Redefines is a powerful feature in COBOL language that facilitates memory utilization wisely. It enables a programmer to use the same memory space for storing different data at different times. The process of using redefines increases code efficiency. To further explore the functionality, let’s delve into its solution followed by a step-by-step explanation of the code.
Utilizing Redefines in COBOL
05 CUSTOMER-NAME PIC X(15).
10 AMOUNT PIC 9(6).
10 DATE PIC 9(6).
05 WHOLESALE-RECORD REDEFINES RETAIL-RECORD.
10 QTY PIC 9(4).
10 ITEM PIC X(8).
The redefines clause in COBOL allows a data item to be defined with multiple descriptions. The memory allocated to these data items, such as `RETAIL-RECORD` and `WHOLESALE-RECORD `above, occupy the same memory space in working storage.
Note: The Redefines clause can only be used with data items of equal or smaller size.
Step-By-Step Code Explanation
In the example given above, the wholesale and retail records are stored under customer records. They occupy the same memory space but serve different purposes. It effectively allows either of these two records to be present or used at a given point in time.
The retail record holds amount and date, while wholesale record accommodates quantity and item. However, we do not use them together at the same time.
- The `REDEFINES` clause is used to state that `WHOLESALE-RECORD` is an alternate description of `RETAIL-RECORD`. It does not allocate separate memory but uses the space allocated by `RETAIL-RECORD`.
- The `RETAIL-RECORD` holds the `AMOUNT` and `DATE` whereas, `WHOLESALE-RECORD` accommodates `QTY` and `ITEM` data.
- `CUSTOMER-NAME` is independent of the redefine as it operates separately.
Usage of Redefines
Redefines are commonly used in scenarios where different layouts of data are loaded at different times and, based on some condition, the program will choose which layout to process. This has a significant effect on reducing memory space and increasing processing speed, a primary concern in mainframe applications.
It serves as a way to view the same portion of memory in different ways, based on the needs of the program at a given time.
Overall, utilizing the `REDEFINES` clause in COBOL programs is an efficient way of managing memory by avoiding unnecessary duplication of data items in the memory. Using the `REDEFINES` can also result in making your COBOL programs more maintainable, easier to read, and understand.