PCX
The DOS paint format that time forgot.
Where it came from
PCX was created by ZSoft in 1985 for PC Paintbrush, one of the first popular DOS painting programs. It rode the early PC graphics wave and was everywhere in the late-80s shareware scene.
As Windows and true-color formats arrived, PCX faded. You mainly find it in old archives and retro software now.
How it works
PCX uses simple run-length encoding (RLE): repeat-byte counts compress solid areas without complex math. It supports 1–32 bit color and a palette.
The format is obsolete but trivial to decode. UWC converts PCX → PNG/JPEG server-side for those occasional legacy files.