Monochrome Display Adapter (MDA)

Introduced in 1981, MDA was a pure text display showing 80 character lines with 25 vertical lines on the screen. Typically, the display was green text on a black background. Individual characters were 9 pixels wide by 14 pixels high (7×11 for the character, the rest for spacing). If you multiply that out you get a resolution of 720×350 but since the individual pixels were not capable of being addressed there were no graphics. Although, some programs managed some interesting bar charts and line art using various ASCII characters; particularly those above 128 used by code page 437.

The IBM MDA card had 4 KB of video memory. Display attributes included: invisible, underline, normal, bright/bold, reverse video, and blinking. Some attributes could be combined. IBM graphic’s card also contained a parallel printer port giving it the full name: Monochrome Display and Printer Adapter.

The monitor’s refresh rate was 50 Hz and users tended to complain about eyestrain after long days in front of the monitor.