.
XTreeMac for the Mac was also introduced.


XVT
(EXtensible Virtual Toolkit)  Developers toolkit
for creating user interfaces across multiple
environments from XVT Software, Inc., Boulder, CO.
Programmers create the XVT functions, which are
translated to DOS, Windows, OS/2, PM or the Mac.


XyWrite III Plus
Pronounced "zy-write."  PC word processing program
from The Technology Group (XYQUEST division),
Baltimore, MD, used extensively by major newspapers
and magazines.  It is noted for its flexibility and
typesetting orientation as well as its speed on
slow PCs.  It is both command and menu driven, has
a completely-customizable interface, provides nine
document windows and includes a programmer-oriented
macro language.

   Signature, a more sophisticated version jointly
developed by XYQUEST (Billerica, MA) and IBM, is
the successor to XyWrite III Plus and IBM's
DisplayWrite.  It automatically converts XyWrite,
DisplayWrite and DCA documents.  XyWrite 4.0,
successor to both XyWrite and Signature, includes
an auto resume feature.

   Nota Bene, originally developed by Dragonfly
Software, adds indexed text retrieval,
bibliographic and citation management to XyWrite.
In 1992, The Technology Group acquired all of these
products and created the XYQUEST division.


y-axis
See x-y matrix.


yacc
(Yet Another Compiler Compiler)  UNIX compiler that
is used to create C compilers.  Part of its code is
included in the generated compiler.  See bison.


Yellow Pages
See NIS and naming service.


Ymodem
File transfer protocol identical to Xmodem-1K plus
batch file transfer (also called Ymodem Batch).  It
is faster than standard Xmodem and sends file name
before sending the data.  Ymodem-G transmits
without acknowledgment (for error-free channels or
when modems are self correcting), but transmission
is cancelled upon any error.


Z
Mathematical language used for developing the
functional specification of a software program.
Developed in the late 1970s at Oxford University,
IBM's CICS software is specified in Z.


z-axis
Third dimension in a graphics image.  The width is
the x-axis and the height is the y-axis.


Z80
8-bit microprocessor from Zilog Corp. that was the
successor to the Intel 8080.  The Z80 was widely
used in first-generation personal computers that
used the CP/M operating system.


Z8000
16-bit microprocessor from Zilog Corporation that
is the successor to the Z80.


zap
Command that typically deletes the data within a
file but leaves the file structure intact so that
new data can be entered.


ZBR
(Zone Bit Recording)  Technique that records more
bits on a disk.  The tracks on a disk become longer
the farther they are from the center.  However, on
regular disks, the clock rate that records the bits
doesn't change, which results in the outer tracks
being less densely packed than the inner tracks.
With ZBR, the clock rate is changed based on which
track is being written, and each track is filled to
capacity.


zenix
See SCO XENIX.


zero-slot LAN
Refers to transmitting between computers over a
serial or parallel port, thus freeing up an
expansion slot normally used by LAN cards (NICs).


zero wait state
Refers to a high-speed memory that transfers its
data immediately upon being accessed without
waiting one or more machine cycles to respond.


ZiffNet
Online information service from Ziff Desktop
Information for PC users.  Provides a wide of
variety of shareware and public domain software as
well as technical forums and information.  ZiffNet
can be accessed via PRODIGY and CompuServe.
Address: 25 First St., Cambridge, MA 02141,
617/252-5000.  See online services.


zinc air
Rechargeable battery technology that provides more
charge per pound than NiCad or nickel hydride and
does not suffer from the memory effect.  It uses a
carbon membrane that absorbs oxygen, a zinc plate
and potassium hydroxide as the electrolyte.  AER
Energy Systems, Smyrna, GA, is the pioneer in this
emerging battery technology.


zip
(1) To compress a file with PKZIP.  See PK
software.

(2) (ZIP) (Zig-Zag Inline Package)  Similar to a
DIP, but smaller and tilted on its side for
mounting on boards with limited space.


Zmodem
File transfer protocol that has become very popular
because it handles noisy and changing line
conditions very well, including satellite
transmission.  It sends file name, date and size
first, uses variable length blocks and CRC error
correction.  If a download is interrupted using
Zmodem or Ymodem, Zmodem will transmit only the
remainder of the file on the next try. This is
great insurance when sending extremely long files.


Zoo
Freeware compression program, including source
code, used in UNIX, DOS and other environments.


zoom
To change from a distant view to a more close-up
view (zoom in) and vice versa (zoom out).  An
application may provide fixed or variable levels of
zoom.  A video display board (graphics adapter) may
also have built-in zoom, which provides zoom
capability for everything that is displayed
independent of and in addition to the application's
zoom levels.


zywrite
See XyWrite.



0K
(Zero Kilobytes)  Typically references motherboards
that do not include memory as priced.


0x
In programming, the symbol for a hexadecimal
number.  See x.


1-2-3
See Lotus 1-2-3.


1.2M
Refers to the 1.2MB high-density 5.25" floppy disk
used in PCs.


1.44M
Refers to the 1.44MB high-density 3.5" disk used in
PCs.


10BaseT
See Ethernet.


1401
Second-generation IBM computer introduced in 1959
and used until the late 1960s.  It had 16K of core
memory, six tape drives and used punched cards for
input.  It was an outstanding success due to its
reliability (18,000 installed).  For migration,
1401 emulators were built into IBM's 360 series.


16-bit
See bit specifications.


16450, 16550
See UART.


24-bit
See bit specifications.


2780, 3780
Standard communications protocols for transmitting
batch data.  The numbers originated with early IBM
remote job entry (RJE) terminals that included a
card reader and a printer.


286
Successor to the 8088 CPU used in the first PC (XT-
class).  Refers to the Intel 80286 CPU chip or to a
PC (AT class) that uses it.  It is more responsive
than an XT and isn't limited to its infamous one-
megabyte barrier, but is still sluggish for Windows
and graphics-intensive applications.  See PC and
x86.

              286 CPU Technical Specs
16-bit multitasking microprocessor in a 68-pin PGA,
PLCC or LCC package.  Has 15 16-bit registers
including eight general-purpose.  Operational
modes:  "Real Mode" performs as a fast 8086 CPU and
addresses 1MB memory.  "Protected Mode" addresses
16MB physical and 1GB virtual memory and provides
access to memory protection capabilities.  Contains
130,000 transistors.


286/12, 286/16...
Specification of CPU speed for a 286.  The second
number is the clock rate: 286/12 means 12MHz.


3 C's
See "PROCESSING" under computer.


3.5"
(1) Refers to the common 3 1/2 inch microfloppy
disk used in personal computers.

(2) Refers to disk drives and other devices with a
3 1/2 inch horizontal form factor.


303x
Series of medium to large-scale IBM mainframes
introduced in 1977, which includes the 3031, 3032
and 3033.  See IBM mainframes.


308x
Series of large-scale IBM mainframes introduced in
1980, which includes the 3081, 3083 and 3084.  See
IBM mainframes.


3090
Series of large-scale IBM mainframes introduced in
1986.  Before the ES/9000 models (System/390),
3090s were the largest mainframes in the System/370
line.  Models 120, 150 and 180 are single CPUs.
Models 200 through 600 are multiprocessor systems
(first digit indicates the number of CPUs).  The E,
S and J models represent increased speed
respectively.  See IBM mainframes.


32-bit
See bit specifications.


32-bit processing
In a PC, refers to programs written for the 386's
native mode, which run the fastest.  All registers,
pointers and addresses use the full 32 bits.
Although the 386 is a 32-bit machine, under DOS, it
runs applications in Real Mode, which functions as
a 16-bit 8088, the CPU in the first PC.


3270
Family of IBM mainframe terminals and related
protocols (includes 3278 mono and 3279 color
terminal).  See 3270 emulator.


3270 Data Stream
Format for transmitting data from an application to
a 3270-type terminal.


3270 emulator
Plug-in board that converts a personal computer or
workstation into an interactive IBM mainframe
terminal.  The first 3270 emulator in widespread
use was the IRMAboard.


34010, 34020
General-purpose microprocessors from TI that are
optimized for graphics and conform to the TIGA
interface.


360
See System/360.


360K
May refer to the 360K 5.25" minifloppy disk used
with PCs.


370
See System/370.


370 architecture
Refers to a computer that will run IBM mainframe
applications.  See System/370 and IBM mainframes.


370/XA
(370 EXtended Architecture)  Major enhancement
(1981) to System/370 architecture which improved
multiprocessing, introduced a new I/O system and
increased addressing from 24 to 31 bits (16MB to
2GB).


3770
Standard communications protocol for batch
transmission in an IBM SNA environment.


3780
See 2780, 3780.


37xx
IBM communications controllers that includes the
3704, 3705, 3720, 3725 and 3745 models.  The 3704
and 3705 are early units, and the 3745 models are
newer and more versatile.  The 3745 includes a
cluster controller that can connect 512 terminals,
eight token ring networks and 16 T1 lines.


386
Successor to the 286.  Also known as the 386DX, it
refers to the Intel 386 CPU chip or to a PC that
uses it.  The 386 is faster than the 286, addresses
more memory, and allows both extended and expanded
(EMS) memory to be allocated on demand.  It is more
responsive to Windows and graphics-intensive
applications than the 286.  See PC and x86.


              386 CPU Technical Specs
32-bit multitasking microprocessor in a 132-pin PGA
package.  Supports 8, 16 and 32-bit data types.
Has 32 32-bit registers including eight general-
purpose.  Operational modes:  "Real Mode" performs
as a fast 8086 CPU and addresses 1MB memory.
"Protected Mode" addresses 4GB physical and 64TB
virtual memory and provides access to memory
management, paging and memory protection
capabilities.  "Virtual 8086 Mode" is a Protected
Mode subset that runs tasks as if each were in an
individual 8086 CPU.  See Virtual 8086 mode.


                 386 CPU Family

   386 Version  Clock  Bus           Number
   (Word size   Speed  Size Maximum    of
      in bits)  (MHz) (bits)  RAM  Transistors
   ────────────┬──────┬─────┬─────┬───────────
     386DX     │16-40 │ 32  │ 4G  │ 275,000
      (32)     │      │     │     │
               │      │     │     │
     386SX     │16-33 │ 16  │ 16M │ 275,000
      (32)     │      │     │     │
               │      │     │     │
     386SL     │20-25 │ 16  │ 32M │ 857,000
      (32)     │      │     │     │



386/25, 386/33...
Specification of CPU speed for a 386.  The second
number is the clock rate: 386/25 means 25MHz.


386 Enhanced Mode
Windows operation mode.  See Windows.


386DX
See 386.


386MAX
DOS memory manager for 386s and up from Qualitas,
Inc., Bethesda, MD, noted for its advanced
capabilities.  BlueMAX is a version for PS/2
models.


386SL
Version of the 386SX designed for laptops.   It has
built in power management, and its variable clock
rate allows it to idle for long suspend and resume
periods.  Except for memory and video controller,
the 386SL and the 82360SL chip make up almost the
entire computer.  See x86.


386SLC
IBM version of the 386SX that includes an internal
8KB memory cache.  It includes power management
capabilities and runs as fast as a 386DX.


386SX
Version of the 386 from Intel that runs at slower
speeds than the 386DX, addresses only 16MB of
memory (not 4GB) and supports only a 16-bit data
bus (not 32).  It uses less power and dispells less
heat than the 386DX.  See 386SL and x86.


387
Math coprocessor for the 386.


390
See System/390.


3Com 3+
Network operating systems from 3Com Corp., Santa
Clara, CA.  3+Share is a DOS-based system that
supports PC and Mac workstations.  3+Open is OS/2
based and supports DOS, OS/2 and Mac stations.  As
of May 1993, 3Com is discontinuing its operating
system line and will remain in the LAN hardware
business offering a wide variety of adapters, hubs
and related products.


3GL
See third-generation language.


4004
First microprocessor.  Designed by Marcian E. "Ted"
Hoff at Intel, it was a 4-bit, general-purpose CPU
that was initially developed for the Japanese
Busicom calculator.


43xx
A series of medium-scale IBM mainframes initially
introduced in 1979, which include the 4300, 4321,
4331, 4341, 4361 and 4381.


486
Successor to the 386.  Also known as the 486DX, it
refers to the Intel 486 CPU chip or to a PC that
uses it.  It runs twice as fast as the 386 and
provides the speed necessary for today's graphical
interfaces.  Its built-in math coprocessor is often
required by CAD applications.

   The "Speed Doubler" DX2 is a 486 CPU with double
the internal speed.  For example, a 486/50DX2
accesses RAM and other chips on the motherboard at
25MHz, but processes internally at 50MHz.  DX chips
may be replaced with Intel's OverDrive DX2 chip.
See PC and x86.

              486 CPU Technical Specs
32-bit multitasking microprocessor in a 168-pin PGA
package.  Same registers and operational modes as
the 386 (see 386).  Uses RISC design techniques and
obtains its speed from an internal 8KB memory cache
that it quickly fills in burst mode.  The 486DX
contains 1.2 million transistors, the 486SX
contains 1.1 million.


486/25, 486/33...
Specification of CPU speed for a 486.  The second
number is the clock rate: 486/25 means 25MHz.


486DLC
486SX-compatible CPU from Cyrix Corp. that is pin
compatible with the 386DX.  Designed for upgrading
386s, it comes in a variety of speeds including
clock doubling versions.


486DX
See 486.


486DX2
See 486.


486SL
Version of the 486 from Intel designed for laptops.
It runs on 3.3 volts (instead of 5) and includes
power management features like the 386SL.


486SLC
(1) 486SX-compatible CPU from Cyrix Corporation
that is pin compatible with the 386SX, has a 1K
cache and uses a 16-bit bus.  It provides an
upgrade path for 386SXs.

(2) IBM version of the 486SX.


486SX
Version of the 486 from Intel that runs at slower
clock speeds than the 486DX and does not include
the math coprocessor.  486SXs can be upgraded to
486DX2s with Intel's OverDrive chip, which includes
the coprocessor.  The DX2 chip is plugged into the
empty coprocessor socket, disabling the original
CPU.  See 486.


487
Math coprocessor for the 486.


4GL
See fourth-generation language.


4mm tape
See DAT.


5.25"
(1) Refers to the common 5 1/4 inch floppy disk
used in personal computers.

(2) Refers to disk drives and other devices with a
5 1/4 inch horizontal form factor.


5100
First IBM desktop computer (1974).  It came with up
to 64K of RAM, a built-in tape drive and used APL
or BASIC.  Eight inch floppy disks became available
in 1976.


5250
Family of terminals and related protocols for IBM
midrange computers (System 3x, AS/400).


586
See Pentium.


64-bit
See bit specifications.


650
IBM's first major computer success.  Introduced in
1954, it used magnetic drum memory, magnetic tape
and punched cards.  By the end of the 1950s, there
were an estimated 1,800 units installed, making it
the most widely used computer in the world.


6502
8-bit microprocessor from Rockwell Int'l., Corp.
used in the Apple II and earlier Atari and
Commodore computers.


6800
8-bit microprocessor from Motorola.  The 6801 is a
computer-on-a-chip version.


68000
Family of microprocessors from Motorola that are
the CPUs in Macintoshes and a variety of
workstations.

68000 - 32-bit CPU that can address up to 16MB of
        memory and uses a 16-bit data bus.

68020 - 32-bit CPU that can address up to 4GB of
        memory and uses a 32-bit data bus.

68030 - 32-bit CPU that can address up to 4GB of
        memory and uses a 32-bit data bus.  The
        68030 runs at higher clock speeds than the
        68020 and has built-in cache memory.

68040 - Redesigned version of the 68030 that can
        run up to three times as fast.


7-bit ASCII
Refers to transferring ASCII text in which an 8-bit
byte holds the ASCII character plus a parity bit.
Some PBXs allow only 7-bit transmission.


7-track
Refers to older magnetic tape formats that record
6-bit characters plus a parity bit.


720K
May refer to the 720K microfloppy disk used in PCs.


750
See i750.


8-bit
See bit specifications.


8-N-1
(8 bits, No parity, 1 stop bit)  Common parameters
for modem transmission.


80186/80188
Integrated version of the 8086/8088 CPU that
includes additional system components, such as the
clock, DMA and interrupt controller, on the same
chip.


802.1, 802.2, etc.
See IEEE 802.


80286
See 286.


80287
See 286.


80386
See 386.


80386DX
See 386.


80386SL
See 386SL.


80386SX
See 386SX.


80387
See 386.


80486
See 486.


80486DX
See 486.


80486SX
See 486SX.


80487
See 486SX.


8080
Intel 8-bit CPU chip introduced in 1974.  It was
the successor to the first commercial 8-bit
microprocessor (8008) and precursor to the x86
family.


8086
Introduced in 1978, the CPU chip that defines the
base architecture of Intel's x86 family (XT, AT,
386, 486, Pentium).  8086s are used in some XT-
class machines.  See PC and x86.


             8086 CPU Technical Specs
16-bit microprocessor in a 40-pin CERDIP package.
Has 14 16-bit registers including eight general-
purpose.  Addresses 1MB memory using base addresses
contained in segment registers.  Contains 29,000
transistors.


80860
See 860.


8087
Math coprocessor for the 8086/8088.


8088
Intel CPU chip used in first-generation PCs (XT
class).  It is a slower version of the 8086, chosen
for migration from CP/M programs, the predominate
business applications of the early 1980s.  See PC
and x86.

             8088 CPU Technical Specs
Same as the 8086 CPU except that is uses an 8-bit
data bus instead of a 16-bit data bus.  Designed to
ease conversion from 8-bit, Z80-based CP/M
programs.  Contains 25,000 transistors.


80x86
See x86.


8100
IBM minicomputer introduced in 1978 that was
designed for departmental computing and used the
DPPX/SP operating system.


82385
Intel controller chip that manages the memory cache
in 386 and 486 CPUs.


8250A
See UART.


8514
IBM monitor used with its 8514/A display adapter.


8514/A
IBM high-resolution display adapter that provides
an interlaced display of 1024x768 with 256 colors
or 64 shades of gray.  It contains an on-board
coprocessor for performing 2-D graphics and it is
designed to coexist with VGA for dual monitor
capability.  Introduced on Micro Channel machines,
third-party vendors provide non-interlaced versions
for the ISA bus.


860
See i860.


88000
Family of 32-bit RISC microprocessors from
Motorola.  The 88100 is the first processor in the
88000 family.  Introduced in 1988, it incorporates
four built-in execution units that allow up to five
operations to be performed in parallel.


8mm tape
Tape format used in high-capacity tape drives for
backup.  See Exabyte.


9-track
Refers to magnetic tape that records 8-bit bytes
plus parity, or nine parallel tracks.  This is the
common format for 1/2" tape reels.


9370
Series of IBM entry-level mainframes introduced in
1986 that use the 370 architecture.  In 1990, the
Enterprise System models (ES/9370) were introduced,
which use the Micro Channel bus and a 386 for I/O
processing.  The ES/9370 Model 14 biprocessor
system adds a second 386 that can run DOS and OS/2
applications.  A high-speed link is available
between the 386 and 370 processors.