Video Display And Display Adapters
A video display unit is one of the most useful output components of the computer system. This system comprises the following components:
1. Video screen where text and picture can be displayed
2. Video display adapter card, which is plugged into one of the expansion slots, provided on the motherboard.
The display adapter facilitates the programmer to show the various figures and text on to the screen with different resolutions. Resolution is decided by number of pixels (small dots) available on the screen. The display resolution is a combination of number of rows from top to bottom and number of pixels from left to right on each scan line. Higher the resolution more clear is the picture. With higher number of pixels the picture becomes clearer. Commonly available display adapters are Video display adapters, Color graphics adapters, and super video graphs adapters. All these adapters operate both in text and graphics modes. The clarity and quality of picture with VGA, SVGA etc are better than CGA and monochrome adapters. CGA adapters were used earlier and now it is absolute. Now a day, programmers prefer to use high resolution adapters such as EGA, VGA or SVGA.
The display adapter acts as an inter-mediator between processor and monitor. The display adapter has two parts a) VDU memory b) Circuitry that passes contents of VDU memory to the screen. The microprocessor writes the information into VDU memory. The display adapter transfers the information written by processor to screen. Every address of the VDU memory corresponds to the specific location of monitor screen.