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COBOL ASSIGN TO Clause - Quick Reference

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Overview

The ASSIGN TO clause is used in the FILE-CONTROL paragraph to specify the external name or device for a file. It establishes the connection between the logical file name used in the program and the physical file or device in the operating system.

Purpose and Usage

  • File assignment - Connect logical files to physical datasets
  • Device specification - Assign files to specific devices
  • External naming - Specify external file names
  • System integration - Interface with operating system resources
  • Dynamic assignment - Use variables for runtime file assignment

File Assignment Concept

Logical Name: CUSTOMER-FILE
ASSIGN TO: "CUSTOMER.DAT"
Physical File: /data/customer.dat
Program ↔ External Name ↔ Physical File

ASSIGN TO creates the bridge between program logic and physical storage.

Syntax

The ASSIGN TO clause follows specific syntax patterns within SELECT statements and can use various types of values for file assignment.

Basic Syntax

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* Basic ASSIGN TO syntax
SELECT file-name ASSIGN TO external-name
 
* With literal string
SELECT CUSTOMER-FILE ASSIGN TO "CUSTOMER.DAT"
 
* With data name (variable)
SELECT CUSTOMER-FILE ASSIGN TO WS-FILE-NAME
 
* With figurative constant
SELECT OUTPUT-FILE ASSIGN TO PRINTER
 
* Complete example with other clauses
SELECT CUSTOMER-FILE ASSIGN TO "CUSTOMER.DAT"
    ORGANIZATION IS SEQUENTIAL
    ACCESS MODE IS SEQUENTIAL
    FILE STATUS IS WS-FILE-STATUS

ASSIGN TO can use literal strings, data names, or figurative constants.

Value Types for ASSIGN TO

TypeExampleUsage
Literal String"CUSTOMER.DAT"Fixed file names
Data NameWS-FILE-NAMEDynamic assignment
Figurative ConstantPRINTER, CONSOLESystem devices
Environment Variable$DATAFILESystem configuration

Common Figurative Constants

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* System devices and standard files
SELECT OUTPUT-FILE ASSIGN TO PRINTER    * System printer
SELECT INPUT-FILE ASSIGN TO SYSIN       * Standard input
SELECT OUTPUT-FILE ASSIGN TO SYSOUT     * Standard output
SELECT ERROR-FILE ASSIGN TO SYSERR      * Error output
SELECT CONSOLE-FILE ASSIGN TO CONSOLE   * Console I/O
 
* Mainframe specific
SELECT TAPE-FILE ASSIGN TO TAPE         * Tape device
SELECT DISK-FILE ASSIGN TO DISK         * Disk device
SELECT CARD-FILE ASSIGN TO CARD-READER  * Card reader

Figurative constants provide standard device references.

Practical Examples

These examples demonstrate how to use the ASSIGN TO clause effectively in different file handling scenarios.

Sequential File Assignment

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IDENTIFICATION DIVISION.
PROGRAM-ID. SEQUENTIAL-FILE-EXAMPLE.
 
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT CUSTOMER-FILE ASSIGN TO "CUSTOMER.DAT"
        ORGANIZATION IS SEQUENTIAL
        ACCESS MODE IS SEQUENTIAL
        FILE STATUS IS WS-FILE-STATUS.
 
DATA DIVISION.
FILE SECTION.
FD  CUSTOMER-FILE.
01  CUSTOMER-RECORD.
    05  CUSTOMER-ID       PIC 9(6).
    05  CUSTOMER-NAME     PIC X(30).
    05  CUSTOMER-BALANCE  PIC 9(8)V99.
 
WORKING-STORAGE SECTION.
01  WS-FILE-STATUS        PIC X(2).
 
PROCEDURE DIVISION.
MAIN-PROCESS.
    OPEN INPUT CUSTOMER-FILE
    IF WS-FILE-STATUS NOT = "00"
        DISPLAY "Error opening file: " WS-FILE-STATUS
        STOP RUN
    END-IF
    
    * Process file records
    PERFORM UNTIL WS-FILE-STATUS = "10"
        READ CUSTOMER-FILE
        IF WS-FILE-STATUS = "00"
            DISPLAY "Customer: " CUSTOMER-NAME
        END-IF
    END-PERFORM
    
    CLOSE CUSTOMER-FILE
    STOP RUN.

Basic sequential file assignment with literal string and file status checking.

Dynamic File Assignment

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IDENTIFICATION DIVISION.
PROGRAM-ID. DYNAMIC-FILE-ASSIGNMENT.
 
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT INPUT-FILE ASSIGN TO WS-INPUT-FILE-NAME
        ORGANIZATION IS SEQUENTIAL
        ACCESS MODE IS SEQUENTIAL
        FILE STATUS IS WS-FILE-STATUS.
 
DATA DIVISION.
WORKING-STORAGE SECTION.
01  WS-INPUT-FILE-NAME    PIC X(50).
01  WS-FILE-STATUS        PIC X(2).
01  WS-USER-INPUT         PIC X(50).
 
PROCEDURE DIVISION.
MAIN-PROCESS.
    * Get file name from user
    DISPLAY "Enter input file name: "
    ACCEPT WS-USER-INPUT
    
    * Set the file name for assignment
    MOVE WS-USER-INPUT TO WS-INPUT-FILE-NAME
    
    * Open the dynamically assigned file
    OPEN INPUT INPUT-FILE
    IF WS-FILE-STATUS NOT = "00"
        DISPLAY "Error opening file: " WS-FILE-STATUS
        STOP RUN
    END-IF
    
    DISPLAY "File opened successfully: " WS-INPUT-FILE-NAME
    CLOSE INPUT-FILE
    STOP RUN.

Dynamic file assignment using a data name that can be set at runtime.

Device Assignment

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IDENTIFICATION DIVISION.
PROGRAM-ID. DEVICE-ASSIGNMENT.
 
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT REPORT-FILE ASSIGN TO PRINTER
        ORGANIZATION IS SEQUENTIAL
        ACCESS MODE IS SEQUENTIAL.
    
    SELECT LOG-FILE ASSIGN TO "LOG.TXT"
        ORGANIZATION IS SEQUENTIAL
        ACCESS MODE IS SEQUENTIAL.
    
    SELECT CONSOLE-OUTPUT ASSIGN TO CONSOLE
        ORGANIZATION IS SEQUENTIAL
        ACCESS MODE IS SEQUENTIAL.
 
DATA DIVISION.
FILE SECTION.
FD  REPORT-FILE.
01  REPORT-LINE         PIC X(80).
 
FD  LOG-FILE.
01  LOG-LINE            PIC X(80).
 
FD  CONSOLE-OUTPUT.
01  CONSOLE-LINE        PIC X(80).
 
PROCEDURE DIVISION.
MAIN-PROCESS.
    * Write to printer
    OPEN OUTPUT REPORT-FILE
    MOVE "This goes to the printer" TO REPORT-LINE
    WRITE REPORT-LINE
    CLOSE REPORT-FILE
    
    * Write to log file
    OPEN OUTPUT LOG-FILE
    MOVE "This goes to the log file" TO LOG-LINE
    WRITE LOG-LINE
    CLOSE LOG-FILE
    
    * Write to console
    OPEN OUTPUT CONSOLE-OUTPUT
    MOVE "This goes to the console" TO CONSOLE-LINE
    WRITE CONSOLE-LINE
    CLOSE CONSOLE-OUTPUT
    
    STOP RUN.

Different types of device assignments including printer, file, and console.

Indexed File Assignment

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IDENTIFICATION DIVISION.
PROGRAM-ID. INDEXED-FILE-ASSIGNMENT.
 
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT INVENTORY-FILE ASSIGN TO "INVENTORY.IDX"
        ORGANIZATION IS INDEXED
        ACCESS MODE IS RANDOM
        RECORD KEY IS PRODUCT-ID
        FILE STATUS IS WS-FILE-STATUS.
 
DATA DIVISION.
FILE SECTION.
FD  INVENTORY-FILE.
01  INVENTORY-RECORD.
    05  PRODUCT-ID        PIC 9(6).
    05  PRODUCT-NAME      PIC X(30).
    05  QUANTITY-ON-HAND  PIC 9(5).
    05  UNIT-PRICE        PIC 9(6)V99.
 
WORKING-STORAGE SECTION.
01  WS-FILE-STATUS        PIC X(2).
01  WS-PRODUCT-ID         PIC 9(6).
 
PROCEDURE DIVISION.
MAIN-PROCESS.
    OPEN I-O INVENTORY-FILE
    IF WS-FILE-STATUS NOT = "00"
        DISPLAY "Error opening indexed file: " WS-FILE-STATUS
        STOP RUN
    END-IF
    
    * Read a specific record
    MOVE 123456 TO WS-PRODUCT-ID
    READ INVENTORY-FILE
    IF WS-FILE-STATUS = "00"
        DISPLAY "Product: " PRODUCT-NAME
    ELSE
        DISPLAY "Product not found"
    END-IF
    
    CLOSE INVENTORY-FILE
    STOP RUN.

Indexed file assignment with random access and record key specification.

Best Practices and Considerations

Understanding best practices ensures proper file assignment and system integration.

File Assignment Best Practices

  • Use meaningful names - Choose descriptive external file names
  • Validate file existence - Check file status after OPEN operations
  • Handle errors gracefully - Provide meaningful error messages
  • Use appropriate devices - Match file purpose to device type
  • Consider security - Ensure proper file permissions and access

Common Pitfalls to Avoid

PitfallProblemSolution
Hardcoded pathsPoor portabilityUse environment variables or configuration
Missing error handlingProgram crashesCheck file status codes
Incorrect device namesAssignment failuresVerify device availability
Case sensitivityFile not foundMatch exact case requirements
Permission issuesAccess deniedCheck file permissions

Platform Considerations

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* Windows file assignment
SELECT DATA-FILE ASSIGN TO "C:\DATA\CUSTOMER.DAT"
 
* Unix/Linux file assignment  
SELECT DATA-FILE ASSIGN TO "/data/customer.dat"
 
* Mainframe dataset assignment
SELECT DATA-FILE ASSIGN TO "USER.CUSTOMER.DATA"
 
* Environment variable usage
SELECT DATA-FILE ASSIGN TO "$DATADIR/customer.dat"
 
* Relative path assignment
SELECT DATA-FILE ASSIGN TO "./data/customer.dat"

Different platforms may require different assignment syntax.

ASSIGN TO Clause Quick Reference

UsageSyntaxExample
Literal file nameASSIGN TO "filename"ASSIGN TO "CUSTOMER.DAT"
Variable assignmentASSIGN TO data-nameASSIGN TO WS-FILE-NAME
System deviceASSIGN TO device-constantASSIGN TO PRINTER
Standard I/OASSIGN TO SYSIN/SYSOUTASSIGN TO SYSIN
Console I/OASSIGN TO CONSOLEASSIGN TO CONSOLE

Test Your Knowledge

1. What is the primary purpose of the ASSIGN TO clause in COBOL?

  • To assign variables
  • To assign files to external devices or datasets
  • To assign memory
  • To assign program names

2. In which division is the ASSIGN TO clause typically used?

  • IDENTIFICATION DIVISION
  • ENVIRONMENT DIVISION
  • DATA DIVISION
  • PROCEDURE DIVISION

3. What type of value can be used with ASSIGN TO?

  • Only literal values
  • Only variable names
  • Literal values, variable names, or figurative constants
  • Only figurative constants

4. What is the relationship between ASSIGN TO and file organization?

  • They are the same thing
  • ASSIGN TO specifies the device, organization specifies the structure
  • ASSIGN TO is only for sequential files
  • They cannot be used together

5. Which of the following is a valid ASSIGN TO usage?

  • ASSIGN TO "CUSTOMER.DAT"
  • ASSIGN TO CUSTOMER-FILE
  • ASSIGN TO PRINTER
  • All of the above

Frequently Asked Questions

Related Concepts

SELECT Statement

Understanding the SELECT statement for file definition.

FILE-CONTROL Paragraph

File control paragraph structure and usage.

File Organization

Different file organization types in COBOL.

File Status

File status codes and error handling.

Environment Division

Environment division structure and components.

ADVANCING PAGE ClauseCALL-CONVENTION