JEDMICS C4 is a bi-level raster image file format. It is also known as EDMICS C4 or CALS Raster Type 4.
The name comes from an entity named JEDMICS (Joint Engineering Data Management Information and Control System), which is related in some way to the U.S. Department of Defense.
Files have a 128-byte header, followed by a tile index, followed by the pixel data in the form of a set of 512×512-pixel tiles. Each tile is compressed with CCITT Group 4, or is uncompressed.
The specification implies that files begin with (hex) bytes
80 00 00 00.