(^382) PC Hardware: A Beginner’s Guide
follow a pattern that moves left to right over the top row of pixels and at the end of that
row returns to the beginning of the next row and so forth. At the bottom of the screen, the
swee pmoves back to the beginning of the to prow and begins again. The intensity of
electron beam, which controls the color and brightness of each pixel on the screen, is
adjusted as it moves across the screen to “paint” the display’s image.
On a color monitor, the electron beam is made u pof three electron streams that come
from three separate electron guns. There is one stream for each of the red, green, and blue
dots on the display. The streams are arranged to match the standard arrangement of the
dots in the pixels. By changing the intensity of the streams, the closely grouped dots will
appear to the human eye to produce a certain color. Its color depth sets the number of
colors the monitor can produce, but the VGA standard is 256 colors. Most of today’s
monitors are SVGA (see below) and are capable of displaying over 16 million colors.
Refreshing the Display
One pass of the entire display by the electron beam requires only a fraction of a second.
However, the phosphor begins to lose its glow just as fast and must be refreshed constantly.Figure 16-6. The pattern used by the electron beam to illuminate the CRT’s phosphorous material