cga

Color Graphics Adapter (CGA) is a display adapter introduced by IBM in 1981 for the IBM PC family. It was the first widely available color graphics option for the platform and helped establish color display as a standard feature of early personal computers. CGA cards were produced by IBM and various third-party manufacturers, and they remained common in the early PC market before being superseded by more capable adapters.

CGA supports two principal graphics modes. The 320 by 200 pixel mode displays four colors chosen from a 16-color palette, while the 640 by 200 pixel mode displays two colors from the same palette. In addition, CGA provides text modes that render 80 columns by 25 rows with color-enabled attributes. The 16-color palette is fixed, and color selections affect both graphics and text output.

In terms of hardware, CGA relies on video memory and a digital-to-analog converter to produce the display signal. Software interacts with the card through simple memory layouts and BIOS routines. The four-color mode is prone to color attribute clash, a limitation where certain color combinations in adjacent pixels can produce confusing results. While modest by later standards, CGA’s capabilities were adequate for early games, productivity software, and demonstrations, contributing to a broad base of software support across IBM PC compatibles.

Legacy and impact: CGA established the baseline for color graphics on IBM-compatible PCs and influenced subsequent standards such as EGA and VGA. It helped popularize color graphics in the early PC ecosystem and remains a reference point in the history of computer graphics and emulation, illustrating the early balance between cost, capability, and compatibility.