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the old ones automatically fade away.
In fact, the electron gun does not draw an image directly by focusing and shooting on the
pixels forming the image. Instead, it traverses the screen in a fixed pattern as shown in
Figure 9.21. That is, it systematically aims at every pixel on the screen, starting at the
top-left corner and scanning to the right horizontally, then dropping down a small distance and scanning another line. Each horizontal line of pixels is called a scan line.
There are a fixed number of pixels on every scan line, and a pixel can be written or not in
each position by turning the beam on and off. When the beam gets to the right end of a
scan line, it is turned off and moved to the starting point of the next scan line. This is
called the horizontal trace. After scanning all the scan lines, when the beam gets to the
right end of the bottom-most scan line, it is turned off and moved to the starting point of
the top-most scan line. This is called the vertical trace.
In one pass of scanning the entire screen, if the electron beam travels all the scan lines
sequentially from top to bottom, it is called a. progressive scan (see Figure 9.21 (a)). On
the other hand, if the electron beam travels only 9.21 (b)). In case of interlaced scan since
the monitor scans every other line instead of each line in order, so it has to transmit only
half as much data in a single pass, but takes two passes to draw the entire screen. As
interlaced scan may cause flicker of images drawn on the screen, it is used in lowerquality monitors. High quality monitors use progressive scan.
How to Compare CRT Monitors
CRT Monitors are normally compared based on the following attributes:
1. Screen Size. Display screens of monitors vary in size from 5 to 25 inches (diagonal
dimension). Monitors with 17 inch to 21 inch screen size are common today with
personal computers and other desktop computers.
With users increasingly viewing
multiple windows, video clips, animated objects, and complex graphics, monitors...
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- Spring '14