Exec procedure

  DECLARATION:  Exec(FileName, CommandLine)

      PURPOSE:  Executes a specified program or dos command.

         UNIT:  The DOS unit

      REMARKS:  Exec takes two arguments including the path of the
                filename and the command line.  To execute a dos command,
                COMMAND.COM must be given as the filename and '/C' must
                preceed the command. ie: Exec('COMMAND.COM','/C DIR/P');

                NOTE:  Errors are reported through DosExitCode and DosError.

 RESTRICTIONS:  The Exec procedure will not modify memory, therefore
                sufficient memory must be available before performing the
                Exec procedure or DosError will return a value of 8.