COBOL Tutorial

COBOL DATA DIVISION

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DATA DIVISION Overview

The DATA DIVISION is the third division of a COBOL program and is used to describe all data items that the program will use. It defines the structure, characteristics, and relationships of data including files, working storage, and parameters.

What the DATA DIVISION Defines

The DATA DIVISION describes:

File Records - Structure of data files and their records
Working Storage - Temporary data items used during program execution
Parameters - Data passed between programs or subprograms
Local Variables - Local data items for subprograms
Data Relationships - How data items are organized and related

Each section serves specific purposes in data management.

DATA DIVISION Structure

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DATA DIVISION.
FILE SECTION.
    [File descriptions and record layouts]
 
WORKING-STORAGE SECTION.
    [Temporary data items and variables]
 
LINKAGE SECTION.
    [Parameters and shared data]
 
LOCAL-STORAGE SECTION.
    [Local variables for subprograms]

The DATA DIVISION consists of four main sections, each serving different purposes in data management.

DATA DIVISION Sections

Section	Purpose	Required	Use Case
FILE SECTION	Define file records and structure	Only if using files	File processing programs
WORKING-STORAGE SECTION	Define temporary data items	Optional but common	Counters, flags, calculations
LINKAGE SECTION	Define parameters and shared data	Only for subprograms	Program communication
LOCAL-STORAGE SECTION	Define local variables	Optional	Subprogram local data

FILE SECTION

The FILE SECTION defines the structure of files and their records. Each file used by the program must have a File Description (FD) entry followed by record layouts.

Basic FILE SECTION Structure

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DATA DIVISION.
FILE SECTION.
FD  file-name
    LABEL RECORDS ARE STANDARD
    RECORD CONTAINS n CHARACTERS.
01  record-name.
    05  field-name-1    PIC 9(5).
    05  field-name-2    PIC X(30).
    05  field-name-3    PIC 9(7)V99.

Each file must have an FD entry that corresponds to a SELECT statement in the ENVIRONMENT DIVISION.

Complete FILE SECTION Example

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DATA DIVISION.
FILE SECTION.
FD  CUSTOMER-FILE
    LABEL RECORDS ARE STANDARD
    BLOCK CONTAINS 10 RECORDS
    RECORD CONTAINS 80 CHARACTERS.
01  CUSTOMER-RECORD.
    05  CUSTOMER-ID       PIC 9(5).
    05  CUSTOMER-NAME     PIC X(30).
    05  CUSTOMER-ADDRESS  PIC X(35).
    05  CUSTOMER-BALANCE  PIC 9(7)V99.
    05  FILLER            PIC X(5).
 
FD  TRANSACTION-FILE
    LABEL RECORDS ARE STANDARD
    RECORD CONTAINS 50 CHARACTERS.
01  TRANSACTION-RECORD.
    05  TRANS-ID          PIC 9(8).
    05  TRANS-AMOUNT      PIC 9(7)V99.
    05  TRANS-DATE        PIC 9(8).
    05  TRANS-TYPE        PIC X.
        88  DEBIT          VALUE "D".
        88  CREDIT         VALUE "C".
    05  FILLER            PIC X(26).

This example shows two files with their record structures, including condition names for transaction types.

FD Clauses

Clause	Purpose	Example
LABEL RECORDS	Specify file labeling	LABEL RECORDS ARE STANDARD
RECORD CONTAINS	Specify record size	RECORD CONTAINS 80 CHARACTERS
BLOCK CONTAINS	Specify blocking factor	BLOCK CONTAINS 10 RECORDS
CODE-SET	Specify character encoding	CODE-SET IS ASCII-ALPHABET

WORKING-STORAGE SECTION

The WORKING-STORAGE SECTION defines temporary data items that are used during program execution. These items are initialized when the program starts and retain their values throughout program execution.

Basic WORKING-STORAGE Structure

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WORKING-STORAGE SECTION.
01  counter           PIC 9(3) VALUE 0.
01  flag              PIC X VALUE "N".
    88  end-of-file     VALUE "Y".
01  total-amount      PIC 9(7)V99 VALUE 0.
01  output-message    PIC X(50) VALUE SPACES.

WORKING-STORAGE items can have initial values and condition names.

Complex WORKING-STORAGE Example

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WORKING-STORAGE SECTION.
01  PROGRAM-COUNTERS.
    05  RECORD-COUNT      PIC 9(5) VALUE 0.
    05  ERROR-COUNT       PIC 9(3) VALUE 0.
    05  PROCESS-COUNT     PIC 9(5) VALUE 0.
 
01  PROGRAM-FLAGS.
    05  EOF-FLAG          PIC X VALUE "N".
        88  END-OF-FILE     VALUE "Y".
        88  NOT-END-OF-FILE VALUE "N".
    05  ERROR-FLAG        PIC X VALUE "N".
        88  ERROR-OCCURRED  VALUE "Y".
        88  NO-ERROR        VALUE "N".
 
01  CALCULATION-FIELDS.
    05  TOTAL-AMOUNT      PIC 9(9)V99 VALUE 0.
    05  AVERAGE-AMOUNT    PIC 9(7)V99 VALUE 0.
    05  HIGHEST-AMOUNT    PIC 9(7)V99 VALUE 0.
    05  LOWEST-AMOUNT     PIC 9(7)V99 VALUE 999999.99.
 
01  OUTPUT-FIELDS.
    05  REPORT-HEADER     PIC X(80) VALUE "CUSTOMER PROCESSING REPORT".
    05  ERROR-MESSAGE     PIC X(50) VALUE SPACES.
    05  SUCCESS-MESSAGE   PIC X(50) VALUE "Processing completed successfully".

This example shows organized WORKING-STORAGE with groups, condition names, and meaningful field names.

LINKAGE SECTION

The LINKAGE SECTION defines data items that are passed between programs or subprograms. It is essential for programs that receive parameters or communicate with other programs.

Basic LINKAGE SECTION Structure

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LINKAGE SECTION.
01  input-parameter    PIC 9(5).
01  output-parameter   PIC X(30).
01  shared-data.
    05  data-field-1   PIC 9(3).
    05  data-field-2   PIC X(20).

LINKAGE SECTION items do not have initial values as they receive their values from the calling program.

Subprogram LINKAGE SECTION Example

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IDENTIFICATION DIVISION.
PROGRAM-ID. CALCULATE-TAX.
 
LINKAGE SECTION.
01  INCOME-PARAMETER.
    05  GROSS-INCOME     PIC 9(7)V99.
    05  DEDUCTIONS       PIC 9(7)V99.
    05  TAX-RATE         PIC 9(3)V99.
 
01  RESULT-PARAMETER.
    05  NET-INCOME       PIC 9(7)V99.
    05  TAX-AMOUNT       PIC 9(7)V99.
    05  RETURN-CODE      PIC 9(2).
 
PROCEDURE DIVISION USING INCOME-PARAMETER, RESULT-PARAMETER.
MAIN-PROCESS.
    COMPUTE NET-INCOME = GROSS-INCOME - DEDUCTIONS
    COMPUTE TAX-AMOUNT = NET-INCOME * TAX-RATE / 100
    MOVE 0 TO RETURN-CODE
    EXIT PROGRAM.

This example shows a subprogram that receives income parameters and returns calculated tax results.

LOCAL-STORAGE SECTION

The LOCAL-STORAGE SECTION defines local variables that are specific to a subprogram. These items are reinitialized each time the subprogram is called.

Basic LOCAL-STORAGE Structure

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LOCAL-STORAGE SECTION.
01  local-counter      PIC 9(3) VALUE 0.
01  temp-calculation   PIC 9(7)V99 VALUE 0.
01  local-flag         PIC X VALUE "N".
    88  processing      VALUE "Y".

LOCAL-STORAGE items are reinitialized on each subprogram call, unlike WORKING-STORAGE items.

LOCAL-STORAGE vs WORKING-STORAGE

Aspect	WORKING-STORAGE	LOCAL-STORAGE
Initialization	Once at program start	Each subprogram call
Persistence	Retains values	Reinitialized each call
Use Case	Program-wide data	Subprogram-specific data
Memory	Static allocation	Dynamic allocation

PICTURE Clauses

The PICTURE clause (or PIC) defines the size, type, and format of a data item. It is one of the most important aspects of COBOL data definition.

Basic PICTURE Syntax

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01  field-name    PIC 9(5).           * Numeric, 5 digits
01  field-name    PIC X(30).          * Alphanumeric, 30 characters
01  field-name    PIC A(20).          * Alphabetic, 20 characters
01  field-name    PIC 9(7)V99.        * Numeric with decimal
01  field-name    PIC S9(5).          * Signed numeric
01  field-name    PIC 9(3)P.          * Assumed decimal scaling

PICTURE and PIC are identical - PIC is an abbreviation of PICTURE.

PICTURE Symbols

Symbol	Purpose	Example	Description
9	Numeric digit	PIC 9(5)	5-digit number
X	Any character	PIC X(30)	30-character field
A	Letters and spaces	PIC A(20)	20 alphabetic characters
S	Sign	PIC S9(5)	Signed 5-digit number
V	Implied decimal	PIC 9(5)V99	5 digits, 2 decimal places
P	Assumed decimal	PIC 9(3)P	3 digits, assumed decimal scaling

Edited PICTURE Examples

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01  EDITED-FIELDS.
    05  ZERO-SUPPRESSED    PIC ZZZ,ZZ9.99.    * Suppress leading zeros
    05  ASTERISK-FILL      PIC ***,***9.99.   * Fill with asterisks
    05  CURRENCY-FORMAT    PIC $ZZZ,ZZ9.99.   * Currency format
    05  DATE-FORMAT        PIC 99/99/9999.    * Date format
    05  PHONE-FORMAT       PIC 999-999-9999.  * Phone number format
    05  PERCENTAGE         PIC 999.99%.       * Percentage format

Edited PICTURE clauses format data for display with special characters and formatting.

Condition Names (88-Level Items)

Condition names are defined at the 88-level and represent specific values that another field can have. They make code more readable and maintainable.

Basic Condition Name Syntax

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01  status-field     PIC X.
    88  active          VALUE "A".
    88  inactive        VALUE "I".
    88  suspended       VALUE "S".
 
01  account-type      PIC 9.
    88  savings         VALUE 1.
    88  checking        VALUE 2.
    88  loan            VALUE 3.
    88  credit          VALUE 4.

Condition names are used in IF statements and SET statements to make code more readable.

Condition Name Usage Example

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WORKING-STORAGE SECTION.
01  CUSTOMER-STATUS    PIC X VALUE "A".
    88  ACTIVE          VALUE "A".
    88  INACTIVE        VALUE "I".
    88  SUSPENDED       VALUE "S".
    88  CLOSED          VALUE "C".
 
01  ACCOUNT-TYPE       PIC 9 VALUE 1.
    88  SAVINGS         VALUE 1.
    88  CHECKING        VALUE 2.
    88  LOAN            VALUE 3.
    88  CREDIT          VALUE 4.
 
PROCEDURE DIVISION.
MAIN-PROCESS.
    IF ACTIVE
        DISPLAY "Customer is active"
    END-IF
    
    IF SAVINGS
        DISPLAY "Account type is savings"
    END-IF
    
    SET INACTIVE TO TRUE
    SET CHECKING TO TRUE
    
    DISPLAY "Status: " CUSTOMER-STATUS
    DISPLAY "Type: " ACCOUNT-TYPE.

This example shows how condition names are defined and used in conditional statements and SET operations.

Tables and Arrays

Tables in COBOL are defined using the OCCURS clause. They allow you to store multiple values of the same type in a structured way.

Basic Table Definition

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01  customer-table.
    05  customer-entry  OCCURS 100 TIMES.
        10  customer-id     PIC 9(5).
        10  customer-name   PIC X(30).
        10  customer-balance PIC 9(7)V99.
 
01  product-table.
    05  product-entry   OCCURS 50 TIMES
        INDEXED BY product-index.
        10  product-code    PIC X(10).
        10  product-name    PIC X(40).
        10  product-price   PIC 9(5)V99.

Tables can be indexed for efficient access, and the OCCURS clause specifies the number of elements.

Variable-Length Tables

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01  dynamic-table.
    05  table-size       PIC 9(3) VALUE 0.
    05  table-entry      OCCURS 1 TO 100 TIMES
        DEPENDING ON table-size
        INDEXED BY table-index.
        10  entry-id      PIC 9(5).
        10  entry-data    PIC X(50).

Variable-length tables use OCCURS DEPENDING ON to specify the actual number of elements at runtime.

Nested Tables

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01  department-table.
    05  department-entry OCCURS 10 TIMES.
        10  dept-id       PIC 9(3).
        10  dept-name     PIC X(20).
        10  employee-list.
            15  employee  OCCURS 20 TIMES.
                20  emp-id    PIC 9(5).
                20  emp-name  PIC X(30).
                20  emp-salary PIC 9(6)V99.

Tables can be nested to create complex data structures like departments containing employees.

Practical Examples

These examples demonstrate real-world applications of DATA DIVISION concepts for common business scenarios.

Example 1: Complete DATA DIVISION Structure

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IDENTIFICATION DIVISION.
PROGRAM-ID. CUSTOMER-PROCESSING.
 
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT CUSTOMER-FILE ASSIGN TO "CUSTOMER.DAT"
        ORGANIZATION IS SEQUENTIAL
        ACCESS MODE IS SEQUENTIAL
        FILE STATUS IS FILE-STATUS.
 
DATA DIVISION.
FILE SECTION.
FD  CUSTOMER-FILE
    LABEL RECORDS ARE STANDARD
    RECORD CONTAINS 100 CHARACTERS.
01  CUSTOMER-RECORD.
    05  CUSTOMER-ID       PIC 9(5).
    05  CUSTOMER-NAME     PIC X(30).
    05  CUSTOMER-ADDRESS  PIC X(40).
    05  CUSTOMER-BALANCE  PIC 9(7)V99.
    05  CUSTOMER-STATUS   PIC X.
        88  ACTIVE         VALUE "A".
        88  INACTIVE       VALUE "I".
        88  SUSPENDED      VALUE "S".
    05  FILLER            PIC X(23).
 
WORKING-STORAGE SECTION.
01  PROGRAM-COUNTERS.
    05  RECORD-COUNT      PIC 9(5) VALUE 0.
    05  ACTIVE-COUNT      PIC 9(5) VALUE 0.
    05  INACTIVE-COUNT    PIC 9(5) VALUE 0.
 
01  PROGRAM-FLAGS.
    05  EOF-FLAG          PIC X VALUE "N".
        88  END-OF-FILE     VALUE "Y".
        88  NOT-END-OF-FILE VALUE "N".
 
01  CALCULATION-FIELDS.
    05  TOTAL-BALANCE     PIC 9(9)V99 VALUE 0.
    05  AVERAGE-BALANCE   PIC 9(7)V99 VALUE 0.
 
01  OUTPUT-FIELDS.
    05  REPORT-HEADER     PIC X(80) VALUE "CUSTOMER PROCESSING REPORT".
    05  ERROR-MESSAGE     PIC X(50) VALUE SPACES.
 
LINKAGE SECTION.
01  INPUT-PARAMETERS.
    05  PROCESS-TYPE      PIC X.
        88  FULL-PROCESS   VALUE "F".
        88  SUMMARY-ONLY   VALUE "S".
    05  OUTPUT-FORMAT     PIC X.
        88  DETAILED       VALUE "D".
        88  SUMMARY        VALUE "S".
 
01  OUTPUT-RESULTS.
    05  PROCESS-STATUS    PIC X.
        88  SUCCESS        VALUE "S".
        88  ERROR          VALUE "E".
    05  RETURN-CODE       PIC 9(2).
 
PROCEDURE DIVISION USING INPUT-PARAMETERS, OUTPUT-RESULTS.
MAIN-PROCESS.
    PERFORM INITIALIZATION
    PERFORM PROCESS-CUSTOMERS UNTIL END-OF-FILE
    PERFORM FINALIZATION
    EXIT PROGRAM.

This example shows a complete DATA DIVISION structure with all sections and various data types.

Example 2: Table Processing

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WORKING-STORAGE SECTION.
01  PRODUCT-TABLE.
    05  PRODUCT-ENTRY OCCURS 10 TIMES
        INDEXED BY PRODUCT-INDEX.
        10  PRODUCT-CODE      PIC X(5).
        10  PRODUCT-NAME      PIC X(30).
        10  PRODUCT-PRICE     PIC 9(5)V99.
        10  PRODUCT-STATUS    PIC X.
            88  AVAILABLE      VALUE "A".
            88  OUT-OF-STOCK   VALUE "O".
            88  DISCONTINUED   VALUE "D".
 
01  TABLE-STATISTICS.
    05  TOTAL-PRODUCTS    PIC 9(2) VALUE 0.
    05  AVAILABLE-COUNT   PIC 9(2) VALUE 0.
    05  TOTAL-VALUE       PIC 9(8)V99 VALUE 0.
 
PROCEDURE DIVISION.
MAIN-PROCESS.
    PERFORM INITIALIZE-TABLE
    PERFORM PROCESS-TABLE
    PERFORM DISPLAY-STATISTICS
    STOP RUN.
 
INITIALIZE-TABLE.
    MOVE 1 TO PRODUCT-INDEX
    MOVE "P001" TO PRODUCT-CODE(PRODUCT-INDEX)
    MOVE "LAPTOP" TO PRODUCT-NAME(PRODUCT-INDEX)
    MOVE 999.99 TO PRODUCT-PRICE(PRODUCT-INDEX)
    SET AVAILABLE TO TRUE
    ADD 1 TO TOTAL-PRODUCTS
    
    SET PRODUCT-INDEX UP BY 1
    MOVE "P002" TO PRODUCT-CODE(PRODUCT-INDEX)
    MOVE "MOUSE" TO PRODUCT-NAME(PRODUCT-INDEX)
    MOVE 25.50 TO PRODUCT-PRICE(PRODUCT-INDEX)
    SET OUT-OF-STOCK TO TRUE
    ADD 1 TO TOTAL-PRODUCTS.

This example shows table definition and processing with indexes and condition names.

Best Practices and Tips

Following these best practices ensures efficient and maintainable DATA DIVISION definitions.

DATA DIVISION Best Practices

Use meaningful field names that clearly describe the data
Organize data into logical groups using 01-level items
Use condition names (88-level items) for better code readability
Choose appropriate PICTURE clauses for data types and sizes
Use FILLER for unused positions in fixed-length records
Initialize WORKING-STORAGE items with appropriate default values
Use consistent naming conventions throughout the program
Document complex data structures with comments
Use appropriate USAGE clauses for performance optimization
Validate data sizes to ensure they match requirements

PICTURE Clause Best Practices

Use 9 for numeric data that will be used in calculations
Use X for alphanumeric data that may contain any characters
Use A for alphabetic data that contains only letters and spaces
Use V for implied decimal points in numeric fields
Use S for signed numbers when negative values are possible
Use edited PICTURE clauses for display formatting
Choose appropriate field sizes to avoid truncation
Consider storage efficiency when defining field sizes

Table Best Practices

Use INDEXED BY for efficient table access instead of subscripts
Initialize table counters before using tables
Check table bounds before accessing elements
Use meaningful table names that describe the data
Consider using OCCURS DEPENDING ON for variable-length tables
Document table structures with comments
Use nested tables carefully to avoid complexity

Common Pitfalls to Avoid

Incorrect PICTURE clauses for data types
Field size mismatches between files and programs
Not initializing WORKING-STORAGE items that need default values
Using wrong section for data items (e.g., WORKING-STORAGE vs LINKAGE)
Inconsistent naming conventions throughout the program
Not using condition names for better code readability
Incorrect table indexing leading to out-of-bounds access
Not documenting complex data structures for maintenance
Using inappropriate data types for the intended use
Not considering performance implications of data definitions

Performance Considerations

Use appropriate USAGE clauses (BINARY, PACKED-DECIMAL) for performance
Choose efficient field sizes to minimize memory usage
Use indexes for table access instead of subscripts for large tables
Consider alignment requirements for optimal performance
Use LOCAL-STORAGE for subprograms to avoid memory conflicts
Minimize REDEFINES usage unless necessary for memory optimization

Test Your Knowledge

1. What is the purpose of the DATA DIVISION in COBOL?

To define program logic and procedures
To describe all data items used by the program
To specify file connections and environment
To identify the program name and author

2. Which section of the DATA DIVISION is used to define data items that are shared between programs?

FILE SECTION
WORKING-STORAGE SECTION
LINKAGE SECTION
LOCAL-STORAGE SECTION

3. What does the PICTURE clause define?

The physical appearance of data
The size, type, and format of a data item
The location of data in memory
The relationship between data items

4. Which PICTURE symbol is used for numeric data?

5. What is a condition name in COBOL?

A variable that stores conditions
An 88-level item that represents a specific value of another field
A file status code
A program name

COBOL Tutorial

COBOL DATA DIVISION

DATA DIVISION Overview

What the DATA DIVISION Defines

DATA DIVISION Structure

DATA DIVISION Sections

FILE SECTION

Basic FILE SECTION Structure

Complete FILE SECTION Example

FD Clauses

WORKING-STORAGE SECTION

Basic WORKING-STORAGE Structure

Complex WORKING-STORAGE Example

LINKAGE SECTION

Basic LINKAGE SECTION Structure

Subprogram LINKAGE SECTION Example

LOCAL-STORAGE SECTION

Basic LOCAL-STORAGE Structure

LOCAL-STORAGE vs WORKING-STORAGE

PICTURE Clauses

Basic PICTURE Syntax

PICTURE Symbols

Edited PICTURE Examples

Condition Names (88-Level Items)

Basic Condition Name Syntax

Condition Name Usage Example

Tables and Arrays

Basic Table Definition

Variable-Length Tables

Nested Tables

Practical Examples

Example 1: Complete DATA DIVISION Structure

Example 2: Table Processing

Best Practices and Tips

DATA DIVISION Best Practices

PICTURE Clause Best Practices

Table Best Practices

Common Pitfalls to Avoid

Performance Considerations

Test Your Knowledge

Frequently Asked Questions

What are the main sections of the DATA DIVISION?

What is the difference between PICTURE and PIC clauses?

How do I define a table or array in COBOL?

What are the different data types available in COBOL?

What is the purpose of the REDEFINES clause?

Related Concepts

Data Types

DATA DIVISION Sections

File Description

Table Handling

Conditional Variables

Related Pages