Video Graphics Array

See also: VGA

Video Graphics Array (VGA) is a standard of posting for computers. It is launched in 1987 by IBM under the name MCGA like an improvement of the EGA and CGA during the launching of range PS/2. VGA belongs to a family of standards of IBM and remains compatible with the preceding formats.

Like other achievements of IBM, VGA was very largely clone by other manufacturers. Although its form obsolete, was exceeded by the standard XGA, it is ultimate IBM which the majority of the manufacturers decided to follow for architectures PC. It was then exceeded by the standard SVGA.

Term VGA as well indicates a view (640 × 480, etc) that a connector industry (Connecteur VGA).

Specifications

The format uses 356 kibioctets (Kio) of video memory and functions according to two modes: 16 colors or 256 colors chosen among a pallet of: 262144 colors. The maximum definition is of 720 columns by 480 lines (720 × 480) with a rate of cooling of 70 Hertz.

Standard VGA also supports 4 video plans, the material scrolling, the division of the screen in independent zones and the font faces defined by software.

The standard graphic modes are:

  • 640 × 480 × 4 (16 colors)
  • 640 × 400 × 4 (16 colors)
  • 320 × 200 × 4 (16 colors)
  • 320 × 200 × 8 (256 colors) or Mode 13:00

It also supports the preceding standards: EGA, CGA and MDA, and other not documented. Another graphic mode called Mode X allows other technical solutions and definitions which are not available in Mode 13:00.

The mode text Alphanumérique is of 80×25 or 43×25 characters. Each cell can be defined by using 16 colors of text which can be made twinkling. In this case, only 8 colors are available for the bottom against 16 if the text is not twinkling. Although a monochromic mode is available, the majority of the programmers use the color mode with a gray text and a black bottom.

Materially, monochromic video space is in the beach of address memory 0xB0000-0xB7FFF, and spaces it color in the beach 0xB8000-0xBFFFF. In color mode, each cell of the screen is associated with two bytes one for the character and the other used for its attributes (flickering, police force, color…)

Connector industry

Connection between a computer and a monitor was done traditionally using connectors D-sub of high density to 15 pins (Connecteur VGA), or of miniature connectors Mini-VGA. However, the connectors DVI are spread more and more.

See too

External bonds

  • VGA DB-15, pin functions

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