I've got the answer. Use a 4-byte magic number (either in the file or in the directory - in the file is easier for the program that creates it or that wants to know what kind of file it is, but in the directory is easier for the DIR command). Have an /etc/magic file that the user can alter or obtain from somewhere. Write a program which is able to update the DOS with the /etc/magic file and install the new DOS on the disk. Write a DIR program that can (optionally) look at the magic number of each file and the /etc/magic file and print out what the file is.
imc
