COBOL OPEN AND CLOSED SUBROUTINES

最新推荐文章于 2022-04-25 17:48:00 发布

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本文介绍了COBOL语言中两种子程序的概念：开放式子程序和封闭式子程序。开放式子程序通过PERFORM语句定义，其内的GOBACK、STOP RUN和EXIT PROGRAM指令与主程序相同。封闭式子程序则使用CALL语句调用，并可以是内嵌或外部子程序。

COBOL supports open and closed subroutines.

Open subroutinesThey are implemented using the first format of the PERFORM verb.
For example:
PERFORM SUBPREFORM.
...
SUBPROFORM.
COBOL-STATEMENTS
Closed subroutines They are implemented using the CALL verb and contained or external subprograms.
For example:
CALL "SUBPROG"

Open subroutine is not a real routine, it's in fact a instructions block, so instructions GOBACK/STOP RUN/EXIT PROGRAM on a open subroutines work like on main program.

For example: (RED instructions will not be executed)

STOP RUN

       IDENTIFICATION DIVISION.       
       PROGRAM-ID.    MAINPROG.       
       ENVIRONMENT DIVISION.          
       DATA DIVISION.                 
       PROCEDURE DIVISION.            
           DISPLAY "MAIN ENTRY".
           PERFORM PERFORM-SUB.        
           DISPLAY "MAIN EXIT".
           STOP RUN.
       PERFORM-SUB.            
           DISPLAY 'SUB ENTRY'.
           STOP RUN.             *> PROGRAM STOP HERE
           DISPLAY 'SUB EXIT'.

EXIT PROGRAM

       IDENTIFICATION DIVISION.       
       PROGRAM-ID.    MAINPROG.       
       ENVIRONMENT DIVISION.          
       DATA DIVISION.                 
       PROCEDURE DIVISION.            
           DISPLAY "MAIN ENTRY".
           PERFORM PERFORM-SUB.        
           DISPLAY "MAIN EXIT".
           STOP RUN.
       PERFORM-SUB.            
           DISPLAY 'SUB ENTRY'.
           EXIT PROGRAM.         *> STATEMENT IS IGNORED
           DISPLAY 'SUB EXIT'.

(EXIT PROGRAM is ignored)

GOBACK

       IDENTIFICATION DIVISION.       
       PROGRAM-ID.    MAINPROG.       
       ENVIRONMENT DIVISION.          
       DATA DIVISION.                 
       PROCEDURE DIVISION.            
           DISPLAY "MAIN ENTRY".
           PERFORM PERFORM-SUB.        
           DISPLAY "MAIN EXIT".
           STOP RUN.
       PERFORM-SUB.            
           DISPLAY 'SUB ENTRY'.
           GOBACK.               *> PROGRAM STOP HERE
           DISPLAY 'SUB EXIT'.

(GOBACK works as STOP RUN)