IDENTIFICATION DIVISION.
       PROGRAM-ID. QUERY-INDEX-FILE.
       AUTHOR.     DEAN-BROCK.
      *
       ENVIRONMENT DIVISION.
       CONFIGURATION SECTION.
       SOURCE-COMPUTER. DEC-VAX.
       OBJECT-COMPUTER. DEC-VAX.
       INPUT-OUTPUT SECTION.
       FILE-CONTROL.
           SELECT BOOK-UPDATE-FILE
               ASSIGN TO 'UPDATE.TXT'.
           SELECT BOOK-INDEX-FILE
               ASSIGN TO 'BOOK.IND'
               ORGANIZATION IS INDEXED
               ACCESS MODE IS RANDOM
               RECORD KEY IS BXR-ISBN.
           SELECT REPORT-FILE
               ASSIGN TO 'BOOK.LPT'.
      *
       DATA DIVISION.
      *
       FILE SECTION.
       FD  BOOK-UPDATE-FILE.
       01  BOOK-UPDATE-RECORD.
           05  BUR-ISBN                PIC X(10).
           05  BUR-TITLE               PIC X(50).
       FD  BOOK-INDEX-FILE.
       01  BOOK-INDEX-RECORD.
           05  BXR-ISBN                PIC X(10).
           05  BXR-TITLE               PIC X(50).
       FD  REPORT-FILE.
       01  REPORT-RECORD.
           05  FILLER         PIC X(2) VALUE SPACES.
           05  REP-MESSAGE    PIC X(8).
           05  FILLER         PIC X(5) VALUE SPACES.
           05  REP-ISBN       PIC X(10).
           05  FILLER         PIC X(5) VALUE SPACES.
           05  REP-TITLE      PIC X(50).
      *
       WORKING-STORAGE SECTION.
      *
       01  WS-EOF-FLAG        PIC X.
       01  WS-NEW-FLAG        PIC X.
      *
       PROCEDURE DIVISION.
      *
       A000-MAIN.
           OPEN INPUT  BOOK-UPDATE-FILE
                I-O    BOOK-INDEX-FILE
                OUTPUT REPORT-FILE
           PERFORM B000-UPDATE-RECORDS
           CLOSE BOOK-UPDATE-FILE,
                 BOOK-INDEX-FILE,
                 REPORT-FILE
           STOP RUN.
      *
       B000-UPDATE-RECORDS.
           MOVE "N" TO WS-EOF-FLAG
           READ BOOK-UPDATE-FILE
               AT END MOVE "Y" TO WS-EOF-FLAG
           END-READ
           PERFORM UNTIL WS-EOF-FLAG IS EQUAL TO "Y"
               PERFORM B010-OUTPUT-REPORT
               READ BOOK-UPDATE-FILE
                   AT END MOVE "Y" TO WS-EOF-FLAG
               END-READ
           END-PERFORM.
      *
       B010-OUTPUT-REPORT.
           MOVE BUR-ISBN TO BXR-ISBN
           MOVE "N" TO WS-NEW-FLAG
           READ BOOK-INDEX-FILE
               INVALID KEY
                   MOVE "Y" TO WS-NEW-FLAG
           END-READ
           IF WS-NEW-FLAG IS EQUAL TO "N" THEN
               MOVE "PRESENT" TO REP-MESSAGE
               MOVE BXR-ISBN TO REP-ISBN
               MOVE BXR-TITLE TO REP-TITLE
               WRITE REPORT-RECORD
      *  Now you need write out an updated record to the index file
           ELSE
      *  Now you need write out a new record to the index file
           END-IF
      *  And do any appropriate cleanup