Using Recursive Calls

Code the RECURSIVE clause on the PROGRAM-ID clause so your program can be recursively reentered while a previous invocation is still active. Below is an example of how you could use the RECURSIVE clause to make a program a recursive program, and how a Local-Storage Section data item can be used in a recursive program.

Figure 1. Example of a recursive call to calculate the factorial of a number

5722WDS V5R4M0 060210 LN  IBM ILE COBOL                 MYLIB/FACTORIAL          ISERIES    06/02/15 17:25:51        Page      2
                                     S o u r c e
 STMT PL SEQNBR -A 1 B..+....2....+....3....+....4....+....5....+....6....+....7..IDENTFCN  S COPYNAME   CHG DATE
    1     000100 IDENTIFICATION DIVISION.
    2     000200 PROGRAM-ID. FACTORIAL RECURSIVE.
          000300
    3     000400 ENVIRONMENT DIVISION.
    4     000500 CONFIGURATION SECTION.
    5     000600    SOURCE-COMPUTER. IBM-ISERIES.
    6     000700    OBJECT-COMPUTER. IBM-ISERIES.
          000800
    7     000900 DATA DIVISION.
    8     001000 WORKING-STORAGE SECTION.
    9     001100 01 NUMB PIC 9(4) VALUE 5.
   10     001200 01 FACT PIC 9(8) VALUE 0.
          001300
   11     001400 LOCAL-STORAGE SECTION.
   12     001500 01 NUM PIC 9(4).
          001600
   13     001700 PROCEDURE DIVISION.
   14     001800     MOVE NUMB TO NUM.
   15     001900     IF NUMB = 0
   16     002000         MOVE 1 TO FACT
          002100     ELSE
   17     002200         SUBTRACT 1 FROM NUMB
   18     002300         CALL "FACTORIAL"
   19     002400         MULTIPLY NUM BY FACT
          002500     END-IF.
   20     002600     DISPLAY NUM "! = " FACT.
   21     002700     GOBACK.
   22     002800 END PROGRAM FACTORIAL.
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