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COBOL Tutorial

COBOL START and END-START Statements - Quick Reference

The START and END-START statements in COBOL are used to position the file pointer within indexed and relative files. START establishes a position based on key values, while END-START marks the end of the START statement scope. These statements enable efficient file positioning and retrieval operations.

Primary Use

Position within indexed and relative files

Division

PROCEDURE DIVISION

File Types

Indexed and Relative

Status

Required for positioning

Overview

The START statement is used to position the file pointer at a specific record within indexed and relative files based on key values. It does not retrieve data but establishes a position from which subsequent READ statements can retrieve records. The END-START statement marks the end of the START statement scope and is used in structured programming to clearly define the statement boundaries.

Syntax

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START file-name
    [KEY IS {EQUAL TO | GREATER THAN | NOT LESS THAN} data-name]
    [INVALID KEY imperative-statement]
    [NOT INVALID KEY imperative-statement]
END-START
 
* Examples:
START CUSTOMER-FILE
    KEY IS EQUAL TO WS-CUSTOMER-KEY
    INVALID KEY DISPLAY "Customer not found"
END-START
 
START PRODUCT-FILE
    KEY IS GREATER THAN WS-PRODUCT-KEY
    INVALID KEY PERFORM ERROR-HANDLING
    NOT INVALID KEY PERFORM PROCESS-RECORDS
END-START

Practical Examples

Basic START Statement Usage

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* Basic START statement example
IDENTIFICATION DIVISION.
PROGRAM-ID. START-EXAMPLE.
 
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT CUSTOMER-FILE ASSIGN TO "CUSTOMER.DAT"
        ORGANIZATION IS INDEXED
        ACCESS MODE IS SEQUENTIAL
        RECORD KEY IS CUSTOMER-ID
        FILE STATUS IS WS-FILE-STATUS.
 
DATA DIVISION.
FILE SECTION.
FD  CUSTOMER-FILE.
01  CUSTOMER-RECORD.
    05  CUSTOMER-ID         PIC 9(5).
    05  CUSTOMER-NAME       PIC X(30).
    05  CUSTOMER-ADDRESS    PIC X(50).
 
WORKING-STORAGE SECTION.
01  WS-FILE-STATUS         PIC XX.
01  WS-CUSTOMER-KEY        PIC 9(5) VALUE 10001.
01  WS-RECORD-FOUND        PIC X(1) VALUE 'N'.
 
PROCEDURE DIVISION.
MAIN-LOGIC.
    DISPLAY "START Statement Example"
    
    * Open the file
    OPEN INPUT CUSTOMER-FILE
    
    * Check file status
    IF WS-FILE-STATUS NOT = "00"
        DISPLAY "Error opening file: " WS-FILE-STATUS
        STOP RUN
    END-IF
    
    * Use START to position at specific customer
    START CUSTOMER-FILE
        KEY IS EQUAL TO WS-CUSTOMER-KEY
        INVALID KEY 
            DISPLAY "Customer " WS-CUSTOMER-KEY " not found"
            MOVE 'N' TO WS-RECORD-FOUND
        NOT INVALID KEY
            MOVE 'Y' TO WS-RECORD-FOUND
    END-START
    
    * If record found, read and display it
    IF WS-RECORD-FOUND = 'Y'
        READ CUSTOMER-FILE
            AT END
                DISPLAY "End of file reached"
            NOT AT END
                DISPLAY "Customer ID: " CUSTOMER-ID
                DISPLAY "Customer Name: " CUSTOMER-NAME
                DISPLAY "Customer Address: " CUSTOMER-ADDRESS
        END-READ
    END-IF
    
    * Close the file
    CLOSE CUSTOMER-FILE
    
    STOP RUN.

Explanation: This example demonstrates basic usage of the START statement. The program opens an indexed customer file, uses START to position at a specific customer ID, and then reads the record if found. The START statement positions the file pointer at the record with the specified key, and the subsequent READ retrieves that record. Error handling is included for cases where the key is not found.

START with Different Key Conditions

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* START with different key conditions example
IDENTIFICATION DIVISION.
PROGRAM-ID. START-CONDITIONS-EXAMPLE.
 
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT PRODUCT-FILE ASSIGN TO "PRODUCT.DAT"
        ORGANIZATION IS INDEXED
        ACCESS MODE IS SEQUENTIAL
        RECORD KEY IS PRODUCT-CODE
        FILE STATUS IS WS-FILE-STATUS.
 
DATA DIVISION.
FILE SECTION.
FD  PRODUCT-FILE.
01  PRODUCT-RECORD.
    05  PRODUCT-CODE        PIC X(10).
    05  PRODUCT-NAME        PIC X(30).
    05  PRODUCT-PRICE       PIC 9(5)V99.
 
WORKING-STORAGE SECTION.
01  WS-FILE-STATUS         PIC XX.
01  WS-SEARCH-KEY          PIC X(10).
01  WS-RECORD-COUNT        PIC 9(3) VALUE ZERO.
 
PROCEDURE DIVISION.
MAIN-LOGIC.
    DISPLAY "START with Different Key Conditions"
    
    * Open the file
    OPEN INPUT PRODUCT-FILE
    
    * Example 1: START with EQUAL TO
    MOVE "PROD001" TO WS-SEARCH-KEY
    DISPLAY "Searching for exact match: " WS-SEARCH-KEY
    
    START PRODUCT-FILE
        KEY IS EQUAL TO WS-SEARCH-KEY
        INVALID KEY 
            DISPLAY "Exact match not found"
        NOT INVALID KEY
            DISPLAY "Exact match found"
            PERFORM READ-AND-DISPLAY
    END-START
    
    * Example 2: START with GREATER THAN
    MOVE "PROD005" TO WS-SEARCH-KEY
    DISPLAY "Searching for records greater than: " WS-SEARCH-KEY
    
    START PRODUCT-FILE
        KEY IS GREATER THAN WS-SEARCH-KEY
        INVALID KEY 
            DISPLAY "No records greater than key"
        NOT INVALID KEY
            DISPLAY "Records greater than key found"
            PERFORM READ-MULTIPLE-RECORDS
    END-START
    
    * Example 3: START with NOT LESS THAN
    MOVE "PROD010" TO WS-SEARCH-KEY
    DISPLAY "Searching for records not less than: " WS-SEARCH-KEY
    
    START PRODUCT-FILE
        KEY IS NOT LESS THAN WS-SEARCH-KEY
        INVALID KEY 
            DISPLAY "No records found"
        NOT INVALID KEY
            DISPLAY "Records found starting from key"
            PERFORM READ-MULTIPLE-RECORDS
    END-START
    
    CLOSE PRODUCT-FILE
    STOP RUN.
 
READ-AND-DISPLAY.
    READ PRODUCT-FILE
        AT END
            DISPLAY "End of file"
        NOT AT END
            DISPLAY "Product Code: " PRODUCT-CODE
            DISPLAY "Product Name: " PRODUCT-NAME
            DISPLAY "Product Price: " PRODUCT-PRICE
    END-READ.
 
READ-MULTIPLE-RECORDS.
    MOVE 0 TO WS-RECORD-COUNT
    PERFORM UNTIL WS-RECORD-COUNT >= 5
        READ PRODUCT-FILE
            AT END
                DISPLAY "End of file reached"
                EXIT PERFORM
            NOT AT END
                ADD 1 TO WS-RECORD-COUNT
                DISPLAY "Record " WS-RECORD-COUNT ": " PRODUCT-CODE " - " PRODUCT-NAME
        END-READ
    END-PERFORM.

Explanation: This example shows different key conditions that can be used with the START statement. EQUAL TO finds an exact match, GREATER THAN positions at the first record with a key greater than the specified value, and NOT LESS THAN positions at the first record with a key greater than or equal to the specified value. Each condition provides different positioning behavior for efficient file access patterns.

START with Error Handling

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* START with comprehensive error handling example
IDENTIFICATION DIVISION.
PROGRAM-ID. START-ERROR-HANDLING.
 
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT EMPLOYEE-FILE ASSIGN TO "EMPLOYEE.DAT"
        ORGANIZATION IS INDEXED
        ACCESS MODE IS SEQUENTIAL
        RECORD KEY IS EMPLOYEE-ID
        FILE STATUS IS WS-FILE-STATUS.
 
DATA DIVISION.
FILE SECTION.
FD  EMPLOYEE-FILE.
01  EMPLOYEE-RECORD.
    05  EMPLOYEE-ID         PIC 9(6).
    05  EMPLOYEE-NAME       PIC X(30).
    05  EMPLOYEE-DEPT       PIC X(20).
 
WORKING-STORAGE SECTION.
01  WS-FILE-STATUS         PIC XX.
01  WS-SEARCH-KEY          PIC 9(6).
01  WS-ERROR-MESSAGE       PIC X(50).
01  WS-PROCESSING-STATUS   PIC X(1) VALUE 'C'.
    * C = Continue, S = Stop, R = Retry
 
PROCEDURE DIVISION.
MAIN-LOGIC.
    DISPLAY "START with Error Handling Example"
    
    * Open the file
    OPEN INPUT EMPLOYEE-FILE
    
    * Check file status
    IF WS-FILE-STATUS NOT = "00"
        PERFORM HANDLE-FILE-ERROR
        STOP RUN
    END-IF
    
    * Get search key from user
    DISPLAY "Enter Employee ID to search: "
    ACCEPT WS-SEARCH-KEY
    
    * Use START with error handling
    PERFORM SEARCH-EMPLOYEE
    
    CLOSE EMPLOYEE-FILE
    STOP RUN.
 
SEARCH-EMPLOYEE.
    START EMPLOYEE-FILE
        KEY IS EQUAL TO WS-SEARCH-KEY
        INVALID KEY 
            PERFORM HANDLE-INVALID-KEY
        NOT INVALID KEY
            PERFORM PROCESS-EMPLOYEE-RECORD
    END-START.
 
HANDLE-INVALID-KEY.
    * Check specific file status for different error conditions
    EVALUATE WS-FILE-STATUS
        WHEN "23"
            MOVE "Employee not found" TO WS-ERROR-MESSAGE
            DISPLAY "Error: " WS-ERROR-MESSAGE
        WHEN "24"
            MOVE "Key out of range" TO WS-ERROR-MESSAGE
            DISPLAY "Error: " WS-ERROR-MESSAGE
        WHEN "30"
            MOVE "File not found" TO WS-ERROR-MESSAGE
            DISPLAY "Error: " WS-ERROR-MESSAGE
        WHEN "35"
            MOVE "File not open" TO WS-ERROR-MESSAGE
            DISPLAY "Error: " WS-ERROR-MESSAGE
        WHEN OTHER
            MOVE "Unknown file error" TO WS-ERROR-MESSAGE
            DISPLAY "Error: " WS-ERROR-MESSAGE " Status: " WS-FILE-STATUS
    END-EVALUATE.
 
PROCESS-EMPLOYEE-RECORD.
    READ EMPLOYEE-FILE
        AT END
            DISPLAY "Unexpected end of file"
        NOT AT END
            DISPLAY "Employee found:"
            DISPLAY "ID: " EMPLOYEE-ID
            DISPLAY "Name: " EMPLOYEE-NAME
            DISPLAY "Department: " EMPLOYEE-DEPT
    END-READ.
 
HANDLE-FILE-ERROR.
    DISPLAY "File error occurred: " WS-FILE-STATUS
    DISPLAY "Cannot continue processing".

Explanation: This example demonstrates comprehensive error handling with the START statement. The program checks file status after each operation and handles different error conditions appropriately. File status "23" indicates no record found, "24" indicates key out of range, and other status codes indicate different file-related errors. This ensures robust error handling and provides meaningful feedback to users when operations fail.

START for Range Processing

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* START for range processing example
IDENTIFICATION DIVISION.
PROGRAM-ID. START-RANGE-PROCESSING.
 
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT ORDER-FILE ASSIGN TO "ORDER.DAT"
        ORGANIZATION IS INDEXED
        ACCESS MODE IS SEQUENTIAL
        RECORD KEY IS ORDER-NUMBER
        FILE STATUS IS WS-FILE-STATUS.
 
DATA DIVISION.
FILE SECTION.
FD  ORDER-FILE.
01  ORDER-RECORD.
    05  ORDER-NUMBER       PIC 9(8).
    05  CUSTOMER-ID        PIC 9(5).
    05  ORDER-DATE         PIC 9(8).
    05  ORDER-AMOUNT       PIC 9(7)V99.
 
WORKING-STORAGE SECTION.
01  WS-FILE-STATUS         PIC XX.
01  WS-START-RANGE         PIC 9(8) VALUE 10000000.
01  WS-END-RANGE           PIC 9(8) VALUE 10000999.
01  WS-CURRENT-KEY         PIC 9(8).
01  WS-RECORD-COUNT        PIC 9(5) VALUE ZERO.
01  WS-TOTAL-AMOUNT        PIC 9(9)V99 VALUE ZERO.
 
PROCEDURE DIVISION.
MAIN-LOGIC.
    DISPLAY "START for Range Processing Example"
    DISPLAY "Processing orders from " WS-START-RANGE " to " WS-END-RANGE
    
    * Open the file
    OPEN INPUT ORDER-FILE
    
    * Position at start of range
    MOVE WS-START-RANGE TO WS-CURRENT-KEY
    
    START ORDER-FILE
        KEY IS GREATER THAN OR EQUAL TO WS-CURRENT-KEY
        INVALID KEY 
            DISPLAY "No orders found in range"
            GO TO END-PROCESSING
        NOT INVALID KEY
            DISPLAY "Starting range processing"
    END-START
    
    * Process records in range
    PERFORM PROCESS-RANGE-RECORDS
    
END-PROCESSING.
    CLOSE ORDER-FILE
    DISPLAY "Range processing completed"
    DISPLAY "Total records processed: " WS-RECORD-COUNT
    DISPLAY "Total amount: " WS-TOTAL-AMOUNT
    STOP RUN.
 
PROCESS-RANGE-RECORDS.
    PERFORM UNTIL WS-CURRENT-KEY > WS-END-RANGE
        READ ORDER-FILE
            AT END
                DISPLAY "End of file reached"
                EXIT PERFORM
            NOT AT END
                * Check if record is within range
                IF ORDER-NUMBER <= WS-END-RANGE
                    ADD 1 TO WS-RECORD-COUNT
                    ADD ORDER-AMOUNT TO WS-TOTAL-AMOUNT
                    DISPLAY "Order: " ORDER-NUMBER " Amount: " ORDER-AMOUNT
                    MOVE ORDER-NUMBER TO WS-CURRENT-KEY
                ELSE
                    EXIT PERFORM
                END-IF
        END-READ
    END-PERFORM.

Explanation: This example shows how to use START for range processing. The program positions at the beginning of a range of order numbers and then processes all records within that range. This is useful for batch processing, reporting, and data analysis where you need to process records within specific key ranges. The START statement efficiently positions the file pointer, and subsequent READ statements retrieve records in sequence.

Best Practices and Considerations

Important Considerations

  • START only works with indexed and relative files
  • Always check file status after START operations
  • Use appropriate key conditions for positioning
  • Handle INVALID KEY conditions properly
  • Ensure file is open before using START

Advantages

  • Efficient file positioning
  • Supports range processing
  • Enables selective record access
  • Improves file access performance
  • Provides flexible key-based positioning

Limitations

  • Only works with indexed and relative files
  • Requires proper error handling
  • May not find records if key doesn't exist
  • Performance depends on index structure
  • Requires understanding of file organization

Best Practices

  • • Always check file status after START operations
  • • Use appropriate key conditions for your needs
  • • Handle INVALID KEY conditions properly
  • • Ensure files are properly opened before START
  • • Use START for efficient range processing

Test Your Knowledge

1. What is the primary purpose of the START statement in COBOL?

  • To begin program execution
  • To position within indexed and relative files
  • To start a new file
  • To initialize variables

2. Which file organizations support the START statement?

  • Sequential files only
  • Indexed and relative files
  • All file types
  • VSAM files only

3. What is the relationship between START and READ statements?

  • They are the same thing
  • START positions the file, READ retrieves the record
  • START reads the record, READ positions the file
  • They cannot be used together

4. What happens if a START statement fails to find a matching record?

  • The program crashes
  • The file status is set to indicate the condition
  • The program continues normally
  • The file is automatically closed

5. Can the START statement be used with sequential files?

  • Yes, always
  • No, only with indexed and relative files
  • Only in some implementations
  • Only with VSAM files

Related Concepts

READ Statement

Reading records from files

Indexed Files

Working with indexed file organization

Relative Files

Working with relative file organization

File Status

Handling file status codes

File Processing

Complete guide to file processing

STANDARD-2STATIC