, .com was the extension of executable
s - as far as I know, .com files were just raw binary with no headers, so they could be created with things like debug
easily. IIRC, they were also limited to 64 kilobytes in size, which is why they were later largely replaced with .exe
files. DOS 6 had only a handful of COM files.
One of the most widely remembered .com file is, of course, COMMAND.COM. (Also registered as a domain name? You betcha. =)