WadC

WadC ("Wad Compiler") is a programming language and designed for constructing Doom levels. Originally written by Wouter "Aardappel" van Oortmerssen, it is now maintained by Jon Dowland. The system takes the form of a two pane window. In the left pane, WadC code can be written. A preview of the resulting level is displayed in the right pane. WadC has advantages over traditional level editors in that it is easy to form repeating structures: a function can be written to create a pillar, for example, and then invoked any number of times to create many pillars.

Notable levels
Perhaps the best known WadC maps were created by Aardappel himself, including his submission to Doomworld's 10 Sectors competition, and Crucified Dreams MAP12. The source code files for both maps are included in the WadC zip file as and  respectively.