*> ============================================================
      *> caller : 计费子程序调用者 (Billing Subprogram Caller)
      *> Input : WS-N1, WS-N2 (用量参数)
      *> Output: WS-RESULT (CALL计算结果)
      *> Coverage: C-N001~N008, C-A001, C-R001, C-R002
      *> ============================================================
       IDENTIFICATION DIVISION.
       PROGRAM-ID. caller.

       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01 WS-PGM-NAME        PIC X(8) VALUE "callee  ".
       01 WS-N1              PIC 9(10).
       01 WS-N2              PIC 9(10).
       01 WS-RESULT1         PIC 9(10).
       01 WS-RESULT2         PIC 9(10).
       01 WS-RESULT3         PIC 9(10).
       01 WS-ALL-PASS        PIC X VALUE 'Y'.
           88 WS-ALL-PASS-YES VALUE 'Y'.

       PROCEDURE DIVISION.
       MAIN.

      *> Test 1: CALL literal program name
           MOVE 100 TO WS-N1
           MOVE 200 TO WS-N2
           CALL "callee" USING WS-N1 WS-N2 WS-RESULT1
           IF WS-RESULT1 = 300
               DISPLAY "Test 1: PASS"
           ELSE
               DISPLAY "Test 1: FAIL (expected 300, got " WS-RESULT1 ")"
               MOVE 'N' TO WS-ALL-PASS
           END-IF

      *> Test 2: CALL variable program name
           MOVE 10 TO WS-N1
           MOVE 20 TO WS-N2
           CALL WS-PGM-NAME USING WS-N1 WS-N2 WS-RESULT2
           IF WS-RESULT2 = 30
               DISPLAY "Test 2: PASS"
           ELSE
               DISPLAY "Test 2: FAIL (expected 30, got " WS-RESULT2 ")"
               MOVE 'N' TO WS-ALL-PASS
           END-IF

      *> Test 3: CALL IS INITIAL (forces subprogram reinitialization)
           MOVE 1 TO WS-N1
           MOVE 2 TO WS-N2
           CALL "callee" IS INITIAL USING WS-N1 WS-N2 WS-RESULT3
           IF WS-RESULT3 = 3
               DISPLAY "Test 3: PASS"
           ELSE
               DISPLAY "Test 3: FAIL (expected 3, got " WS-RESULT3 ")"
               MOVE 'N' TO WS-ALL-PASS
           END-IF

           IF WS-ALL-PASS-YES
               DISPLAY "25-subprogram: PASS"
               STOP RUN RETURNING 0
           ELSE
               DISPLAY "25-subprogram: FAIL"
               STOP RUN RETURNING 1
           END-IF
           .

       END PROGRAM caller.