To get info into and out of the computer, you need input/output devices (I/O devices). Here they are.…
The computer’s screen is an ordinary TV (the same kind you watch Bill Cosby on) or resembles a TV. The screen shows what you typed on the keyboard and also shows the computer’s responses.
The computer’s screen is also called the display.
A standard computer uses a kind of screen that’s called a standard monitor. A standard monitor resembles a TV but produces a sharper picture and costs more. It has no antenna and no dial for selecting channels: the only channel you get is “computer”. Like a TV, it contains a picture tube. The picture tube (in a TV or standard monitor) is called a cathode-ray tube (CRT).
Stand-alone versus built-in The monitor can be either stand-alone or built-in.
If your computer is standard, its monitor is stand-alone, which means the monitor sits separately from the system unit. Before buying a computer that uses a stand-alone monitor, ask whether the computer’s price includes the monitor: the monitor might cost extra. The monitor’s price includes a cable that runs from the monitor to the system unit.
Some Macs and other non-standard computers use a
built-in monitor, which is a screen that’s permanently screwed into the front of the computer’s system unit. That included screen makes the system unit heavy and big so it’s difficult for a thief to lift, hide, and steal. Built-in monitors are particularly popular in public schools in high-crime areas. Most other organizations prefer stand-alone monitors, which are easier to move (to a more convenient place on your desk or a more convenient room) and which are easier to replace (if you need repairs or you want to switch to a fancier monitor).
Colors versus monochrome When buying a TV, you ask for either “color” or “black-and-white”. Similarly, when buying a computer monitor, ask for either color or monochrome. A color monitor displays all colors of the rainbow; a monochrome monitor displays just black-and-light.
Four kinds of monochrome monitors have been popular:
But now monochrome monitors are all obsolete: standard computer use color monitors instead, which cost between $100 and $800.
How colors are produced On the monitor’s screen, the picture shown is made of thousands of tiny dots. Each tiny dot is called a picture’s element (pixel).
In a color monitor, each pixel is made of three phosphors: one kind glows red if hit by an electron; another kind turns green, another kind turns blue.
Inside the monitor, three guns can shoot beams of electrons at the phosphors. The red gun can shoot electrons at the red phosphors (to make them glow red); the green gun can shoot at the green phosphors (to make them glow green); the blue gun can shoot at the red phosphors (to make them glow blue).
To make a pixel turn red, the computer tells the monitor’s red gun to shoot at that pixel’s red phosphor, so the pixel’s phosphor glows red. To make a pixel turn green, the computer makes the monitor’s green gun shoot at the pixel’s green phosphor. Blue is similar.
To make a pixel be very bright, the computer makes the monitor’s three guns all fire at the same pixel, so the pixel’s red, green, and blue phosphors all glow simultaneously. That makes the pixel be very bright —a hot white flash.
To make a pixel be black, the computer makes none of the guns fire at the pixel.
To make the pixel be cyan (greenish blue), the computer makes the green and blue guns fire simultaneously at the pixel. To make the pixel be magenta (purplish red), the computer makes the red and blue guns fire. To make the pixel be yellow, the computer makes the red and green guns fire (which produces a color that’s brighter and lighter than red or green alone).
That’s how to produce 8 colors: red, green, blue, white, black, cyan, magenta, and yellow.
Although a primitive monitor produces just those 8 colors, a modern monitor can produce extra colors by varying the strength of the electron beams. For example, instead of the red gun being either “on” or “off”, it can be “completely on”, “partly on”, or “off”.
Here are the names for the different levels of monitors:
VGA has become the standard. Primitive RGB, CGA, and EGA monitors are obsolete.
For a VGA monitor, the cable to the computer includes 1 red-gun wire, 1 green-gun wire, 1 blue-gun wire, and several other wires to help administer the signals. Altogether, the VGA cable contains 15 wires.
CGA and EGA cables each contain just 9 wires. If you see a monitor whose cable contains just 9 wires, the monitor is either CGA or EGA. It’s therefore obsolete.
Size The typical VGA color monitor’s screen is 17-inch (17"). That means the distance from the picture tube’s top left corner to the picture tube’s bottom right corner is 17 inches, measured diagonally.
Although the picture tube’s diagonal size is 17-inch, you see just 16 inches, because 1 inch is hidden behind the plastic that makes up the monitor’s case.
Most monitors are made by companies whose US headquarters are in California. Consumers complained to California’s attorney general that such a monitor shouldn’t be called “17-inch”, since just 16 inches are viewable. California now requires all ads for “17-inch” monitors to include a comment, in parentheses, saying that the viewable image size (vis) is just 16 inches, so the ad looks like this:
Instead of buying a 17-inch monitor, you can buy a bigger one (19-inch or 21-inch) or a smaller one (15-inch or 14-inch). In each case, the viewable image size is about an inch less than the size of the tube.
Here’s what VGA color monitors cost:
Those are the prices charged by discount dealers such as Insight (phone 800-INSIGHT or 480-333-3001) and TriState Computer (phone 800-433-5199 or 212-633-2530).
A 14" monitor (13" vis) is adequate for most people and most software, but few companies still offer 14" monitors. 15" shows the same info as 14" but slightly magnified, so you can read “the fine print” on the screen more easily. 17", 19", and 21" monitors are much more pleasant; they’re especially helpful if you’re trying to create fine graphics (or ads) or many side-by-side columns (as in a newspaper, magazine, newsletter, textbook, or big table of numbers). The newest programs (and many parts of the Internet) expect you to have at least a 17" monitor. Big monitors are also helpful if you have poor eyesight (or you’re sharing the computer with somebody who has poor eyesight).
Most folks buy 17" monitors. Richer folks buy 19" or 21".
Resolution Each position on the screen is called a pixel. The pixels are arranged in rows and columns, to form a grid. In a primitive VGA monitor, the screen is wide enough to hold 640 columns of pixels, and the screen is tall enough to hold 480 rows of pixels, so altogether the number of pixels in the grid is “640 times 480”, which is written “640´480”, which is pronounced “640 by 480”. That’s called the screen’s resolution.
If you buy a big VGA monitor (such as 21-inch), the screen is big enough to hold lots of pixels. You can use such a screen in two ways: you can make the screen either show lots of tiny pixels or show a smaller number of fat pixels.
Here’s how many pixels the typical screen can display:
Those resolutions have nicknames:
Refresh rate Here’s how the red gun works:
If the gun doesn’t get back to the first pixel soon enough, that pixel’s glow will have faded too much, and your eye will notice the fading and consider it an annoying flicker.
To avoid annoying flicker, the gun must get back to the phosphor fast, in less than an 85th of a second. That means it must refresh the phosphor at least 85 times per second. Instead of saying “the gun must refresh the phosphor at least 85 times per second,” engineers say “the vertical refresh rate must be at least 85 hertz (85 Hz).”
If the vertical refresh rate is less than 85 hertz, your eye might detect some flicker, which will annoy you. The flicker will be noticeable mainly if you look at the screen out of the corner of your eye, since your eye’s peripheral vision is most sensitive to flicker.
The typical cheap 17" monitor can show 1024´768 resolution well (at 85 hertz) but shows 1280´1024 resolution poorly (at 60 hertz). The ad for such a monitor typically begins by bragging that it can display 1280´1024 but then admits it handles that resolution poorly and should be used at just 1024´768; it says:
Trinitron In a traditional picture tube, each pixel is a trio of phosphor dots (red, green, and blue), arranged as three points of a triangle. That technique is called a dot-trio shadow mask.
Sony invented a more expensive kind of picture tube, called the Trinitron, using a technique called aperture grille: each pixel is a trio of vertical stripes (red, green, and blue), arranged side-by-side, like fence posts. That technique produces brighter colors and straighter vertical lines. But it makes diagonal lines look too bumpy; and if your eyesight is good, you’ll notice an annoying grid of thin horizontal wires, which hold the vertical phosphors in place.
Dot pitch The distance from a red phosphor to the closest nearest red phosphor is called the dot pitch. On a standard monitor, the dot pitch is .28 millimeters (.28mm).
The smaller the dot pitch, the better. The best monitors have a dot pitch of .26, .25, .24, .23, .22, or .21.
Terrible monitors have a dot pitch of .31, .39, .42, or .51. Their screens are too blurry to let you read small characters.
On a Sony Trinitron monitor, the dot pitch is usually .25.
Flat screen In a typical monitor, the picture tube’s surface is curved. If you pay slightly extra, you can buy a flat-screen monitor instead, whose picture tube’s surface is flat. It has two advantages:
Where to put the monitor According to researchers such as the government’s National Institute of Occupational Safety and Health (NIOSH), here’s where you should put the monitor so you’ll be comfortable while you’re working at the computer.…
Put the monitor slightly lower than your eyes, so you look down at the monitor (instead of looking up, which would strain your neck). When you’re looking at the center of the monitor’s screen, you should be looking down slightly (at an angle that’s 15 degrees below horizontal).
Put the monitor a moderate distance from your face. NIOSH recommended that the distance from your eyes to the center of the monitor’s screen be 17 inches; but that recommendation was made several years ago, when the typical monitor screen was just 12-inch. Now screens are bigger, so you need to sit farther from the screen to see the whole screen: a distance of 23 inches feels good to me.
Keep the room rather dark, to avoid having light reflected off the monitor’s surface. Put the monitor perpendicular to any light source, so no light source shines directly onto the monitor’s screen (which would create an annoying reflection) and no light source shines directly onto the monitor’s back (since such a light source would also be shining into your eyes and create an annoying glare).
Video terminals A video-display terminal (VDT) is a monitor that has an attached keyboard and communicates with a big computer.
If 200 people are using a maxicomputer simultaneously, just one of them is sitting at the maxicomputer’s main console. The other 199 people typically sit at 199 video-display terminals (or 199 personal computers), which are in different rooms or even different cities.
If your computer is old and primitive (such as an Apple 2 or Radio Shack Color Computer or Commodore 64 or Commodore VIC or Atari 800), you can attach it to an ordinary TV set instead of to a monitor. Here’s how to attach such a computer to a TV set:
Besides writing messages on your TV’s screen, the computer can also draw its own pictures on the TV. If your TV has color, you’ll see the pictures in color.
When you watch Bill Cosby on TV, his face’s size depends on the size of your TV’s screen. If your TV’s screen is tiny (less than 12 inches), his face looks small; if your TV’s screen is 25 inches, his face looks bigger; and if you have a projection TV with a gigantic 60-inch screen, his face looks gigantic. The same is true for the messages & pictures that the computer sends to the TV: the bigger the TV’s screen, the more magnified the computer’s messages & pictures.
The computer can make the TV screen show words, numbers, and formulas. Those words, numbers, and formulas are made of characters: each character is a letter of the alphabet, a digit, or any other symbol you can type.
The ideal TV computer would make the TV display 25 lines of info, with each line of info containing 40 characters, so the total number of characters you see on the screen simultaneously is “25 times 40”, which is 1000.
But most TV computers are less than perfect: they display slightly fewer than 25 lines of info and slightly fewer than 40 characters per line, so the total number of characters you see on the TV screen simultaneously is slightly less than 1000.
If your computer is tiny, it comes with a tiny screen, called a liquid-crystal display (LCD). That’s the kind of screen you see on digital watches, pocket calculators, handheld computers, and laptop computers (1ľ pounds to 16 pounds).
Those computers use LCD screens instead of traditional picture tubes because LCD screens consume less electricity, weigh less, and are less bulky. Since an LCD screen uses little electricity, it can run on batteries. A traditional picture tube cannot run on batteries. If your computer system runs on batteries, its screen is an LCD.
Desktop and tower computers use traditional picture tubes, for these reasons:
Kinds of LCD screens A traditional LCD screen displays black characters on a white background. The screen consists of thousands of tiny crystals. Each crystal is normally white, but temporarily changes to black when an electrical charge passes through it. Newer LCD screens can display colors.
The main manufacturer of LCD screens is Sharp. Sharp’s LCD screens are used in many brands of computers.
The price of a handheld or laptop computer depends on what kind of LCD screen it includes. You’ll find color LCD screens on most of the modern handheld and laptop computers; you’ll find monochrome screens just on the cheapest handheld computers and the oldest laptop computers.
Among color LCD screens, the old-fashioned kind is called passive; the next step up is dual-scan passive, which is brighter and works faster; the next step up is high-performance addressing (HPA); the most expensive is active-matrix, which is the brightest and works the fastest.
The newest laptop computers all have the best screens (color LCD active-matrix).
LCD monitors The typical LCD screen is built into a small computer (such as a handheld or laptop computer). A different way to get an LCD screen is to buy an LCD monitor, which looks like a monitor but includes an LCD screen instead of a CRT. You can attach an LCD monitor to a desktop or tower computer.
An LCD monitor is convenient because it consumes less desk space than a CRT. Unfortunately, an LCD monitor is expensive:
LCD projector An LCD projector resembles an LCD monitor but projects the image onto a huge movie screen (or your room’s white wall), so the image is many feet wide and can be seen by a big audience in a movie theater (or big conference room).
The cheapest LCD projectors cost $899 (or $999 minus $100 rebate) and are made by Dell, Toshiba, Epson, and InFocus. They project an SVGA image (800´600 pixels).
If you want higher resolution, you must pay more:
The usual way to communicate with the computer is to type messages on the computer’s keyboard.
Now “104 keys” has become the standard. Microsoft, IBM, and competitors all sell keyboards containing 104 keys.
The 104 keys are arranged like this:
The keyboard can print all the letters of the alphabet (from A to Z), all the digits (from 0 to 9), and these symbols:
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’s a “wildcard” that matches any other card.
In the diagram, I wrote the words “Shift”, “Backspace”, “LeftTab”, “Tab”, “Enter”, “Windows”, and “Menu” on some keys. To help people who don’t read English, keyboard manufacturers usually put symbols on those keys.
Stare at your computer’s keyboard and find these keys:
The keyboard contains special keys that help you do special activities (such as moving around the screen while you type):
The CapsLock, NumLock, ScrollLock, and Insert keys are called toggle keys: they create special effects, which end when you press the toggle key again.
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 keyboard’s main section. (For example, to type 4, press the key that has a 4 and a dollar sign.)
To keep your life simple, do not press the number keys on the right side of the keyboard. Those keys produce numbers just if the NumLock key is pressed beforehand, by you or the computer.
If the NumLock key was pressed to produce numbers, and you want to stop making the right-hand keys produce numbers, tap the NumLock key again.
If your keyboard has 101 keys instead of 104, your keyboard is missing the Menu key and the two Windows keys. Those 3 keys are unimportant, since most folks prefer to use a mouse instead of tapping those keys. If you wish, you can substitute other keys instead:
If your keyboard has just 83 keys, you suffer:
83-key keyboards work just with outdated computers. If you’re using an 83-key keyboard, that’s proof your computer is outdated! Buy a new computer system!
Kinds of keyboards
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 keyboard (101 keys plus 3 special keys that help run software called “Windows”). 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 you’re 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 doesn’t mind having coffee or soda spilled on it).
The best split keyboard is the one made by Addison because it’s 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 you’ve read The Secret Guide to Computers.
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 four methods.…
Method 1: point a traditional video camera (or camcorder) at the object, while the camera is wired to the computer.
Method 2: take a picture of the object by using a digital camera, which contains a disk or RAM chips that record the image, then transfer the image to a computer.
Method 3: draw on paper, which you then feed to an optical scanner wired to the computer. Of the optical scanners that cost under $150, the best are Microtek’s X6 (which handles colors the best) and Visioneer’s One Touch (which is much easier to use and reads words the best but handles colors less accurately).
Method 4: 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.
Let’s look more closely at method 4.…
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.
A touch screen is a special overlay that covers the screen and lets you draw with your finger instead of with a light pen.
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 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 a free mouse comes with each IBM PC and clone, too.
Microsoft Mouse The nicest mouse for the IBM PC is the Microsoft Mouse. Its first version was boring, but 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.
Then came a further improvement, nicknamed “The Dog’s Paw” because it was shaped like a dog’s lower leg: it was long with an asymmetrical bump (paw) at the end. It felt even better than The Dove Bar, if your hand was big enough to hold it.
The next improvement, nicknamed “The Wheel Mouse”, looked like The Dog’s Paw but added a wheel you could rotate with your fingers.
The newest version, nicknamed “The Sneaker” and officially called the Intellimouse Pro, resembles the Wheel Mouse but its left side is taller, like the raised arch of a fancy sneaker. It costs $65.
Mice from no-name manufacturers cost under $10. Microsoft made a cheap mouse too, called the Home Mouse, in the shape of a home, with the mouse’s cord coming out of the chimney. Microsoft’s newest cheap mouse is called the Basic Mouse; at $16, it’s small enough to be used by kids, lefties, and short people.
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 trackball’s 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 — 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.
You can make the computer hear and produce sounds.
To produce sounds, the standard computer includes speakers.
One tiny speaker hides inside the system unit. It’s called the internal speaker. That speaker’s main purpose is to beep at you if you make a mistake.
A pair of stereo speakers are bigger and can produce good, loud stereo music. Hey, baby, let’s rock!
Those stereo speakers are usually separate boxes that sit outside the system unit. (Exception: some Compaq and Mac computers hide the stereo speakers in the monitor; most notebook computers hide the stereo speakers in the keyboard.)
If your computer is fancy, it includes a trio of stereo speakers: the third speaker is called the subwoofer and produces a big, loud, booming bass.
If your computer is extra-fancy, it gives you surround sound, where you’re surrounded by 4 normal speakers (front left, front right, back left, and back right) plus a subwoofer, making a total of 5 speakers. Since that system includes 4 normal speakers plus 1 subwoofer, it’s called a 4.1 speaker system.
If your computer is even fancier (super-duper fancy), it gives you 5 normal speakers (front left, front right, back left, back right, and center) plus a subwoofer, making a total of 6 speakers. Since that system includes 5 normal speakers plus 1 subwoofer, it’s called a 5.1 speaker system.
To handle the stereo speakers, a standard computer’s system unit contains a sound card.
The most popular sound card is the Sound Blaster, made by a company called Creative Technology, founded by Mr. Sim Wong Hoo in Singapore. It’s still run by him there, and he owns 35% of the stock, making him rich. Creative Technology is called “the Singapore surprise” because it surprises novices who think the best hardware companies are all based in the US & Japan. It was the first Singapore company to be listed on the Nasdaq stock exchange. Its US division is based in California and called Creative Labs.
Fancy computers speak words by including circuitry called a speech synthesizer.
The newest computers come with a microphone (mike). By using the mike, 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!
A computer usually displays its answers on a screen. If you want the computer to copy the answers onto paper, attach the computer to a printer, which is a device that prints on paper.
The typical printer looks like a typewriter but lacks a keyboard. To feed information to the printer, you type on the computer’s keyboard. The computer transmits your request through a cable of wires running from the back of the computer to the back of the printer.
A computer’s advertised price usually does not include a printer and cable. The cable costs about $8; the typical printer costs several hundred dollars.
Printers are more annoying than screens. Printers are noisier, slower, cost more, consume more electricity, need repairs more often, and require you to buy paper and ink. But you’ll want a printer anyway, to copy the computer’s answers onto paper that you can give your computerless friends. Another reason to get a printer is that a sheet of paper is bigger than a screen and lets you see more information at once.
To get a printer cheaply, phone these mail-order discount dealers:
Micro Warehouse offers the greatest variety of printers but charges more than the other companies.
To get low prices locally, walk into chains of discount superstores, such as Comp USA (which sells all kinds of computer equipment) and Staples (which sells all kinds of office supplies and some computer equipment).
Kinds of printers
Three kinds of printers are popular.
A dot-matrix printer looks like a typewriter but has no keyboard. Like a typewriter, it smashes an inked ribbon against the paper. Like a typewriter, it’s cheap: it typically costs about $150.
An inkjet printer looks like a dot-matrix printer; but instead of containing a ribbon, it contains tiny hoses that squirt ink at the paper. It prints more beautifully than a dot-matrix printer and costs more. It typically costs about $200.
A laser printer looks like a photocopier. Like a photocopier, it contains a rotating drum and inky toner. It prints even more beautifully than the other two kinds of printers. Like a photocopier, it’s expensive: it typically costs about $400.
As you progress from a dot-matrix printer to an inkjet printer to a laser printer, the quality tends to go up, and so does the price. But here are exceptions.…
Color If you need to print in color (instead of just black-and-white), get an inkjet printer. The typical inkjet printer can print in color beautifully. (Dot-matrix printers produce colors too crudely and slowly. Laser printers produce just black-and-white, except for laser printers that are ridiculously expensive.)
Mailing labels Although you can print mailing labels on all three kinds of printers, the easiest way to print mailing labels is on a dot-matrix printer.
Multi-part forms If you want to print on a multipart form (using carbon paper or carbonless NCR paper), you must buy a dot-matrix printer.
Old accounting software Some old accounting software requires that you buy a dot-matrix printer. It also requires that the printer be an expensive kind that can handle extra-wide paper.
Cost of consumables
After you’ve bought the printer and used it for a while, the ink supply will run out, so you must buy more ink.
Those prices assume you’re printing black text. If you’re printing graphics or color, the cost per page goes up drastically. For example, full-color graphics on an inkjet printer cost about 50 cents per page.
If you use your printer a lot, you’ll have to buy ink often: every few months. The cost adds up: after a few years, you’ll discover that the total cost of all the ink you’ve bought is more than the cost of the printer! If a printer is advertised at a low price, beware: the “almost free” printer is just a ruse to get you to spend lots of money on ink. (It’s like buying an “almost free” razor, which is just a ruse to get you to spend lots on blades.)
For all three kinds of printers, you must also pay for the paper, which costs about 1 cent per sheet if you buy a small quantity (such as a 500 sheets), or a half a cent per sheet if you buy a large quantity (such as 5000 sheets). For low prices on paper, go to Staples.
You must also pay for the electricity to run the printer; but the electricity’s cost is negligible (much less than a penny per page) if you turn the printer off when you’re not printing.
Warning: if you leave a laser printer on even when not printing, its total yearly electric cost can get high, since the laser printer contains a big electric heater. (You might even notice the lights in your room go dim when the heater kicks on.)
Although the most popular kinds of printers are dot-matrix, inkjet, and laser, some folks still use an older kind of printer, called a daisy-wheel printer. It’s cute! Here’s how it works.…
Like a typewriter and a dot-matrix printer, a daisy-wheel printer smashes an inked ribbon against paper. To do that, the daisy-wheel printer contains a device called a daisy wheel, which is an artificial daisy flower made of plastic or metal. On each of the daisy’s petals is embossed a character: a letter, a digit, or a symbol. For example, one petal has the letter A embossed on it; another petal has B; another petal has C; etc.
Notice that each character is embossed. (The word “embossed” is like “engraved”, but an “embossed” character is raised up from the surface instead of etched into the surface.)
To print the letter C, the printer spins the daisy wheel until the C petal is in front of the inked ribbon. Then a hammer bangs the C petal against the ribbon, which in turn hits the paper, so that an inked C appears on the paper.
Different wheels You can remove the daisy wheel from the printer and insert a different daisy wheel instead. Each daisy wheel contains a different font. For example, one daisy wheel contains italics (which are slanted letters, like this); a different daisy wheel contains Greek symbols used by scientists.
The printer holds just one daisy wheel at a time. To switch to italics in the middle of your printing, you must stop the printer, switch daisy wheels (a tedious activity requiring your own manual labor!), then press a button for the printer to resume printing.
Manufacturers The most famous daisy-wheel printer manufacturer was Diablo, founded by Mr. Lee in California. He sold the company to Xerox, then founded a second daisy-wheel printer company, Qume (pronounced “kyoom”), which he sold to ITT. In 1988 he bought Qume back. Other companies (such as Brother and Juki) invented imitations that claimed to be Diablo & Qume compatible.
Variants of the daisy wheel Over the years, many variants of the daisy wheel were invented.
For example, Nippon Electric Company (NEC) invented a “wilted” daisy wheel, whose petals are bent. The wilted daisy wheel is called a thimble. Computerists like it because it spins faster than a traditional daisy and also produces a sharper image. It’s used just in NEC’s Spinwriter and Elf printers.
Another variation of the daisy wheel is the plastic golf ball, which has characters embossed all over it. IBM calls it a Selectric typing element. IBM uses it in typewriters, typesetting machines, and printers. It produces better-looking characters than daisy wheels or thimbles; but it spins too slowly and needs too many repairs, so IBM has discontinued it.
Some maxicomputers and minicomputers use gigantic printers that have characters embossed on bands, chains, and drums instead of daisies. Those printers are fast and cost many thousands of dollars.
A dot-matrix printer resembles a daisy-wheel printer; but instead of containing a daisy wheel, it contains a few guns, as if it were a super-cowboy whose belt contains several holsters.
Each gun shoots a pin at the inked ribbon. When the pin’s tip hits the ribbon and smashes the ribbon against the paper, a dot of ink appears on the paper. Then the pin retracts back into the gun that fired it.
Since each gun has its own pin, the number of guns is the same as the number of pins.
9-pin printers If the printer is of average quality, it has 9 guns — and therefore 9 pins. It’s called a 9-pin printer. The 9 guns are stacked on top of each other, in a column that’s called the print head. If all the guns fire simultaneously, the pins smash against the ribbon simultaneously, so the paper shows 9 dots in a vertical column. The dots are very close to each other, so that the column of dots looks like a single vertical line. If just some of the 9 pins press against the ribbon, you get fewer than 9 dots, so you see just part of a vertical line.
To print a character, the print head’s 9 guns print part of a vertical line; then the print head moves to the right and prints part of another vertical line, then moves to the right again and prints part of another vertical line, etc. Each character is made of parts of vertical lines — and each part is made of dots.
The pattern of dots that makes up a character is called the
dot matrix. That’s why such a printer’s called a 9-pin dot-matrix printer.
Inside the printer is a ROM chip that holds the definition of each character. For example, the ROM’s definition of “M” says which pins to fire to produce the letter “M”. To use the ROM chip, the printer contains its own CPU chip and its own RAM.
When microcomputers first became popular, most dot-matrix printers for them were built by a New Hampshire company, Centronics. In 1980, Japanese companies took over the marketplace. Centronics went bankrupt. The two Japanese companies that dominate the industry now are Epson and Panasonic.
Epson became popular because it was the first company to develop a disposable print head — so that when the print head wears out, you can throw it away and pop in a new one yourself, without needing a repairman. Also, Epson was the first company to develop a low-cost dot-matrix impact printer whose dots look “clean and crisp” instead of looking like "fuzzy blobs”. Epson was the main reason why Centronics went bankrupt.
For a 9-pin printer, I recommend buying the Panasonic 1150 instead, because it prints more beautifully and costs just $149 from discount dealers such as Harmony. Too bad it can’t handle extra-wide paper!
Besides Epson and Panasonic, four other Japanese companies are also popular: NEC, Oki, Citizen, and Star.
Printers from all six of those Japanese companies are intended mainly for the IBM PC, though they work with Apple 2 and Commodore computers also.
The most popular printers for the Mac were the Imagewriter and the Imagewriter 2. They were designed by Apple to print exact copies of the Mac’s screen. They even print copies of the screen’s wild fonts and graphics. Apple stopped selling them.
7-pin printers Although the average dot-matrix printer uses 9 pins, some older printers use just 7 pins instead of 9. Unfortunately, 7-pin printers can’t print letters that dip below the line (g, j, p, q, and y) and can’t underline. Some 7-pin printers print just capitals; other 7-pin printers “cheat” by raising the letters g, j, p, q, and y slightly.
24-pin printers Although 9 pins are enough to print English, they’re not enough to print advanced Japanese, which requires 24 pins instead.
The first company to popularize 24-pin printers was Toshiba. Its printers printed Japanese — and English — beautifully. 24-pin Toshiba printers became popular in America, because they print English characters more beautifully than 9-pin printers.
Epson and all the other Japanese printer companies have copied Toshiba. Here are the cheapest wonderful 24-pin printers:
You can get those prices from Tri State and Harmony. While supplies last, Tri State has an even better deal: get a refurbished Epson LQ-570+ for just $160! Phone Tri State at 800-433-5199 or 212-633-2530.
The cheapest 24-pin printer that handles wide paper is the Epson LQ-2080 ($400).
24-pin printers print more beautifully than 9-pin printers but print slower, are less rugged, and don’t bang hard enough to print multiple copies on thick multi-part forms.
In a typical, cheap 24-pin printer (such as the Epson Action Printer 3250), the even-numbered pins are slightly to the right of the odd-numbered pins, so you see two columns of pins. After firing the even-numbered pins, the print head moves to the right and fires the odd-numbered pins, whose dots on paper overlap the dots from the even-numbered pins. The overlap insures that the vertical column of up to 24 dots has no unwanted gaps.
In fancier 24-pin printers (such as the Panasonic 2130 & 2135), the 24 pins are arranged as a diamond instead of two columns, so that the sound of firing pins is staggered: when you print a vertical line you hear a quiet hum instead of two bangs.
Beyond 24 pins The fastest dot-matrix printers use multiple print heads, so that they can print several characters simultaneously.
Why the daisies died During the 1970’s, daisy-wheel printers were popular; but during the 1980’s, computerists switched to dot-matrix printers instead. Here’s why.…
The mechanism that spins the daisy is expensive, slow, and frequently needs repairs.
Dot-matrix printers can easily print graphics by making the pictures out of little dots. Daisy wheels cannot.
Although the first dot-matrix printers had just 7 pins and printed ugly characters, 24-pin printers can print prettier characters than the average daisy wheel. Moreover, you can make the typical 9-pin printer print will and imitate an 18-pin printer by doing 2-pass printing, in which the printer prints a line of text, jerks the paper up very slightly, and then prints the line again so the new dots fill the gaps between the old dots.
If you have a daisy-wheel printer and want to change to a different font (such as italics), you must spend your time manually switching daisy wheels. If you have a dot-matrix printer instead, just tell the printer which font you want (by pressing a button on the printer or on your computer’s keyboard), and the printer will automatically switch to different patterns of dots to produce the different font, since the printer’s ROM contains the definitions of many fonts. To make a daisy-wheel printer print so many fonts, you must buy dozens of daisy wheels, costing a total of several hundred dollars.
So daisy-wheel printers died because of competition from dot-matrix printers — and from inkjet and laser printers, which print even more beautifully! Let’s examine those super-beautiful printers now.…
An inkjet printer resembles a dot-matrix printer but contains hoses instead of guns. The hoses (called nozzles) squirt ink at the paper. There are no pins or ribbons.
When you use an inkjet printer, you hear the splash of ink squirting the paper. That splash is quieter than the bang produced when a dot-matrix printer’s pins smash a ribbon. If you like quiet, you’ll love inkjet printers!
Most inkjet printers can print in color. They mix together the three primary ink colors (red, blue, and yellow) to form all the colors of the rainbow.
3 main manufacturers The first popular inkjet printers were made by Hewlett-Packard (HP). Later, Epson and Canon started making inkjet printers also.
The inkjet printers from all 3 of those companies are excellent. Each company makes a wide variety of inkjet printers, at prices ranging from about $25 to about $1000. Here are some general tendencies:
Each manufacturer has its own brand names:
How does the ink get out of the nozzle and onto the paper?
When using an inkjet printer, try different brands of paper.
3 new competitors HP, Canon, and Epson are being attacked by three aggressive competitors (Xerox, Brother, and Lexmark), which sometimes offer better deals.
Discount dealers You can buy from discount dealers:
Dual-cartridge color Inkjet printers come in several styles. The most popular style is dual-cartridge color. If you buy this style of inkjet printer, you can insert two ink cartridges simultaneously, side by side.
One cartridge contains black ink. The other cartridge contains the color trio (red, blue, and yellow). The computer mixes together all 4 (black, red, blue, and yellow) to form all possible colors. That method is called the 4-color process.
Epson’s most famous such printer has been the Stylus Color 777, which costs just $89 from Harmony. It prints precisely: the resolution is 2880 dots per inch vertically, 720 dots per inch horizontally, and the dots are squirted onto the paper neatly, without splatter. It prints fast: up to 8 pages per minute for black, 6 pages per minute for color. Those high speeds are obtained just while printing text in low resolution (360 dots per inch). To print a color photo in high resolution takes 1˝ minutes for 4"´6", 3 minutes for 8"´10". It comes with a 1-year warranty. The cartridges are long-lasting: they’ll print 600 pages of black text, 300 pages of color text; before the ink runs out and you must insert new cartridges. The black print head contains 144 nozzles; the color print head contains 144 nozzles (48 per color).
To compete against Epson, Canon offers several competitors. Canon’s cheapest is the Bubble Jet Color 2100 (BJC-2100). It lists for $100, but you get a $50 rebate, bringing the final cost down to just $50! That gets you 720´360 dpi, 5 ppm black, 2 ppm color, 1-year warranty. The price includes a cartridge containing all 4 colors. An all-black cartridge costs extra and is needed to achieve the “5 ppm black” speed.
HP offers these:
In that chart, “price” is the list price (discount dealers charge less), and duty cycle is how many pages per month the printer can reasonably handle (without overheating and without “worn or loose” parts or “slow speed” making you curse excessively).
Single-cartridge color A cheaper style is single-cartridge color. This category lets you insert either a black cartridge or a color cartridge, but you cannot insert both cartridges simultaneously.
If you try to print black while the color cartridge is in, the computer tries to imitate “black” by printing red, blue, and yellow on top of each other. That produces a “mud” instead of a true black, and it’s also very slow. If you try to make such a printer reproduce a photograph, the image produced looks slightly “muddy”, “washed-out”, with poor contrast.
But the price is deliciously low!
The main such printer has been Canon’s BJC-1000. Here’s why it costs little:
It’s been selling for $75, sometimes minus a $30 rebate (bringing the final cost down to $45), but it’s being discontinued in favor of the BJC-2100, which costs just slightly more and is much better.
Lexmark’s Z-12 Color Jetprinter is a single-cartridge color printer that’s better than the BJC-1000. You can order it directly from Lexmark for $50 (plus tax and shipping) at Lexmark’s Internet Web site (www.lexmark.com). Like the BJC-1000, its price includes a color cartridge but no black cartridge (which costs extra). Lexmark claims “1200 dpi” and “6 ppm black, 3 ppm color”. Lexmark also includes discount coupons so you can get good software cheap.
Portable You can buy these portable inkjet printers, which are tiny and weigh little: Brother’s MP-21C ($240, 2 pounds), Canon’s BJC-80 ($190, 4 pounds), and Canon’s BJC-50 ($305, 2 pounds, prints slower and more crudely than the BJC-80 but has the advantage of weighing less). They all work slowly, print less beautifully than desktop printers, and can’t handle big stacks of paper.
Instead of buying a portable printer, consider buying Canon’s BJC-1000. At 4.8 pounds, it weighs just slightly more than a portable printer and tends to work faster, print more beautifully, handle paper better, and cost less!
Wide-carriage Most inkjet printers handle just normal-width paper, which is 8˝ inches wide. Canon, Epson, and HP all make expensive inkjet printers that To print colors on wider paper, get Canon’s BJC-4550 ($269, 11"-by-17" paper) or Epson’s Stylus 1520 ($449, 17"-by-22").
4-cartridge color Suppose you’re printing a picture that contains lots of red but not much blue or yellow. When you use up all the red ink in a tricolor cartridge, you must throw the whole cartridge away, even though blue and yellow ink remain in the cartridge. What a waste! Canon’s BJC-3000 prevents such waste.
It uses 4 separate cartridges (a black cartridge, a red cartridge, a blue cartridge, and a yellow cartridge), so when the red ink runs out you can discard the red cartridge without having to discard any blue or yellow ink. It prints 9ppm black, 4ppm color. It costs just $99. Unfortunately, its cartridges are rather expensive.
HP offers the Business Inkjet 2300. It’s expensive ($500) but its ink is cheap: just 2.1˘ per page for black, 1.9˘ per page for yellow, 1.9˘ per page for blue (cyan), and 1.9˘ per page for red (magenta). It has good specs for black (26 ppm, 1200 dpi) and for color (22 ppm, 4800´1200 dpi). It’s reliable (10,000 pages/month).
A laser printer, like an office photocopier, contains a drum and uses toner made of ink. The printer shines a laser beam at the drum, which picks up the toner and deposits it on the paper.
LaserJet 5 For the IBM PC, the most popular laser printers are made by Hewlett-Packard (HP), whose laser printers are called LaserJets. After inventing its first LaserJet, HP invented a better version (the LaserJet 2), then an even better version (the LaserJet 3), then an even better version (the LaserJet 4).
Finally, in 1996, HP invented a truly great version: the LaserJet 5. I used it to print earlier editions of this book. It’s terrific! Here are its specs:
Discount dealers were selling it for $988.
Cheaper LaserJets For folks who couldn’t afford a LaserJet 5 at $988, HP invented a cheap Personal version (called the LaserJet 5P) and an even cheaper Lower-cost version (called the LaserJet 5L).
Afterwards, HP invented an improved 5P (called the 6P) and an improved 5L (called the 6L).
Newer LaserJets HP has stopped selling all those LaserJets (the LaserJet 1, 2, 3, 4, 5, 5P, 5L, 6P, and 6L). Now HP sells newer LaserJets that are even better and cost less!
These print just monochrome (black):
These can print in color:
All those LaserJets are better than the charts imply, since they use RET (to make the resolution seem nearly twice as high as what’s in the chart) and data compression (to make the RAM hold twice as much data as what’s in the chart).
Those are the list prices. Discount dealers charge less. HP will give you a $50 rebate if you buy the printer at the same time as the computer (even if the computer is not by HP).
I bought a LaserJet 2300. It’s great! I printed this 29th edition of the book on it. (Then I told a commercial printing company to photograph each page the LaserJet 2300 printed and feed each photo’s negative to a printing press.)
Duty cycle In that chart, duty cycle means how many pages per month the printer can print reliably (without overheating and without “worn or loose” parts making you curse excessively).
Processor When your computer’s system unit sends data to the LaserJet, the LaserJet handles that data with the help of a printer processor chip, which hides inside the printer. The charts show how fast the printer processor chip can think.
size Each LaserJet printer in the charts can handle letter-size paper
(8˝ inches wide, 11 inches tall) and
legal-size paper (8˝ inches wide, 14 inches tall). If you want to handle
tabloid-size paper instead (11"x17"), you must buy a wide-format printer, such as the Laserjet 5100, which is expensive ($1440), monochrome, and disappointing (just 21 ppm, 16M, 300MHz, 65,000 pages/month).
Printer codes When your computer wants to give the printer an instruction (such as “draw a diagonal line across the paper” or “make that scalable font bigger”), the computer sends the printer a code.
HP’s LaserJets understand a code called Printer Control Language (PCL), invented by HP. The newest versions of PCL are PCL 5e (which is plain), PCL 5c (which can handle colors), and PCL 6 (which can handle 1200 dpi). They’re understood by the new LaserJets. Older LaserJets understand just older versions of PCL and can’t perform as many tricks.
Most IBM-compatible laser printers (such as the ones by Epson, Panasonic, and Sharp) understand PCL, so that they imitate HP’s laser printers, run the same software as HP’s laser printers, and are HP-compatible. But most of them understand just old versions of PCL and can’t perform as many tricks as HP’s newest LaserJets.
Some laser printers understand a different code, called PostScript (PS), invented by a company called Adobe.
Back in the 1980’s, when PCL was still very primitive, Postscript was more advanced than PCL. The fanciest laser printers from HP’s competitors used PostScript. The very fanciest laser printers were bilingual: they understood both PCL and PostScript.
Now that PCL has improved, it’s about as good as PostScript. PCL printers cost less to manufacture than PostScript printers.
In PostScript, each command that the computer sends the printer is written by using English words. Unfortunately, those words are long and consume lots of bytes. In PCL, each command is written as a brief series of code numbers instead. Since PCL commands consume fewer bytes than Postscript commands, the computer can transmit PCL commands to the printer faster than Postscript commands, and PCL commands can fit in less RAM.
Some Apple Mac programs require a PostScript printer. Some big printing companies that run printing presses require PostScript.
Most new LaserJet printers understand both PCL and PostScript.
HP’s competitors HP has many competitors.
But I recommend buying from HP, because people who own HP LaserJets are very happy, including me! HP LaserJets are more reliable than other brands, need repairs less often than other brands, cause fewer software headaches than other brands, cost just slightly more than other brands, and let you buy more toner from your local store more easily. The only exception to my “buy HP” advice is HP’s Color LaserJets, which always get worse ratings than Magicolor laser printers, which are made by QMS. But you shouldn’t buy a color laser printer anyway: color laser printers are too expensive; and they’re much slower than black-only laser printers, even when printing just black! To get color, buy a nice, cheap color inkjet printer instead!
Older LaserJets Many offices still use older LaserJets. Here’s how famous old LaserJets compare with modern ones:
Now let’s plunge into the technical details of printer technology.…
Impact versus non-impact
A printer that smashes an inked ribbon against the paper is called an impact printer. The most popular kind of impact printer is the dot-matrix printer. Other impact printers use daisy wheels, thimbles, golf balls, bands, chains, and drums. They all make lots of noise, though manufacturers have tried to make the noise acceptable by putting the printers in noise-reducing enclosures and by modifying the timing of the smashes.
A printer that does not smash an inked ribbon is called a non-impact printer. Non-impact printers are all quiet! The most popular non-impact printers are inkjet printers and laser printers.
Other non-impact printers are thermal printers (whose hot pins scorch the paper), and thermal-transfer printers (which melt hot colored wax onto the paper). Unfortunately, thermal printers require special “scorchable” paper; thermal-transfer printers require expensive ribbons made of colored wax.
If a printer creates characters out of dots, the quality of the printing depends on how fine the dots are — the “number of dots per inch”, which is called the print resolution.
9-pin printers 9-pin printers usually print 72 dots per inch vertically. That’s called draft quality, because it’s good enough for rough drafts but not for final copy. It’s also called business quality, because it’s good enough for sending internal memos to your colleagues and accountant — and bills to your customers.
If you make a 9-pin printer do 2 passes, it prints 144 dots per inch. That’s called correspondence quality, because it’s good enough for sending pleasant letters to your friends. It’s also called near-letter-quality (NLQ), because it looks nearly as good as the letters produced on a typewriter. The typical 9-pin printer has a switch you can flip, to choose either 1-pass draft quality (which is fast) or 2-pass correspondence quality (which is slower but prettier).
24-pin printers A 24-pin printer prints 180 dots per inch. That’s called letter quality (LQ), because it looks as good as the letters printed by a typical typewriter or daisy-wheel printer. It’s good enough for writing letters to people you’re trying to impress.
Laser printers A traditional laser printer prints 300 dots per inch. That’s called desktop-publishing quality, because it’s good enough for printing newsletters. It’s also called near-typeset-quality, because it looks nearly as good as a typesetting machine.
A standard typesetting machine prints 1200 or 2400 dots per inch. Those are the resolutions used for printing America’s popular magazines, newspapers, and books. Most of the modern laser printers can print 1200 dots per inch.
Inkjet printers Most inkjet printers can print 600 dots per inch.
To measure a character’s size, you must measure both its width and its height.
Width Like an old-fashioned typewriter, an old-fashioned printer makes each character a tenth of an inch wide. That’s called “10 characters per inch” or 10 cpi or 10-pitch or pica (pronounced “pike uh”). Some printers make all the characters narrower so you get 12 characters per inch. That’s called 12 cpi or 12-pitch or elite.
The typical dot-matrix printer lets you choose practically any width you wish. For example, the Epson LQ-850 can print 5, 6, 7˝, 8 1/3, 10, 12, 15, 162/3, and 20 cpi. The widest sizes (5, 6, 7˝, and 81/3 cpi) are called double-width, because they’re twice as wide as 10, 12, 15, and 162/3 cpi. The narrowest sizes (162/3 and 20 cpi) are called condensed or compressed; they’re 60% as wide as 10 and 12 cpi.
Modern printers can make each character a different width, so that a “W” is very wide and an “i” is narrow; that’s called proportional spacing. It looks much nicer than uniform spacing (such as 10 cpi or 12 cpi). Modern printers let you choose either proportional spacing or uniform spacing. Uniform spacing is usually called monospacing.
Height The typical sheet of paper is 11 inches tall. If you put one-inch margins at the top and bottom, you’re left with 9 inches to print on.
After printing a line of type, the typical typewriter or printer jerks up the paper a sixth of an inch, then prints the next line. As a result, you get 6 lines of type per inch, so the entire sheet of paper shows “9 times 6” lines of type, which is 54 lines.
The fanciest printers, such as laser printers, can make characters extra-tall or extra-short. The character’s height is measured in points. Each point is 1/72 of an inch. A character that’s an inch tall is therefore called “72 points tall”. A character that’s half an inch tall is 36 points tall.
Like a typewriter, a printer normally makes characters 10 points tall. (More precisely, it makes the top of a capital “Y” 10 points higher than the bottom of a small “y”.) It also leaves a 2-point gap above the top of the “Y”, to separate it from the characters on the previous line. That 2-point gap is called the leading (pronounced “ledding”). That technique is called “10-point type with 2-point leading”. Since the type plus the leading totals 12 points, it’s also called “10-point type on 12” (or “10 on 12” or “10/12”).
You can make a capital T in two ways. The simple way is draw a horizontal bar and a vertical bar, like this: T. The fancy way is to add serifs at the ends of the bars, like this: T. A character such as T, which is without serifs, is called sans serif, because “sans” is the French word for “without”.
Monospaced fonts The most popular monospaced fonts have been Courier (which has serifs) and Letter Gothic (which is sans serif).
They were invented for typewriters. (Letter Gothic was invented by IBM in 1956.)
A new version of Courier, for computers, is called Courier New. A new version of Letter Gothic, for computers, is called Lucida Console.
Proportionally-spaced fonts The most popular proportionally spaced fonts are Times Roman (which has serifs) and Helvetica (which is sans serif).
They were invented for typesetting machines. (Times Roman was invented by The Times newspaper of London in 1931. Helvetica was invented by Max Miedinger of Switzerland in 1954; the name “Helvetica” comes from “Helvetia”, the Latin name for Switzerland.)
A new version of Times Roman, for computers, is called Times New Roman. A new version of Helvetica, for computers, is called Arial.
Samples Here are samples (each 9 points high) from the laser printer that printed this book (an HP LaserJet 2300 printer):
Laser printers and most inkjet printers accept a stack of ordinary copier paper. You put that paper into the printer’s paper tray (which is also called the paper bin and also called the cut-sheet paper feeder).
Dot-matrix printers Some dot-matrix printers can handle stacks of ordinary copier paper, but most dot-matrix printers handle paper differently. Here’s how.…
To pull paper into the printer, dot-matrix printers can use two methods.
The simplest method is to imitate a typewriter: use a rubber roller that grabs the paper by friction. That method’s called friction feed. Unfortunately, friction is unreliable: the paper will slip slightly, especially when you get near the sheet’s bottom edge.
A more reliable method is to use paper that has holes in the margins. The typical dot-matrix printer has feeder pins that fit in the holes and pull the paper up through the printer very accurately. That method, which is called pin feed, has just one disadvantage: you must buy paper having holes in the margins.
If your printer uses pin feed and is fancy, it has a clamp that helps the pins stay in the holes. The clamp (with its pins) is called a tractor. You get two tractors: one for the left margin and one for the right. A printer having tractors is said to have tractor feed. Usually the tractors are movable, so that you can move the right-hand tractor closer to the left tractor, to handle narrower paper or mailing labels.
A dual-feed printer can feed the paper both ways — by friction and by pins — because it has a rubber roller and also has sets of pins. The printer’s left edge has a lever: if you pull the lever one way, the paper will rub against the roller, for friction feed; if you pull the lever the other way, the paper will rub against the pins instead, for pin feed.
Most dot-matrix printers have dual feed with movable tractors.
Paper that has holes in it is called pin-feed paper (or tractor-feed paper).
Like a long tablecloth (folded up and stored in your closet), pin-feed paper comes in a long, continuous sheet that’s folded. Since it comes folded but can later be unfolded (“fanned out”), it’s also called fanfold paper. It’s perforated so you can rip it into individual sheets after the printer has printed on it. If the paper’s fancy, its margin is perforated too, so that after the printing is done you can rip off the margin and its ugly holes, leaving you with what looks like ordinary typing paper.
The fanciest perforated paper, called micro-perf, has a perforation so fine that when you rip along the perforation, the edge is almost smooth.
Paper width Most printers can use ordinary typing paper (or copier paper), which is 8˝ inches wide. Pin-feed paper is usually an inch wider (9˝ inches wide), so that the margins are wide enough to include the holes.
Some printers can handle pin-feed paper that’s extra-wide (15 inches). Those wide-carriage printers typically cost about $130 more than standard-width printers.
The typical printer’s advertisement brags about the printer’s speed by measuring it in characters per second (cps) or lines per minute (lpm) or pages per minute (ppm). But those measurements are misleading.
Dot-matrix printers For example, Epson advertised its LQ-850 dot-matrix printer as “264 cps”, but it achieved that speed only when making the characters small (12 cpi) and ugly (draft quality). To print characters that were large (10 cpi) and pretty (letter quality), the speed dropped to 73 cps.
Panasonic advertised its KX-P1091 dot-matrix printer as “192 cps”, but it achieved that speed only if you threw an internal switch that made the characters even uglier than usual!
For dot-matrix printers, the advertised speed ignores how long the printer takes to jerk up the paper. For example the typical “80-cps” printer will print 80 characters within a second but then take an extra second to jerk up the paper to the next line, so at the end of two seconds you still see just 80 characters on the paper.
Daisy-wheel printers To get an amazingly high cps rating, one daisy-wheel manufacturer fed its printer a document consisting of just one character repeated many times, so the daisy never had to rotate!
Laser printers To justify a claim of “8 pages per minute”, Apple salesmen noticed that their Laserwriter 2 NT printer took a minute to produce 8 extra copies of a page. They ignored the wait of several minutes for the first copy!
Like Apple, most other laser-printer manufacturers say “8 pages per minute” when they should really say: “1/8 of a minute per additional copy of the same page”.
Keep your eyes open Don’t trust any ads about speed! To discover a printer’s true speed, hold a stopwatch while the printer prints many kinds of documents (involving small characters, big characters, short lines, long lines, draft quality, letter quality, and graphics).
A cable of wires runs from the printer to the computer’s main part (the system unit). The cable costs about $8 and is not included in the printer’s advertised price: the cable costs extra.
One end of the cable plugs into a socket at the back of the printer. The cable’s other end plugs into “a socket at the back of the system unit”, which is called the computer’s printer port.
If you open the system unit, you’ll discover which part of the computer’s circuitry the printer port is attached to. In a standard system unit, a cable runs directly from the printer port to the motherboard; but in some system units (such as the original IBM PC), the printer port is attached to a small PC card instead, called a printer interface card, which might not be included in the computer’s advertised price.
When the computer wants the printer to print some data, the computer sends the data to the printer port; then the data flows through the cable to the printer.
Serial versus parallel The cable from the system unit to the printer contains many wires. Some of them are never used: they’re in the cable just in case a computer expert someday figures out a reason to use them. Some of the wires in the cable transmit info about scheduling: they let the computer and printer argue about when to send the data.
If the computer’s port is serial, just one of the wires transmits the data itself. If the computer’s port is parallel, 8 wires transmit the data simultaneously.
A parallel port tends to be faster than a serial port, since a parallel port transmits 8 streams of data simultaneously. Unfortunately, a parallel cable is limited to shorter distances (about 12 feet instead of 50 feet), since it’s hard to keep 8 signals strong and synchronized over long distances.
Classic cables Back in the 1970’s, the typical serial cable contained 25 wires (1 of which transmitted the data). That cable was called the recommended standard 232C serial cable (RS-232C cable). At that time, the typical parallel cable contained 36 wires (8 of which transmitted the data), using a scheme invented by a printer manufacturer called Centronics and called the industry-standard Centronics-compatible parallel cable (Centronics cable).
IBM printer cable In 1981, when IBM invented the IBM PC, IBM decided that the 36-wire parallel cable was silly, since just 8 of the wires transmitted data; so IBM switched to a 25-wire cable instead; but to be compatible with the 36-wires printers that had already been invented, IBM glued a 36-pin connector/adapter to the printer’s end of the cable; so the cable winds up with 36 pins on the printer’s end but just 25 pins on the system unit’s end. That weird cable is called an IBM-PC compatible parallel printer cable (IBM printer cable).
If that cable is fancy enough to handle transmissions in both directions, it’s called a bidirectional IBM printer cable. If it’s even fancier and can handle transmissions quickly in both directions, it’s called an Institute of Electrical & Electronics Engineers standard 1284 cable (IEEE 1284 cable).
If the system unit’s circuitry for handling the IBM printer cable is ordinary, you have a standard parallel port (SPP). If that port’s circuitry is faster, you have an enhanced parallel port (EPP). If that port’s circuitry is even faster, it’s called an extended capability port (ECP). It transmits data about 10 times as fast as SPP. Most of the new computers have ECP ports.
EPP was invented by Intel, Zenith, and Xircom. ECP was invented by HP and Microsoft. EPP and ECP have both been approved by IEEE and are part of the 1284 standard. To make full use of an IEEE 1284 cable, you need an ECP port and an ECP-capable printer. You also need software to control them: to use EPP or ECP, you or your dealer must inform the computer that you bought an EPP or ECP port; if you folks don’t inform the computer, your printer will print slowly.
USB cable In 1988, when Apple invented the iMac computer, Apple decided that the 25-wire serial cable was silly, so Apple switched to a 4-wire serial cable instead, called the Universal Serial Bus cable (USB cable). Recently, some manufacturers of IBM-PC compatible computers have copied Apple’s idea of using the USB cable for printing.
Printers for the iMac use the USB cable. Most printers for IBM-compatible PCs use the IBM printer cable, but some use the USB cable instead.
The USB cable can be used for many other purposes, too. For example, the USB cable is the most popular cable for attaching a scanner (to an iMac or an IBM-PC compatible computer). The iMac also uses the USB cable to attach the keyboard, mouse, and floppy-disk drives.
One nice thing about the USB cable is that it’s hot-swappable: you can plug and unplug USB devices from the USB cable, even while they and the system unit are turned on, without damage. The system unit automatically figures out which USB devices are plugged into it at the moment.
A faster version of USB has been invented, called USB 2.
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 $50, 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.
External versus internal
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 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.
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.
The first popular modems for personal computers transmitted 300 bits per second (300 bps). That speed is also called 300 baud. Since 10 bits make a character, that kind of modem transmitted 30 characters per second.
After inventing 300 bps modems, engineers invented faster modems: they invented 1200 bps, then 2400 bps, then 9600 bps, then 14400 bps, then 28800 bps, then 33600 bps, then 56600 bps.
Now most modems are 56600 bps. That speed means 56600 bits per second. Since a kilobit is a thousand bits, that speed is 56.6 kilobits per second (56.6 kbps). Most computerists are too lazy to say that; instead they say 56.6 kbps or 56 kilobaud or simply 56K. So a 56K modem is a modem that can transmit 56600 bits per second (which is 5660 characters per second, which is much faster than a human can read).
Unfortunately, if you buy a 56K modem, several limitations prevent you from actually transmitting at 56K. Those limitations force the modem to downshift to a slower speed. Here’s why.…
The government’s Federal Communications Commission (FCC) restricts phone transmissions to 53K, to prevent phone switches from overheating. In most communities, the phone wires are so bad that they can’t handle transmissions faster than 45K reliably. So if you buy a 56K modem, it will probably be restricted to about 45K. In 25% of all communities, the phone system is so poor that a 56K modem will go no faster than a 33.6K modem.
Moreover, 56K modems go faster than 33.6K just when you’re using the Internet (not when you’re communicating directly with friends), and just when you’re receiving (not sending) Internet data, and just when you’re receiving the data from an Internet service provider that uses the same type of 56K modem as yours.
One type of 56K modem, called x2, was invented by modem-maker U.S. Robotics, which is now a division of 3Com. The other type of 56K modem, called k56flex, was invented by modem-chip-maker Rockwell and AT&T-spinoff Lucent. The two types of 56K modems are not compatible with each other.
A third type of 56k modem, called V.90, has been developed by an international committee: the International Telecommunications Union (ITU). Most modem makers promised that if you bought an x2 or k56flex modem, you’d get a free upgrade to V.90. Now most modems sold are V.90.
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 can transmit modem data (to other computers) at 56K but transmits faxes (to fax machines) at just 14.4K.
The most famous modems were made by Hayes, which charged high prices. Now many companies make cheaper modems that imitate Hayes’ and are called Hayes-compatible. Nearly all modems sold today are Hayes-compatible. Hayes gave up trying to compete against those cheap imitations: Hayes went out of business.
Now you can get a Hayes-compatible 56K fax/modem (made by Hawking Technologies) for just $14 from discount dealers such as PC Connection (800-800-5555).
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.)