Halt procedure

  DECLARATION:  Halt [ (ExitCode : Word) ]

      PURPOSE:  Stops program and returns to operating system

         UNIT:  System

      REMARKS:  ExitCode is an optional word-type expression that specifies
                the exit code of the program.  The exit code can be examined
                by ErrorLevel in a DOS batch file, or by a parent process
                using the DosExitCode function in the DOS Unit.

                Halt without any parameter is the same as Halt(0).  Halt will
                initiate any unit Exit procedures.