COBOL- PERFORM for Multi-dimensional arrays

• Also referred to as "PERFORM with VARYING AFTER"
• This kind of PERFORM browse through each elements of multi-dimensional array. For this purpose, we can use PERFORM in below specified format (below is simplified syntax for 2-dimentional array look up)
• Basic syntax:-
  PERFORM [para-1 [{THRU/THROUGH} para-n]]       VARYING id-1 FROM id-2       BY id-3 UNTIL condition-1       AFTER VARYING id-4 FROM id-5       BY id-6 UNTIL condition-2       [statement-block  END-PERFORM]
  Where,
  • para-1, para-n are paragraph names which we want to call
  • id-1,id-4 can be numeric data item or index data item
  • id-2,id-5 can be numeric data item or index data item or literal
  • id-3,id-6 can be numeric data item or literal
  • condition-1, condition-2 is any conditional-expression which can return either true or false
  • [statement-block END-PERFORM] is used for Inline PERFORM.
• Example:-
  Suppose we have data stored in our array (table) in below format
  In DATA DIVISION,
  01 DEPARTMENT-TABLE. 05 DEPARTMENT OCCCURS 3 TIMES. 10 DEPT-NAME PIC X(20). 10 EMP-NAME PIC X(20) OCCURS 2 TIMES.
  Visually it will have data like:-
  Reference visual:-

  DEPT-NAME(1)	EMP-NAME(1,1)	EMP-NAME(1,2)
  DEPT-NAME(2)	EMP-NAME(2,1)	EMP-NAME(2,2)
  DEPT-NAME(3)	EMP-NAME(3,1)	EMP-NAME(3,2)

  Values visual:-

  MANUFACTURING	RAMESH	AKSHAY
  QUALITY	STEVE	JOY
  MARKETING	ASHWANI	JEFF

  In PROCUEDURE DIVISION, we can write below code to display each elements of above multi-dimensional table
  PARA-0. PERFORM PARA-1 THRU PARA-1-EXIT VARYING DEPT-I FROM 1 BY 1 UNTIL DEPT-I > 3 AFTER VARYING DEPT-J 1 BY 1 UNTIL DEPT-J > 2. STOP RUN. PARA-1. DISPLAY ‘DEPARTMENT: ’ DEPT-NAME(DEPT-I) DISPLAY ‘EMP-NAME: ’ EMP-NAME(DEPT-I, DEPT-J) PARA-1-EXIT. EXIT.
  SYSOUT display (output):-
  DEPARTMENT: MANUFACURING EMP-NAME: RAMESH DEPARTMENT: MANUFACURING EMP-NAME: AKSHAY DEPARTMENT: QUALITY EMP-NAME: STEVE DEPARTMENT: QUALITY EMP-NAME: JOY DEPARTMENT: MARKETING EMP-NAME: ASHWANI DEPARTMENT: MARKETING EMP-NAME: JEFF

• You will be able to understand how the program has processed in above example by mapping reference visuals, values visuals and SYSOUT displays.