COBOL code appearing in The Terminator (1984)

terminator.cob

     IDENTIFICATION DIVISION.
       PROGRAM-ID. ADD.
       ENVIRONMENT DIVISION.
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       77 IDX  PICTURE 9999.
       77 SUMX PICTURE 999999.
       77 X    PICTURE X.
       PROCEDURE DIVISION.
       BEGIN.
           ACCEPT X.
           MOVE ZERO TO IDX.
           MOVE ZERO TO SUMX.
           PERFORM ADD-PAR UNTIL IDX = 1001.
           DISPLAY SUMX.
           STOP RUN.
       ADD-PAR.
           COMPUTE SUMX = SUMX + IDX.
           ADD 1 TO IDX.