Dangerous Dave level format
From Just Solve the File Format Problem
Dangerous Dave was a game by John Romero published by Softdisk around 1990, first for the Apple IIgs and later the PC (under DOS). It was one of Romero's earlier published works, preceding the founding of id Software. It was succeeded by a number of sequels in the Dangerous Dave series.
The game levels were embedded in the executable as a series of 1280-byte chunks with 1000 bytes containing tile data in a 100 x 10 array.