SYSTEM UNIX

        [SIC\]SYSTEM ["command name"]
                    Unix version

    If no argument is given, start a subshell by running  the  default  user
    shell  (sh, csh or ksh). The subshell can be terminated by typing 'exit'
    or 'bye' or 'logout', depending on Unix version, and controls return  to
    SIC in this case.

    If an argument is given, execute the Unix command in a subshell.

    Note that new Unix environment variables canot be defined in such a way,
    since  it  is  a  subshell.  In particular, use command SIC DIRECTORY to
    change your working directory.

    SHORT CUTS:

    Unix commands can also be executed directly from the SIC level using the
    token, e.g.
        No case conversion occurs in such a case, and the "unix is  directly
    executed in a subshell.