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 85^th 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, pocket computers, subnotebook computers, notebook computers, and laptop computers.

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.

A notebook computer’s price depends mainly on what kind of LCD screen it includes. Most folks buy color LCD screens, though blank-and-white monochrome LCD screens are cheaper. For 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.

Most folks buy color screens that are active-matrix (which is the best type) or dual-scan passive (which costs $100 less).

LCD monitors

The typical LCD screen is built into a small computer (such as a notebook computer). A different way to get an LCD screen is to buy an LCD monitor, which acts as a monitor but includes an LCD screen instead of a CRT. You can attach the 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 very expensive (over $1,000).

LCD plates

An LCD plate (or LCD overhead-projection panel) is a special LCD screen that you put on an overhead projector, which projects the LCD’s image onto the wall of your office or classroom or auditorium, so that the image becomes several feet across.

The nicest low-cost LCD plate is the Sharp QA-75. It can display many shades of gray. It sells for about $1500. It attaches to the IBM PC, and you can buy a cable to connect it to a Mac.