In this section, we will cover the best practices that can help you write efficient, maintainable, and error-free COBOL programs. These practices are essential for both beginners and experienced programmers to ensure that their code is robust and easy to understand.

• Variables and Constants: Use descriptive names for variables and constants to make the code self-explanatory.

  01 CUSTOMER-NAME PIC X(30).
  01 CUSTOMER-AGE  PIC 99.
  

• Paragraphs and Sections: Name paragraphs and sections clearly to indicate their purpose.

  PROCEDURE DIVISION.
  MAIN-PROCESS.
      PERFORM INITIALIZE-VARIABLES.
      PERFORM READ-CUSTOMER-DATA.
      PERFORM PROCESS-CUSTOMER-DATA.
      PERFORM DISPLAY-RESULTS.
      STOP RUN.
  

• Inline Comments: Use comments to explain complex logic or calculations.

  ADD 1 TO CUSTOMER-AGE.  * Increment age by 1
  

• Block Comments: Use block comments to describe the purpose of sections or paragraphs.

  *--------------------------------------------------*
  * This section initializes all the variables used  *
  * in the program.                                  *
  *--------------------------------------------------*
  INITIALIZE-VARIABLES.
      MOVE SPACES TO CUSTOMER-NAME.
      MOVE ZERO TO CUSTOMER-AGE.
  

• Modular Code: Break down the program into sections and paragraphs to make it modular and easier to debug.

  PROCEDURE DIVISION.
  MAIN-PROCESS.
      PERFORM INITIALIZE-VARIABLES.
      PERFORM READ-CUSTOMER-DATA.
      PERFORM PROCESS-CUSTOMER-DATA.
      PERFORM DISPLAY-RESULTS.
      STOP RUN.
  

• Control Flow: Avoid using GO TO statements as they can make the code difficult to follow and maintain. Use PERFORM instead.

  * Instead of using GO TO
  GO TO ERROR-HANDLING.
  
  * Use PERFORM
  PERFORM ERROR-HANDLING.
  

• Declaratives: Use declaratives to handle file-related errors and other exceptions.

  DECLARATIVES.
  FILE-ERROR SECTION.
  USE AFTER ERROR PROCEDURE ON INPUT-FILE.
  FILE-ERROR-PARA.
      DISPLAY "Error reading input file".
      STOP RUN.
  END DECLARATIVES.
  

• File Status Codes: Always check file status codes after file operations to handle errors gracefully.

  OPEN INPUT INPUT-FILE.
  IF FILE-STATUS NOT = "00"
      DISPLAY "Error opening input file".
      STOP RUN.
  END-IF.
  

• Minimize I/O Operations: Reduce the number of I/O operations by reading and writing data in larger blocks.

  READ INPUT-FILE INTO INPUT-RECORD
      AT END
          SET END-OF-FILE TO TRUE
      NOT AT END
          PERFORM PROCESS-RECORD
  END-READ.
  

• Indexed Files: Use indexed files for faster data retrieval when dealing with large datasets.

  SELECT INPUT-FILE ASSIGN TO "input.dat"
      ORGANIZATION IS INDEXED
      ACCESS MODE IS DYNAMIC
      RECORD KEY IS CUSTOMER-ID.
  

• Subprograms: Use subprograms to encapsulate reusable code.

  CALL 'SUBPROGRAM' USING CUSTOMER-NAME CUSTOMER-AGE.
  

• Indentation and Alignment: Maintain consistent indentation and alignment for better readability.

  IF CUSTOMER-AGE > 18
      DISPLAY "Adult".
  ELSE
      DISPLAY "Minor".
  END-IF.
  

By following these best practices, you can write COBOL programs that are not only efficient and error-free but also easy to read, maintain, and debug. These practices will help you develop a disciplined approach to programming, which is essential for working on large and complex systems. As you continue to learn and grow as a COBOL programmer, always strive to improve your coding standards and keep up with the latest industry practices.