MainframeMaster

COBOL Data Comparison

Data comparison evaluates relationships between values using relational operators, class conditions, and sign conditions. Learn to compare numeric and alphanumeric data effectively in COBOL programs.

Relational Operators

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       *> Numeric comparisons
       IF CUSTOMER-BALANCE > 1000
           DISPLAY 'High balance customer'
       END-IF.
       
       IF TRANSACTION-AMOUNT < 0
           DISPLAY 'Negative transaction'
       END-IF.
       
       IF CUSTOMER-AGE >= 18
           DISPLAY 'Adult customer'
       ELSE
           DISPLAY 'Minor customer'
       END-IF.
       
       IF ACCOUNT-STATUS = 'ACTIVE'
           DISPLAY 'Account is active'
       END-IF.
       
       IF CUSTOMER-ID NOT = 0
           DISPLAY 'Valid customer ID'
       END-IF.

Use relational operators to compare values: > (greater than), < (less than), = (equal), >= (greater than or equal), <= (less than or equal), and NOT = (not equal). These work with both numeric and alphanumeric data.

String Comparison

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       *> Alphanumeric string comparison
       IF CUSTOMER-NAME = 'JOHN SMITH'
           DISPLAY 'Found John Smith'
       END-IF.
       
       IF CUSTOMER-CITY > 'CHICAGO'
           DISPLAY 'City comes after Chicago alphabetically'
       END-IF.
       
       *> Case-insensitive comparison
       IF FUNCTION UPPER-CASE(CUSTOMER-NAME) = 'JOHN SMITH'
           DISPLAY 'Found John Smith (case-insensitive)'
       END-IF.
       
       *> Partial string comparison
       IF CUSTOMER-NAME(1:4) = 'JOHN'
           DISPLAY 'Name starts with JOHN'
       END-IF.

Compare alphanumeric strings using relational operators. COBOL compares strings character by character using the collating sequence. Use FUNCTION UPPER-CASE for case-insensitive comparison and reference modification for partial comparisons.

Class Conditions

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       *> Test data types
       IF CUSTOMER-ID IS NUMERIC
           DISPLAY 'Customer ID is numeric'
       ELSE
           DISPLAY 'Customer ID contains non-numeric characters'
       END-IF.
       
       IF CUSTOMER-NAME IS ALPHABETIC
           DISPLAY 'Customer name contains only letters'
       ELSE
           DISPLAY 'Customer name contains non-alphabetic characters'
       END-IF.
       
       *> Test for specific values
       IF CUSTOMER-STATUS IS ALPHABETIC-UPPER
           DISPLAY 'Status is uppercase alphabetic'
       END-IF.

Use class conditions to test data types: NUMERIC tests for digits only, ALPHABETIC tests for letters only, ALPHABETIC-UPPER tests for uppercase letters only, and ALPHABETIC-LOWER tests for lowercase letters only.

Sign Conditions

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       *> Test numeric signs
       IF TRANSACTION-AMOUNT IS POSITIVE
           DISPLAY 'Credit transaction'
           PERFORM PROCESS-CREDIT
       ELSE IF TRANSACTION-AMOUNT IS NEGATIVE
           DISPLAY 'Debit transaction'
           PERFORM PROCESS-DEBIT
       ELSE IF TRANSACTION-AMOUNT IS ZERO
           DISPLAY 'Zero amount transaction'
           PERFORM PROCESS-ZERO-AMOUNT
       END-IF.
       
       *> Combined with other conditions
       IF BALANCE IS POSITIVE AND BALANCE > 1000
           DISPLAY 'High positive balance'
       END-IF.

Use sign conditions to test numeric values: POSITIVE (greater than zero), NEGATIVE (less than zero), and ZERO (exactly zero). These are useful for financial calculations and business logic.

Complex Comparisons

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       *> Multiple conditions with AND/OR
       IF CUSTOMER-AGE >= 18 AND CUSTOMER-INCOME > 30000
           DISPLAY 'Eligible for premium account'
       END-IF.
       
       IF CUSTOMER-TYPE = 'INDIVIDUAL' OR CUSTOMER-TYPE = 'CORPORATE'
           DISPLAY 'Valid customer type'
       END-IF.
       
       *> Complex logical expressions
       IF (CUSTOMER-BALANCE > 1000 AND CUSTOMER-STATUS = 'ACTIVE')
           OR (CUSTOMER-TYPE = 'PREMIUM' AND CUSTOMER-BALANCE > 500)
           DISPLAY 'Eligible for special service'
       END-IF.
       
       *> Using NOT operator
       IF NOT (CUSTOMER-STATUS = 'CLOSED' OR CUSTOMER-STATUS = 'SUSPENDED')
           DISPLAY 'Account is active'
       END-IF.

Combine conditions using AND, OR, and NOT operators. Use parentheses to control evaluation order. Complex comparisons allow sophisticated business logic while maintaining readability.

Range Comparisons

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       *> Numeric range checking
       IF CUSTOMER-AGE >= 18 AND CUSTOMER-AGE <= 65
           DISPLAY 'Working age customer'
       END-IF.
       
       IF TRANSACTION-AMOUNT > 0 AND TRANSACTION-AMOUNT <= 10000
           DISPLAY 'Standard transaction amount'
       END-IF.
       
       *> Using THRU for ranges
       IF CUSTOMER-GRADE >= 'A' AND CUSTOMER-GRADE <= 'C'
           DISPLAY 'Good customer grade'
       END-IF.
       
       *> Multiple range conditions
       IF (CUSTOMER-AGE >= 18 AND CUSTOMER-AGE <= 30)
           OR (CUSTOMER-AGE >= 50 AND CUSTOMER-AGE <= 65)
           DISPLAY 'Target age group'
       END-IF.

Check if values fall within specific ranges using AND operators. Use >= and <= for inclusive ranges. Multiple range conditions can be combined with OR for complex business rules.

Comparison with Variables

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       WORKING-STORAGE SECTION.
       01 COMPARISON-VARIABLES.
           05 MIN-BALANCE PIC 9(9)V99 VALUE 1000.
           05 MAX-BALANCE PIC 9(9)V99 VALUE 100000.
           05 TARGET-STATUS PIC X VALUE 'A'.
       
       PROCEDURE DIVISION.
       *> Compare with variables
       IF CUSTOMER-BALANCE >= MIN-BALANCE AND CUSTOMER-BALANCE <= MAX-BALANCE
           DISPLAY 'Balance within acceptable range'
       END-IF.
       
       IF CUSTOMER-STATUS = TARGET-STATUS
           DISPLAY 'Customer has target status'
       END-IF.
       
       *> Dynamic comparison values
       IF CURRENT-DATE > CUTOFF-DATE
           MOVE 'NEW-RULES' TO RULE-VERSION
       ELSE
           MOVE 'OLD-RULES' TO RULE-VERSION
       END-IF.

Compare data with variables for flexible business rules. Use working storage variables for comparison values that may change. This makes programs more maintainable and configurable.

Comparison Best Practices

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       *> Clear, readable comparisons
       IF CUSTOMER-BALANCE > HIGH-BALANCE-THRESHOLD
           PERFORM PROCESS-HIGH-BALANCE-CUSTOMER
       ELSE IF CUSTOMER-BALANCE > MEDIUM-BALANCE-THRESHOLD
           PERFORM PROCESS-MEDIUM-BALANCE-CUSTOMER
       ELSE
           PERFORM PROCESS-LOW-BALANCE-CUSTOMER
       END-IF.
       
       *> Use meaningful variable names
       IF ACCOUNT-STATUS = ACTIVE-STATUS
           PERFORM PROCESS-ACTIVE-ACCOUNT
       END-IF.
       
       *> Document complex logic
       *> Check if customer is eligible for premium service
       IF CUSTOMER-TYPE = PREMIUM-TYPE AND CUSTOMER-BALANCE >= PREMIUM-THRESHOLD
           PERFORM PROCESS-PREMIUM-CUSTOMER
       END-IF.

Follow best practices: use clear, readable comparisons; choose meaningful variable names; document complex logic with comments; and structure comparisons for easy understanding and maintenance.

Comparison Operations

Relational and comparison operators

Conditional Logic

Decision making patterns