[SCA Command] Spawns a subprocess running the DCL command
    interpreter and suspends the editing session.

                                   NOTE

       This function is not available in DECwindows; any attempt to
       invoke it incurs an error.

    Format

      SPAWN   [command]

1  –  Parameter

 command
    Specifies a command line to be executed by the spawned subprocess.
    If you specify this parameter, the subprocess ends and LSE regains
    control upon completion of the command.