Internal Sort in COBOL Language

Sorting is a fundamental operation in data processing, and COBOL provides robust features to perform sorting efficiently. In this blo

g post, we’ll delve into internal sorting in COBOL, explain how it works, and provide an example to illustrate its usage.

Understanding Internal Sorting in COBOL Language

Internal sorting in COBOL refers to the process of sorting data within the program’s memory (RAM) rather than using external sorting techniques. It is particularly useful when you need to sort a relatively small dataset that can fit into memory. COBOL offers the SORT verb to perform internal sorting, making it an efficient and straightforward process.

The SORT Verb in COBOL Language

The SORT verb in COBOL allows you to sort data in memory. Here’s a simplified syntax for the SORT verb:

SORT file-identifier
   ON ASCENDING/DESCENDING key-1 key-2 ...
   USING file-identifier

• file-identifier: Specifies the file or table to be sorted.
• ON ASCENDING/DESCENDING: Indicates the sorting order for each key. You can sort keys in ascending or descending order.
• key-1, key-2, ...: Specifies the key fields by which the data should be sorted.
• USING file-identifier: Identifies the temporary working storage area where the sorted data will be stored.

Example: Internal Sorting

Let’s consider a simple example where we have a file with unsorted records of students’ names and their corresponding scores. We want to sort this data in ascending order of scores using COBOL’s SORT verb:

IDENTIFICATION DIVISION.
PROGRAM-ID. InternalSortingExample.

DATA DIVISION.
FILE SECTION.
FD Student-File
   RECORDING MODE IS F
   BLOCK CONTAINS 0 RECORDS
   DATA RECORD IS Student-Record.

01 Student-Record.
   02 Student-Name   PIC X(30).
   02 Student-Score  PIC 9(3).

WORKING-STORAGE SECTION.
01 Temp-Record.
   02 Temp-Name   PIC X(30).
   02 Temp-Score  PIC 9(3).

PROCEDURE DIVISION.
   OPEN INPUT Student-File
   OPEN OUTPUT Student-File-Sorted

   PERFORM UNTIL EOF
       READ Student-File
           AT END
               SET EOF TO TRUE
           NOT AT END
               MOVE Student-Name TO Temp-Name
               MOVE Student-Score TO Temp-Score
               WRITE Temp-Record FROM Student-Record
       END-READ
   END-PERFORM

   SORT Student-File-Sorted
       ON ASCENDING Student-Score
       USING Temp-Record

   CLOSE Student-File
   CLOSE Student-File-Sorted

   STOP RUN.

In this example:

• We define two file identifiers: Student-File for reading the unsorted data and Student-File-Sorted for writing the sorted data.
• We read each unsorted record, store it temporarily, and write it to the output file.
• Finally, we use the SORT verb to sort the data in ascending order of scores using the Student-Score field as the sorting key.