.CBL File Format – Statements

Shape of a statement

• Imperative statements do something (MOVE, DISPLAY, ADD without SIZE ERROR).
• Conditional statements hold a condition phrase and branch (IF, EVALUATE, SEARCH, READ … AT END, ADD … ON SIZE ERROR). Without its terminator one runs to the next full stop.
• Delimited scope statements are closed by an explicit terminator.
• Phrases shared by many verbs: ROUNDED (with a mode in 2002: ROUNDED MODE IS NEAREST-EVEN, TRUNCATION…), ON SIZE ERROR / NOT ON SIZE ERROR, ON OVERFLOW, ON EXCEPTION, AT END / NOT AT END, INVALID KEY / NOT INVALID KEY, AT END-OF-PAGE, GIVING, CORRESPONDING, BY CONTENT.

       PROCESS-ORDER.
           READ ORDERS NEXT RECORD
               AT END SET NO-MORE-ORDERS TO TRUE
               NOT AT END
                   IF ORDER-QTY > ZERO
                       COMPUTE LINE-TOTAL ROUNDED = ORDER-QTY * UNIT-PRICE
                           ON SIZE ERROR PERFORM REPORT-OVERFLOW
                       END-COMPUTE
                       ADD LINE-TOTAL TO GRAND-TOTAL
                   ELSE
                       CONTINUE
                   END-IF
           END-READ.

All statements

“Std” names the first standard to hold a statement; some statements belong only to one compiler family.

PERFORM in detail

           PERFORM INIT-RTN
           PERFORM PARA-A THRU PARA-C
           PERFORM 5 TIMES
               DISPLAY "HELLO"
           END-PERFORM
           PERFORM VARYING I FROM 1 BY 1 UNTIL I > 10
               PERFORM VARYING J FROM 1 BY 1 UNTIL J > 5
                   ADD T(I, J) TO TOTAL
               END-PERFORM
           END-PERFORM
           PERFORM WITH TEST AFTER UNTIL DONE
               PERFORM STEP
           END-PERFORM

PERFORM without a test runs the named paragraphs once and returns. WITH TEST BEFORE (the default) checks the condition first, WITH TEST AFTER runs the body once before checking. Perform ranges that overlap or end in a GO TO outside the range are legal only in strictly controlled shapes; the compiler cannot always detect them. EXIT PERFORM leaves an inline loop and EXIT PERFORM CYCLE goes to the next pass (2002).

EVALUATE and conditions

           EVALUATE TRUE
               WHEN AGE < 13        MOVE "CHILD" TO CLASS-NAME
               WHEN AGE < 20        MOVE "TEEN"  TO CLASS-NAME
               WHEN OTHER           MOVE "ADULT" TO CLASS-NAME
           END-EVALUATE
           EVALUATE CODE-A ALSO CODE-B
               WHEN 1 ALSO ANY      PERFORM ONE-ANY
               WHEN 2 THRU 5 ALSO 9 PERFORM RANGE-NINE
           END-EVALUATE

Conditions themselves (relations, class, sign, condition-name, abbreviated forms) are on Expressions and conditions.

Declaratives, sections and control flow

• DECLARATIVES. … END DECLARATIVES. opens the procedure division; each declarative is a section that starts with a USE sentence.
• A paragraph is entered by falling through from the one above, or by PERFORM or GO TO. Sections group paragraphs and are performed as a whole.
• NEXT SENTENCE jumps past the next full stop (not past the END-IF); CONTINUE does nothing.
• 2002 exception handling: RAISE, RESUME, USE AFTER EXCEPTION CONDITION, and the directive >>TURN to switch checking of an exception condition on.