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Each screen character is represented by two bytes aligned as a 16-bit word accessible by the CPU in a single operation. The lower (or character) byte is the actual code point for the current character set, and the higher (or attribute) byte is a bit field used to select various video attributes such as color, blinking, character set, and so forth. [6]
In this mode, the video picture is stored as a simple bitmap, with one bit per pixel setting the color to "foreground" or "background". By default the colors are black and bright white, but the foreground color can be changed to any entry in the 16-color CGA palette. The background color cannot be changed from black on an original IBM CGA card.
In some systems, as Hercules and CGA graphic cards for the IBM PC, a bit value of 1 represents white pixels (light on) and a value of 0 the black ones (light off); others, like the Atari ST and Apple Macintosh with monochrome monitors, a bit value of 0 means a white pixel (no ink) and a value of 1 means a black pixel (dot of ink), which it ...
To form a color with RGB, three light beams (one red, one green, and one blue) must be superimposed (for example by emission from a black screen or by reflection from a white screen). Each of the three beams is called a component of that color, and each of them can have an arbitrary intensity, from fully off to fully on, in the mixture.
VGA section on the motherboard in IBM PS/55. The color palette random access memory (RAM) and its corresponding digital-to-analog converter (DAC) were integrated into one chip (the RAMDAC) and the cathode-ray tube controller was integrated into a main VGA chip, which eliminated several other chips in previous graphics adapters, so VGA only additionally required external video RAM and timing ...
A modern consumer graphics card: A Radeon RX 6900 XT from AMD. A graphics card (also called a video card, display card, graphics accelerator, graphics adapter, VGA card/VGA, video adapter, display adapter, or colloquially GPU) is a computer expansion card that generates a feed of graphics output to a display device such as a monitor.
English: Default VGA palette (256 colors) serving for 4 different needs in a single colour table [1] The first 16 colours are encoded exactly as with all 16 colour modes (0Dh/0Eh/10h/12h) which in turn use the same 4 bit encoding as the colour attributes of all text modes (*1)
The later VGA standard built on this by mapping each of the 64 colors in from a larger, customizable, palette of 256. Standard EGA monitors do not support use of the extended color palette in 200-line modes, because the monitor cannot distinguish between being connected to a CGA card or being connected to an EGA card outputting a 200-line mode.