DosExitCode function

  DECLARATION:  DosExitCode

      PURPOSE:  Returns the exit code of a subprocess.

         UNIT:  DOS

  RESULT TYPE:  Word

      REMARKS:  The low byte is the code sent by the terminating process.
                The high byte is set to:

                    0  for normal termination;
                    1  if terminated by CTRL-C
                    2  if terminated by Device Error
                    3  if terminated by the Keep procedure