Documenting legacy code

[mario-campos]

Working with legacy code can be challenging for developers, especially when the code is complex or not well-documented. In such cases, it can be helpful to use Copilot Chat to explain unclear or complex code to other developers or to document it for future reference.

Example scenario

The block of COBOL below connects to a database and inserts a record. The code lacks documentation, which makes it difficult to understand what it does and how it works.

IDENTIFICATION DIVISION.
PROGRAM-ID. INSERT-RECORD.

ENVIRONMENT DIVISION.

DATA DIVISION.
WORKING-STORAGE SECTION.
01  WS-STATUS-FLAGS.
    05 WS-DB-STATUS     PIC X(2).
       88 WS-SUCCESS    VALUE "00".
    05 WS-SQLCODE       PIC S9(9) COMP.
    05 WS-ERROR-MSG     PIC X(50).

LINKAGE SECTION.
01  LS-PARAMETERS.
    05 LS-PERSON-RECORD.
       10 PERSON-ID     PIC 9(6).
       10 PERSON-NAME   PIC X(50).
       10 PERSON-AGE    PIC 9(3).
    05 LS-RESULT        PIC X.
       88 SUCCESS       VALUE 'T'.
       88 FAILED        VALUE 'F'.

PROCEDURE DIVISION USING LS-PARAMETERS.
    PERFORM INSERT-AND-VALIDATE
    GOBACK
    .

INSERT-AND-VALIDATE.
    EXEC SQL
        INSERT INTO persons (id, name, age)
        VALUES (:PERSON-ID, :PERSON-NAME, :PERSON-AGE)
    END-EXEC

    IF SQLCODE = 0
        EXEC SQL COMMIT END-EXEC
        SET SUCCESS TO TRUE
    ELSE
        EXEC SQL ROLLBACK END-EXEC
        SET FAILED TO TRUE
        STRING "DB Error: " SQLCODE
            DELIMITED BY SIZE
            INTO WS-ERROR-MSG
        DISPLAY WS-ERROR-MSG
    END-IF
    .

Example prompt

Document this code

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Source: https://docs.github.com/en/copilot/copilot-chat-cookbook/documenting-code/documenting-legacy-code