How to Compare Two Files in COBOL
Comparing two files in COBOL is a fundamental task that can be crucial for data validation, auditing, and synchronization purposes. COBOL (Common Business-Oriented Language) is a high-level, English-like programming language designed for business, finance, and administrative systems for commercial applications. In this article, we will explore the steps and techniques to compare two files in COBOL, ensuring that you can effectively manage and analyze your data.
Firstly, it is essential to understand the structure of the files you want to compare. COBOL files can be sequential or indexed, and each file may have a different number of fields and data types. Before proceeding with the comparison, make sure that both files have the same structure and that you have identified the fields you want to compare.
To compare two files in COBOL, you can use the following steps:
1. Open the files: Use the OPEN statement to open both files for input. Make sure to specify the correct file names and access modes (INPUT for reading).
2. Read the first record of each file: Use the READ statement to read the first record from each file. This will allow you to compare the records one by one.
3. Compare the records: Use the COMPARE statement to compare the fields of the two records. The COMPARE statement returns various results, such as equal, not equal, or less than.
4. Process the comparison results: Based on the comparison results, you can decide how to proceed. If the records are equal, you can continue to the next record. If they are not equal, you can display a message, write the details to a log file, or perform other actions.
5. Close the files: Once you have finished comparing the files, use the CLOSE statement to close both files.
Here is an example of a COBOL program that compares two sequential files:
“`cobol
IDENTIFICATION DIVISION.
PROGRAM-ID. FILE-COMPARE.
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
SELECT FILE1 ASSIGN TO “FILE1.DAT” ORGANIZATION SEQUENTIAL.
SELECT FILE2 ASSIGN TO “FILE2.DAT” ORGANIZATION SEQUENTIAL.
DATA DIVISION.
FILE SECTION.
FD FILE1.
01 FILE1-RECORD.
05 FILE1-FIELD1 PIC X(10).
05 FILE1-FIELD2 PIC X(20).
FD FILE2.
01 FILE2-RECORD.
05 FILE2-FIELD1 PIC X(10).
05 FILE2-FIELD2 PIC X(20).
WORKING-STORAGE SECTION.
01 WS-FILE1-REC.
05 WS-FILE1-FIELD1 PIC X(10).
05 WS-FILE1-FIELD2 PIC X(20).
01 WS-FILE2-REC.
05 WS-FILE2-FIELD1 PIC X(10).
05 WS-FILE2-FIELD2 PIC X(20).
PROCEDURE DIVISION.
OPEN INPUT FILE1 FILE2.
READ FILE1 INTO WS-FILE1-REC AT END GO TO END-OF-FILE1.
READ FILE2 INTO WS-FILE2-REC AT END GO TO END-OF-FILE2.
PERFORM UNTIL END-OF-FILE1 OR END-OF-FILE2
COMPARE WS-FILE1-FIELD1 TO WS-FILE2-FIELD1
IF WS-FILE1-FIELD1 = WS-FILE2-FIELD1
COMPARE WS-FILE1-FIELD2 TO WS-FILE2-FIELD2
IF WS-FILE1-FIELD2 = WS-FILE2-FIELD2
DISPLAY “Records are equal”
ELSE
DISPLAY “Records are not equal”
ELSE
DISPLAY “Records are not equal”
END-IF
READ FILE1 INTO WS-FILE1-REC AT END GO TO END-OF-FILE1.
READ FILE2 INTO WS-FILE2-REC AT END GO TO END-OF-FILE2.
END-PERFORM.
CLOSE FILE1 FILE2.
STOP RUN.
END-OF-FILE1.
CLOSE FILE1.
STOP RUN.
END-OF-FILE2.
CLOSE FILE2.
STOP RUN.
“`
In this example, the program compares two sequential files named “FILE1.DAT” and “FILE2.DAT.” It reads the records from both files and compares the fields “FILE1-FIELD1” and “FILE2-FIELD1,” as well as “FILE1-FIELD2” and “FILE2-FIELD2.” If the records are equal, it displays a message; otherwise, it displays a different message.
By following these steps and utilizing the example code, you can compare two files in COBOL effectively. Remember to adapt the program to your specific file structure and requirements.
