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COBOL Tutorial

COBOL ELSE Clause

The ELSE clause in COBOL provides an alternative execution path when the condition in an IF statement is false. ELSE is an essential component of conditional logic, allowing programs to handle both true and false cases explicitly. Understanding ELSE is fundamental to writing complete conditional logic in COBOL programs.

ELSE makes conditional logic complete by ensuring that one path always executes - either the IF path when the condition is true, or the ELSE path when the condition is false. This is crucial for handling all possible scenarios and ensuring programs behave correctly in all cases.

Understanding ELSE Clause

The ELSE clause:

  • Provides alternative execution: Executes when the IF condition is false
  • Completes conditional logic: Ensures one path always executes
  • Handles false cases: Allows explicit handling of when conditions aren't met
  • Is optional: Not required but recommended when you need to handle false cases

Basic ELSE Syntax

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       IF condition
           statements-for-true-case
       ELSE
           statements-for-false-case
       END-IF

When the condition is true, statements between IF and ELSE execute. When false, statements between ELSE and END-IF execute.

Simple ELSE Example

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       WORKING-STORAGE SECTION.
       01  AMOUNT              PIC 9(5).
       
       PROCEDURE DIVISION.
       MAIN-LOGIC.
           IF AMOUNT > 1000
               DISPLAY "Large amount: " AMOUNT
               PERFORM PROCESS-LARGE-AMOUNT
           ELSE
               DISPLAY "Small amount: " AMOUNT
               PERFORM PROCESS-SMALL-AMOUNT
           END-IF
           
           STOP RUN.

This example demonstrates basic ELSE usage - handling both large and small amounts explicitly.

ELSE with Nested IF

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       WORKING-STORAGE SECTION.
       01  STATUS-FLAG         PIC X(1).
       01  PROCESS-TYPE        PIC X(1).
       
       PROCEDURE DIVISION.
       MAIN-LOGIC.
           IF STATUS-FLAG = "A"
               IF PROCESS-TYPE = "B"
                   DISPLAY "Active batch processing"
                   PERFORM ACTIVE-BATCH
               ELSE
                   DISPLAY "Active non-batch processing"
                   PERFORM ACTIVE-NON-BATCH
               END-IF
           ELSE
               DISPLAY "Inactive status"
               PERFORM INACTIVE-PROCESSING
           END-IF
           
           STOP RUN.

Nested IF statements can each have their own ELSE clauses. Proper indentation and END-IF matching is crucial.

ELSE Without IF (Not Allowed)

ELSE must always be paired with an IF statement. You cannot use ELSE alone. Every ELSE must have a corresponding IF before it.

IF Without ELSE

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       PROCEDURE DIVISION.
       MAIN-LOGIC.
           IF AMOUNT > 0
               DISPLAY "Positive amount: " AMOUNT
               PERFORM PROCESS-POSITIVE
           END-IF
           
           *> If AMOUNT <= 0, nothing happens - execution continues
           DISPLAY "Processing complete"
           STOP RUN.

IF without ELSE is valid when you only need to handle the true case. The false case results in no action.

Complete ELSE Example

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       IDENTIFICATION DIVISION.
       PROGRAM-ID. ELSE-EXAMPLE.
       
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01  CUSTOMER-BALANCE    PIC S9(8)V99.
       01  TRANSACTION-AMOUNT  PIC S9(7)V99.
       01  NEW-BALANCE         PIC S9(8)V99.
       
       PROCEDURE DIVISION.
       MAIN-LOGIC.
           DISPLAY "=== Account Transaction Processing ==="
           
           MOVE 1000.00 TO CUSTOMER-BALANCE
           MOVE -500.00 TO TRANSACTION-AMOUNT
           
           ADD TRANSACTION-AMOUNT TO CUSTOMER-BALANCE GIVING NEW-BALANCE
           
           IF NEW-BALANCE >= 0
               DISPLAY "Transaction approved"
               DISPLAY "New balance: $" NEW-BALANCE
               MOVE NEW-BALANCE TO CUSTOMER-BALANCE
           ELSE
               DISPLAY "Transaction declined - insufficient funds"
               DISPLAY "Current balance: $" CUSTOMER-BALANCE
               DISPLAY "Transaction amount: $" FUNCTION ABS(TRANSACTION-AMOUNT)
               DISPLAY "Required balance: $" FUNCTION ABS(NEW-BALANCE)
           END-IF
           
           STOP RUN.

This complete example demonstrates ELSE in a practical account transaction scenario, handling both approved and declined transactions.

Best Practices for ELSE

  • Use ELSE when needed: When you must handle the false case
  • Keep ELSE focused: ELSE clauses should be clear and focused
  • Proper indentation: Indent ELSE clauses for readability
  • Match IF with END-IF: Ensure proper pairing
  • Avoid deep nesting: Consider EVALUATE for complex multi-way selection
  • Test both paths: Test both IF and ELSE execution paths
  • Use meaningful conditions: Make conditions clear and readable

Explain Like I'm 5: ELSE

Think of ELSE like choosing between two paths:

  • IF it's sunny - go to the park (first path)
  • ELSE - stay inside (second path)

So ELSE is like having a backup plan - if the first condition isn't true, you do something else!

Test Your Knowledge

1. What does the ELSE clause do?

  • Executes when the IF condition is true
  • Executes when the IF condition is false
  • Always executes
  • Never executes

2. Is ELSE required in an IF statement?

  • Yes, always required
  • No, it's optional
  • Only for nested IFs
  • Only in certain COBOL versions

3. What happens if IF condition is false and there's no ELSE?

  • Program crashes
  • No statements in IF block execute, execution continues after END-IF
  • First statement after IF executes
  • Last statement before END-IF executes

4. Can you nest IF statements with ELSE?

  • No, nesting is not allowed
  • Yes, each IF can have its own ELSE
  • Only one level of nesting
  • Only without ELSE

5. Where does ELSE appear in an IF statement?

  • Before IF
  • After IF condition, before statements
  • After the true-case statements, before END-IF
  • After END-IF

6. What is the relationship between ELSE and WHEN OTHER?

  • They are the same
  • ELSE is for IF statements, WHEN OTHER is for EVALUATE
  • ELSE is for EVALUATE, WHEN OTHER is for IF
  • They cannot be used together