COBOL REDEFINES













COBOL REDEFINES






The REDEFINES clause allows the same memory area to be described 
by different data items. In program if we are sure that 2 or more 
date names are not in use at same time then we go for redefines 
clause.



	01 WS-NAME.             					
	   05 WS_FST-NAME	PIC X(05)	VALUE “John”.
	   05 WS_FST-NAME	PIC X(05)	VALUE “Mike”.

	01 WS-TOTAL-NAME	REDEFINES   WS-NAME   	PIC X(10).



In above example WS-TOTAL-NAME will use same memory area allocated 
to WS-NAME. So Ws-TOTAL-NAME will have “John Mike”


1. Level numbers of WS-DATA-NAME1 and WS-DATA-NAME2 should be same.
2. REDEFINES clause cannot be used for level numbers 66 and 88.
3. REDEFINES may not be used in a level 01 entry in the File Section.
4. Number of characters need not be the same for WS-DATA-NAME1 and 
   WS-DATA-NAME2. Compiler generates warning if number of characters 
   in WS-DATA-NAME2 is greater than WS-DATA-NAME2.
5. Several data items can redefine the same data item.
6. Data items redefining the storage of a data item must immediately 
   follow the description of that data item.  

Difference between REDEFINES and RENAMES:
RENAMES clause is used for regrouping elementary data items and gives 
one name to it. REDEFINES clause allow you to use different data 
descriptions entries to describe same memory area