"Doom was developed on NeXT workstations, under the NEXTSTEP operating system.[6] The Doom game engine was programmed in C, and the editing tools were written i

"Doom was developed on NeXT workstations, under the NEXTSTEP operating system.[6] The Doom game engine was programmed in C, and the editing tools were written in Objective-C. The engine was first compiled with Intel's C compiler for DOS, but later Watcom's C/C++ compiler was used" [1] John Carmack is nothing if non-partisan when it comes to tools and platforms. Most everything he wrote was reasonably cross-platform C until id Tech 4, released in 2004. I'd say Carmack has zero years invested in C++ programming for Windows games. He instead has decades invested in making cross platform game engines written in a variety of C-based languages. [1] http://en.wikipedia.org/wiki/Making_of_Doom http://en.wikipedia.org/wiki/Making_of_Doom