IWAD

Doom WAD is the default format of package files for the video game Doom and its sequel Doom II: Hell on Earth, that contain sprites, levels, and game data. WAD stands for Where's All the Data?. Immediately after its release in 1993, Doom attracted a sizeable following of players who created their own mods for WAD files—packages containing levels, graphics, and other game data—and played a vital part in spawning the mod-making culture which is now commonplace for first-person shooters. Thousands of WADs have been created for Doom, ranging from single custom levels to full original games; most of these can be freely downloaded over the Internet. Several WADs have also been released commercially, and for some people the WAD-making hobby became a gateway to a professional career as a level designer.

There are two types of WADs: IWADs (internal WADs) and PWADs (patch WADs). IWADs contain the data necessary to load the game, while PWADs contain additional data, such as new character sprites, as necessary for custom levels.

When developing Doom, id Software was aware that many players had tried to create custom levels and other modifications for their previous game, Wolfenstein 3D. However, the procedures involved in creating and loading modifications for that game were cumbersome.

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?".

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