Watcom C/C++ OpenWatcom

The Watcom C/C++ is a powerful compiler for DOS, Windows, and OS/2. Its key selling point was superior cross platform support. It supported DOS, extended DOS 32-bit, Win16, Win32, and OS/2. Notably, it was used to produce the video game DOOM as a 32-bit DOS extended program.

Watcom also produced other language compilers including Watcom Fortran