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COBOL INPUT Procedure |
The COBOL INPUT Procedure or OUTPUT Procedure is a powerful feature that allows developers to add, delete, alter, edit, or otherwise modify records in a COBOL program. In this tutorial, we will explore the best practices for implementing the COBOL INPUT Procedure, advanced techniques, COBOL INPUT Procedure syntax, common errors to avoid, and examples of its usage.
Understanding the COBOL INPUT Procedure.
The COBOL INPUT Procedure is used to read records from an input file and process them in a COBOL program. It allows developers to define the structure of the input file and specify how the records should be processed. The INPUT PROCEDURE statement is typically used in conjunction with the COBOL SORT statement to sort the input records before processing.
The Input Procedure is a process that handles one or multiple input files before the sorting process takes place. When the Sort statement is executed, it transfers control to this procedure. However, if you don't need to process the input file before sorting, you can use the Using clause instead of the Input Procedure clause. It's important to note that the file should not be open when the Sort statement is executed because it will be automatically opened and closed. Additionally, the file must have either sequential or dynamic access so that it can be accessed sequentially.
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COBOL SORT Input Procedure/Output Procedure. |
Example: Input procedure used with SORT verb.
The following code snippet demonstrates how to use COBOL's input procedure with the Sort statement.
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COBOL Input Procedure Example. |
Best Practices for Implementing the COBOL INPUT Procedure.
When implementing the COBOL INPUT Procedure, it is important to follow best practices to ensure efficient and effective processing of the input records. The following are some of the practices that programmers must consider:
- Define the input file structure accurately: It is crucial to define the structure of the input file correctly, including the record layout and field definitions. This will ensure that the program can read and process the records accurately.
- Use appropriate file organization: Choose the appropriate file organization for the input file, such as sequential or indexed. This will depend on the access requirements and performance considerations of the program.
- Optimize the input file access: Use appropriate access techniques, such as using an index or key to access specific records efficiently. This can significantly improve the performance of the COBOL program.
- Handle errors gracefully: Implement error handling routines to handle any errors that may occur during the input procedure. This would assist programmers to resolve issues quickly.
Advanced Techniques for COBOL INPUT Procedure.
Once you have mastered the basics of the COBOL INPUT Procedure, you can explore advanced techniques to further enhance your programs. Some advanced techniques include:
- Using multiple input files: You can read records from multiple input files and process them together in a COBOL program. This can be useful when you need to combine data from different sources.
- Performing calculations on input records: You can perform calculations on the input records, such as aggregating data or calculating derived values. This can help in generating meaningful reports or performing complex data manipulations.
- Implementing input record validation: You can validate the input records against predefined rules or criteria. This can help in ensuring the integrity and accuracy of the data being processed.
Common Errors in COBOL INPUT Procedure.
While working with the COBOL INPUT Procedure, it is common to encounter errors. The following are common mistakes that programmers generally commit.
- Incorrect file definition: Make sure the file definition in the program matches the actual file structure. Any mismatch can lead to errors during the input procedure.
- Missing or incorrect record layout: Ensure that the record layout definition matches the actual record structure in the input file. Any discrepancy can result in data corruption or incorrect processing.
- Incorrect file organization: Using the wrong file organization can lead to performance issues or incorrect results. Make sure to choose the appropriate file organization based on the program requirements.
Examples of COBOL INPUT Procedure in Use
Let's take a look at some examples of the COBOL INPUT Procedure in action:
IDENTIFICATION DIVISION.
PROGRAM-ID. INP001.
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
SELECT INPUT-FILE ASSIGN TO INPFLDD.
DATA DIVISION.
FILE SECTION.
FD INPUT-FILE.
01 INPUT-RECORD.
05 FIELD-1 PIC X(10).
05 FIELD-2 PIC 9(5).
PROCEDURE DIVISION.
SORT INPUT-FILE
ON ASCENDING KEY FIELD-1
INPUT PROCEDURE IS PROCESS-RECORDS.
PROCESS-RECORDS.
PERFORM UNTIL EOF-INPUT-FILE
READ INPUT-FILE
AT END MOVE 'Y' TO EOF-INPUT-FILE
NOT AT END PERFORM PROCESS-RECORD
END-READ
END-PERFORM.
PROCESS-RECORD.
DISPLAY "Field 1: " FIELD-1
DISPLAY "Field 2: " FIELD-2.
STOP RUN.
In this example, we have a COBOL program that reads records from an input file "INPFLDD" and processes them. The SORT statement is used to sort the input records based on FIELD-1, and the INPUT PROCEDURE statement is used to specify the procedure for processing the records.
Integrating COBOL INPUT Procedure with Output Processing
The COBOL INPUT Procedure can be seamlessly integrated with output processing to create powerful and flexible programs. Once the input records have been processed, you can generate output files or reports based on the processed data. This allows you to perform complex data transformations and generate meaningful outputs.
Conclusion
The COBOL INPUT Procedure is a valuable feature that allows developers to read and process input records in a COBOL program. By following best practices, exploring advanced techniques, and avoiding common errors, you can optimize your COBOL programs and achieve efficient and accurate data processing. With the ability to integrate the INPUT Procedure with output processing, you can create powerful and flexible programs that meet your specific requirements.
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