BS is an image file format used for storing bitmap images. The format was developed in 1986 by German developer for Commodore 64 system. An interesting fact about BS files is that first bit of each BS file is always 0x42, which translates to the letter "B".

Raster image file that use .BS extension support only 320x200 pixel resolution. BG (support up to 640x400 pixels) and PG (support for 8x8 to 640x800 pixels) are file formats similar in structure to BS format. It is still possible to view this type of files with XnView image viewer.