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1994-09-21
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KEYBOARDS
The usual way to communicate with the computer is to type
messages on the computer's keyboard.
Famous keyboards
These pages show pictures of famous keyboards:
Keyboard Page
the ideal keyboard324
IBM PC 83-key keyboard422
IBM PC 101-key keyboard422
Mac keyboard 427
Apple 2 keyboard431
Commodore keyboard438
Tandy model 4 keyboard443
Tandy Color keyboard445
IBM PC
The IBM PC's keyboard can print all the letters of the alphabet
(from A to Z), all the digits (from 0 to 9), and these symbols:
SymbolOfficial nameNicknames used by computer enthusiasts
. period dot, decimal point, point, full stop
, comma cedilla
: colon dots, double stop
; semicolon semi
! exclamation pointbang, shriek
? question markques, query, what, huh, wildchar
" quotation markquote, double quote, dieresis, rabbit ears
' apostrophesingle quote, acute accent, prime
` grave accentleft single quote, open single quote, open
quote, backquote
^ circumflexcaret, hat
~ tilde squiggle, twiddle, not
= equals is, gets, takes
+ plus add
- minus dash, hyphen
_ underline underscore, under
* asterisk star, splat, wildcard, Nathan Hale
& ampersand amper, amp, and, pretzel
@ at sign at, whorl, strudel
$ dollar signdollar, buck, string
# number signpound sign, pound, tic-tac-toe
% percent signpercent, grapes, James Bond
/ slash forward slash, rising slash, slant, stroke
\ backslash reverse slash, falling slash, backwhack
| vertical linevertical bar, bar, pipe, enlarged colon
( )parenthesesopen parenthesis & close parenthesis, left
paren & right paren
[ ]brackets open bracket & close bracket, square brackets
{ }braces curly brackets, curly braces, squiggly braces,
left tit & right tit
<>brockets angle brackets, less than & greater than, from &
to, suck & blow
For example, the symbol * is officially called an ``asterisk''.
More briefly, it's called a ``star''. It's also called a
``splat'', since it looks like a squashed bug. In some programs,
an asterisk means ``match anything'', as in a card game where the
Joker is a ``wildcard'' that matches any other card. The asterisk
is also called a ``Nathan Hale'', since he was the American
patriot who during the Revolutionary War declared this final
thought before being hanged by the British: ``I regret that I
have just one ass to risk for my country.''
The % sign
is called a ``James Bond'' because it looks like that spy's code
number: 007.
The IBM PC's
keyboard also contains special keys that help you do special
activities, such as move around the screen while you type:
Key Usual
purpose
move up,
to the line above
move
down, to the line below
move
left, to the previous character
■ move
right, to the next character
Home move
back to the beginning
End move
ahead to the end
Page Up move
back to the previous page
Page Down move
ahead to the next page
Tab hop to
next field or far to the right
Enter finish a
command or paragraph
Pause pause
until you press Enter
Print Scrn copy
from the screen to paper
Shift
capitalize a letter
Caps Lock
capitalize a whole phrase
Num Lock use
numbers on keyboard's right side
Scroll Lock change
how text moves up & down
Insert insert
new character in middle of text
Delete delete
the current character
Backspace delete
the previous character
Esc escape
from a mistake
F1 get help
from the computer
F2, F3, etc. do
special activities
Ctrl do
special activities
Alt do
special activities
Many programs make those keys serve different purposes instead.
Be safe: avoid those keys until you read the details in later
chapters.
GRAPHICS-INPUT DEVICES
If you feed the computer a picture (such as a photograph,
drawing, or diagram), the computer will analyze the picture and
even help you improve it. To feed the computer a picture, you can
use three methods. . . .
Method 1: point a video camera at what you want to take a
picture of, while the video camera is wired to a box called
Computer Eyes, which is wired to the computer.
Method 2: draw the picture on paper, then put that paper
underneath an optical scanner wired to the computer.
Method 3: draw the picture by using a pen wired to the
computer. The six popular kinds of computerized pens are light
pens, touch screens, graphics tablets, mice, trackballs, and
joysticks.
Light pens
A light pen is a computerized pen that you point at the screen
of your TV or monitor. To draw, you move the pen across the
screen.
Light pens are cheap: prices begin at $20. But light pens are
less reliable, less convenient, and less popular than other
graphics-input devices.
Touch screens
A touch screen is a special overlay that covers the screen and
lets you draw with your finger instead of with a light pen.
Graphics tablets
A graphics tablet is a computerized board that lies flat on
your desk. To draw, you move either a pen or your finger across
the board.
The cheapest graphics tablet is the Koala pad. Koala makes
versions of it for all the popular computers by IBM, Apple,
Commodore, and Radio Shack.
Fancier tablets for the IBM PC are made by Wacom.
Mice
A mouse is a
computerized box that's about as big as a pack of cigarettes. To
draw, you slide the mouse across your desk, as if it were a fat
pen.
When you slide the
typical mouse, a ball in its belly rolls on the table. The
computer senses how many times the ball rotated and in what
direction.
The mouse was invented
at Xerox's Palo Alto Research Center (PARC). The first company to
provide mice to the general public was Apple, which provided a
free mouse with every Lisa and Mac computer. Now every Mac,
Commodore Amiga, and Atari ST computer comes with a free mouse
___ and so do many IBM computers and clones.
Microsoft Mouse The
nicest mouse for the IBM PC is the Microsoft Mouse.
Its first version was
boring. Then came an improved version, nicknamed ``The Dove Bar''
because it was shaped like a bar of Dove soap. It felt great in
your hand; but trying to draw a picture by using that mouse ___
or any mouse ___ was as clumsy as drawing with a bar of soap.
The newest version of
the Microsoft Mouse is nicknamed ``The Dog's Paw'' because it's
shaped like a dog's lower leg: it's long with an asymmetrical
bump (paw) at the end. It feels even better than The Dove Bar,
unless your hand is too small to wrap around it. Discount dealers
sell it for $59.
Cheaper mice If you're
nearly broke, buy a cheaper brand of mouse. Prices start at just
$10.
Trackballs
A trackball is a box
that has a ball sticking out the top of it. To draw, just put
your fingers on the ball and rotate it.
Most notebook computers
have a trackball built into the keyboard.
Technologically, a
trackball is the same as a typical mouse: each is a box
containing a ball. For a trackball, the ball sticks up from the
box and you finger it directly; for a mouse, the ball hides
underneath and gets rotated when you move the box.
The mouse feels more
natural (somewhat like gripping a pen) but requires lots of desk
space (so you can move the box).
The trackball was
invented first. The mouse came later.
Joysticks
A joystick is a box with
a stick coming out of its top. To draw, you move the stick in any
direction (left, right, forward, back, or diagonally) as if you
were the pilot of a small airplane.
The most popular
joysticks are made by Atari and Kraft.
Atari joysticks work
just on Atari and Commodore computers. Kraft joysticks are nicer,
more expensive, and work on all popular computers by IBM, Apple,
Commodore, and Radio Shack.
SPEAKERS
To produce sounds, the typical computer uses a speaker (similar
to the speakers in your stereo system, but smaller).
The speaker is typically inside the system unit. Some computers
use the speaker in your TV or monitor instead. By using the
speaker, the computer beeps at you whenever you make an error.
Aesthetic computers, such as the Mac, can make the speaker play
nice music. The IBM PC is a boring business computer that
produces just harsh beeps, unless you make the IBM PC sound as
good as a Mac by inserting a sound card (such as the Sound
Blaster).
The fanciest computers can speak words, by attaching the
speaker to a speech synthesizer.
The newest Mac computers come with a microphone. (You can also
add a microphone to other computers.) By using the microphone,
you can make the computer record sounds. For example, you can
make the computer record the sound of your voice and imitate it,
so the computer sounds just like you!
MODEMS
You can connect your computer to a
telephone line so your computer can chat with other computers
around the world! Here's how. . . .
To let your computer chat with a
computer that's far away, attach each computer to telephone lines
by using a ``special device'' that turns computer signals into
telephone signals, and turns telephone signals back into computer
signals.
Turning a computer signal into a
telephone signal is called modulating the signal. Turning a
telephone signal back into a computer signal is called
demodulating the signal. Since the ``special device'' can
modulate and also demodulate signals, the device is called a
modulator/demodulator (or modem, which is pronounced ``mode
em'').
Acoustic versus direct-connect
You can buy two kinds of modems.
The old-fashioned kind is a black
box that has big ears on top, so that it can listen to the
telephone. Because of its big ears, it's called a Mickey Mouse
modem or an acoustic coupler. It usually costs $120.
The newer kind of modem plugs
directly into the phone system, as if it were an answering
machine. It doesn't have any ears: it has telephone wires
instead. It's called a direct-connect modem. It usually costs
under $100, and it's cheaper and more reliable than a Mickey
Mouse modem. It's more popular than a Mickey Mouse modem because
it's better than a Mickey Mouse modem in every way, except that
you can't attach it to pay phones or to phones in hotel rooms.
Kinds of direct-connect modems
A direct-connect modem can be either
external or internal. If it's external, it's a box that sits next
to your computer. If it's internal, it's a printed-circuit card
that hides inside your computer. Regardless of whether it's
external or internal, a wire runs from it to the phone system.
Internal modems are more popular
than external ones, because external modems typically cost more
and require that you buy a cable to run from the modem to the
computer. But external modems have the advantage of being easier
to control, since they give you push-buttons and blinking lights.
Many notebook computers include
internal modems at no extra charge. So do some desktop computers.
Most direct-connect modems have
fancy features, such as auto-dial (which means the modem can
memorize the other computer's phone number and dial it for you)
and auto-answer (which means the modem automatically answers the
phone whenever the other computer calls). A direct-connect modem
having many such fancy features is called smart. Nearly all
modems sold today are smart.
10 bits per character
To transmit a character, the modem
usually transmits a 10-bit number, like this: 1001011101.
The first bit (which is always a 1)
is called the start bit; it means ``hey, wake up, and get ready
to receive the data I'm going to send you''. The last bit (which
is always a 1) is called the stop bit; it means ``hey, I'm done,
you can go back to sleep until I send you more data''. The eight
middle bits (such as 00101110) are usually called the data bits:
they're a code that represents 1 byte of information (1
character). So to transmit 1 character, the modem transmits 10
bits.
Speed
The typical modem transmits 2400
bits per second (2400 bps). That speed is also called 2400 baud.
Since 10 bits make a character, that kind of modem transmits 240
characters per second. That speed is quite fast: it's about as
fast as the average person can read.
Faster modems can transmit 9600 bits
per second (which is 9600 bps, 9600 baud, 960 characters per
second). That's faster than you can read, but it's great for
transmitting documents that you want to skim, programs that you
want to run, and graphics.
Even faster modems can transmit 14400 bits per second. Since
1000 bits is called a kilobit, 14400 bits per second is called
14.4 kilobits per second (or 14.4 kbps or 14.4 kilobaud).
Some computerists still use old modems transmitting just 1200
bits per second (1200 baud) or 300 bits per second.
If you buy a fast modem, you can tell it to go slower. For
example, if you buy a 9600-baud modem, you can tell it to go at
five popular speeds: fast (9600 baud), medium (2400 baud), slow
(1200 baud), and super-slow (300 baud).
To communicate with a friend's computer, your modem must go at
the same speed as your friend's. For example, if you buy a 9600
baud modem but your friend has just a 300-baud modem, your
modem's software will detect the slowness of your friend's modem
and automatically downshift (slow down) to 300 baud.
Standards
Standards for modem communication have been invented by AT&T
and a French-speaking international committee called the Comité
Consultatif International Télégraphique et Téléphonique (CCITT).
Here's what they call their standards:
SpeedCCITT standardAT&T standard
300 bpsV.21 Bell 103
1200 bpsV.22 Bell 212a
2400 bpsV.22bis
9600 bpsV.32
14400 bpsV.32bis
19200 bpsV.32terbo
28800 bpsV.34 (or V.fast)
For example, if you see an ad for a V.22-compatible modem or a
Bell 212a modem, the ad is trying to sell you a 1200 bps modem.
Notice that the second version of V.22 is called V.22bis,
because bis is a French word that means ``2nd version''. Notice
that the third version of V.32 is called V.32terbo, because terbo
is an international word that combines the French ``ter'' (which
means 3) with the English word ``turbo'' (which means ``fast'').
Find all those terms confusing? That's why computerists say
that ``CCITT'' really stands for ``Committee for Confusing
International Telecommunications Terms''.
Data compression
Modems sometimes use a shorthand notation that lets data to be
expressed in fewer bits than normal, so more data can be
transmitted per second. The shorthand notation is called a
data-compression technique.
The most popular data-compression techniques are Microcom's MNP
level 5 (which compresses data to half as many bits as normal),
Microcom's MNP level 7 (which compresses data to a third as many
bits as normal), and CCITT's V.42bis (which compresses data to a
fourth as many bits as normal). For example, if you see an ad for
a 2400-baud modem with MNP level 5, that modem will transmit
about as much data per second as a plain 4800-baud modem.
Fax
You can send messages from your computer to fax machines around
the world, if you buy a fax/modem, which is a modem that can also
send faxes. If the fax/modem is
fancy, it can also receive faxes and print them on your printer.
The typical fax/modem
transmits modem information (to other computers) at 2400 baud. It
transmits faxes (to fax machines) at 9600 baud. It's called a
2400/9600-baud fax/modem. (Most ads list the modem speed first,
then the fax speed, because the modem speed is more important.)
More briefly, it's called a 2496 fax/modem. Warning: though every
2496 fax/modem can send faxes at 9600 baud, the cheapest 2496
fax/modems receive faxes at just 4800 baud ___ or can't receive
faxes at all!
Faster fax/modems can
transmit 14400 baud (14.4 kilobaud) for faxes and modem data.
Brands
The most famous modems
are made by Hayes, which charges high prices. Other companies
make cheaper modems that imitate Hayes' and are called
Hayes-compatible. Nearly all modems sold today are
Hayes-compatible.
For example,
high-quality Hayes-compatible modems have been built by Everex
and Practical Peripherals. To avoid competition from those
companies, Hayes sued Everex and bought Practical Peripherals. So
Everex had to pay Hayes a royalty (and eventually stopped selling
modems), and Practical Peripherals become owned by Hayes.
To pay less for a
Hayes-compatible modem, get the ones made by Zoom.
You can get another
brand, Infotel, at even lower prices. For example, you can get a
14400-baud Infotel fax/modem for just $85 internal, $99 external,
from a discount dealers such as Midwest Micro (in Ohio at
800-972-8822).
If even $85 is beyond
your budget, spend just $40, which gets you an internal fax/modem
handling modem data at 2400 baud, sending faxes at 9600 baud, and
receiving faxes at 4800 baud. That's the price for the cheapest
Best Data modem at Staples (a chain of office-supply stores);
it's also the price for the cheapest Boca Research modem at USA
Flex (an Illinois discount dealer at 800-944-5599 or
708-582-6206).
COM1 versus COM2
A modem is an example of
a serial device. You might own another serial device also, such
as a serial mouse or a serial printer.
The IBM PC can handle
two serial devices simultaneously. The first serial device is
called communication device #1 (COM1). The second serial device
is called COM2.
If you add a modem to
your IBM PC or clone, you must decide whether to call the modem
COM1 or COM2.
Most hardware and
software assume the modem is COM2. To avoid headaches, make the
modem be COM2. Here's how.
If the modem is
external, run its cable to your computer's COM2 port. (If your
computer doesn't have a COM2 port yet, buy a serial interface
card containing it.)
If the modem is
internal, make sure the switch or jumper on the modem is set to
the COM2 position; and make sure no other hardware in your
computer system is called COM2. For example, if your computer
contains a serial interface card having a COM2 port on it, you
must disable the serial interface card's COM2 port (by moving a
jumper or switch on it).
Avoid using COM3 or
COM4, since the computer has trouble handling COM3 and COM4
reliably. (COM3 often conflicts with COM1, and COM4 often
conflicts with COM2.)
TAPES
Like a disk, a magnetic tape consists of magnetized rust. Just
as you put a disk into a disk drive, you put a tape into a tape
drive.
Tape drives are slower than disk drives. To skip from the
disk's beginning to the disk's end, the disk drive's arm simply
hops from the outermost track to the innermost track. But to skip
from the beginning of a tape to the end of a tape, you must wait
for the tape drive to wind the entire tape.
Cassettes for primitive computers
The cheapest kind of tape drive is an audio cassette tape
recorder ___ the same kind you use for listening to music, at the
beach or in your car. You can attach that kind of tape recorder
to an old Radio Shack computer (such as the Radio Shack TRS-80
model 1, 3, or 4 or the Radio Shack Color Computer). Wires run
from the tape recorder to the computer, and the computer sings a
song into the tape recorder; the song is a code that represents
the data.
Unfortunately, audio cassette tape recorders aren't very
reliable. If you're using one of those old Radio Shack computers,
you can improve the reliability somewhat by getting Radio Shack's
own tape recorder, which is specially designed to work well with
computers and automatically controls the tape's volume. But since
a tape recorder is so much slower than a disk drive, I recommend
that you not buy Radio Shack's tape recorder, and instead keep
saving your pennies until someday you can afford a disk drive.
Once you've experienced the thrilling speed, convenience, and
pleasure of a disk drive, you'll never want to use a tape
recorder ever again!
Commodore & Atari Old computers by Commodore and Atari (such as
the Commodore Vic, Commodore 64, Commodore 128, and Atari 800) do
not attach to ordinary audio cassette tape recorders; you must
buy special cassette tape recorders sold by Commodore and Atari
or ___ better yet ___ buy a disk drive instead, if you can afford
it.
Coleco The Coleco Adam computer comes with a built-in cassette
tape recorder, at no extra charge. Coleco's tape recorder is
high-speed and requires specially lubricated tapes, sold by
Coleco. Since it handles just tapes that contain computer
information and cannot play ordinary musical tapes, it's called a
digital cassette tape drive instead of an audio cassette
recorder. But even though Coleco's tape recorder is
``high-speed'' and handles computer data rather well, it's still
not nearly as fast or convenient as a disk drive.
Modern microcomputers
Most people who buy
modern computers (such as the Mac, Commodore Amiga, IBM PC, and
clones) buy disk drives and don't bother using tapes at all.
If you buy a hard disk,
how do you make a backup copy of that hard disk, and where do you
put the backup? You could put the backup copy onto a second hard
disk or onto a pile of about 50 floppy disks. Another possibility
is to put the backup copy onto a special super-fast digital
cassette tape drive that holds super-long cassette tapes that can
contain backups.
Colorado The most
popular such tape drives are the Jumbo 120 and the Jumbo 250,
both built by Colorado Memory Systems (which used to be an
independent company but is now owned by Hewlett-Packard). Those
Jumbo drives work with the IBM PC and clones.
The Jumbo 120 can back
up a 120-megabyte hard disk by taking the hard disk's data,
compressing it into a shorthand notation, and then storing the
compressed data on a 60-megabyte tape. Because of that scheme,
the Jumbo 120 is called a 60/120M tape drive.
The Jumbo 250 can back
up a 250-megabyte hard disk by compressing the hard disk's data
onto a 120-megabyte tape. It's called a 120/250M tape drive.
The Jumbo 120 uses the
same blank tape as the Jumbo 250. The Jumbo 120 formats that tape
to hold 60 megabytes of data (from a 120-megabyte drive), whereas
the Jumbo 250 takes the same tape but formats it differently, to
hold 120 megabytes of data (from a 250-megabyte drive).
To buy those drives
cheaply, phone discount dealers such as USA Flex (800-USA-FLEX)
and Insight (800-755-3874). Here's what they'll charge you:
Item Price
Jumbo 120 drive $99
Jumbo 250 drive $165
tape, unformatted $15 each
(if you buy 5)
tape, formatted for Jumbo 250 $16 each
(if you buy 5)
Each Jumbo drive is
internal: it goes inside your computer. It uses the same
controller card that controls your floppy disk drives. If you
want to put the drive outside the computer, put the drive in an
external case that costs $80.
Alternatives Instead of
buying a tape drive, the typical computerist uses a pile of
floppy disks or buys a second hard drive.
Big reels for big computers
Maxicomputers and
minicomputers use big reels of tape for three purposes: to backup
big disks, to send data by mail, and to store the archives (old
files that are used rarely if ever).
The reel's diameter is
10½ inches. If you unwind the tape, you'll find the tape is half
an inch wide and almost half a mile long! The exact length is
2400 feet.
To use a reel of tape,
you put the reel into a reel-to-reel tape drive, which typically
costs about $5000 and writes 1600 bytes per inch, so that the
entire tape holds 43 megabytes. Super-fancy drives, used only on
the largest maxicomputers, squeeze 6250 bytes onto every inch
(instead of 1600), so that they squeeze 171 megabytes onto a
single reel of tape.
IBM's fanciest drive not
only writes 6250 bytes per inch but also does the writing
amazingly quickly. It moves the tape at 200 inches per second, so
that it transfers about 1.2 megabytes per second.
CASES
The motherboard and other main circuitry are enclosed in a box.
The box and the circuitry inside it are called the system unit.
The box itself ___ without its contents ___ is called the case.
Interference
The computer thinks at about the same speed (number of cycles
per second) as radio & TV waves. If you put your computer next to
a radio or TV, the computer's electromagnetic ``thought waves''
cause static on the radio or TV. To decrease that interference,
move the computer away from the radio or TV (or change the
position of the radio or TV's antenna).
The Federal Communications Commission (FCC) prohibits you from
owning any device (such as a computer) that interferes with your
neighbors' radio and TV. The FCC requires all computers to pass
the FCC class A non-interference test. Any computer used in a
residential area must also pass the FCC class B non-interference
test, which is harder to pass than the class A test.
To help the computer pass the class A and class B tests,
manufacturers line the insides of cases with metal that breaks up
the electromagnetic waves.
When you buy a computer, ask whether it's FCC class B approved.
If it's not ___ if it's just FCC class A approved ___ you cannot
legally use it in a residential area.
SURGE SUPPRESSORS
Instead of plugging your
computer into the wall, you can plug it into a surge suppressor,
which is a special extension cord that protects your computer
against surges in electrical power.
Unless you live in a
neighborhood or building that has extremely poor electricity,
don't bother buying a surge suppressor. The typical computer has
some surge protection built into it already.
If you're worried about
thunderstorms sending surges to your computer, just unplug your
computer during storms! If your air conditioner or electric
heater consumes too much electricity and causes a brownout (so
your computer acts unreliably), use a plain extension cord to
plug your computer into a different outlet, so that the
computer's not on the same circuit as the power-hungry appliance.
During the summer, most
computer errors are caused by temperatures over 95°, not by power
surges.