COBOL: How to Use PERFORM Varying Correctly

Perform varying best examples explained in this post. These are top ideas to work with COBOL Tables or Arrays.

1). How to Use OCCURS depending ON. The best example to create a variable array:

01 ORG-LIMIT            PIC 99 COMP VALUE 50.
01 DIVISION-NAME-TABLE.
   05 DIVISION-ENTRY   OCCURS 1 TO 50 TIMES DEPENDING ON 
                         ORG-LIMIT  INDEXED BY DIV-IX.
      10 DIVISION-CODE PIC X(5).
      10 DIVISION-NAME PIC X(30).

2). How to Use Perform VARYING…AFTER in Multidimensional Tables

The AFTER clause of the PERFORM…The VARYING statement was designed specifically to support multidimensional tables in COBOL. It pre-dates the inline PERFORM statement (which was added with the 1985 Standard):

a). How to Use Perform…Varying

PERFORM
VARYING 
ROW-NR FROM 3 BY 2 UNTIL ROW-NR > 9

PERFORM 
VARYING 
COL-NR FROM 12 BY 2 UNTIL COL-NR > 18
ADD 1 TO CTR
MOVE CTR TO SCREEN-CHAR (ROW-NR COL-NR).

b). How to Use Perform…Varying…After

PERFORM
VARYING 
ROW-NR FROM 3 BY 2 UNTIL ROW-NR > 9
AFTER 
COL-NR FROM 12 BY 2 UNTIL COL-NR > 18
ADD 1 TO CTR
MOVE CTR TO SCREEN-CHAR (ROW-NR COL-NR).

In the above logic ROW-NR and COL-NR are two indexed/subscripts referencing two arrays. So, the above PERFORM statement work for multi dimensional Table.

3). How to initialize or increment or decrement of an Index

SET index TO positive integer

Example: SET IX-1 to 1; (For initialization)

SET IX-1 UP BY 1; (For increment)
SET IX-1 DOWN BY 1; (For decrement)

How to initialize or increment or decrement of a Subscript:

Examples:

MOVE 1  TO SUB-1 (For initialization)
ADD 1 TO SUB-1 (For increment)
SUBTRACT  1  FROM SUB-1 (For decrement)

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