CAT(4) Kernel Interfaces Manual CAT(4)
cat - phototypesetter interface
Cat provides the interface to a Graphic Systems C/A/T phototypesetter.
Bytes written on the file specify font, size, and other control infor-
mation as well as the characters to be flashed. The coding will not be
Only one process may have this file open at a time. It is write-only.
Phototypesetter interface specification