段落和执行

In COBOL, modularity and logical structuring of code inside the PROCEDURE DIVISION do not occur via functions or methods, but rather through Paragraphs and the PERFORM statement.

Defining Paragraphs

A paragraph is a labeled section of code starting with a name at column 8 (Area A) ending with a period ., followed by a sequence of instructions at column 12 (Area B).

DISPLAY-MESSAGE.
    DISPLAY "This is a paragraph!".

Paragraphs allow splitting potentially very long programs into reusable and self-documenting blocks.

Executing Paragraphs with PERFORM

The PERFORM statement invokes and executes a paragraph, then returns control to the instruction immediately following the PERFORM statement.

PROCEDURE DIVISION.
MAIN-PROCEDURE.
    DISPLAY "Starting program...".
    PERFORM PROCESS-DATA.
    DISPLAY "Ending program.".
    STOP RUN.

PROCESS-DATA.
    DISPLAY "Processing data in memory...".

In the above listing:

1. The DISPLAY inside MAIN-PROCEDURE is executed.
2. PERFORM PROCESS-DATA branches execution to the PROCESS-DATA paragraph.
3. Once the PROCESS-DATA paragraph ends, execution returns to MAIN-PROCEDURE to print "Ending program." and halt using STOP RUN..

Try it yourself