MainframeMaster

COBOL DIVISION Structure

Master COBOL program organization through the four fundamental divisions that provide structure, clarity, and maintainability to mainframe applications.

Overview

COBOL programs are organized into four main divisions, each serving a specific purpose in program structure and functionality. This divisional structure is fundamental to COBOL's design philosophy, promoting clear separation of concerns and making programs more readable, maintainable, and standardized across different implementations.

The division structure reflects COBOL's business-oriented design, where each division addresses different aspects of a business application: program identification, environmental considerations, data organization, and processing logic. Understanding this structure is essential for writing well-organized COBOL programs.

Each division follows specific rules for content, organization, and sequence. The divisions must appear in a prescribed order, and each contains sections and paragraphs that further organize the program's components. This hierarchical structure ensures consistency and predictability in COBOL program organization.

The Four COBOL Divisions

1. IDENTIFICATION DIVISION

The IDENTIFICATION DIVISION provides program identification and documentation information:

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       IDENTIFICATION DIVISION.
       PROGRAM-ID. CUSTOMER-REPORT.
       AUTHOR. DEVELOPMENT TEAM.
       INSTALLATION. CORPORATE DATA CENTER.
       DATE-WRITTEN. 2024-01-15.
       DATE-COMPILED.
       SECURITY. CONFIDENTIAL.

This division is required in every COBOL program and must be the first division. It contains metadata about the program including its name, author, creation date, and security classification.

2. ENVIRONMENT DIVISION

The ENVIRONMENT DIVISION specifies the computer environment and file assignments:

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       ENVIRONMENT DIVISION.
       CONFIGURATION SECTION.
       SOURCE-COMPUTER. IBM-Z15.
       OBJECT-COMPUTER. IBM-Z15.
       SPECIAL-NAMES.
           DECIMAL-POINT IS COMMA.
           
       INPUT-OUTPUT SECTION.
       FILE-CONTROL.
           SELECT CUSTOMER-FILE
               ASSIGN TO "CUSTOMER.DAT"
               ORGANIZATION IS SEQUENTIAL.

This division is optional but commonly used. It defines the computing environment, file assignments, and special system configurations needed for the program.

3. DATA DIVISION

The DATA DIVISION defines all data structures and storage areas:

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       DATA DIVISION.
       FILE SECTION.
       FD  CUSTOMER-FILE.
       01  CUSTOMER-RECORD.
           05  CUST-ID         PIC X(10).
           05  CUST-NAME       PIC X(30).
           05  CUST-BALANCE    PIC 9(7)V99.
           
       WORKING-STORAGE SECTION.
       01  WS-COUNTERS.
           05  WS-RECORD-COUNT PIC 9(5) VALUE ZERO.
           05  WS-TOTAL-AMOUNT PIC 9(9)V99 VALUE ZERO.

This division is optional but used in most programs. It defines file structures, working storage variables, linkage parameters, and other data elements used by the program.

4. PROCEDURE DIVISION

The PROCEDURE DIVISION contains the executable logic and processing instructions:

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       PROCEDURE DIVISION.
       MAIN-LOGIC.
           PERFORM INITIALIZATION
           PERFORM PROCESS-CUSTOMERS
           PERFORM FINALIZATION
           GOBACK.
           
       INITIALIZATION.
           OPEN INPUT CUSTOMER-FILE
           DISPLAY "Customer Report Started".
           
       PROCESS-CUSTOMERS.
           PERFORM UNTIL WS-EOF = "Y"
               READ CUSTOMER-FILE
                   AT END
                       MOVE "Y" TO WS-EOF
                   NOT AT END
                       PERFORM PROCESS-CUSTOMER-RECORD
               END-READ
           END-PERFORM.

This division is required and contains all the executable statements that define what the program does. It's organized into sections, paragraphs, and sentences.

Division Organization and Structure

Hierarchical Structure

COBOL programs follow a strict hierarchical structure within divisions:

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       DIVISION-NAME DIVISION.
       SECTION-NAME SECTION.
       PARAGRAPH-NAME.
           SENTENCE.
           SENTENCE.
           
       ANOTHER-PARAGRAPH.
           SENTENCE.

Each division can contain sections, which contain paragraphs, which contain sentences. This hierarchy provides multiple levels of organization for complex programs.

Section Usage

Sections provide logical groupings within divisions:

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       DATA DIVISION.
       FILE SECTION.
       * File definitions go here
       
       WORKING-STORAGE SECTION.
       * Working variables go here
       
       LINKAGE SECTION.
       * Parameters go here
       
       PROCEDURE DIVISION.
       INITIALIZATION SECTION.
       * Startup logic goes here
       
       MAIN-PROCESSING SECTION.
       * Main business logic goes here

Sections help organize related functionality and make programs more maintainable and readable.

Complete Program Example

Customer Processing Program

Here's a complete COBOL program demonstrating all four divisions:

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       IDENTIFICATION DIVISION.
       PROGRAM-ID. CUSTOMER-PROCESSOR.
       AUTHOR. COBOL DEVELOPMENT TEAM.
       DATE-WRITTEN. 2024-01-15.
       
       ENVIRONMENT DIVISION.
       CONFIGURATION SECTION.
       SOURCE-COMPUTER. IBM-MAINFRAME.
       OBJECT-COMPUTER. IBM-MAINFRAME.
       
       INPUT-OUTPUT SECTION.
       FILE-CONTROL.
           SELECT CUSTOMER-INPUT
               ASSIGN TO "CUSTINP"
               ORGANIZATION IS SEQUENTIAL.
           SELECT REPORT-OUTPUT
               ASSIGN TO "CUSTRPT"
               ORGANIZATION IS SEQUENTIAL.
               
       DATA DIVISION.
       FILE SECTION.
       FD  CUSTOMER-INPUT.
       01  CUSTOMER-RECORD.
           05  CUST-ID         PIC X(5).
           05  CUST-NAME       PIC X(25).
           05  CUST-BALANCE    PIC 9(7)V99.
           
       FD  REPORT-OUTPUT.
       01  REPORT-LINE         PIC X(80).
       
       WORKING-STORAGE SECTION.
       01  WS-FLAGS.
           05  WS-EOF          PIC X(1) VALUE "N".
           
       01  WS-COUNTERS.
           05  WS-RECORD-COUNT PIC 9(5) VALUE ZERO.
           05  WS-TOTAL-BALANCE PIC 9(9)V99 VALUE ZERO.
           
       PROCEDURE DIVISION.
       MAIN-LOGIC.
           PERFORM OPEN-FILES
           PERFORM PROCESS-RECORDS
           PERFORM CLOSE-FILES
           GOBACK.

This example shows how all four divisions work together to create a complete, functional COBOL program.

Advanced Division Concepts

Nested Programs

COBOL supports nested programs, where each nested program has its own divisions:

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       IDENTIFICATION DIVISION.
       PROGRAM-ID. MAIN-PROGRAM.
       
       * Main program divisions...
       
       PROCEDURE DIVISION.
       MAIN-LOGIC.
           CALL "UTILITY-PROGRAM"
           GOBACK.
           
       * Nested program starts here
       IDENTIFICATION DIVISION.
       PROGRAM-ID. UTILITY-PROGRAM.
       
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01  WS-UTILITY-DATA     PIC X(100).
       
       PROCEDURE DIVISION.
           DISPLAY "Utility program executing"
           GOBACK.
           
       END PROGRAM UTILITY-PROGRAM.
       END PROGRAM MAIN-PROGRAM.

Nested programs allow for modular design while keeping related functionality together.

Division Headers and Documentation

Good practice includes comprehensive documentation within divisions:

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       IDENTIFICATION DIVISION.
       PROGRAM-ID. PAYROLL-PROCESSOR.
       AUTHOR. PAYROLL SYSTEMS TEAM.
       INSTALLATION. CORPORATE DATA CENTER.
       DATE-WRITTEN. 2024-01-15.
       DATE-COMPILED.
       SECURITY. PAYROLL-CONFIDENTIAL.
       REMARKS.
           THIS PROGRAM PROCESSES WEEKLY PAYROLL DATA
           AND GENERATES PAYROLL REPORTS AND CHECKS.
           MODIFIED: 2024-01-20 - ADDED OVERTIME CALCULATION
           MODIFIED: 2024-01-25 - ENHANCED ERROR HANDLING.

Comprehensive documentation in the IDENTIFICATION DIVISION helps with program maintenance and understanding.

Best Practices for Division Organization

Structural Guidelines

Follow these best practices for organizing divisions:

  • Always include comprehensive IDENTIFICATION DIVISION documentation
  • Use meaningful section names that describe their purpose
  • Organize paragraphs logically within the PROCEDURE DIVISION
  • Keep related data definitions together in the DATA DIVISION
  • Use consistent naming conventions across all divisions
  • Include comments to explain complex logic or business rules

Maintainability Considerations

Structure divisions for long-term maintainability:

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       PROCEDURE DIVISION.
       * Main control logic
       0000-MAIN-CONTROL.
           PERFORM 1000-INITIALIZATION
           PERFORM 2000-MAIN-PROCESSING
           PERFORM 3000-FINALIZATION
           GOBACK.
           
       * Initialization routines
       1000-INITIALIZATION.
           PERFORM 1100-OPEN-FILES
           PERFORM 1200-INITIALIZE-VARIABLES
           PERFORM 1300-VALIDATE-PARAMETERS.
           
       * Main processing logic
       2000-MAIN-PROCESSING.
           PERFORM 2100-READ-INPUT
           PERFORM 2200-PROCESS-RECORDS
           PERFORM 2300-GENERATE-REPORTS.

Using numbered paragraph names and logical groupings makes programs easier to navigate and maintain.

Common Division Patterns

Batch Processing Pattern

Common structure for batch processing programs:

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       PROCEDURE DIVISION.
       MAIN-LOGIC.
           PERFORM HOUSEKEEPING
           PERFORM PROCESS-DATA UNTIL END-OF-FILE
           PERFORM WRAP-UP
           GOBACK.
           
       HOUSEKEEPING.
           OPEN INPUT INPUT-FILE
           OPEN OUTPUT OUTPUT-FILE
           READ INPUT-FILE
               AT END MOVE "Y" TO EOF-FLAG
           END-READ.
           
       PROCESS-DATA.
           PERFORM BUSINESS-LOGIC
           READ INPUT-FILE
               AT END MOVE "Y" TO EOF-FLAG
           END-READ.
           
       WRAP-UP.
           CLOSE INPUT-FILE
           CLOSE OUTPUT-FILE
           DISPLAY "Processing complete".

This pattern separates initialization, processing, and cleanup into distinct sections.

Interactive Program Pattern

Structure for interactive or menu-driven programs:

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       PROCEDURE DIVISION.
       MAIN-MENU.
           PERFORM DISPLAY-MENU
           PERFORM GET-USER-CHOICE
           PERFORM PROCESS-CHOICE
           IF NOT END-SESSION
               GO TO MAIN-MENU
           END-IF
           GOBACK.
           
       DISPLAY-MENU.
           DISPLAY "1. Add Customer"
           DISPLAY "2. Update Customer"
           DISPLAY "3. Delete Customer"
           DISPLAY "4. Exit"
           DISPLAY "Enter choice: " WITH NO ADVANCING.
           
       PROCESS-CHOICE.
           EVALUATE USER-CHOICE
               WHEN "1" PERFORM ADD-CUSTOMER
               WHEN "2" PERFORM UPDATE-CUSTOMER
               WHEN "3" PERFORM DELETE-CUSTOMER
               WHEN "4" MOVE "Y" TO END-SESSION-FLAG
               WHEN OTHER DISPLAY "Invalid choice"
           END-EVALUATE.

Interactive programs benefit from clear menu structures and user input validation.

Hands-on Exercise

Exercise: Employee Report Program

Create a complete COBOL program using all four divisions to process employee data and generate a summary report.

Requirements:

  • Include all four divisions with proper documentation
  • Define file structures for employee input and report output
  • Implement proper program organization with sections and paragraphs
  • Include error handling and summary statistics
  • Follow COBOL naming conventions and best practices
View Solution
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       IDENTIFICATION DIVISION.
       PROGRAM-ID. EMPLOYEE-REPORT.
       AUTHOR. COBOL TUTORIAL TEAM.
       DATE-WRITTEN. 2024-01-15.
       REMARKS. PROCESSES EMPLOYEE DATA AND GENERATES SUMMARY REPORT.
       
       ENVIRONMENT DIVISION.
       CONFIGURATION SECTION.
       SOURCE-COMPUTER. IBM-MAINFRAME.
       OBJECT-COMPUTER. IBM-MAINFRAME.
       
       INPUT-OUTPUT SECTION.
       FILE-CONTROL.
           SELECT EMPLOYEE-FILE
               ASSIGN TO "EMPLOYEE.DAT"
               ORGANIZATION IS SEQUENTIAL
               FILE STATUS IS WS-FILE-STATUS.
           SELECT REPORT-FILE
               ASSIGN TO "EMPREPORT.TXT"
               ORGANIZATION IS SEQUENTIAL.
               
       DATA DIVISION.
       FILE SECTION.
       FD  EMPLOYEE-FILE.
       01  EMPLOYEE-RECORD.
           05  EMP-ID          PIC X(5).
           05  EMP-NAME        PIC X(25).
           05  EMP-DEPT        PIC X(10).
           05  EMP-SALARY      PIC 9(6)V99.
           
       FD  REPORT-FILE.
       01  REPORT-LINE         PIC X(80).
       
       WORKING-STORAGE SECTION.
       01  WS-FLAGS.
           05  WS-EOF          PIC X(1) VALUE "N".
           05  WS-FILE-STATUS  PIC X(2).
           
       01  WS-COUNTERS.
           05  WS-EMP-COUNT    PIC 9(4) VALUE ZERO.
           05  WS-TOTAL-SALARY PIC 9(8)V99 VALUE ZERO.
           05  WS-AVG-SALARY   PIC 9(6)V99 VALUE ZERO.
           
       01  WS-REPORT-LINES.
           05  WS-HEADER-LINE  PIC X(80) VALUE
               "EMPLOYEE SUMMARY REPORT".
           05  WS-DETAIL-LINE.
               10  FILLER      PIC X(5) VALUE SPACES.
               10  WS-RPT-ID   PIC X(5).
               10  FILLER      PIC X(3) VALUE SPACES.
               10  WS-RPT-NAME PIC X(25).
               10  FILLER      PIC X(3) VALUE SPACES.
               10  WS-RPT-DEPT PIC X(10).
               10  FILLER      PIC X(3) VALUE SPACES.
               10  WS-RPT-SAL  PIC Z,ZZZ,ZZ9.99.
               
       PROCEDURE DIVISION.
       0000-MAIN-CONTROL.
           PERFORM 1000-INITIALIZATION
           PERFORM 2000-PROCESS-EMPLOYEES
           PERFORM 3000-FINALIZATION
           GOBACK.
           
       1000-INITIALIZATION.
           OPEN INPUT EMPLOYEE-FILE
           OPEN OUTPUT REPORT-FILE
           WRITE REPORT-LINE FROM WS-HEADER-LINE
           PERFORM 1100-READ-EMPLOYEE.
           
       1100-READ-EMPLOYEE.
           READ EMPLOYEE-FILE
               AT END
                   MOVE "Y" TO WS-EOF
               NOT AT END
                   ADD 1 TO WS-EMP-COUNT
                   ADD EMP-SALARY TO WS-TOTAL-SALARY
           END-READ.
           
       2000-PROCESS-EMPLOYEES.
           PERFORM UNTIL WS-EOF = "Y"
               PERFORM 2100-FORMAT-DETAIL-LINE
               WRITE REPORT-LINE FROM WS-DETAIL-LINE
               PERFORM 1100-READ-EMPLOYEE
           END-PERFORM.
           
       2100-FORMAT-DETAIL-LINE.
           MOVE EMP-ID TO WS-RPT-ID
           MOVE EMP-NAME TO WS-RPT-NAME
           MOVE EMP-DEPT TO WS-RPT-DEPT
           MOVE EMP-SALARY TO WS-RPT-SAL.
           
       3000-FINALIZATION.
           IF WS-EMP-COUNT > ZERO
               COMPUTE WS-AVG-SALARY = WS-TOTAL-SALARY / WS-EMP-COUNT
           END-IF
           PERFORM 3100-WRITE-SUMMARY
           CLOSE EMPLOYEE-FILE
           CLOSE REPORT-FILE.
           
       3100-WRITE-SUMMARY.
           MOVE SPACES TO REPORT-LINE
           WRITE REPORT-LINE
           STRING "TOTAL EMPLOYEES: " WS-EMP-COUNT
                  INTO REPORT-LINE
           WRITE REPORT-LINE
           STRING "AVERAGE SALARY: " WS-AVG-SALARY
                  INTO REPORT-LINE
           WRITE REPORT-LINE.

Quiz

Test Your Knowledge

1. What is the correct order of COBOL divisions?

2. Which divisions are required in every COBOL program?

3. What is the primary purpose of the DATA DIVISION?

View Answers

1. IDENTIFICATION, ENVIRONMENT, DATA, PROCEDURE - This is the required order that cannot be changed in COBOL programs.

2. IDENTIFICATION and PROCEDURE only - These are the only two divisions that must be present in every COBOL program.

3. Defines data structures and storage - The DATA DIVISION defines all data elements, file structures, and storage areas used by the program.

Frequently Asked Questions

Related Concepts

Program Structure

Understanding COBOL program organization and hierarchical structure

Modular Programming

Organizing code into logical divisions and sections for maintainability

COBOL Basics

Fundamental concepts of COBOL programming and structure

Documentation Standards

Best practices for documenting and organizing COBOL programs