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Listening and Monitoring

If you want your computer to do anything useful, you have to be able to tell it what to do. Although some computers actually do listen to you speak using voice-recognition technology, most systems depend on traditional control systems, the keyboard, and the mouse to put you in command. In addition, many applications require that you fill your computer with data—keystrokes, images, and sounds. Your computer acquires this information by electronically listening to any of several input devices—scanners, digital cameras, sound board samplers, and so on.

Your window into the mind of your computer that lets you monitor what it does is its display system, itself a combination of a graphics adapter or video board and a monitor or flat-panel display. The display system gives your computer the means to tell you what it is thinking and to show you your data in the form that you best understand—be it numbers, words, or pictures. The two halves of the display system work hand in hand. The graphics adapter uses the digital signals inside your computer to build an electronic map of what the final image should look like, storing the data for every dot on your monitor in memory. Electronics generate the image that appears on your monitor screen.


The keyboard remains the most efficient way to enter text into applications, faster than even the most advanced voice-recognition systems, which let you talk to your computer. Scientists believe that keyboarding is a more direct route from your brain. Speaking requires more work, and the mechanics of sounding your voice take more time. But the keyboard lets you do more than mere typing. It is the primary command-and-control center for your computer.

The keyboard is probably the most identifiable part of any computer. You can't miss an array of over 100 buttons meant to be individually activated by your fingers. They come built into notebook computers, tethered on short cords to most desktop systems, and warped and bent in magnificent curves meant to soothe tired hands.

Pointing Devices

Although computers once recognized only text—for which a keyboard sufficed—today's computers work with pictures (what computer-people call graphics). The keyboard is notoriously poor at picking out pieces of pictures, but the mouse—more correctly termed a pointing device to include mouse-derived devices such as trackballs and the proprietary devices used by notebook computers—readily relays graphic instructions to your computer. Not only can the pointing device point, but it also lets you draw, sketch, and paint.

The most familiar pointing device is the hand-size mouse that you move around your desktop to cause a mouse pointer to move analogously on the screen. But some people prefer upside-down mice called trackballs for rolling the pointer around. Notebook computers use specialized pointing devices called pointing sticks (IBM's TrackPoint is the premier example) or touchpads, which let you move around the desktop by scratching your finger across a plastic pad.


The range of input devices naturally grows to embrace whatever kind of information you want to get into your computer. Say you have on-paper images you want to capture—drawings your kids made in first grade, your likeness on a poster from the post office, portraits of presidents on small sheets of paper—so that you can get into your graphics program to clean them up. Engineers developed the scanner to do just that. A scanner dissects the image into bits of graphic information like little dots that your computer can manipulate and store digitally.

Although engineers have developed an entire zoo of scanners to suit different kinds of original material (for example, photos or documents), most of today's scanners prefer to look at flat sheets. They take the form of flat boxes with glass plates on top, on which you lay printed images that you want to capture to your computer.

Digital Cameras

Scanners work when you have an image already fixed on paper, but when you want to get something you see in the real world into computer-compatible form, you need a digital camera. As with a scanner, a digital camera reduces an image—in this case, a scene you see in the real world—into tiny dots that your computer can store as digital data. The digital camera is a completely self-contained system for capturing and saving real-world images. It works with and without a computer, but the full power of the digital camera is realized best when you can edit its images with software on your computer.

A digital camera looks and works much like old-time film cameras with a lens in front and a viewfinder to help you frame the scenes you want to save. Some digital cameras are as simple as old box cameras—press a button and let the camera do the rest. Others have more controls than a small space shuttle, letting you unleash your full creative powers.

Display Systems

Your computer's thoughts, like your own, are invisible. Making your thoughts visible to others is what language and art are all about. The computer's equivalent is the graphics adapter. This component takes the digital thoughts of your computer and turns them into an electronic image, essentially a picture saved in the computer's electronic memory.

Once a graphics adapter has an image in this form—be it a page of text or a picture of an oasis—a monitor (sometimes called a display) connected to your computer makes the actual image that you can see. Monitors are essentially television sets built to military specifications. They produce sharper, higher-quality images than any television (including a new digital, high-resolution models) can hope to show.

Almost any monitor will let you work with your desktop computer (the monitor is built in to notebook machines), but the quality of the monitor attached to your computer determines the quality of the image you see and, often, of the work you do. Although no monitor can make anything look better than what's in the signals from your graphics adapter, a bad monitor can make them look much worse and limit both the range of colors and the resolution (or sharpness) of the images.

In most desktop computers, the graphics adapter is an expansion board, often the only one that comes as factory equipment, although notebook computers and many desktop systems have their graphics adapter functionality built in to the circuitry of the main circuit boards. Modern monitors for desktop computers come in two types: Cathode-ray tube (CRT) monitors use picture tubes like old-fashioned television sets and are big boxes that sit on your desk and, often, crowd everything off. Flat-panel monitors use liquid-crystal displays (LCDs) that run cooler and take up less room than CRTs (but cost substantially more). Either type is tethered to a desktop computer by a short cable. Notebook computers universally have built-in flat-panel displays.


A pretty picture is not enough in today's world. You need a total experience, one that involves both pictures and sound. After all, silent films went out of date in 1927. Consequently, every computer now has a sound system. In business computers, it's often nothing more than a beeper to warn you when you've pressed the wrong key. In most of today's computers, however, the sound system is on par with those in theaters (only not as loud). They can generate any sound you can hear and make it appear to be anywhere in the room.

Speakers are the most obvious part of any sound system, if just because you've got to find a place for two or three more boxes on your office desk. The real sound-generating capability of a computer comes from its sound board, however, which either slides into an expansion slot in the computer or is built into its main circuitry.


The electronic thoughts of a computer are notoriously evanescent. Pull the plug and your work disappears. Moreover, monitors are frustratingly difficult to pass around and post through the mail when you want to show off your latest digital art creation. Hard copy (the printout on paper) solves this problem. A printer is the device of choice for making hard copy from your computer's thoughts.

Printers come in many varieties. The most common are laser printers and inkjet printers. Either is a box with two paper trays that connects to your computer with a short cord. Lasers make fast, cheap, black-and-white pages. Inkjets are low-cost printers that excel at printing color but do so at a higher price per page because of their use of expensive inks.


Fax combines both the telecommunications capability of a modem with the hard-copy output of a printer. In effect, a fax machine becomes a remote printer for your computer—a system that allows your computer to print remotely to anywhere in the world you can get a telephone connection.

Today, fax is an invisible part of nearly every modem. If you can get online through a dial-up connection with your computer, you can fax. In most cases, you need nothing more than the modem already in your computer. The only addition required is invisible software.

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