*> ============================================================
      *> caller-nested : 计费子程序嵌套调用 (Nested Subprogram Call)
      *> Input : WS-VAL-A, WS-VAL-B (传递参数)
      *> Output: WS-RESULT (嵌套计算结果)
      *> Coverage: C-N009
      *> ============================================================
       IDENTIFICATION DIVISION.
       PROGRAM-ID. CallerNested.

       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01 WS-LEVEL          PIC 9(1).
       01 WS-VAL-A          PIC 9(5).
       01 WS-VAL-B          PIC 9(5).
       01 WS-RESULT         PIC 9(10).
       01 WS-PASS           PIC 9(2) VALUE 0.
       01 WS-FAIL           PIC 9(2) VALUE 0.

       PROCEDURE DIVISION.
       MAIN.
           DISPLAY "CALLER-NESTED: 3-level CALL test (C-N009)"

      *> Test: CALLER → SUB-A → SUB-B → SUB-C RETURNING
           MOVE 1 TO WS-LEVEL.
           MOVE 10 TO WS-VAL-A.
           MOVE 20 TO WS-VAL-B.

           CALL 'SUB-A' USING WS-LEVEL WS-VAL-A WS-VAL-B WS-RESULT.

           IF WS-RESULT = 100  *> (10+20) + (10+20) + 20 = 100
               ADD 1 TO WS-PASS
               DISPLAY "C-N009: PASS - 3-level result=" WS-RESULT
           ELSE
               ADD 1 TO WS-FAIL
               DISPLAY "C-N009: FAIL - result=" WS-RESULT
           END-IF.

      *> Test: CALL with RETURN-CODE from nested
           MOVE 2 TO WS-LEVEL.
           MOVE 5 TO WS-VAL-A.
           MOVE 7 TO WS-VAL-B.
           CALL 'SUB-A' USING WS-LEVEL WS-VAL-A WS-VAL-B WS-RESULT.

           IF WS-RESULT = 31  *> (5+7) + (5+7) + 7 = 31
               ADD 1 TO WS-PASS
               DISPLAY "C-N009-2: PASS - nested result=" WS-RESULT
           ELSE
               ADD 1 TO WS-FAIL
               DISPLAY "C-N009-2: FAIL - result=" WS-RESULT
           END-IF.

      *> CALL nonexistent program (TC-A051)
           DISPLAY "TC-A051: CALL non-existent program"
           CALL 'NOPGM00' USING WS-VAL-A
               ON EXCEPTION
                   ADD 1 TO WS-PASS
                   DISPLAY "TC-A051: PASS - exception raised"
               NOT ON EXCEPTION
                   ADD 1 TO WS-FAIL
                   DISPLAY "TC-A051: FAIL - no exception"
           END-CALL.

           DISPLAY " "
           DISPLAY "CALLER-NESTED: PASS=" WS-PASS " FAIL=" WS-FAIL
           IF WS-FAIL = 0
               DISPLAY "CALLER-NESTED: ALL PASSED"
               STOP RUN RETURNING 0
           ELSE
               DISPLAY "CALLER-NESTED: FAILED"
               STOP RUN RETURNING 1
           END-IF
           .

       END PROGRAM CallerNested.

       IDENTIFICATION DIVISION.
       PROGRAM-ID. SUB-A.
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01 WS-RET            PIC 9(10).
       LINKAGE SECTION.
       01 LK-LEVEL          PIC 9(1).
       01 LK-VAL-A          PIC 9(5).
       01 LK-VAL-B          PIC 9(5).
       01 LK-RESULT         PIC 9(10).
       PROCEDURE DIVISION USING LK-LEVEL LK-VAL-A LK-VAL-B LK-RESULT.
           ADD LK-VAL-A TO LK-VAL-B GIVING WS-RET.
           CALL 'SUB-B' USING LK-LEVEL LK-VAL-A LK-VAL-B WS-RET LK-RESULT.
           GOBACK.
       END PROGRAM SUB-A.

       IDENTIFICATION DIVISION.
       PROGRAM-ID. SUB-B.
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01 WS-TEMP           PIC 9(10).
       LINKAGE SECTION.
       01 LK-LEVEL          PIC 9(1).
       01 LK-VAL-A          PIC 9(5).
       01 LK-VAL-B          PIC 9(5).
       01 LK-INPUT          PIC 9(10).
       01 LK-RESULT         PIC 9(10).
       PROCEDURE DIVISION USING LK-LEVEL LK-VAL-A LK-VAL-B
                                LK-INPUT LK-RESULT.
           COMPUTE WS-TEMP = LK-INPUT + LK-VAL-B.
           IF LK-LEVEL = 1
               COMPUTE LK-RESULT = WS-TEMP
           ELSE
               CALL 'SUB-C' USING LK-VAL-A LK-VAL-B WS-TEMP LK-RESULT
           END-IF.
           GOBACK.
       END PROGRAM SUB-B.

       IDENTIFICATION DIVISION.
       PROGRAM-ID. SUB-C.
       DATA DIVISION.
       LINKAGE SECTION.
       01 LK-VAL-A          PIC 9(5).
       01 LK-VAL-B          PIC 9(5).
       01 LK-INPUT          PIC 9(10).
       01 LK-RESULT         PIC 9(10).
       PROCEDURE DIVISION USING LK-VAL-A LK-VAL-B LK-INPUT LK-RESULT.
           COMPUTE LK-RESULT = LK-INPUT + LK-VAL-B.
           GOBACK.
       END PROGRAM SUB-C.