Open Watcom
The Watcom C/C++ compiler is a compiler for the computer programming languages C and C++ that produces executable programs for several platforms and operating systems. In the mid-1990s some of the most technically ambitious MS-DOS computer games such as Doom, Descent, Duke Nukem 3D, and Rise of the Triad were built using Watcom C/C++, some such as ROTT using the DOS/4GW protected mode extender with the Watcom compiler.