Can I have more than one monitor on my pc?

If you have ever been to the trading floor of a large brokerage company, you have seen some of the most advanced workstations around. Traders often use UNIX or NT workstations with two or even four monitors so they can display dozens of windows simultaneously. Multiple monitors have also been possible on the Macintosh for several years, and are often used by artists and editors to give the computer more screen real estate.

You might want to have multiple monitors for the same reason that you might like to work at a big table sometimes. For example, when you are doing your taxes or working on a big science fair project, it is nice to have several books and four stacks of paper open simultaneously. It works the same way on the computer. For certain tasks, it is helpful to have lots of open windows that are all visible simultaneously. This is especially true for computer programmers working on large projects, artists and editors cutting and pasting from multiple sources, etc.

It turns out that Windows 98 comes with multiple monitor support that allows two (or more) monitors to be used simultaneously. To try this feature you need a second graphics card and (obviously…) a second monitor. It makes things more symmetric if the two monitors and cards are the same, but they don't have to be. You can either place the monitors side by side to create a wide desktop, or you can place one on top of the other. With three or more you can arrange them almost any way you like.

How do touch-screen monitors know where you're touching?

Touch-screen monitors have become more and more commonplace as their price has steadily dropped over the past decade. There are three basic systems that are used to recognize a person's touch:

* Resistive
* Capacitive
* Surface acoustic wave

The resistive system consists of a normal glass panel that is covered with a conductive and a resistive metallic layer. These two layers are held apart by spacers, and a scratch-resistant layer is placed on top of the whole setup. An electrical current runs through the two layers while the monitor is operational. When a user touches the screen, the two layers make contact in that exact spot. The change in the electrical field is noted and the coordinates of the point of contact are calculated by the computer. Once the coordinates are known, a special driver translates the touch into something that the operating system can understand, much as a computer mouse driver translates a mouse's movements into a click or a drag.

In the capacitive system, a layer that stores electrical charge is placed on the glass panel of the monitor. When a user touches the monitor with his or her finger, some of the charge is transferred to the user, so the charge on the capacitive layer decreases. This decrease is measured in circuits located at each corner of the monitor. The computer calculates, from the relative differences in charge at each corner, exactly where the touch event took place and then relays that information to the touch-screen driver software. One advantage that the capacitive system has over the resistive system is that it transmits almost 90 percent of the light from the monitor, whereas the resistive system only transmits about 75 percent. This gives the capacitive system a much clearer picture than the resistive system.

On the monitor of a surface acoustic wave system, two transducers (one receiving and one sending) are placed along the x and y axes of the monitor's glass plate. Also placed on the glass are reflectors -- they reflect an electrical signal sent from one transducer to the other. The receiving transducer is able to tell if the wave has been disturbed by a touch event at any instant, and can locate it accordingly. The wave setup has no metallic layers on the screen, allowing for 100-percent light throughput and perfect image clarity. This makes the surface acoustic wave system best for displaying detailed graphics (both other systems have significant degradation in clarity).

Another area in which the systems differ is in which stimuli will register as a touch event. A resistive system registers a touch as long as the two layers make contact, which means that it doesn't matter if you touch it with your finger or a rubber ball. A capacitive system, on the other hand, must have a conductive input, usually your finger, in order to register a touch. The surface acoustic wave system works much like the resistive system, allowing a touch with almost any object -- except hard and small objects like a pen tip.

As far as price, the resistive system is the cheapest; its clarity is the lowest of the three, and its layers can be damaged by sharp objects. The surface acoustic wave setup is usually the most expensive.