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 WAD
John Carmack, lead programmer at id Software, designed the "Doom" internals from the ground up to allow players to extend the game. For that reason, game data such as levels, graphics, sound effects, and music are stored separately from the game engine, in "WAD files". This allowed players to make their own data without making any modifications to the engine. According to "Doom"s initial design document, WAD stands for "Where's All the Data?".