PERFORM UNTIL

• This format is used when you want to execute set of instructions multiple times until some condition is met
• Syntax:-
  PERFORM [para-1 [{THRU/THROUGH} para-n]]        UNTIL condition-1       [statement-block  END-PERFORM]
  Where,
  • para-1, para-n are paragraph names which we want to call
  • condition-1 is any conditional-expression which can return either true or false
  • [statement-block END-PERFORM] is used for Inline PERFORM.
• The data items used in condition(s) must be modified within the paragraph(s) being executed; otherwise the paragraphs will be executed indefinitely
• If the condition coded in UNTIL phrase is met at first time of execution, then specified paragraph(s) will not be executed at all
• Example:-
  In PROCUEDURE DIVISION,
  PARA-0. DISPLAY 'IN PARA-0'. MOVE 1 TO WS-COUNT. PERFORM PARA-1 THRU PARA-1-EXIT UNTIL WS-COUNT < 5. DISPLAY 'IN PARA-0 AGAIN' STOP RUN. PARA-1. DISPLAY 'IN PARA-1 WS-COUNT:' WS-COUNT ADD 1 TO WS-COUNT. PARA-1-EXIT. EXIT.
  SYSOUT display (output):-
  IN PARA-0 IN PARA-1 WS-COUNT: 1 IN PARA-1 WS-COUNT: 2 IN PARA-1 WS-COUNT: 3 IN PARA-1 WS-COUNT: 4 IN PARA-0 AGAIN