Doom (1993 video game)
Doom (typeset as DOOM in official documents and stylized as DooM in other media) is a 1993 first-person shooter (FPS) video game by id Software. It is considered one of the most significant and influential titles in video game history, for having helped to pioneer the now-ubiquitous first-person shooter. The original game was divided into three nine-level episodes and was distributed via shareware and mail order. The Ultimate Doom, an updated release of the original game featuring a fourth episode, was released in 1995 and sold at retail.
Doom (1993 video game)
"Doom" was programmed largely in the ANSI C programming language, with a few elements done in assembly language. Development was done on NeXT computers running the NeXTSTEP operating system. The data used by the game engine, including both level designs and graphics files, are all stored in WAD files, short for "Where's All the Data". This allows for any part of the game's design to be easily changed without needing to adjust the engine code. Carmack designed this system specifically to enable fans to be able to easily modify the game; he had been impressed by the modifications made by fans of "Wolfenstein 3D", and wanted to support that with an easily swappable file structure along with releasing the map editor online.