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HP COBOL
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In Figures 11-14 and 11-15, the output from the sample program is shown.

Figure 11-14 MENU-SCREEN Output (Alpha, I64)




+------------------------------------------------------------------------------+
|                               Daily Calendar                                 |
|                                                                              |
|                                                                              |
|                                                                              ||                                                                              |
|                                                                              |
|                           Show appointments for a day                        |
|                                                                              |
|                           Schedule an appointment                            |
|                                                                              |
|                           Cancel an appointment                              |
|                                                                              |
|                           Print your appointments                            |
|                                                                              |
|                                                                              |
|                                                                              |
|                                                                              |
|                                                                              |
|          Use the arrow keys to move the cursor among menu items.             |
|          Press <Return> when the cursor is at the desired item.              |
|          Press <F10> to exit.                                                |
|                                                                              |
|                                                                              ||                                                                              |
|                                                                              |
+------------------------------------------------------------------------------+

Figure 11-15 SCHEDULE-SCREEN Output (Alpha, I64)




+------------------------------------------------------------------------------+
|                             Schedule Appointment                             |
|                                                                              |
|                                                                              |
|                                                                              |
| Description of Appointment:                                                  |
|Meeting with Bill and Susan                                                   |
|                                                                              |
|                                                                              |
| Date of Appointment (DD/MM/YY):   01/03/94                                   |
|                                                                              |
| Time of Appointment (HH:MM mm):   11:00 AM                                   |
|                                                                              |
|                                                                              |
|                                                                              |
|                                                                              |
|                  Use Cursor Keys to move within the fields.                  |
|                  Press <Tab> to enter next field.                            |
|                  Press <Return> when finished.                               |
|                                                                              |
|                                                                              |
|                                                                              |
|                                                                              |
+------------------------------------------------------------------------------+


Chapter 12
Interprogram Communication

COBOL programs can communicate with each other, as well as with non-COBOL programs. Program-to-program communication is conducted by using one (or combinations) of the following:

  • The CALL statement
  • External data
  • cobcall routine
  • cobcancel routine
  • cobfunc routine

This chapter includes the following information about interprogram communication:

12.1 Multiple COBOL Program Run Units

A multiple COBOL program run unit consists of either of the following:

  • One main (driver) program and one or more separately compiled programs; each program may or may not have contained programs
  • One main program with one or more contained (nested) programs

Separately compiled programs can be concatenated in one source file, or can be written as separate source files.

12.1.1 Examples of COBOL Run Units

Example 12-1 shows a run unit with three separately compiled programs, none of which have contained programs. MAIN-PROGRAM ((1)) calls separate program SUB1 ((2)), that calls separate program SUB2 ((3)).

Example 12-1 Run Unit with Three Separately Compiled Programs

  IDENTIFICATION DIVISION.               IDENTIFICATION DIVISION.
  PROGRAM-ID. MAIN-PROGRAM. (1)           PROGRAM-ID.  SUB1.       (2)
  .                                      .
  .                                      .
  .                                      .
  CALL SUB1.                             CALL SUB2.
  .                                      .
  .                                      .
  .                                      .

  STOP RUN.                              EXIT PROGRAM.
  END PROGRAM MAIN-PROGRAM               END PROGRAM SUB1.

                     IDENTIFICATION DIVISION.
                     PROGRAM-ID.  SUB2.      (3)
                     .
                     .
                     .
                     EXIT PROGRAM.
                     END PROGRAM SUB2.

Note

A separately compiled program has a nesting level number of 1. If this program contains other source programs, it is the outermost containing program. A contained program has a nesting level number greater
than 1.

Example 12-2 shows a run unit with one main program ((4)) and two contained programs (SUB1 ((5)) is a directly contained program of MAIN-PROGRAM; SUB2 ((6)) is an indirectly contained program of MAIN-PROGRAM).

Example 12-2 Run Unit with a Main Program and Two Contained Programs

                IDENTIFICATION DIVISION.
                PROGRAM-ID.  MAIN-PROGRAM. (4)
                .
                .
                .
                CALL SUB1.
                .
                .
                .
                STOP RUN.

                IDENTIFICATION DIVISION.
                PROGRAM-ID.  SUB1.       (5)
                .
                .
                .
                CALL SUB2.
                EXIT PROGRAM.

                IDENTIFICATION DIVISION.
                PROGRAM-ID.  SUB2.       (6)
                .
                .
                .
                EXIT PROGRAM.

                END PROGRAM  SUB2.
                END PROGRAM  SUB1.
                END PROGRAM MAIN-PROGRAM.

Example 12-3 shows a run unit with three separately compiled programs ((7), (10), and (11)). One of the separately compiled programs, MAIN-PROGRAM ((7)), has two directly contained programs, SUB1 and SUB2 ((8) and (9)).

Example 12-3 Run Unit with Three Separately Compiled Programs, One with Two Contained Programs

                IDENTIFICATION DIVISION.
                PROGRAM-ID.  MAIN-PROGRAM. (7)
                .
                .
                .
                CALL SUB1.
                CALL SUB2.
                .
                STOP RUN.

                IDENTIFICATION DIVISION.
                PROGRAM-ID.  SUB1.        (8)
                .
                .
                .
                CALL SUB3.
                EXIT PROGRAM.
                END PROGRAM SUB1.

                IDENTIFICATION DIVISION.
                PROGRAM-ID.  SUB2.       (9)
                .
                .
                .
                EXIT PROGRAM.
                END PROGRAM  SUB2.
                END PROGRAM MAIN-PROGRAM.

                IDENTIFICATION DIVISION.
                PROGRAM-ID.  SUB3.       (10)
                .
                .
                .
                CALL SUB4.
                .
                .
                .
                STOP RUN.

                IDENTIFICATION DIVISION.
                PROGRAM-ID.  SUB4.       (11)
                .
                .
                .
                EXIT PROGRAM.


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