REDEFINES

• REDEFINES defines a new variable for the existing variable, which means two variables share the same memory area.
• It is a way to declare multiple variables for a single memory area in different ways based on the requirement.
• The data items involved in a REDEFINES should be at the same level number.
• Redefining the target variable should follow the source item declaration.

Syntax -

level-number target-variable REDEFINES source-variable [PIC ...].

Parameters -

• level-number - The level number at which the variable is defined. It should be the same for both source and target variables.
• target-variable - Name of the new variable that is going to share the storage of source-variable.
• source-variable - Name of the variable whose storage is being redefined by target-variable.
• PIC .. - Optional. Additional clauses that describe the data, like PIC, VALUE, etc.

Rules to remember -

• The source variable can redefine unlimited times without any restrictions.
• The source and target variables should be at the same level.
• We can redefine variables declared with level numbers 01-49 or 77 can be redefined. However, We should not redefine the variables declared with levels 66 or 88.
• We should not redefine variables declared with an OCCURS DEPENDING ON clause.
• PICTURE clause is optional for REDEFINES.
• We can change the data type of the variable the variable.
• Ideally, the source and target variables should have the same length. However, the lengths may differ, and that is acceptable.
• The source or target variables may have elementary variables.

Practical Example -

Scenario - Redefining a variable with same length in COBOL programming.

Code -

----+----1----+----2----+----3----+----4----+----5----+
       ...
       WORKING-STORAGE SECTION.
       01 WS-VAR.
	      05 WS-VAR1                      PIC X(20).
          05 WS-REQ-VAR1 REDEFINES WS-VAR PIC X(20).
       ...
       PROCEDURE DIVISION.
           MOVE "MAINFRAME TECHNOLOGY"     TO WS-VAR1.
           DISPLAY "WS-VAR1:        " WS-VAR1.
           DISPLAY "WS-REQ-VAR1:    " WS-REQ-VAR1.
           DISPLAY " ".

           MOVE "MAINFRAME APPLICATION SYSTEM" TO WS-REQ-VAR1.
           DISPLAY "WS-VAR1:        " WS-VAR1.
           DISPLAY "WS-REQ-VAR1:    " WS-REQ-VAR1.
		   ...

Output -

WS-VAR1:        MAINFRAME TECHNOLOGY
WS-REQ-VAR1:    MAINFRAME TECHNOLOGY

WS-VAR1:        MAINFRAME APPLICATIO
WS-REQ-VAR1:    MAINFRAME APPLICATIO