What does it do?
The monitor is the most visible part of your computer, converting your Mac’s video output into images on its TV-like screen. Because larger colour monitors used to be expensive, some very old models may work only in monochrome (greys). But almost all recent products work in full colour: if your Mac can generate sufficient colours, the monitor will display them. However, the resolution of the image is limited by the size and capabilities of the monitor. Better monitors also offer increasingly sophisticated facilities to keep colours true, often using ColorSync and software controls to match their output. How does it work?
Your Mac’s video output (from its graphics or video adaptor, or a PowerBook’s external monitor port) is connected by a special cable to the monitor’s input. During startup, the Mac and monitor may talk to one another to auto-sense the right screen resolution and signal format. The monitor then takes the input signal and displays it, one dot or pixel at a time, scanning across each line and, line by line, down the whole screen image. Unlike TVs, most monitors scan down the entire screen in one go, and don’t interlace alternate lines. Monitors also try to use high refresh rates (the number of times the whole screen is redrawn), generally 60 to 85 times per second (Hz) or even higher. This improves image quality and prevents the screen from visibly flickering. What can go wrong with it?
Monitors are essentially sealed units, and even when integral to computers (as in the iMac) can retain very high voltages for many hours after use. Tampering with a monitor is very dangerous, as these voltages can kill. This isn’t normally true of flatscreen panels, whether separate or in a PowerBook or iBook. Problems which can’t be fixed by adjusting accessible controls (in software or physical controls on the monitor) need attention from an Apple dealer’s trained engineer. You should also check cables are properly connected, and are of the correct type. How can I upgrade it?
Software drivers are needed for more sophisticated models for example, with ADB or USB control. These are part of Mac OS or third-party products. Otherwise, there’s nothing to upgrade. Further info
Better Mac books explain monitor technology and options. Griffin Technology has two superb Web pages: a massive compilation of monitor specs is at www.nashville.net/~griffin/monitor.html, and tools, including DDC, to check out plug and play, and other monitors, at www.nashville.net/~griffin/ftp.html | 
