Linux Notes: indexed-file-demo1.cob

The information presented here is intended for educational use by qualified computer technologists.
The information presented here is provided free of charge, as-is, with no warranty of any kind.

Edit: 2026-09-23
Back to: Linux Notes: GnuCOBOL

indexed-file-demo1.cob

Notes:

ISAM was all the rage from 1965 to 1990 on mainframes and minicomputers.
- ISAM = Indexed Sequential Access Method (predates an SQL-compliant relational database).
- Recall that ISAM support was built into DEC-BASIC on VMS and OpenVMS.
  - It was also built into DEC-COBOL but could be called by other DEC languages including Pascal and C.
- Inspect the program below then notice that the record is defined using a group of PIC statements (In DEC-BASIC you would declare a MAP containing fixed-length strings)
  - PIC 9 = numeric [[[ so PIC 9(4) reserves space for 4 numbers ]]]
  - PIC X = alphanumeric [[[ so PIC X(20) reserves space for 20 alpha-numeric characters ]]]
  - PIC A = alphabetic [[[ so PIC A(10) reserves space for 10 alphabetic characters) ]]]
- Notice that PIC statements are also used to define working storage (program variables)
The following example was recently sent by a peer following one of our discussions about ISAM
Apparently this demo was auto-created by Google's Gemini A.I. in 2026
It does not compile "as-is" using GnuCOBOL because one of the lines (109 in this file) is longer than 72 characters.
Since the format of line 109 is different than 126, I would say that the A.I. must have FUBARed line 109.
Anyway, this can be easily compiled using GnuCOBOL with the inclusion of the "-ftext-column=132" switch

The code:

      * ===============================================================
      * FILE : indexed-file-demo1.cob
      * NOTES:
      * 1) this is the original demo cobol program sent by Roland.
      *
      * 2) When using cobc (GnuCobol 3.2.0), the following command will
      *    fail because one of the cobol source lines is too long (the
      *    syntax error will be obvious if you are using "vim" rather
      *    than "vi"):
      *
      *       cobc -x                   indexed-file-demo1.cob
      *
      * 3) But this command will work:
      *
      *       cobc -x -ftext-column=132 indexed-file-demo1.cob
      *
      * 4) Compiling with switch "-free" chooses a column limit of 511
      *    but will require you to modify all the remark statements
      *    from ">" to ">*"
      *
      * Neil Rieck (2026-09-22)
      * ===============================================================
       IDENTIFICATION DIVISION.
       PROGRAM-ID. INDEXED-DEMO.

       ENVIRONMENT DIVISION.
       INPUT-OUTPUT SECTION.
       FILE-CONTROL.
           SELECT OPTIONAL EMP-FILE
               ASSIGN TO "EMPLOYEE.DAT"
               ORGANIZATION IS INDEXED
               ACCESS MODE IS DYNAMIC
               RECORD KEY IS EMP-ID
               FILE STATUS IS WS-FS.

       DATA DIVISION.
       FILE SECTION.
       FD  EMP-FILE.
       01  EMP-RECORD.
           05  EMP-ID        PIC 9(4).
           05  EMP-NAME      PIC X(20).
           05  EMP-DEPT      PIC X(10).

       WORKING-STORAGE SECTION.
       01  WS-FS             PIC XX.
       01  WS-EOF-SWITCH     PIC X         VALUE "N".
           88  END-OF-FILE                 VALUE "Y".
       PROCEDURE DIVISION.
       MAIN-LOGIC.
      *    1. Open the file in I-O mode (reads, writes, and updates allowed)
           OPEN I-O EMP-FILE
           IF WS-FS = "35"
      *        File didn't exist; Open as OUTPUT to create it initially
               OPEN OUTPUT EMP-FILE
               CLOSE EMP-FILE
               OPEN I-O EMP-FILE
           END-IF

      *    2. Write records to the indexed file
           DISPLAY "--- WRITING RECORDS ---"
           END-DISPLAY
           PERFORM WRITE-SAMPLE-DATA

      *    3. Random access lookup (Direct retrieval using key)
           DISPLAY " "
           DISPLAY "--- RANDOM ACCESS LOOKUP ---"
           END-DISPLAY
           PERFORM READ-RANDOM-RECORD

      *    4. Sequential readout (Indexed files automatically sort by key)
           DISPLAY " "
           DISPLAY "--- SEQUENTIAL READOUT (SORTED BY KEY) ---"
           PERFORM READ-ALL-SEQUENTIAL

           CLOSE EMP-FILE
           STOP RUN.

       WRITE-SAMPLE-DATA.
           MOVE 1003 TO EMP-ID
           MOVE "Alice Smith" TO EMP-NAME
           MOVE "Engineering" TO EMP-DEPT
           PERFORM WRITE-RECORD

           MOVE 1001 TO EMP-ID
           MOVE "Bob Jones" TO EMP-NAME
           MOVE "Marketing" TO EMP-DEPT
           PERFORM WRITE-RECORD

           MOVE 1002 TO EMP-ID
           MOVE "Charlie Brown" TO EMP-NAME
           MOVE "Finance" TO EMP-DEPT
           PERFORM WRITE-RECORD.

       WRITE-RECORD.
           WRITE EMP-RECORD
               INVALID KEY
                   DISPLAY "ERROR: Duplicate Key " EMP-ID "!"
               NOT INVALID KEY
                   DISPLAY "Successfully wrote: " EMP-ID " - " EMP-NAME
           END-WRITE.

       READ-RANDOM-RECORD.
      *    Set the primary key to find exactly what we want
           MOVE 1002 TO EMP-ID
           READ EMP-FILE
               INVALID KEY
                   DISPLAY "Record " EMP-ID " not found."
               NOT INVALID KEY
                   DISPLAY "Found Key 1002 -> " EMP-NAME " (" EMP-DEPT ")"
           END-READ.

       READ-ALL-SEQUENTIAL.
      *    Point the index back to the beginning of the file
           MOVE 0000 TO EMP-ID
           START EMP-FILE KEY IS GREATER THAN EMP-ID
               INVALID KEY
                   DISPLAY "No records to read."
           END-START

      *    Loop through the file sequentially
           PERFORM UNTIL END-OF-FILE
               READ EMP-FILE NEXT RECORD
                   AT END
                       SET END-OF-FILE TO TRUE
                   NOT AT END
                       DISPLAY "Seq Record: ID=" EMP-ID
                               " Name=" EMP-NAME
                               " Dept=" EMP-DEPT
               END-READ
           END-PERFORM.

The test run (looks like insufficient bytes were reserved in EMP-DEPT because "Engineering" is truncated):

$ ./indexed-file-demo1
--- WRITING RECORDS ---
Successfully wrote: 1003 - Alice Smith
Successfully wrote: 1001 - Bob Jones
Successfully wrote: 1002 - Charlie Brown

--- RANDOM ACCESS LOOKUP ---
Found Key 1002 -> Charlie Brown        (Finance   )

--- SEQUENTIAL READOUT (SORTED BY KEY) ---
Seq Record: ID=1001 Name=Bob Jones            Dept=Marketing
Seq Record: ID=1002 Name=Charlie Brown        Dept=Finance
Seq Record: ID=1003 Name=Alice Smith          Dept=Engineerin

Back to Home
Neil Rieck
Waterloo, Ontario, Canada.