Monochrome Display Adapter

The Monochrome Display Adapter (MDA) was developed by IBM in the early 1980s. It is a standard video display card and computer display standard used to display text characters in monochrome text mode. It has no real graphics mode of any kind. It displayed 80 columes X 25 lines of text characters on a monitor, driven by its 4KB of video memory. It was meant to facilitate business and word processing use, and actually originally features a parallel printer port on the card.

Text characters were rendered in a box 9x14 (7x11 fpr the text character itself with the rest used for spacing) pixels in size. Theoretically, the maximum resolution of MDA was 720 x 350 pixels. The MDA supported text formatting that is commonplace in any text editor today, including underline, bold, blinking text etc. but the only way to even simulate a feeling of graphics, or anything beyond plain text, was with ANSI art. Unlike its successors, MDA could not address individual pixels, only working in text mode with a limit of 256 characters stored in ROM on the card and unalterable by software.

Launxched at the same time as the MDA was the Color Graphics Adapter (CGA), also released by IBM. CGA was needed by users who required bitmapped graphics and color technology. MDA still had one major advantage over CGA for business use however; CGA did not have a printer port. A non-IBM competitior sprung up in 1982 also. The Hercules Graphics Card (HGC) offered both MDA-compatible text mode and monochrome graphics mode, and could address individual pixels and produce large black and white images.