qsort - subprograma

IDENTIFICATION DIVISION.
PROGRAM-ID. QSORT RECURSIVE.
DATA DIVISION.

LOCAL-STORAGE SECTION.
01 I-IZ     INDEX.
01 I-DE     INDEX.

01 A        INDEX.
01 B        INDEX.

01 AUX      PIC 9.

LINKAGE SECTION.
01 PRIMERO  INDEX.
01 ULTIMO   INDEX.

01 ARRAY.
    05 ELEMENTO PIC 9 OCCURS 10.

PROCEDURE DIVISION USING BY REFERENCE ARRAY, PRIMERO, ULTIMO.
MAIN-PROCEDURE.
    SET I-IZ TO PRIMERO.
    SET I-DE TO ULTIMO.

    IF PRIMERO < ULTIMO
        PERFORM UNTIL I-IZ NOT < I-DE
            PERFORM UNTIL ELEMENTO(I-IZ) NOT < ELEMENTO(ULTIMO) OR I-IZ = I-DE
                SET I-IZ UP BY 1
            END-PERFORM

            PERFORM UNTIL ELEMENTO(I-DE) NOT > ELEMENTO(ULTIMO) OR I-IZ = I-DE
                SET I-DE DOWN BY 1
            END-PERFORM

            SET A TO I-IZ
            SET B TO I-DE
            PERFORM SWAP
        END-PERFORM

        SET A TO I-IZ
        SET B TO ULTIMO
        PERFORM SWAP

        SET I-IZ DOWN BY 1
        SET I-DE UP   BY 1
        CALL 'QSORT' USING ARRAY, PRIMERO, I-IZ
        CALL 'QSORT' USING ARRAY, I-DE, ULTIMO
    END-IF.
    GOBACK.

SWAP.
    MOVE ELEMENTO(A) TO AUX.
    MOVE ELEMENTO(B) TO ELEMENTO(A).
    MOVE AUX TO ELEMENTO(B).

END PROGRAM QSORT.