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Precision Software Appli…tions Silver Collection 1
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Precision Software Applications Silver Collection Volume One (PSM) (1993).iso
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INTRO.TXT
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INTRODUCTION TO COMPUTER TECHNOLOGY - INPUT, STORAGE, OUTPUT
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Before we examine computer technology let's cover two items
which seem to confuse EVERY computer beginner. It's a wonder
computer manufacturers don't include these two ESSENTIAL points
in instruction books.
First item: Booting.
Many times an instruction manual refers to "booting up" or
"booting DOS" before you can start a program. This means
inserting your DOS diskette in a floppy drive and starting the
machine with the DOS diskette in place. When you see the
familiar A> or C> prompt symbol, you have booted up! If you have
a hard drive which starts the machine automatically, the hard
drive "boots DOS" for you and you do NOT need to use the DOS
diskette. This seems simple, but many beginners are confused by
the term "booting up."
Second item: Working with floppy diskettes.
A standard floppy diskette is either 5 1/4 inches or 3 and 1/2
inches square. To insert a floppy diskette into your computer
drive, first remove it from the paper or plastic slipcover if
one protects it. The proper way to insert a floppy diskette in
most drives is as follows.
For larger 5 - 1/4 inch floppies, turn the printed label side up
and locate the TWO VERY TINY notches along one edge. Near the
notches will be a jelly bean shaped hole about one inch long cut
into the plastic surface of the diskette. This oblong hole is
the read/write opening. Insert the diskette into the drive with
the label side up and the two tiny notches FIRST into the drive
opening then close the drive locking handle. Along one edge of
the diskette you will also see a SINGLE square shaped hole which
is the write protect notch. If this write protect notch is
UNCOVERED you can BOTH read and write data to the diskette. If
the write protect notch is covered with a piece of tape, then
you can READ information from the diskette but you CANNOT write
information to the diskette. This is a safeguard feature you may
wish to use from time to time. Keep fragile diskettes away from
smoke, hair, dirt and ESPECIALLY sources of magnetism such as
motors, loudspeakers or even childrens magnetic toys which may
ERASE your data!
For smaller 3 - 1/2 inch size diskettes, turn the label side up
and locate the metal "shutter". Insert the diskette into the
drive with the label up and the shutter FIRST into the drive.
The write protect notch or opening is a small square hole with a
SLIDING PLASTIC TAB which is slid CLOSED (cannot see an open
hole) to enable BOTH reading and writing to the diskette. The
sliding tab is placed OPEN (visible open hole) to enable reading
but NOT writing.
Here is how to tell the different densities of various diskettes
your computer might need: a standard 5 - 1/4 inch, 360K
(Kilobyte) diskette has a plastic reinforcing ring around the
center hole. A 1.2MB (Megabyte) diskette does not. Small 3 - 1/2
inch, 720K diskettes have one small notch cut in the plastic
diskette casing while 1.44MB diskettes have two notches.
Time to move on to basic computer technology . . .
Computers vary widely in size and use. However all computers are
similar in what the hardware does. So-called microcomputers
(like your desktop pc) are designed for personal use, relatively
low price, and modest data processing tasks. Minicomputers are
moderate sized (a small refrigerator size) and perform more
complex tasks with larger amounts of data. Minicomputers might
be used in a small engineering office or a local bank branch to
send transaction data to a head office computer. Mainframe
computers are large, expensive and process billions of
characters of data rapidly and fill entire rooms. Finally
supercomputers are built to minimize distance between circuit
boards and operate at very high speed for complex uses such as
designing airplanes, animating complex movie sequences
graphically or solving complex engineering formulas having
billions of steps mathematically. Supercomputers are built for
raw speed.
Some terms apply to all computers. INPUT is how data gets into a
computer. The keyboard and mouse are familiar INPUT devices.
OUTPUT references how data is provided from the computer. A
Monitor or printer are good examples of OUTPUT devices. PRIMARY
STORAGE or MEMORY is the computer's immediate data storage area
- usually this is in small integrated circuit chips which hold
data ONLY while power is supplied. This PRIMARY STORAGE area is
thus temporary. More permanent SECONDARY STORAGE is used when
computer power is off or when data overflows primary storage.
This is usually floppy or hard disk drives but can include paper
tapes, punch cards, or even non-volatile magnetic bubble
memories.
How do computers store data and programs? For the PC (personal
computer) storage of data can take place either in an integrated
circuit chip or IC when the machine is on or a magnetic disk
when the machine is turned off.
The magnetic disk used to store information works in a manner
similar to a tape recorder - magnetic impressions are placed on
the tape and can be later replayed. Magnetic sound tape as a
long strip of plastic with a thin coating of a metallic, easily
magnetized powder glued to the surface of the plastic strip.
When a electrically driven coil is placed near the surface of
the plastic strip, thousands of little magnets are created on
the surface of the tape as it rapidly streams beneath the coil.
Later these little magnets can induce current to flow in the
coil as the tape is pulled past the coil a second time. Thus the
information or music is replayed. During recording, the
electrical coil receives electric pulses which produce small
magnetic "blips" along the tape. During playback, the coil is
passive and the little magnetic pulses passing below its surface
create electric pulses in the coil which are amplified.
A magnetic computer disk works in the same fashion but spins in
a circle like a music record rather than moving in a straight
line like recording tape. Magnetic computer disks are available
in two basic types: floppy and hard disks. A hard disk can hold
considerably more information than a floppy disk - frequently
millions of computer words (or "bytes") while a floppy disk
holds less than a million in many cases. However what the floppy
disk loses in capacity in gains in the advantage of portability
since it can easily be removed from the pc and stored which is
not true of the hard disk.
On a typical music cassette tape you will find two channels
(left and right speakers) and a total of four tracks (side A of
the tape and side B.) Think of this as four lines of
"information" running the length of the music tape. On a
computer disk data is stored in a similar manner except there
are far more tracks of information and of course the tracks are
arranged in circles on a flat surface like a music record or
compact CD disk.
Tracks of computer information are written to and read from the
computer disk by a read/write coil (head) that moves rapidly
across the surface of the disk in a fashion similar to a record
player needle on a music record. Most current disks (360K IBM
format) have 40 tracks which are numbered from 0 to 39. The low
numbers are towards the edge of the disk - the high numbers
towards the center.
Tracks, the circular data paths on the disk, are divided into
still smaller units called sectors with the number of sectors
varying with the exact DOS operating system you use on your PC.
MS-DOS version 2.0 and higher versions use nine sectors per
track. DOS 2.0 and above can read the older eight sector disks
created by DOS version 1.1 but the reverse is not true. Each
track is divided into the same number of sectors like pieces of
apple pie. The sectors contain the magnetic bits or pulses of
information which the computer records in a special index
(called the file allocation table or FAT) so that it can quickly
move from sector to sector sniffing out information on the disk.
When you format a disk you ask the computer to inspect the
magnetic surface of the disk for any errors, prepare it for use
by future data and create an index "file allocation table (FAT)"
which is like a card index for a large library of books.
Formatting a disk is a little like taking a blank piece of paper
and using a pencil and ruler to turn it into graph paper with
both horizontal and vertical lines. What was blank before now
has little cells or file drawers which can hold information.
The file allocation table is so crucial to keeping track of
where the data is on the disk that DOS (the disk operating
system) usually keeps two copies in case of errors. Without a
file allocation table the disk is like a large public library
with no card catalog index and (worse still) every light in the
building has been turned off! Certain utilities contained in DOS
(i.e., the debug utility) and other software programs can adjust
or repair the file allocation table but generally this is a
delicate operation a beginner should not attempt.
Floppy disks are available in two types: single and double
sided. This means that the manufacturer guarantees only one (or
both) sides of the disk as capable of holding magnetic pulses.
Usually both sides of all disks are chemically coated, but the
manufacturer may have found defects and advises use of only one
side. IBM compatible machines usually use double sided, double
density disks (abbreviated as DSDD on the package.) Single
density disks record magnetic pulses or computer bits at 2,768
bits per inch and double density at 5,876 bits per inch. A
single sided disk may work in a machine for a while, but you DO
stand a risk that the data may be lost in time on the second
"non-certified" side of a single sided disk. Do NOT turn over a
disk and attempt to use the other side! Two problems arise: the
disk spins in the opposite direction which may cause data errors
and the small write protect notch is in the wrong location which
may damage the floppy drive mechanism.
What is the difference between a bit and a byte? The IBM PC and
its clones generally use 8 bits (electrical pulses) to make up
a byte (computer word.) A ninth "odd bit" is used for error
checking (parity testing) to make sure the other eight bits are
not accidentally erased or lost during storage or use by the
computer.
Bits are like alphabet characters and bytes are like the words
made up from alphabet characters. So how many bytes are stored
on a floppy disk? 40 tracks per side x 2 sides per disk x 9 sectors
per track x 512 bytes per sector = 368,640 bytes stored per disk
assuming DOS version 2.0 or later. Basically this means about one
third of a million pieces of data information - quite a bit!
On the side of all floppy disks is a small square notch. If the
notch is uncovered, data can be freely written to the disk. If
covered with tape, the PC will NOT write to the disk but CAN
read from the disk. This is called the write protect tab. Be
careful when handling disks! Since the read/write magnetic head
on a floppy rides delicately in contact with the disk, tiny
obstructions can cause it to jump, skip or scratch the disk and
lose your data. Fingerprints, smoke, hair and moisture can cause
problems. Always handle a floppy disk by the edges of its
protective plastic "jacket" and replace it in a paper or plastic
Tyvek slipcover sleeve when not in use. In addition, magnets, x-
rays, televisions and other sources of stray magnetism can cause
a floppy disk to lose data.
Hard disks have many of the same characteristics as floppy
disks, but are managed and maintained in a different manner as
we will see in a later expanded tutorial on hard disks within
package. In brief, however, hard disks use aluminum or hardened
glass platters rather than flexible plastic mylar. Usually
several platters are stacked together within a single hard drive
unit. The number of stacked platters determine the data capacity
of the hard drive unit. Because the hard disk platter spins much
faster and holds data packed more tightly that a floppy disk,
the hard drive unit is usually sealed in a metal shroud or
container to eliminate dust or other contaminants. A sealed hard
drive is sometimes referred to as a Winchester disk or Fixed
drive. Where a floppy disk might hold approximately 360,000
bytes (abbreviated as 360K), a hard drive holds 10 Megabytes
(million bytes) or more. As we will discuss later, backing up
(making spare copies of hard drive data onto floppy or tape) is
a necessary task since hard drives can and do fail - taking
precious data with them. The bottom line is that once you get
started with a computer, quite quickly your data becomes far
more valuable than the computer in which it resides!
Since we have briefly covered data storage we need to talk about
data input. Two primary input devices are central to getting
data into a pc. The keyboard and the mouse. We will discuss the
keyboard in greater detail in a later tutorial. The mouse is an
alternate input device which is rolled or moved across the
desktop to position a cursor or pointer on the computer screen.
The mouse also contains several buttons to help select items on
data on the monitor screen. A mouse is not necessary for
computer input - it is an optional device.
Another introductory topic is that of output devices such as a
monitor, printer or plotter.
A plotter is a device which uses a motor to move pens or drawing
implements in tightly controlled horizontal and vertical motions
on a piece of paper or film. The computer can control a plotter
to combine on one piece of paper differing pen colors and text
and pictures stored within the computer. Computer plotter can be
purchased with flat table or flat bed configurations or in
models which move the pen(s) back and forth with gears that also
drive the paper movement at the same time.
The printer is probably the most common and useful output device
attached to your computer. There are many types of modern
computer printer with differing speeds and capabilities. The
most common printer is the dot matrix printer which provides
characters made up from tiny dots of ink on paper. The Daisy
wheel printer uses a rapidly spinning wheel to imprint each
letter separately like any ordinary typewriter. Line printers
print entire lines of text in one sweep then move to the next
line and are thus very fast. Ink jet printers produce characters
made from individual dots of ink sprayed onto the paper. Thermal
printers contain tiny wires which burn and thus darken special
thermal paper into tiny letters and dots which we can read.
Finally laser printers use a rapidly scanning laser to sensitize
a polished drum with an entire page of information quickly and
look and work roughly like an office copier. The first three
types of printer are classified as impact printers since
something strikes the paper which the later three are non impact
printers.
The oldest printer design is the thermal printer which
maintained some popularity and was easy to manufacture, however
the use of thermal printers is fading since the special heat
sensitive paper is expensive and subject to random extraneous
marks and blurring.
The laser and ink jet printers are becoming more popular due to
rapid speed of printing and quiet mode of operation. They are
expensive with prices ranging from $600 to $2000. The ink jet
printer squirts individual dots of ink onto the paper to form
letters or other characters. A high quality paper is necessary
since the wet ink can smear if not carefully handled.
The laser printer is used for quickly producing one page of text
at a time. In operation, the laser scans a polished drum with an
image which is then dusted with dark toner particles which stick
to the exposed areas made sensitive by the laser. Paper is then
placed in contact with the drum and the toner is transferred to
the page and is finally fused with heat to "fix" or seal the
toner particles to the page.
Dot matrix and daisy wheel printers are common and affordable
alternatives for many small offices and home computer hobbyists.
The two differ in the sharpness and quality of the final printed
document.
Dot matrix printers produce letters via small pins which strike
the ink ribbon and paper to produce print which can be jagged
looking. Nine pin dot matrix printers produce somewhat rough
looking letters while 24 pin dot matrix printers produce
crisper, fully-formed letters. In many cases the 24 pin dot
matrix printer approaches the quality of the daisy wheel printer
which seems to be fading from the computer printer scene. Both
dot matrix and daisy wheel printers strike the paper through a
ribbon to transfer ink to the printed page.
Connecting a printer via a cable to the computer is always done
through one of two plugs (or interfaces) on the back of the
computer. One type of interface (computer plug) is serial, the
other called parallel. The most commonly used interface for
printers today is the parallel interface but serial interface
printers do exist. What is the difference? Recall that there are
eight bits (computer dots and dashes) to a byte (or computer
word). The serial interface has each bit sent one at a time to
the printer - like men in single file at the supermarket
checkstand. The parallel interface sends all eight bits at once
- like eight men all entering eight supermarket checkstands at
once. Each interface is different, the printer manufacturer will
tell you which interface to use. As a clue, frequently modems or
mouse devices use the serial interface leaving the printer to
the parallel interface.
We have talked about output to paper, next let's briefly discuss
output to a monitor or screen. The monitor or video display
works much like your television - some older home computers
still use a TV. Another term for a monitor is the cathode ray
tube or CRT. Monitors differ in the sharpness or resolution they
can display. On the low end of the resolution spectrum is the
monochrome (single color) monitor frequently available in either
green or amber screens. Next is the color RGB monitor (RGB
stands for Red, Green and Blue) which displays low resolution
color dots to make up an image. Higher resolution is obtained
with an EGA monitor (Enhanced Graphics Adapter) and still higher
with a VGA (Video Graphics Array) Monitor. Each monitor is mated
to work with a circuit card located within the body of the
computer. One way to upgrade a computer is to switch both the
monitor and display/graphics circuit card to produce a sharper,
more colorful image. The dots which make up all images on the
monitor screen are called pixels. The smaller the pixels, the
higher and sharper the image resolution.
What is the difference between computer hardware and software?
In simplest terms, hardware is the physical parts associated
with a computer - the circuit boards, floppy drives, printers,
cables and physical pieces of a system. Software is the
electronic instructions necessary to make the computer perform.
These instructions are usually stored inside a piece of hardware
(e.g., software instructions stored inside a circuit chip or
floppy drive) but they are nevertheless software. There are two
major types of software: operating system software and
applications software.
Operating system software (like DOS) performs very elemental
housekeeping instructions (e.g., where is monitor, how can I
keep track of what data is on which track or sector of a floppy
drive.)
Applications programs perform tasks on a higher level (e.g.,
word processing programs or database programs are applications.)
Generally an application software package uses the lower level
operating system (DOS) to do routine tasks (e.g., your word
processing application uses the lower level DOS operating system
frequently to write and store data on a disk.
We interrupt this tutorial for a brief reminder: be sure to
submit your registration fee to receive your BONUS DISKS!
Now back to our regularly scheduled tutorial . . .
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INTRODUCTION TO COMPUTER TECHNOLOGY - PROCESSING AND THE CPU
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You can pause for a while if you like or go onto to another
tutorial. But if you want delve into great complexity, read on.
Now it's time to delve deeper into the heart of the computer.
The central processing unit or CPU is the "brains" of every
computer. On the PC, the CPU is simply a tiny integrated
circuit. It is the control center and contains two circuit
elements to perform tasks plus several special locations or
memory areas called registers which hold instructions.
Registers, located within the CPU chip are temporary storage
locations which hold instructions. Secondly, the arithmetic
logic unit or ALU is the location within the CPU where seven
basic math and logic operations take place (such as addition and
subtraction.) Finally, the control unit is a portion of the CPU
which directs all elements of the computer. It does not add or
subtract like the ALU, it only directs the activity.
Let's first examine the registers within the CPU. Four registers
are present in the CPU - some computers contain more than four.
The storage register is simply a parking area for information
taken from or sent to memory. The accumulator register
accumulate the results of calculations. The address register
stores the location of where the information or instructions are
located. Finally, one or more general purpose registers are
usually available and have several functions which can
interchangeably include addressing (where is it?) or arithmetic
(add or subtract it.)
Registers can vary in size or bits with the variety of the
computer. 8-bit registers are common on small computers. 16-bits
for larger personal computers. And finally minis, mainframes and
supercomputers have 64-bit or larger registers. This length (8-
bit, 16-bit, etc) is called a word and frequently larger and
more powerful computers feature larger register size.
Despite this seeming complexity a basic fact remains: all
digital computers can only add and subtract two numbers: zero
and one! Let's back up a bit. For purposes of digital computer
electronics, internally a computer can only respond to two
things: on and off - just like a light switch. These electronic
states of being might actually be a positive and negative
voltage or a high and low voltage stored in a series of
transistors etched in silicon on a chip, but to the computer the
logic is on or off. Two conditions, that is all.
Back in the human world we can represent these as one and zero
(1 and 0). A special branch of mathematics deals with
calculations of numbers represented by 1 and 0 which is called
binary arithmetic.
Each one or zero is a pulse of electricity or magnetism
(electricity inside a chip, magnetism out on the surface of a
floppy disk.) Each pulse, either a 1 or 0 is called a bit. Whole
series of bits in a row can be used to represent numbers larger
than 9 in our human decimal system. Bits in strings of eight
units are called bytes. One byte represents a single character
of data in the computer. As a curious aside, a nibble is half a
byte or four bits.
We go back to our analogy of the light switch (on and off
representing one and zero to a computer.) In simplest terms, if
we have two light switches we have the following ideas:
OFF OFF = 0 0 = (human decimal number) zero = 0
OFF ON = 0 1 = (human decimal number) one = 1
ON OFF = 1 0 = (human decimal number) two = 2
ON ON = 1 1 = (human decimal number) three = 3
Notice something peculiar: in the above we find FOUR binary
numbers (0,1,2,3) but THREE human decimal numbers (1,2,3.) We
rarely think of 0 as a number since we consider it NOTHING.) To
computers ZERO is always a number!!!
Going a little further a single bit can only represent two
numbers: (ON or OFF = 1 or 0 ). Two bits (our above example can
represent four numbers (0,1,2,3). And four bits could represent
16 numbers. If you go all the way to a byte (eight bits) you
could get 256 numbers. The pattern is that each additional bit
doubles the quantity of possible numbers.
To a computer these binary numbers march together in a long
string, one after another. Remember, the CPU has only two
numbers to work with: 1 and 0.
Human Computer
Decimals Binary
0 - 0
1 - 1
2 - 10
3 - 11
4 - 100
5 - 101
6 - 110
7 - 111
8 - 1000
9 - 1001
10 - 1010
11 - 1011
12 - 1100
13 - 1101
14 - 1110
15 - 1111
Notice several eccentricities about this system. In binary,
start on the right and keep adding digits to the left. When you
fill a space with all 1's, you zero out everything, add one
digit to the left, and start with "1" again. When you reach
binary 111 you start the WHOLE series over again with a 1 in
front of it. One bit counts two numbers, two bits count four,
three bits count eight and so on as we mentioned earlier. When
you add a binary digit to the growing string of 1's and 0's you
double the number of total decimal digits you can use!
These eccentricities appear odd, but to the computer they are
shortcuts which simplify calculations and keep things to 1's and
0's. It is this simple system of on and off (like light
switches) which make computers and their odd binary system so
FAST!
Now that we understand the basic binary arithmetic of a computer
we can say a few words about addressing. Simply put, each piece
of information in the computer lives in a little memory location
(like eggs in a carton -each egg is a piece of data, each carton
hole is an address or location.) Each address is unique, of
course. The first address, the second, and so on. How many
addresses can an 8-bit binary number describe? 256. A 16-bit
number can specify 65536 addresses or possible locations for
data.
As we finish our introduction to computer technology we should
briefly list a few terms. There are more in the glossary
contained elsewhere on this disk.
Kilo - Thousand units. Example: kilobyte. Because of the binary
math associated, this is actually 1024 bytes. Frequently
abbreviated as the simple letter "K".
Meg - Million. Example: 20 Meg hard disk which hold 20 million
bytes approximately.
Millisecond - One thousandth of a second.
Microsecond - One millionth of a second.
Nanosecond - One billionth of a second.
Picosecond - One trillionth of a second.
Tutorial finished. Be sure to order your THREE BONUS DISKS which
expand this software package with vital tools, updates and
additional tutorial material for laptop users! Send $29.95 to
Seattle Scientific Photography, Department LAP, PO Box 1506,
Mercer Island, WA 98040. Bonus disks shipped promptly! Some
portions of this software package use sections from the larger
PC-Learn tutorial system which you will also receive with your
order. Modifications, custom program versions, site and LAN
licenses of this package for business or corporate use are
possible, contact the author. This software is shareware - an
honor system which means TRY BEFORE YOU BUY. Press escape key to
return to menu.