Many of the Doom engine graphics, including wall patches, sprites, and all menu graphics, are stored in the WAD files in a special picture format. Notably excepted are the textures for floors and ceilings, which are known as flats. Details of the picture format in Doom are given in the Unofficial Doom Specs. A picture header gives its width and height, and offset values. Following the header are pointers to data for each column of pixels; the number of these pointers is equal to the picture width.