SB_INTERFACE = RECORD
                 PREV_CMD : CHAR;       (* SET BY CALLING PROG IF IT WISHES *)
                                        (* TO RETURN AFTER CALLED PROG      *)
                 NEXT_CMD : CHAR;       (* SET BY CALLING PROG TO INDICATE  *)
                                        (* WHAT PROG IS TO BE CALLED        *)
                                        (* SET TO BLANK IF NONE DESIRED     *)
                 END_STAT : (OK,IOERR,SYNERR,XTRA1,XTRA2,XTRA3);
                                        (* ERROR CODE RETURNED FROM CALLED  *)
                                        (* PROGRAM                          *)
                 BUFIDX   : INTEGER;    (* POINTER INTO BUFFER RETURNED BY  *)
                                        (* CALLED PROGRAM                   *)
		 ERRNUM   : INTEGER;	(* ERROR NUMBER FOR END_STAT	    *)
               END;