In this section, we will explore some of the most common errors encountered in COBOL programming and provide solutions to help you debug and resolve these issues effectively. Understanding these common pitfalls will enhance your ability to write robust and error-free COBOL programs.
- Syntax Errors
Description
Syntax errors occur when the code does not conform to the rules of the COBOL language. These errors are usually detected by the compiler.
Common Examples
- Missing periods at the end of statements.
- Incorrect use of reserved words.
- Misplaced or missing sections and divisions.
Example
IDENTIFICATION DIVISION. PROGRAM-ID. HelloWorld DATA DIVISION. WORKING-STORAGE SECTION. 01 WS-MESSAGE PIC X(20) VALUE 'Hello, World!'. PROCEDURE DIVISION. DISPLAY WS-MESSAGE STOP RUN.
Solution
Ensure that each statement ends with a period and that all divisions and sections are correctly defined.
IDENTIFICATION DIVISION.
PROGRAM-ID. HelloWorld.
DATA DIVISION.
WORKING-STORAGE SECTION.
01 WS-MESSAGE PIC X(20) VALUE 'Hello, World!'.
PROCEDURE DIVISION.
DISPLAY WS-MESSAGE.
STOP RUN.
- Data Type Mismatches
Description
Data type mismatches occur when operations are performed on incompatible data types.
Common Examples
- Adding a numeric field to an alphanumeric field.
- Using a numeric field where a string is expected.
Example
IDENTIFICATION DIVISION.
PROGRAM-ID. DataTypeMismatch.
DATA DIVISION.
WORKING-STORAGE SECTION.
01 WS-NUMBER PIC 9(5) VALUE 12345.
01 WS-TEXT PIC X(10) VALUE 'TEXT'.
PROCEDURE DIVISION.
ADD WS-NUMBER TO WS-TEXT.
STOP RUN.Solution
Ensure that operations are performed on compatible data types. Use appropriate conversion functions if necessary.
IDENTIFICATION DIVISION.
PROGRAM-ID. DataTypeMismatch.
DATA DIVISION.
WORKING-STORAGE SECTION.
01 WS-NUMBER PIC 9(5) VALUE 12345.
01 WS-TEXT PIC X(10) VALUE 'TEXT'.
01 WS-NUMBER-TEXT PIC X(5).
PROCEDURE DIVISION.
MOVE WS-NUMBER TO WS-NUMBER-TEXT.
STRING WS-NUMBER-TEXT DELIMITED BY SPACE
' ' DELIMITED BY SIZE
WS-TEXT DELIMITED BY SIZE
INTO WS-TEXT.
DISPLAY WS-TEXT.
STOP RUN.
- Uninitialized Variables
Description
Uninitialized variables can lead to unpredictable behavior and incorrect results.
Common Examples
- Using a variable before it has been assigned a value.
- Assuming default values for variables.
Example
IDENTIFICATION DIVISION.
PROGRAM-ID. UninitializedVar.
DATA DIVISION.
WORKING-STORAGE SECTION.
01 WS-NUMBER PIC 9(5).
PROCEDURE DIVISION.
DISPLAY WS-NUMBER.
STOP RUN.Solution
Always initialize variables before using them.
IDENTIFICATION DIVISION.
PROGRAM-ID. UninitializedVar.
DATA DIVISION.
WORKING-STORAGE SECTION.
01 WS-NUMBER PIC 9(5) VALUE 0.
PROCEDURE DIVISION.
DISPLAY WS-NUMBER.
STOP RUN.
- File Handling Errors
Description
File handling errors occur when there are issues with opening, reading, writing, or closing files.
Common Examples
- File not found.
- Incorrect file status handling.
- Reading from a file that is not open.
Example
IDENTIFICATION DIVISION.
PROGRAM-ID. FileHandlingError.
DATA DIVISION.
FILE SECTION.
FD INPUT-FILE
LABEL RECORDS ARE STANDARD
BLOCK CONTAINS 0 RECORDS
RECORD CONTAINS 80 CHARACTERS.
01 INPUT-RECORD PIC X(80).
WORKING-STORAGE SECTION.
01 WS-FILE-STATUS PIC XX.
PROCEDURE DIVISION.
OPEN INPUT INPUT-FILE.
READ INPUT-FILE INTO INPUT-RECORD.
DISPLAY INPUT-RECORD.
CLOSE INPUT-FILE.
STOP RUN.Solution
Always check the file status after file operations and handle errors appropriately.
IDENTIFICATION DIVISION.
PROGRAM-ID. FileHandlingError.
DATA DIVISION.
FILE SECTION.
FD INPUT-FILE
LABEL RECORDS ARE STANDARD
BLOCK CONTAINS 0 RECORDS
RECORD CONTAINS 80 CHARACTERS.
01 INPUT-RECORD PIC X(80).
WORKING-STORAGE SECTION.
01 WS-FILE-STATUS PIC XX.
PROCEDURE DIVISION.
OPEN INPUT INPUT-FILE.
IF WS-FILE-STATUS NOT = '00'
DISPLAY 'Error opening file: ' WS-FILE-STATUS
STOP RUN.
END-IF.
READ INPUT-FILE INTO INPUT-RECORD
AT END
DISPLAY 'End of file reached.'
CLOSE INPUT-FILE
STOP RUN.
DISPLAY INPUT-RECORD.
CLOSE INPUT-FILE.
STOP RUN.
- Logic Errors
Description
Logic errors occur when the program runs without crashing but produces incorrect results due to flaws in the logic.
Common Examples
- Incorrect loop conditions.
- Misplaced statements.
- Incorrect calculations.
Example
IDENTIFICATION DIVISION.
PROGRAM-ID. LogicError.
DATA DIVISION.
WORKING-STORAGE SECTION.
01 WS-COUNT PIC 9(2) VALUE 0.
PROCEDURE DIVISION.
PERFORM VARYING WS-COUNT FROM 1 BY 1 UNTIL WS-COUNT > 10
DISPLAY 'Count: ' WS-COUNT
END-PERFORM.
STOP RUN.Solution
Carefully review the logic and ensure that conditions and calculations are correct.
IDENTIFICATION DIVISION.
PROGRAM-ID. LogicError.
DATA DIVISION.
WORKING-STORAGE SECTION.
01 WS-COUNT PIC 9(2) VALUE 0.
PROCEDURE DIVISION.
PERFORM VARYING WS-COUNT FROM 1 BY 1 UNTIL WS-COUNT > 10
DISPLAY 'Count: ' WS-COUNT
END-PERFORM.
STOP RUN.Conclusion
Understanding and resolving common errors in COBOL programming is crucial for developing reliable and efficient applications. By familiarizing yourself with these common pitfalls and their solutions, you can enhance your debugging skills and write more robust COBOL programs. In the next section, we will delve into COBOL and databases, exploring how to integrate COBOL programs with DB2 databases.