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Enterprise
COBOL (Common Business-Oriented Language) is a compiled English-like computer programming language designed for business use. It is an imperative, procedural language that was designed in 1959.
COBOL, despite its longevity and importance in business applications, has several common anti-patterns that can lead to maintainability problems and bugs. Here are the most important anti-patterns to avoid when writing COBOL code.
* Anti-pattern: Excessive use of GO TO
PROCEDURE DIVISION.
PERFORM INITIALIZE-ROUTINE.
GO TO PROCESS-DATA.
INITIALIZE-ROUTINE.
MOVE ZEROS TO TOTAL-AMOUNT.
MOVE SPACES TO ERROR-MESSAGE.
PROCESS-DATA.
READ INPUT-FILE
AT END GO TO END-OF-FILE
END-READ.
IF AMOUNT-FIELD > 1000
GO TO LARGE-AMOUNT-ROUTINE
ELSE
GO TO SMALL-AMOUNT-ROUTINE
END-IF.
LARGE-AMOUNT-ROUTINE.
ADD AMOUNT-FIELD TO LARGE-TOTAL.
GO TO PROCESS-DATA.
SMALL-AMOUNT-ROUTINE.
ADD AMOUNT-FIELD TO SMALL-TOTAL.
GO TO PROCESS-DATA.
END-OF-FILE.
DISPLAY "Processing complete".
STOP RUN.
* Better approach: Structured programming
PROCEDURE DIVISION.
PERFORM INITIALIZE-ROUTINE.
PERFORM PROCESS-DATA UNTIL END-OF-FILE.
DISPLAY "Processing complete".
STOP RUN.
INITIALIZE-ROUTINE.
MOVE ZEROS TO TOTAL-AMOUNT.
MOVE SPACES TO ERROR-MESSAGE.
PROCESS-DATA.
READ INPUT-FILE
AT END SET END-OF-FILE TO TRUE
NOT AT END PERFORM PROCESS-RECORD
END-READ.
PROCESS-RECORD.
IF AMOUNT-FIELD > 1000
PERFORM LARGE-AMOUNT-ROUTINE
ELSE
PERFORM SMALL-AMOUNT-ROUTINE
END-IF.
LARGE-AMOUNT-ROUTINE.
ADD AMOUNT-FIELD TO LARGE-TOTAL.
SMALL-AMOUNT-ROUTINE.
ADD AMOUNT-FIELD TO SMALL-TOTAL.Avoid excessive use of GO TO statements, which create spaghetti code that is difficult to understand and maintain. Use structured programming constructs like PERFORM, IF-ELSE, and EVALUATE instead.
* Anti-pattern: Using magic numbers
IF CUSTOMER-TYPE = 1
COMPUTE DISCOUNT = TOTAL-AMOUNT * 0.10
ELSE IF CUSTOMER-TYPE = 2
COMPUTE DISCOUNT = TOTAL-AMOUNT * 0.15
ELSE IF CUSTOMER-TYPE = 3
COMPUTE DISCOUNT = TOTAL-AMOUNT * 0.20
END-IF.
* Better approach: Use named constants
01 DISCOUNT-RATES.
05 REGULAR-CUSTOMER-RATE PIC 9V99 VALUE 0.10.
05 PREFERRED-CUSTOMER-RATE PIC 9V99 VALUE 0.15.
05 PREMIUM-CUSTOMER-RATE PIC 9V99 VALUE 0.20.
01 CUSTOMER-TYPES.
05 REGULAR-CUSTOMER PIC 9 VALUE 1.
05 PREFERRED-CUSTOMER PIC 9 VALUE 2.
05 PREMIUM-CUSTOMER PIC 9 VALUE 3.
* In PROCEDURE DIVISION
IF CUSTOMER-TYPE = REGULAR-CUSTOMER
COMPUTE DISCOUNT = TOTAL-AMOUNT * REGULAR-CUSTOMER-RATE
ELSE IF CUSTOMER-TYPE = PREFERRED-CUSTOMER
COMPUTE DISCOUNT = TOTAL-AMOUNT * PREFERRED-CUSTOMER-RATE
ELSE IF CUSTOMER-TYPE = PREMIUM-CUSTOMER
COMPUTE DISCOUNT = TOTAL-AMOUNT * PREMIUM-CUSTOMER-RATE
END-IF.Avoid using magic numbers (hardcoded numeric literals) in your code. Use named constants to make your code more readable and maintainable.
* Anti-pattern: Flat data structures
01 CUSTOMER-RECORD.
05 CUSTOMER-ID PIC X(10).
05 CUSTOMER-NAME PIC X(30).
05 CUSTOMER-ADDRESS-1 PIC X(30).
05 CUSTOMER-ADDRESS-2 PIC X(30).
05 CUSTOMER-CITY PIC X(20).
05 CUSTOMER-STATE PIC X(2).
05 CUSTOMER-ZIP PIC X(10).
05 CUSTOMER-PHONE PIC X(15).
05 CUSTOMER-EMAIL PIC X(50).
* Better approach: Use hierarchical data structures
01 CUSTOMER-RECORD.
05 CUSTOMER-ID PIC X(10).
05 CUSTOMER-NAME PIC X(30).
05 CUSTOMER-ADDRESS.
10 STREET-ADDRESS-1 PIC X(30).
10 STREET-ADDRESS-2 PIC X(30).
10 CITY PIC X(20).
10 STATE PIC X(2).
10 ZIP-CODE PIC X(10).
05 CUSTOMER-CONTACT.
10 PHONE-NUMBER PIC X(15).
10 EMAIL-ADDRESS PIC X(50).Use hierarchical data structures to organize related data fields. This makes your code more readable and easier to maintain, especially when passing data between program modules.
* Anti-pattern: Hardcoded file names
SELECT CUSTOMER-FILE
ASSIGN TO "C:\DATA\CUSTOMER.DAT"
ORGANIZATION IS INDEXED
ACCESS MODE IS DYNAMIC
RECORD KEY IS CUSTOMER-ID.
* Better approach: Use configuration files or environment variables
SELECT CUSTOMER-FILE
ASSIGN TO CUSTOMER-FILE-PATH
ORGANIZATION IS INDEXED
ACCESS MODE IS DYNAMIC
RECORD KEY IS CUSTOMER-ID.
* In WORKING-STORAGE SECTION
01 CONFIGURATION-VARIABLES.
05 CUSTOMER-FILE-PATH PIC X(100).
* In PROCEDURE DIVISION
ACCEPT CUSTOMER-FILE-PATH FROM ENVIRONMENT "CUSTOMER_FILE_PATH".
IF CUSTOMER-FILE-PATH = SPACES
MOVE "C:\DATA\CUSTOMER.DAT" TO CUSTOMER-FILE-PATH
END-IF.Avoid hardcoding file paths and names in your programs. Use configuration files or environment variables instead, which makes your code more flexible and portable across different environments.
* Anti-pattern: Not validating input
ACCEPT CUSTOMER-ID.
READ CUSTOMER-FILE
INVALID KEY DISPLAY "Customer not found"
END-READ.
* Better approach: Validate input data
ACCEPT CUSTOMER-ID.
* Validate input format
IF CUSTOMER-ID IS NOT NUMERIC
DISPLAY "Error: Customer ID must be numeric"
EXIT PARAGRAPH
END-IF.
IF CUSTOMER-ID = ZEROS
DISPLAY "Error: Customer ID cannot be zero"
EXIT PARAGRAPH
END-IF.
* Proceed with valid input
READ CUSTOMER-FILE
INVALID KEY DISPLAY "Customer not found"
END-READ.Always validate input data before processing it. This helps prevent runtime errors, data corruption, and potential security issues.
* Anti-pattern: Using PERFORM THRU
PROCEDURE DIVISION.
PERFORM INITIALIZE-ROUTINE THRU INITIALIZE-EXIT.
PERFORM PROCESS-DATA THRU PROCESS-EXIT.
STOP RUN.
INITIALIZE-ROUTINE.
MOVE ZEROS TO TOTAL-AMOUNT.
MOVE SPACES TO ERROR-MESSAGE.
INITIALIZE-EXIT.
EXIT.
PROCESS-DATA.
READ INPUT-FILE
AT END GO TO PROCESS-EXIT
END-READ.
ADD AMOUNT-FIELD TO TOTAL-AMOUNT.
GO TO PROCESS-DATA.
PROCESS-EXIT.
EXIT.
* Better approach: Use structured PERFORM statements
PROCEDURE DIVISION.
PERFORM INITIALIZE-ROUTINE.
PERFORM PROCESS-DATA UNTIL END-OF-FILE.
STOP RUN.
INITIALIZE-ROUTINE.
MOVE ZEROS TO TOTAL-AMOUNT.
MOVE SPACES TO ERROR-MESSAGE.
PROCESS-DATA.
READ INPUT-FILE
AT END SET END-OF-FILE TO TRUE
NOT AT END ADD AMOUNT-FIELD TO TOTAL-AMOUNT
END-READ.Avoid using PERFORM THRU statements, which can lead to maintenance issues if paragraphs are reordered or renamed. Use structured PERFORM statements with well-defined paragraph boundaries instead.
* Anti-pattern: Duplicating data definitions
* In Program A
01 CUSTOMER-RECORD.
05 CUSTOMER-ID PIC X(10).
05 CUSTOMER-NAME PIC X(30).
05 CUSTOMER-ADDRESS.
10 STREET-ADDRESS-1 PIC X(30).
10 STREET-ADDRESS-2 PIC X(30).
10 CITY PIC X(20).
10 STATE PIC X(2).
10 ZIP-CODE PIC X(10).
* In Program B (duplicated definition)
01 CUSTOMER-RECORD.
05 CUSTOMER-ID PIC X(10).
05 CUSTOMER-NAME PIC X(30).
05 CUSTOMER-ADDRESS.
10 STREET-ADDRESS-1 PIC X(30).
10 STREET-ADDRESS-2 PIC X(30).
10 CITY PIC X(20).
10 STATE PIC X(2).
10 ZIP-CODE PIC X(10).
* Better approach: Use COPY books
* In CUSTOMER.CPY file
01 CUSTOMER-RECORD.
05 CUSTOMER-ID PIC X(10).
05 CUSTOMER-NAME PIC X(30).
05 CUSTOMER-ADDRESS.
10 STREET-ADDRESS-1 PIC X(30).
10 STREET-ADDRESS-2 PIC X(30).
10 CITY PIC X(20).
10 STATE PIC X(2).
10 ZIP-CODE PIC X(10).
* In Program A and Program B
COPY CUSTOMER.Use COPY books to share common data definitions and code across multiple programs. This reduces duplication and ensures consistency.
* Anti-pattern: Cryptic variable names
01 X1 PIC 9(5)V99.
01 X2 PIC 9(5)V99.
01 X3 PIC 9(5)V99.
COMPUTE X3 = X1 * X2.
* Better approach: Descriptive variable names
01 ITEM-PRICE PIC 9(5)V99.
01 QUANTITY PIC 9(5)V99.
01 TOTAL-COST PIC 9(5)V99.
COMPUTE TOTAL-COST = ITEM-PRICE * QUANTITY.Use meaningful and descriptive names for variables, paragraphs, and sections. This makes your code more readable and easier to understand and maintain.
* Anti-pattern: Minimal error handling
READ CUSTOMER-FILE
INVALID KEY DISPLAY "Error reading file"
END-READ.
* Better approach: Comprehensive error handling
READ CUSTOMER-FILE
INVALID KEY
MOVE "Y" TO ERROR-FOUND
MOVE "Customer record not found" TO ERROR-MESSAGE
PERFORM LOG-ERROR
PERFORM DISPLAY-ERROR-TO-USER
END-READ.
IF ERROR-FOUND = "Y"
PERFORM ERROR-RECOVERY-ROUTINE
END-IF.Implement proper error handling with detailed error messages, logging, and recovery procedures. This helps diagnose and resolve issues more quickly.
* Anti-pattern: Inappropriate use of REDEFINES
01 MULTI-PURPOSE-FIELD.
05 NUMERIC-VALUE PIC 9(10).
05 TEXT-VALUE REDEFINES NUMERIC-VALUE PIC X(10).
05 DATE-VALUE REDEFINES NUMERIC-VALUE.
10 YEAR PIC 9(4).
10 MONTH PIC 9(2).
10 DAY PIC 9(2).
10 FILLER PIC 9(2).
* Better approach: Use separate fields for different purposes
01 CUSTOMER-DATA.
05 CUSTOMER-ID PIC 9(10).
05 CUSTOMER-NAME PIC X(30).
05 REGISTRATION-DATE.
10 REG-YEAR PIC 9(4).
10 REG-MONTH PIC 9(2).
10 REG-DAY PIC 9(2).Avoid using REDEFINES to repurpose the same memory location for different data types. This can lead to data corruption and maintenance issues. Use separate fields for different purposes instead.
* Anti-pattern: Unstructured code
PROCEDURE DIVISION.
MAIN-LOGIC.
OPEN INPUT CUSTOMER-FILE.
OPEN OUTPUT REPORT-FILE.
READ CUSTOMER-FILE
AT END MOVE "Y" TO END-OF-FILE-FLAG
END-READ.
PERFORM UNTIL END-OF-FILE-FLAG = "Y"
MOVE CUSTOMER-NAME TO REPORT-NAME
MOVE CUSTOMER-BALANCE TO REPORT-BALANCE
WRITE REPORT-RECORD
READ CUSTOMER-FILE
AT END MOVE "Y" TO END-OF-FILE-FLAG
END-READ
END-PERFORM.
CLOSE CUSTOMER-FILE.
CLOSE REPORT-FILE.
STOP RUN.
* Better approach: Structured code with modular design
PROCEDURE DIVISION.
MAIN-LOGIC.
PERFORM INITIALIZATION.
PERFORM PROCESS-RECORDS UNTIL END-OF-FILE.
PERFORM TERMINATION.
STOP RUN.
INITIALIZATION.
OPEN INPUT CUSTOMER-FILE.
OPEN OUTPUT REPORT-FILE.
PERFORM READ-CUSTOMER-RECORD.
PROCESS-RECORDS.
PERFORM WRITE-REPORT-RECORD.
PERFORM READ-CUSTOMER-RECORD.
WRITE-REPORT-RECORD.
MOVE CUSTOMER-NAME TO REPORT-NAME.
MOVE CUSTOMER-BALANCE TO REPORT-BALANCE.
WRITE REPORT-RECORD.
READ-CUSTOMER-RECORD.
READ CUSTOMER-FILE
AT END MOVE "Y" TO END-OF-FILE-FLAG
END-READ.
TERMINATION.
CLOSE CUSTOMER-FILE.
CLOSE REPORT-FILE.Use structured programming principles with modular design. Break down your program into logical, self-contained modules with clear responsibilities.
* Anti-pattern: Nested IF statements
IF TRANSACTION-TYPE = "S"
IF CUSTOMER-TYPE = "R"
IF AMOUNT > 1000
COMPUTE DISCOUNT = AMOUNT * 0.10
ELSE
COMPUTE DISCOUNT = AMOUNT * 0.05
END-IF
ELSE IF CUSTOMER-TYPE = "P"
IF AMOUNT > 1000
COMPUTE DISCOUNT = AMOUNT * 0.15
ELSE
COMPUTE DISCOUNT = AMOUNT * 0.10
END-IF
END-IF
END-IF.
* Better approach: Use EVALUATE
EVALUATE TRUE
WHEN TRANSACTION-TYPE = "S" AND CUSTOMER-TYPE = "R" AND AMOUNT > 1000
COMPUTE DISCOUNT = AMOUNT * 0.10
WHEN TRANSACTION-TYPE = "S" AND CUSTOMER-TYPE = "R"
COMPUTE DISCOUNT = AMOUNT * 0.05
WHEN TRANSACTION-TYPE = "S" AND CUSTOMER-TYPE = "P" AND AMOUNT > 1000
COMPUTE DISCOUNT = AMOUNT * 0.15
WHEN TRANSACTION-TYPE = "S" AND CUSTOMER-TYPE = "P"
COMPUTE DISCOUNT = AMOUNT * 0.10
WHEN OTHER
MOVE ZEROS TO DISCOUNT
END-EVALUATE.Use the EVALUATE statement for complex conditional logic instead of deeply nested IF statements. This makes your code more readable and easier to maintain.