The Video System

When you type with your word processor, characters are added to the screen. If you look closely, you'll see that the characters are composed of dots.

One of the expansion cards, called a display, video or graphics card, is for the monitor. When IBM-compatible computers first became available, you could display only text, or very simple graphics. Choices were limited to medium resolution monochrome (green), 16-color text, or 4-color graphics! Most modern video systems can handle up to 16.7 million colors.

The monitor does not know about text. All it knows is how to put dots on the screen. The display card has to tell it about every character, number and punctuation mark it shows. For instance, a question mark is composed of these dots:

All letters, numbers and punctuation are composed of uniform dots.

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