com format

the com files are raw binary executables and are a leftover from the old cp/m
machines with 64k ram.  a com program can only have a size of less than one
segment (64k), including code and static data since no fixups for segment
relocation or anything else is included. one method to check for a com file is
to check if the first byte in the file could be a valid jump or call opcode, but
this is a very weak test since a com file is not required to start with a jump
or a call. in principle, a com file is just loaded at offset 100h in the segment
and then executed.
offset              count type   description
0000h                   1 byte   id=0e9h
                                 those are not safe ways to determine wether a
                                 file is a com file or not, but most com files
                                 start with a jump.
further information not available.
see also:exe,mz exe,ne exe