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PIXELs

A pixel is short for pixel element. A pixel is one of many tiny dots that make up the computerís video display screen. These are also known as pels. A pixel is a single memory location, which in turn represents an address on the screen. Images and pictures are made up of many pixels all lighted up at the right time. Pixel addresses in memory are accessed using the graphics controller and are usually located between A0000h=BFFFFh. Pixels are lit up on the monitor by an electron gun. The electron gun fires electrons at the screen (from the inside), which excite small phosphors and cause them to glow. On a color monitor the phosphors can produce three colors of various intensities. The red, green, and blue phosphors and different intensities produce the many different colors possible on a screen.

The number of colors a computer can display depends on the video card. Color depth is the number of bits per color that are used. Color depth is determined by how much available memory the video card has. Cards can have 1 (monochrome), 4, 8, 16, 24, or 32 bits per pixel (bpp). Color space is the actual number of colors a card can display. Also, 8 bit color mode uses a palette, so when one pixel entry is changed, all the other pixels using that entry change also. A chart below shows the different color depths and color spaces a card can display:

Color Depth

Color Spaces

1

2 (monochrome)

4

16

8

256 (palletized modes)

15

16,000 (High Color)

16

65,536 (Full High Color)

24

16.7 Million (True Color)

32

4.2 billion (Ultra True Color)

In Windows it is possible to change the resolution. Resolution is how many pixels a screen displays, horizontally by vertically. Common resolutions are 320x200 (usually for games), 640x480, 800x600, and 1024x768. These resolutions tell one how many pixels are displayed along the top (ex: 800) by how many pixels down the side (ex: 600), totaling 480,000 pixels on the screen. Setting a screenís resolution to 1024x768 with 65,536 colors (16 bit, or 2 byte) would use up 1024x768x2 bytes of memory, 1,572,864 (about 1.6 MB)! Most video cards have 1-2 MBís of memory to process all this data.

In Windows 95, increasing the resolution will change the look of your Windows environment. The higher the resolution, the smaller the interface will appear. Also, having more colors will help display more detailed and smoother looking pictures.

Bibliography

Upgrading and Repairing PCs Scott Mueller

1997 Grolier Multimedia Encyclopedia ©1997 Grolier Interactive, Inc.

Windows Game Programming for Dummies Andre LaMothe

A+ Certification Complete CD published by New Riderís Top Score