The usual way to communicate with the computer is to type messages on the computerís keyboard.

On the original IBM PC, the keyboard contained 83 keys. In January 1986, IBM began selling a fancier keyboard, which contained 101 keys:

┌───┐ ┌───┬───┬───┬───┐ ┌───┬───┬───┬───┐ ┌───┬───┬───┬───┐ ┌───────────┬──────────┬─────┐

│Esc│ │F1 │F2 │F3 │F4 │ │F5 │F6 │F7 │F8 │ │F9 │F10│F11│F12│ │PrintScreen│ScrollLock│Pause│

└───┘ └───┴───┴───┴───┘ └───┴───┴───┴───┘ └───┴───┴───┴───┘ └───────────┴──────────┴─────┘

┌─────┬───┬───┬───┬───┬───┬───┬───┬───┬───┬───┬───┬───┬───────┐ ┌────────┬────────┬────────┐ ┌───────┬────┬────┬─────┐

│ ~ │ ! │ @ │ # │ $ │ % │ ^ │ & │ * │ ( │ ) │ │ + │ │ │ │ │ │ │ │ │ │ │

│ ` │ 1 │ 2 │ 3 │ 4 │ 5 │ 6 │ 7 │ 8 │ 9 │ 0 │ - │ = │ Backsp│ │ Insert │ Home │ PageUp │ │NumLock│ / │ * │ - │

├─────┴─┬─┴─┬─┴─┬─┴─┬─┴─┬─┴─┬─┴─┬─┴─┬─┴─┬─┴─┬─┴─┬─┴─┬─┴─┬─────┤ ├────────┼────────┼────────┤ ├───────┼────┼────┼─────┤

│LeftTab│ Q │ W │ E │ R │ T │ Y │ U │ I │ O │ P │ { │ } │ | │ │ │ │ │ │ 7 │ 8 │ 9 │ │

│Tab │ │ │ │ │ │ │ │ │ │ │ [ │ ] │ \ │ │ Delete │ End │PageDown│ │ Home │ │PgUp│ │

├───────┴┬──┴┬──┴┬──┴┬──┴┬──┴┬──┴┬──┴┬──┴┬──┴┬──┴┬──┴┬──┴─────┤ └────────┴────────┴────────┘ ├───────┼────┼────┤ │

│ │ A │ S │ D │ F │ G │ H │ J │ K │ L │ : │ " │ │ │ 4 │ 5 │ 6 │ │

│CapsLock│ │ │ │ │ │ │ │ │ │ ; │ ' │ Enter│ │ │ │ │ + │

├────────┴─┬─┴─┬─┴─┬─┴─┬─┴─┬─┴─┬─┴─┬─┴─┬─┴─┬─┴─┬─┴─┬─┴────────┤ ┌────────┐ ├───────┼────┼────┼─────┤

│ │ Z │ X │ C │ V │ B │ N │ M │ < │ > │ ? │ │ │ │ │ 1 │ 2 │ 3 │ │

│Shift │ │ │ │ │ │ │ │ , │ . │ / │ Shift│ │ │ │ End │ │PgDn│ │

├──────────┴┬──┴──┬┴───┴───┴───┴───┴───┴───┴──┬┴───┴┬─────────┤ ┌────────┼────────┼────────┐ ├───────┴────┼────┤ │

│ │ │ │ │ │ │ │ │ │ │ 0 │ . │ │

│Ctrl │ Alt │ Space │ Alt │ Ctrl│ │ │ │ Ins │Del │Enter│

└───────────┴─────┴───────────────────────────┴─────┴─────────┘ └────────┴────────┴────────┘ └────────────┴────┴─────┘

Now IBM sells just that 101-key keyboard; it no longer sells the old 83-key keyboard.

The keyboard can print all the letters of the alphabet (from A to Z), all the digits (from 0 to 9), and these symbols:

Symbol Official name Nicknames used by computer enthusiasts

. period dot, decimal point, point, full stop

, comma cedilla

: colon dots, double stop

; semicolon semi

! exclamation point bang, shriek

? question mark ques, query, what, huh, wildchar

" quotation mark quote, double quote, dieresis, rabbit ears

Ď apostrophe single quote, acute accent, prime

` grave accent left single quote, open single quote, open quote, backquote

^ circumflex caret, hat

~ tilde squiggle, twiddle, not

= equals is, gets, takes

+ plus add

- minus dash, hyphen

_ underline underscore, under

* asterisk star, splat, wildcard

& ampersand amper, amp, and, pretzel

@ at sign at, whorl, strudel

$ dollar sign dollar, buck, string

# number sign pound sign, pound, tic-tac-toe

% percent sign percent, grapes

/ slash forward slash, rising slash, slant, stroke

\ backslash reverse slash, falling slash, backwhack

| vertical line vertical bar, bar, pipe, enlarged colon

( ) parentheses open 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, itís called a "star". Itís 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 Jokerís a "wildcard" that matches any other card.

In the diagram above, I wrote just the words "Shift", "Backsp", "LeftTab", "Tab", and "Enter" on some keys; but to help people who donít read English, IBM put arrows on those keys.

The SHIFT key shows an arrow pointing up.

The BACKSPACE key shows arrow pointing left.

The TAB key shows arrows crashing into walls.

The ENTER key shows an arrow thatís bent.

Stare at your computerís keyboard and find these keys:

Key Where to find it

TAB key left of the Q key

BACKSPACE if 101 keys, left of INSERT key

if 83 keys, left of NUM LOCK

SHIFT keys if 101 keys, above the Ctrl keys

if 83 keys, above Alt & CapsLock

ENTER key if 101 keys, above right SHIFT key

if 83 keys, above the PrtSc key

If a key has two symbols on it, the key normally uses the bottom symbol. To type the top symbol instead, press the key while holding down the SHIFT key.

To type a number easily, use the keys in the top row of the keyboardís main section. (For example, to type 4, press the key that has a 4 and a dollar sign.) Do not press the number keys on the right side of the keyboard: they produce numbers just if the NUM LOCK key is pressed beforehand, by you or the computer. If the NUM LOCK key was pressed to produce numbers, and you want to stop making those keys produce numbers, just tap the NUM LOCK key again.

The keyboard contains special keys that help you do special activities (such as moving around the screen while you type):

Key Usual purpose

move up, to the line above

move down, to the line below

Ď move left, to the previous character

í 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 keyboardís 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

Some programs make those keys serve different purposes. Avoid those keys until you read the details in later chapters.

When buying a keyboard, you have many choices. You can buy an XT keyboard (83 keys), AT keyboard (101 keys), augmented AT keyboard (101 keys plus an extra copy of the backslash key), or Windows 95 keyboard (101 keys plus 3 special keys that help run software called "Windows 95"). You can buy a standard-size keyboard (with a ledge above the top row, for placing your pencil or notes), compact keyboard (which has no ledge and consumes less desk space), foldable keyboard (which folds in half, as if youíre closing a book, so it consumes half as much desk space when not in use), or split keyboard (whose left third is separated from the rest, so you can have the comfort of typing while your forearms are parallel to each other). You can buy a tactile keyboard (which gives you helpful feedback by making a click whenever you hit a key), silent keyboard (which helps your neighbors by not making clicks), or spill-resistant keyboard (which is silent and also doesnít mind having coffee or soda spilled on it).

The best split keyboard is the one made by Addison because itís tactile, requires little pressure, and costs just $50 at Staples discount stores.

Phone Janesway at 800-431-1348 or 914-699-6710.

At extension 2230, ask Joel Hudesman for the best spill-resistant keyboards ($30) and foldable keyboards ($70). Get free shipping by saying youíve read the Secret Guide.

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 of an object, you can use three methods.Ö

Method 1: point a video camera at the object, while the video camera is wired to the computer.

Method 2: draw on paper, which you then feed to an optical scanner wired to the computer.

Method 3: draw the picture by using a pen wired to the computer. The computerized pen can be a
light pen, touch screen, graphics tablet, mouse, trackball, or joystick.

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. Modern notebook computers include a tiny graphics tablet (called a touchpad or glidepad), stroked with your finger and built into the keyboard (in front of the SPACE bar).


A mouse is a computerized box thatís 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 Xeroxís 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 a free mouse comes with each IBM PC and clone, too.

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 ó or any mouse ó was as clumsy as drawing with a bar of soap. The newest version of the Microsoft Mouse is nicknamed "The Dogís Paw" because itís shaped like a dogís lower leg: itís 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. Other brands cost less; the cheapest cost just $10.


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. Some notebook computers have a trackball built into the keyboard.

Technologically, a trackballís 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 and has become more popular ó except on notebook computers, which use trackballs and touchpads to save space.


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.


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. The newest computers come with a pair of external stereo speakers, which sit outside the system unit and produce louder sounds. The fanciest new computers come with three external stereo speakers: the third speaker is called the subwoofer and produces a big, loud, booming bass.

Aesthetic computers, such as the Mac, can make speakers play nice music. IBMís first PC was a boring business computer that produced just harsh beeps, but IBMís newest computers let you produce sounds as good as a Mac by inserting a sound card (such as the Sound Blaster).

Fancy computers speak words by including circuitry called a speech synthesizer.

The newest computers come with a microphone. 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!


You can connect your computer to a telephone line so your computer can chat with other computers around the world! Hereís how.Ö

To let your computer chat with a computer thatís 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, itís 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 doesnít have any ears: it has telephone wires instead. Itís called a direct-connect modem. It usually costs under $100, and itís cheaper and more reliable than a Mickey Mouse modem. Itís more popular than a Mickey Mouse modem because itís better than a Mickey Mouse modem in every way, except that you canít 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 itís external, itís a box that sits next to your computer. If itís internal, itís a printed-circuit card that hides inside your computer. Regardless of whether itís external or internal, a wire runs from it to the phone system.

Internal modems are more popular than external ones, because external modems 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.

Most computers include internal modems at no extra charge.

Most direct-connect modems have fancy features, such as auto-dial (which means the modem can memorize the other computerís 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 Iím going to send you". The last bit (which is always a 1) is called the stop bit; it means "hey, Iím 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: theyíre a code that represents 1 byte of information (1 character). So to transmit 1 character, the modem transmits 10 bits.


A traditional 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 reasonably fast: itís 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). Thatís faster than you can read, but itís appropriate 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).

All those modems are obsolete. Now the most common speed for transmitting data is 28.8 kilobits per second (which is 28.8 kbps, 28.8 kilobaud).

Most modems sold today can go even faster, 33.6 kilobits per second, but most people using them still transmit at just 28.8 kilobits per second to be compatible with friends using older modems.

Slowing down A few computerists still use ancient, primitive 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 33.6-kilobaud modem, you can tell it to go at eight popular speeds: super-fast (33.6 kilobaud), fast (28.8 kilobaud), medium-fast 14.4 kilobaud), medium (9600 baud), medium-slow (2400 baud), slow (1200 baud), and super-slow (300 baud).

To communicate with a friendís computer, your modem must go at the same speed as your friendís. For example, if you buy a 33.6-kilobaud modem but your friend has just a 300-baud modem, your modemís software will detect the slowness of your friendís modem and automatically downshift (slow down) to 300 baud.

56-kilobaud modems The newest modems claim to go even faster, about 56 kilobits per second (56 kbps, 56 kilobaud), but those claims are misleading!

The governmentís Federal Communications Commission (FCC) restricts phone transmissions to 53 kilobaud, to prevent phone switches from overheating. In most communities, the phone companies canít handle transmissions faster than 45 kilobaud reliably. So if you buy a 56-kilobaud modem, it will probably be restricted to about 45 kilobaud.

In 25% of all communities, the phone system is so poor that a 56-kilobaud modem wonít go any faster than a 33.6-kilobaud modem.

Moreover, so-called "56-kilobaud modems" go faster than 33.6 kilobaud just when youíre using the Internet (not when youíre communicating directly with friends), and just when youíre receiving (not sending) Internet data, and just when youíre receiving the data from an Internet service provider that uses the same type of 56-kilobaud modem as yours. (One type of 56-kilobaud modem, called x2, was invented by U.S. Robotics, which makes modems and is now a division of 3Com. The other type, called K56flex, was invented by modem-chip-maker Rockwell and AT&T-spinoff Lucent. The two types are not compatible with each other. A third type is being developed. Most modem makers promise a free upgrade to the third type.)


Standards for modem communication have been invented by AT&T and the International Telecommunications Union (ITU). Hereís what they call their standards:

Speed ITU standard AT&T standard

300 bps V.21 Bell 103

1200 bps V.22 Bell 212a

2400 bps V.22bis

9600 bps V.32

14400 bps V.32bis

19200 bps V.32terbo

28800 bps V.34 (or

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.

Though the ITU speaks English, it used to speak French and have a French name (the Comité Consultatif International Télégraphique et Téléphonique, or CCITT).

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"). Those confusing terms made folks complain that "CCITT" stood for "Committee for Confusing International Telecommunications Terms".

In 1998, the ITU expects to develop a standard for 56-kilobaud modems. Modem makers promise that if you buy an X2 or K56flex modem, youíll get a free upgrade to an ITU-standard 56.6-kilobaud modem.


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 modern fax/modem can transmit modem data (to other computers) at 33.6 kilobaud but transmits faxes (to fax machines) at just 14.4 kilobaud. Itís called a 33.6/14.4-kilobaud fax/modem. (Most ads list the modem speed first, then the fax speed, because the modem speed is more important.)

A few years ago, the most common kind of fax/modem was a slow kind that sends modem data at 2400 baud, faxes at 9600 baud. Itís called a 2400/9600-baud fax/modem. More briefly, itís called a 2496 fax/modem. Yes, every 2496 fax/modem can send faxes at 9600 baud; but the cheapest 2496 fax/modems receive faxes at just 4800 baud ó or canít receive faxes at all!


The most famous modems are made by Hayes, which charges high prices. Other companies make cheaper modems that imitate Hayesí 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 became owned by Hayes.

To pay less for a Hayes-compatible modem, get the ones made by U.S. Robotics or competitors. For example, you can get a U.S. Robotics internal 33.6-kilobaud fax/modem for a net cost of just $56 (after you receive a rebate). You can get a U.S. Robotics internal x2 56-kilobaud fax/modem for $106 (after rebate). Those prices are from a New York discount dealer called Tri State Computer (800-433-5199 or 212-633-2530; ask for David Rohinsky at extension 223).

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. Hereís how.

If the modem is external, run its cable to your computerís COM2 port. (If your computer doesnít 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 cardís 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.)


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 diskís beginning to the diskís end, the disk driveís 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 ó the same kind you use for listening to music, at the beach or in your car.

Radio Shack 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 arenít very reliable.

If youíre using one of those old Radio Shack computers, you can improve the reliability somewhat by getting Radio Shackís own tape recorder, which is specially designed to work well with computers and automatically controls the tapeís volume. But since a tape recorder is so much slower than a disk drive, I recommend that you not buy Radio Shackís tape recorder, and instead keep saving your pennies until you can afford a disk drive.

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 ó better yet óbuy a disk drive instead, if you can afford it.

Coleco The Adam computer, manufactured by Coleco, comes with a built-in cassette tape recorder, at no extra charge. That 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, itís called a digital cassette tape drive instead of an audio cassette recorder. But though Colecoís tape recorder handles computer data rather well and is called "high-speed", itís slower than 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 donít 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 have been the Jumbo 120, the Jumbo 250, and the Jumbo 350, all 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 diskís 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 diskís data onto a 120-megabyte tape.

The Jumbo 350 can back up a 350-megabyte hard disk by compressing the hard diskís data onto a 170-megabyte tape. The drive costs $69. The tapes cost $17 each (in quantity 5).

The newest drives from Colorado are the T1000 (which backs up an 800-megabyte hard disk by compressing onto a 400-megabyte tape, $99 for the drive, $29 for the tape) and the T3000 (which backs up a 3.2-gigabyte hard disk by compressing onto a 1.7-gigabyte tape, $159 for the drive, $30 for the tape).

Ditto Instead of buying a Colorado tape drive, you can pay less by getting a different brand, called a Ditto drive, manufactured by Iomega.

The 2-gigabyte version costs $109 for the drive, $20 for the tape.

The 3.2-gigabyte version costs $139 for the drive, $30 for the tape.

Where to buy You can get Colorado and Ditto drives at those low prices from a New York City discount dealer called Harmony (800-441-1144 or 718-692-3232).

Internal versus external All those tape-drive prices are for drives that are internal: they go inside your computer. External versions cost extra.

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 reelís diameter is 10Ĺ inches. If you unwind the tape, youíll 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.

IBMís 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.


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 ó without its contents ó is called the case.


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 computerís 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 TVís antenna).

The Federal Communications Commission (FCC) prohibits you from owning any device (such as a computer) that interferes with your neighborsí 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 itís FCC class B approved. If itís not ó if itís just FCC class A approved ó 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, donít bother buying a surge suppressor. The typical computer has some surge protection built into it already.

If youíre 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 computerís not on the same circuit as the power-hungry appliance.

During the summer, most computer errors are caused by temperatures over 95į, not by power surges.