Function            ROM_id - gets the ROM id byte

  Syntax              byte ROM_id(void);

  Prototype in        ibm.h

  Remarks             finds the ROM id byte at F000:FFFE

  Return value        returns the ROM id byte

  Note                on Compaq machines the ROM id byte is found at a
                      memory location close to, but not at, F000:FFFE.
                      Not having access to a Compaq, I did not include a
                      check for this. Maybe a future version...

  See also            ibm.h
                      machine_id(), ROM_date()

  Example             #include <ibm.h>
                      #include <stdio.h>

                      main()
                      {
                           printf("ROM id byte = %X",ROM_id());
                      }

  Program output      ROM id byte = FF