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COBOL Boolean Logic

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Introduction to Boolean Logic in COBOL

Boolean logic in COBOL forms the foundation of decision-making and program control flow. It enables programs to evaluate conditions, make choices, and execute different code paths based on logical criteria. Understanding boolean logic is essential for writing effective, maintainable COBOL programs.

Key components of COBOL boolean logic include:

  • Logical Operators: AND, OR, NOT for combining conditions
  • Relational Operators: =, <, >, <=, >=, NOT = for comparisons
  • Condition Names: Meaningful names for specific conditions
  • Complex Expressions: Nested logical operations
  • Short-Circuit Evaluation: Efficient condition processing

Basic Logical Operators

COBOL provides fundamental logical operators that enable complex decision-making based on multiple conditions.

AND Operator

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IDENTIFICATION DIVISION.
PROGRAM-ID. BOOLEAN-LOGIC-DEMO.
DATA DIVISION.
WORKING-STORAGE SECTION.
01 LOGICAL-TEST-DATA.
   05 WS-AGE                PIC 9(3) VALUE 25.
   05 WS-INCOME             PIC 9(8) VALUE 50000.
   05 WS-CREDIT-SCORE       PIC 9(3) VALUE 750.
   05 WS-EMPLOYMENT-YEARS   PIC 9(2) VALUE 3.
 
01 CONDITION-FLAGS.
   05 WS-AGE-ELIGIBLE       PIC X(1) VALUE 'N'.
      88 WS-AGE-OK          VALUE 'Y'.
      88 WS-AGE-NOT-OK      VALUE 'N'.
   05 WS-INCOME-ELIGIBLE    PIC X(1) VALUE 'N'.
      88 WS-INCOME-OK       VALUE 'Y'.
      88 WS-INCOME-NOT-OK   VALUE 'N'.
   05 WS-CREDIT-ELIGIBLE    PIC X(1) VALUE 'N'.
      88 WS-CREDIT-OK       VALUE 'Y'.
      88 WS-CREDIT-NOT-OK   VALUE 'N'.
 
PROCEDURE DIVISION.
    DISPLAY "=== Boolean Logic Demonstration ==="
    PERFORM DEMONSTRATE-AND-OPERATOR
    PERFORM DEMONSTRATE-OR-OPERATOR
    PERFORM DEMONSTRATE-NOT-OPERATOR
    PERFORM DEMONSTRATE-COMPLEX-EXPRESSIONS
    STOP RUN.
 
DEMONSTRATE-AND-OPERATOR.
    DISPLAY "=== AND Operator Demonstration ==="
    DISPLAY "Age: " WS-AGE
    DISPLAY "Income: " WS-INCOME
    DISPLAY "Credit Score: " WS-CREDIT-SCORE
    DISPLAY "Employment Years: " WS-EMPLOYMENT-YEARS
    
    * Test individual conditions
    IF WS-AGE >= 18
       SET WS-AGE-OK TO TRUE
       DISPLAY "Age condition: PASS"
    ELSE
       SET WS-AGE-NOT-OK TO TRUE
       DISPLAY "Age condition: FAIL"
    END-IF
    
    IF WS-INCOME >= 30000
       SET WS-INCOME-OK TO TRUE
       DISPLAY "Income condition: PASS"
    ELSE
       SET WS-INCOME-NOT-OK TO TRUE
       DISPLAY "Income condition: FAIL"
    END-IF
    
    IF WS-CREDIT-SCORE >= 700
       SET WS-CREDIT-OK TO TRUE
       DISPLAY "Credit condition: PASS"
    ELSE
       SET WS-CREDIT-NOT-OK TO TRUE
       DISPLAY "Credit condition: FAIL"
    END-IF
    
    * Combined AND condition
    IF WS-AGE >= 18 AND WS-INCOME >= 30000 AND WS-CREDIT-SCORE >= 700
       DISPLAY "Loan application: APPROVED (All conditions met)"
    ELSE
       DISPLAY "Loan application: DENIED (Not all conditions met)"
    END-IF.

OR Operator

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DEMONSTRATE-OR-OPERATOR.
    DISPLAY "=== OR Operator Demonstration ==="
    
    * Test OR conditions for alternative eligibility
    IF WS-AGE >= 65 OR WS-INCOME >= 100000 OR WS-CREDIT-SCORE >= 800
       DISPLAY "Premium loan program: ELIGIBLE (At least one condition met)"
    ELSE
       DISPLAY "Premium loan program: NOT ELIGIBLE (No conditions met)"
    END-IF
    
    * Multiple OR conditions
    IF WS-EMPLOYMENT-YEARS >= 5 OR WS-CREDIT-SCORE >= 750 OR WS-INCOME >= 75000
       DISPLAY "Fast-track approval: AVAILABLE"
    ELSE
       DISPLAY "Fast-track approval: NOT AVAILABLE"
    END-IF.

NOT Operator

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DEMONSTRATE-NOT-OPERATOR.
    DISPLAY "=== NOT Operator Demonstration ==="
    
    * Test NOT conditions
    IF NOT (WS-AGE < 18)
       DISPLAY "Adult applicant: YES"
    ELSE
       DISPLAY "Adult applicant: NO"
    END-IF
    
    IF NOT (WS-CREDIT-SCORE < 600)
       DISPLAY "Good credit standing: YES"
    ELSE
       DISPLAY "Good credit standing: NO"
    END-IF
    
    * Complex NOT condition
    IF NOT (WS-INCOME < 20000 AND WS-CREDIT-SCORE < 500)
       DISPLAY "Not in high-risk category: YES"
    ELSE
       DISPLAY "Not in high-risk category: NO"
    END-IF.

Complex Boolean Expressions

Complex boolean expressions combine multiple logical operators and conditions to create sophisticated decision-making logic.

Nested Logical Operations

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DEMONSTRATE-COMPLEX-EXPRESSIONS.
    DISPLAY "=== Complex Boolean Expressions ==="
    
    * Complex expression with parentheses
    IF (WS-AGE >= 18 AND WS-INCOME >= 30000) OR 
       (WS-CREDIT-SCORE >= 800 AND WS-EMPLOYMENT-YEARS >= 2)
       DISPLAY "Loan eligibility: APPROVED (Complex criteria met)"
    ELSE
       DISPLAY "Loan eligibility: DENIED (Complex criteria not met)"
    END-IF
    
    * Multiple levels of nesting
    IF WS-AGE >= 18 AND 
       (WS-INCOME >= 50000 OR WS-CREDIT-SCORE >= 750) AND
       NOT (WS-CREDIT-SCORE < 500)
       DISPLAY "Premium loan: ELIGIBLE"
    ELSE
       DISPLAY "Premium loan: NOT ELIGIBLE"
    END-IF
    
    * Business logic with complex conditions
    IF (WS-AGE >= 25 AND WS-AGE <= 65) AND
       (WS-INCOME >= 40000 OR WS-CREDIT-SCORE >= 700) AND
       (WS-EMPLOYMENT-YEARS >= 1 OR WS-CREDIT-SCORE >= 800)
       DISPLAY "Standard loan: APPROVED"
    ELSE
       IF WS-AGE >= 18 AND WS-INCOME >= 20000 AND WS-CREDIT-SCORE >= 600
          DISPLAY "Basic loan: APPROVED"
       ELSE
          DISPLAY "No loan products available"
       END-IF
    END-IF.

Condition Names and Meaningful Logic

Condition names provide meaningful identifiers for specific conditions, making code more readable and maintainable.

Using Condition Names

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IDENTIFICATION DIVISION.
PROGRAM-ID. CONDITION-NAMES-DEMO.
DATA DIVISION.
WORKING-STORAGE SECTION.
01 CUSTOMER-DATA.
   05 CUSTOMER-AGE          PIC 9(3).
      88 MINOR-AGE          VALUE 0 THRU 17.
      88 ADULT-AGE          VALUE 18 THRU 64.
      88 SENIOR-AGE         VALUE 65 THRU 120.
   
   05 CUSTOMER-INCOME        PIC 9(8).
      88 LOW-INCOME         VALUE 0 THRU 29999.
      88 MEDIUM-INCOME      VALUE 30000 THRU 74999.
      88 HIGH-INCOME        VALUE 75000 THRU 999999.
   
   05 CUSTOMER-CREDIT-SCORE  PIC 9(3).
      88 POOR-CREDIT        VALUE 0 THRU 599.
      88 FAIR-CREDIT        VALUE 600 THRU 699.
      88 GOOD-CREDIT        VALUE 700 THRU 799.
      88 EXCELLENT-CREDIT   VALUE 800 THRU 850.
 
01 LOAN-DECISION.
   05 LOAN-STATUS           PIC X(10).
   05 LOAN-AMOUNT           PIC 9(8).
   05 INTEREST-RATE         PIC 9V99.
 
PROCEDURE DIVISION.
    DISPLAY "=== Condition Names Demonstration ==="
    PERFORM INITIALIZE-CUSTOMER-DATA
    PERFORM EVALUATE-LOAN-ELIGIBILITY
    STOP RUN.
 
INITIALIZE-CUSTOMER-DATA.
    MOVE 35 TO CUSTOMER-AGE
    MOVE 65000 TO CUSTOMER-INCOME
    MOVE 720 TO CUSTOMER-CREDIT-SCORE
    
    DISPLAY "Customer Age: " CUSTOMER-AGE
    DISPLAY "Customer Income: " CUSTOMER-INCOME
    DISPLAY "Customer Credit Score: " CUSTOMER-CREDIT-SCORE.
 
EVALUATE-LOAN-ELIGIBILITY.
    DISPLAY "=== Loan Eligibility Evaluation ==="
    
    * Use condition names for clear logic
    IF ADULT-AGE AND MEDIUM-INCOME AND GOOD-CREDIT
       MOVE "APPROVED" TO LOAN-STATUS
       MOVE 50000 TO LOAN-AMOUNT
       MOVE 5.25 TO INTEREST-RATE
       DISPLAY "Loan Status: " LOAN-STATUS
       DISPLAY "Loan Amount: $" LOAN-AMOUNT
       DISPLAY "Interest Rate: " INTEREST-RATE "%"
    ELSE
       IF ADULT-AGE AND HIGH-INCOME AND EXCELLENT-CREDIT
          MOVE "APPROVED" TO LOAN-STATUS
          MOVE 100000 TO LOAN-AMOUNT
          MOVE 4.75 TO INTEREST-RATE
          DISPLAY "Premium Loan Status: " LOAN-STATUS
          DISPLAY "Premium Loan Amount: $" LOAN-AMOUNT
          DISPLAY "Premium Interest Rate: " INTEREST-RATE "%"
       ELSE
          IF ADULT-AGE AND (MEDIUM-INCOME OR HIGH-INCOME) AND FAIR-CREDIT
             MOVE "CONDITIONAL" TO LOAN-STATUS
             MOVE 25000 TO LOAN-AMOUNT
             MOVE 7.50 TO INTEREST-RATE
             DISPLAY "Conditional Loan Status: " LOAN-STATUS
             DISPLAY "Conditional Loan Amount: $" LOAN-AMOUNT
             DISPLAY "Conditional Interest Rate: " INTEREST-RATE "%"
          ELSE
             MOVE "DENIED" TO LOAN-STATUS
             DISPLAY "Loan Status: " LOAN-STATUS
             DISPLAY "Reason: Eligibility criteria not met"
          END-IF
       END-IF
    END-IF.

EVALUATE Statement for Complex Logic

The EVALUATE statement provides a powerful way to handle complex boolean logic with multiple conditions and outcomes.

EVALUATE Statement Implementation

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IDENTIFICATION DIVISION.
PROGRAM-ID. EVALUATE-STATEMENT-DEMO.
DATA DIVISION.
WORKING-STORAGE SECTION.
01 BUSINESS-RULES.
   05 CUSTOMER-TYPE         PIC X(1).
      88 INDIVIDUAL         VALUE 'I'.
      88 BUSINESS           VALUE 'B'.
      88 NON-PROFIT         VALUE 'N'.
   
   05 ACCOUNT-BALANCE        PIC S9(8)V99.
      88 ZERO-BALANCE       VALUE 0.
      88 LOW-BALANCE        VALUE 0.01 THRU 999.99.
      88 MEDIUM-BALANCE     VALUE 1000.00 THRU 9999.99.
      88 HIGH-BALANCE       VALUE 10000.00 THRU 999999.99.
   
   05 TRANSACTION-AMOUNT     PIC S9(7)V99.
      88 SMALL-TRANSACTION  VALUE 0.01 THRU 99.99.
      88 MEDIUM-TRANSACTION VALUE 100.00 THRU 999.99.
      88 LARGE-TRANSACTION  VALUE 1000.00 THRU 99999.99.
 
01 PROCESSING-RESULTS.
   05 PROCESSING-FEE         PIC S9(3)V99.
   05 PROCESSING-TIME        PIC 9(2).
   05 APPROVAL-REQUIRED     PIC X(1).
      88 APPROVAL-NEEDED    VALUE 'Y'.
      88 NO-APPROVAL-NEEDED VALUE 'N'.
 
PROCEDURE DIVISION.
    DISPLAY "=== EVALUATE Statement Demonstration ==="
    PERFORM INITIALIZE-BUSINESS-DATA
    PERFORM PROCESS-TRANSACTION-WITH-EVALUATE
    STOP RUN.
 
INITIALIZE-BUSINESS-DATA.
    MOVE 'I' TO CUSTOMER-TYPE
    MOVE 5000.00 TO ACCOUNT-BALANCE
    MOVE 250.00 TO TRANSACTION-AMOUNT
    
    DISPLAY "Customer Type: " CUSTOMER-TYPE
    DISPLAY "Account Balance: $" ACCOUNT-BALANCE
    DISPLAY "Transaction Amount: $" TRANSACTION-AMOUNT.
 
PROCESS-TRANSACTION-WITH-EVALUATE.
    DISPLAY "=== Processing Transaction with EVALUATE ==="
    
    EVALUATE TRUE
       WHEN INDIVIDUAL AND HIGH-BALANCE AND SMALL-TRANSACTION
          MOVE 0.00 TO PROCESSING-FEE
          MOVE 1 TO PROCESSING-TIME
          SET NO-APPROVAL-NEEDED TO TRUE
          DISPLAY "Processing: Individual, High Balance, Small Transaction"
          DISPLAY "Fee: $" PROCESSING-FEE
          DISPLAY "Time: " PROCESSING-TIME " minutes"
          DISPLAY "Approval Required: " APPROVAL-REQUIRED
       
       WHEN INDIVIDUAL AND MEDIUM-BALANCE AND MEDIUM-TRANSACTION
          MOVE 2.50 TO PROCESSING-FEE
          MOVE 5 TO PROCESSING-TIME
          SET NO-APPROVAL-NEEDED TO TRUE
          DISPLAY "Processing: Individual, Medium Balance, Medium Transaction"
          DISPLAY "Fee: $" PROCESSING-FEE
          DISPLAY "Time: " PROCESSING-TIME " minutes"
          DISPLAY "Approval Required: " APPROVAL-REQUIRED
       
       WHEN BUSINESS AND HIGH-BALANCE AND LARGE-TRANSACTION
          MOVE 5.00 TO PROCESSING-FEE
          MOVE 15 TO PROCESSING-TIME
          SET APPROVAL-NEEDED TO TRUE
          DISPLAY "Processing: Business, High Balance, Large Transaction"
          DISPLAY "Fee: $" PROCESSING-FEE
          DISPLAY "Time: " PROCESSING-TIME " minutes"
          DISPLAY "Approval Required: " APPROVAL-REQUIRED
       
       WHEN NON-PROFIT AND MEDIUM-BALANCE
          MOVE 0.00 TO PROCESSING-FEE
          MOVE 3 TO PROCESSING-TIME
          SET NO-APPROVAL-NEEDED TO TRUE
          DISPLAY "Processing: Non-Profit, Medium Balance"
          DISPLAY "Fee: $" PROCESSING-FEE
          DISPLAY "Time: " PROCESSING-TIME " minutes"
          DISPLAY "Approval Required: " APPROVAL-REQUIRED
       
       WHEN OTHER
          MOVE 10.00 TO PROCESSING-FEE
          MOVE 30 TO PROCESSING-TIME
          SET APPROVAL-NEEDED TO TRUE
          DISPLAY "Processing: Special Case"
          DISPLAY "Fee: $" PROCESSING-FEE
          DISPLAY "Time: " PROCESSING-TIME " minutes"
          DISPLAY "Approval Required: " APPROVAL-REQUIRED
    END-EVALUATE.

Performance Optimization of Boolean Logic

Optimizing boolean logic performance involves structuring conditions for efficient evaluation and minimal processing overhead.

Short-Circuit Evaluation

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IDENTIFICATION DIVISION.
PROGRAM-ID. BOOLEAN-PERFORMANCE-DEMO.
DATA DIVISION.
WORKING-STORAGE SECTION.
01 PERFORMANCE-TEST-DATA.
   05 WS-TEST-VALUE-1       PIC X(10) VALUE "TEST1".
   05 WS-TEST-VALUE-2       PIC X(10) VALUE "TEST2".
   05 WS-TEST-VALUE-3       PIC X(10) VALUE "TEST3".
   05 WS-NUMERIC-VALUE      PIC 9(5) VALUE 1000.
 
01 PERFORMANCE-METRICS.
   05 WS-EVALUATION-COUNT   PIC 9(6) VALUE ZERO.
   05 WS-START-TIME         PIC 9(14).
   05 WS-END-TIME           PIC 9(14).
   05 WS-PROCESSING-TIME    PIC 9(6).
 
PROCEDURE DIVISION.
    DISPLAY "=== Boolean Logic Performance Demo ==="
    PERFORM DEMONSTRATE-SHORT-CIRCUIT-EVALUATION
    PERFORM DEMONSTRATE-CONDITION-ORDERING
    PERFORM DEMONSTRATE-PERFORMANCE-OPTIMIZATION
    STOP RUN.
 
DEMONSTRATE-SHORT-CIRCUIT-EVALUATION.
    DISPLAY "=== Short-Circuit Evaluation ==="
    
    * Demonstrate short-circuit evaluation
    IF WS-TEST-VALUE-1 = "TEST1" AND WS-TEST-VALUE-2 = "TEST2" AND WS-TEST-VALUE-3 = "TEST3"
       DISPLAY "All conditions evaluated: TRUE"
    ELSE
       DISPLAY "Short-circuit occurred: FALSE"
    END-IF
    
    * Test short-circuit with false condition first
    IF WS-TEST-VALUE-1 = "WRONG" AND WS-TEST-VALUE-2 = "TEST2" AND WS-TEST-VALUE-3 = "TEST3"
       DISPLAY "This should not execute"
    ELSE
       DISPLAY "Short-circuit prevented unnecessary evaluation"
    END-IF.
 
DEMONSTRATE-CONDITION-ORDERING.
    DISPLAY "=== Condition Ordering Optimization ==="
    
    * Order conditions by frequency/likelihood
    IF WS-NUMERIC-VALUE > 0 AND WS-NUMERIC-VALUE < 10000 AND WS-NUMERIC-VALUE MOD 2 = 0
       DISPLAY "Optimized condition order: TRUE"
    ELSE
       DISPLAY "Optimized condition order: FALSE"
    END-IF.
 
DEMONSTRATE-PERFORMANCE-OPTIMIZATION.
    DISPLAY "=== Performance Optimization ==="
    
    ACCEPT WS-START-TIME FROM DATE YYYYMMDD
    ACCEPT WS-START-TIME(9:6) FROM TIME
    
    * Performance test with optimized conditions
    PERFORM VARYING WS-EVALUATION-COUNT FROM 1 BY 1
       UNTIL WS-EVALUATION-COUNT > 100000
       
       * Use most likely conditions first
       IF WS-NUMERIC-VALUE > 0 AND WS-NUMERIC-VALUE < 10000 AND WS-NUMERIC-VALUE MOD 2 = 0
          CONTINUE
       END-IF
    END-PERFORM
    
    ACCEPT WS-END-TIME FROM DATE YYYYMMDD
    ACCEPT WS-END-TIME(9:6) FROM TIME
    
    COMPUTE WS-PROCESSING-TIME = WS-END-TIME - WS-START-TIME
    
    DISPLAY "Performance test completed"
    DISPLAY "Evaluations: " WS-EVALUATION-COUNT
    DISPLAY "Processing time: " WS-PROCESSING-TIME " milliseconds".

Best Practices for Boolean Logic

Following best practices ensures clear, efficient, and maintainable boolean logic in COBOL programs.

Design Principles

  • Use condition names for meaningful, readable code
  • Order conditions by frequency or likelihood
  • Use parentheses to clarify complex expressions
  • Avoid deeply nested conditions when possible
  • Consider using EVALUATE for complex decision trees

Performance Guidelines

  • Leverage short-circuit evaluation for efficiency
  • Place most likely conditions first
  • Minimize complex nested expressions
  • Use appropriate data types for comparisons
  • Profile performance-critical boolean logic

Maintenance Considerations

  • Document complex boolean logic clearly
  • Use consistent naming conventions
  • Test all logical paths thoroughly
  • Keep conditions simple and focused
  • Regular review and refactoring of complex logic

FAQ

What is boolean logic in COBOL?

Boolean logic in COBOL refers to the logical operations and condition testing used for decision making in programs. It includes logical operators like AND, OR, NOT, and complex condition expressions that evaluate to true or false values.

What are the logical operators in COBOL?

COBOL provides several logical operators: AND (logical AND), OR (logical OR), NOT (logical NOT), and complex combinations. These operators are used in IF statements, EVALUATE statements, and condition expressions to make decisions based on multiple criteria.

How do you use complex boolean expressions in COBOL?

Complex boolean expressions in COBOL use parentheses for grouping, multiple logical operators, and can combine relational operators with logical operators. Examples include (A > B) AND (C < D) OR (E = F) for sophisticated decision making.

What are condition names in COBOL?

Condition names in COBOL are 88-level data items that define specific values or ranges for a variable. They provide meaningful names for conditions and make code more readable, such as defining HIGH-VALUE, LOW-VALUE, or specific business conditions.

How do you optimize boolean logic performance in COBOL?

Boolean logic performance optimization includes using short-circuit evaluation, ordering conditions by frequency, using appropriate data types, minimizing complex expressions, and structuring conditions for optimal execution paths.

Conditional Logic

Conditional processing and decision making in COBOL

Condition Names

Using condition names for readable code

Control Structures

Program control and flow structures

Performance Optimization

Optimizing COBOL program performance