Monochrome display adapter
Monochrome Display Adapter (abbreviation: MDA ) refers to the non- graphics- capable graphics standard of the first IBM PCs from 1981.
MDA only supports text display with 25 lines by 80 characters with a resolution of 720 × 350 pixels, which was relatively high for the time . This is 9 × 14 pixels per character, which means that the letters looked less blocky and the line spacing was larger than on other computers of the time, which usually only used 7 × 8 or 8 × 8 pixels per character. The MDA also allowed characters to be displayed in two levels of brightness, underlined or inverse (dark on light); color representation, however, was not possible. The monitor used defined the color display, e.g. B. Green on black, white on black or amber / amber on black. MDA is also the oldest and first " graphics standard " for PCs, but IBM originally used neither the term Monochrome Display Adapter nor MDA . A chip with the designation 6845 from Motorola was responsible for the entire display . With the help of peripheral components, this chip generates the necessary TTL signal that reaches the monitor.
MDA monitors were mainly used in offices because they are easy on the eyes, i.e. H. Sharp outlines and comparatively flicker-free display of office applications such as word processing and spreadsheets ; MDA was thus one of the decisive factors that contributed to the success of the IBM-compatible PCs.
The alternative graphics-capable IBM standard from the year the IBM XT computers were introduced was CGA , which could display both colored graphics and text, but had a lower resolution and refresh rate.
MDA plug-in cards for XT-compatible PCs are the forerunners of today's graphics cards ; The successor standards include EGA ( 1984 ), MCGA and later VGA and SVGA ( 1989 , specified by VESA ).
See also
literature
- Heinz-Josef Bomanns: The great PC graphics book , chapter 3.1. Data Becker, 1988, ISBN 3-89011-214-5 .