>>SOURCE FORMAT IS FREE
*> cobol-copybook-copy-replacing.cob - ACCT-POST, the first of three
*>          programs sharing one record layout: read last month's
*>          account master, credit a month of interest to every open
*>          account with a balance, write this month's master
*> Dialect: GnuCOBOL 3.x, free format (the copybook itself is laid out
*>          so that it is also valid in fixed format)
*> Status : desk-checked against the GnuCOBOL Programmer's Guide (3.2
*>          COPY, 10.1.4 Locating Copybooks, 7.6.7 ROUNDED) and the IBM
*>          Enterprise COBOL 6.4 Language Reference (pp. 688-697);
*>          compiled and run with GnuCOBOL 3.2 on 2026-10-29
*> Inputs : datasets/cobol-copybook-copy-replacing.dat (LINE SEQUENTIAL,
*>          LF line endings, 39 bytes per record, 18 records in
*>          account-id order)
*>          code/cobol-copybook-copy-replacing.cpy (the layout, brought
*>          in twice under two different prefixes)
*> Outputs: acct-master-new.dat (same 39-byte layout) and DISPLAY lines
*> Build  : cobc -x -I code -o acct-post code/cobol-copybook-copy-replacing.cob
*>          (run from the folder that holds code/ and datasets/)
*> Run    : ./acct-post   then ./acct-list and ./acct-audit
IDENTIFICATION DIVISION.
PROGRAM-ID. ACCT-POST.
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT Old-Master
        ASSIGN TO "datasets/cobol-copybook-copy-replacing.dat"
        ORGANIZATION IS LINE SEQUENTIAL
        FILE STATUS IS WS-Old-FS.
    SELECT New-Master
        ASSIGN TO "acct-master-new.dat"
        ORGANIZATION IS LINE SEQUENTIAL
        FILE STATUS IS WS-New-FS.
DATA DIVISION.
FILE SECTION.
*> One layout, two record areas.  The LEADING phrase renames every
*> word that begins with Acct-, so the old record's fields are Old-Id,
*> Old-Balance and so on, and the new record's are New-Id, New-Balance.
FD  Old-Master.
    COPY "cobol-copybook-copy-replacing.cpy"
        REPLACING LEADING ==Acct-== BY ==Old-==.
FD  New-Master.
    COPY "cobol-copybook-copy-replacing.cpy"
        REPLACING LEADING ==Acct-== BY ==New-==.
WORKING-STORAGE SECTION.
77 WS-Old-FS             PIC XX.
77 WS-New-FS             PIC XX.
01 WS-Flags.
   05 WS-EOF-Flag        PIC X VALUE "N".
      88 End-Of-Old-Master     VALUE "Y".
77 WS-Monthly-Rate       PIC V9999    VALUE .0025.
77 WS-Interest           PIC 9(7)V99  VALUE 0.
77 WS-Interest-Total     PIC 9(7)V99  VALUE 0.
77 WS-Read               PIC 9(5)     VALUE 0.
77 WS-Written            PIC 9(5)     VALUE 0.
77 WS-Credited           PIC 9(5)     VALUE 0.
77 WS-Show-Count         PIC ZZ,ZZ9.
77 WS-Show-Money         PIC Z,ZZZ,ZZ9.99.
PROCEDURE DIVISION.
Main-Paragraph.
    OPEN INPUT Old-Master
    IF WS-Old-FS NOT = "00"
       DISPLAY "Cannot open the old master, status " WS-Old-FS
       STOP RUN
    END-IF
    OPEN OUTPUT New-Master
    IF WS-New-FS NOT = "00"
       DISPLAY "Cannot create acct-master-new.dat, status " WS-New-FS
       CLOSE Old-Master
       STOP RUN
    END-IF
    PERFORM Read-Old
    PERFORM UNTIL End-Of-Old-Master
       PERFORM Post-One-Account
       PERFORM Read-Old
    END-PERFORM
    CLOSE Old-Master New-Master
    MOVE WS-Read TO WS-Show-Count
    DISPLAY "ACCT-POST  records read     " WS-Show-Count
    MOVE WS-Written TO WS-Show-Count
    DISPLAY "ACCT-POST  records written  " WS-Show-Count
    MOVE WS-Credited TO WS-Show-Count
    DISPLAY "ACCT-POST  accounts credited" WS-Show-Count
    MOVE WS-Interest-Total TO WS-Show-Money
    DISPLAY "ACCT-POST  interest posted  " WS-Show-Money
    STOP RUN.

Read-Old.
    READ Old-Master
       AT END
          SET End-Of-Old-Master TO TRUE
    END-READ
    IF WS-Old-FS NOT = "00" AND WS-Old-FS NOT = "10"
       DISPLAY "Old master read failed, status " WS-Old-FS
       STOP RUN
    END-IF.

*> Move the whole 39-byte record across, then change only the balance.
Post-One-Account.
    ADD 1 TO WS-Read
    MOVE Old-Record TO New-Record
    IF Old-Open AND Old-Balance > 0
       COMPUTE WS-Interest ROUNDED = Old-Balance * WS-Monthly-Rate
       ADD WS-Interest TO New-Balance
       ADD WS-Interest TO WS-Interest-Total
       ADD 1 TO WS-Credited
    END-IF
    WRITE New-Record
    IF WS-New-FS NOT = "00"
       DISPLAY "Write failed for account " Old-Id ", status " WS-New-FS
       CLOSE Old-Master New-Master
       STOP RUN
    END-IF
    ADD 1 TO WS-Written.