COBOL Tutorial

COBOL TRUE - Quick Reference

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Overview

TRUE is used in conditional logic, most notably in EVALUATE TRUE, to simplify multi-branch decision structures. Support for boolean literals and types varies by compiler.

Common Patterns

EVALUATE TRUE - Case-like branching by conditions
IF conditions - Standard conditional expressions
88-level flags - Simulated booleans with condition-names

Syntax and Usage

EVALUATE TRUE

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* EVALUATE TRUE for multi-branch logic
       EVALUATE TRUE
           WHEN CUSTOMER-AGE < 18
               PERFORM MINOR-PROCESSING
           WHEN CUSTOMER-AGE >= 18 AND CUSTOMER-AGE < 65
               PERFORM ADULT-PROCESSING
           WHEN OTHER
               PERFORM SENIOR-PROCESSING
       END-EVALUATE

88-Level Condition Example

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* 88-level conditions as booleans
       01  FLAGS.
           05  PAID-FLAG           PIC X VALUE 'N'.
               88 PAID                        VALUE 'Y'.
               88 NOT-PAID                    VALUE 'N'.
       
       IF NOT-PAID
           PERFORM SEND-REMINDER
       END-IF
       
       SET PAID TO TRUE
       IF PAID
           PERFORM POST-RECEIPT
       END-IF

Best Practices

Prefer readability - Use EVALUATE TRUE to reduce nesting
Use WHEN OTHER - Provide a default branch
Avoid overlap - Ensure WHEN conditions are mutually exclusive or ordered
Abstract flags - Use 88-levels for clarity when booleans are unavailable

TRUE Quick Reference

Aspect	Description	Example
Multi-branch	EVALUATE TRUE	WHEN condition-1 ... WHEN OTHER
Flags	88-level condition-names	SET cond TO TRUE
Portability	Boolean support varies	Use 88-levels if needed

Test Your Knowledge

1. What does EVALUATE TRUE enable?

Arithmetic comparisons only
A case-like structure based on conditions that evaluate to true
File handling only
Screen handling only

2. Which of the following is a valid use of TRUE?

As a numeric literal in COMPUTE
As a condition in EVALUATE TRUE and IF statements (dialect dependent for boolean types)
As a file status value
As a PICTURE symbol

3. What is a common replacement when boolean types are not available?

Use "YES/NO" or 88-level condition names for flags
Use COMP-1 for flags
Use REPORT SECTION
Use ENVIRONMENT DIVISION

4. What should you avoid in EVALUATE TRUE?

Combining multiple WHEN clauses
Using overlapping conditions that can both be true
Using default WHEN OTHER
Using nested EVALUATE

5. What is a best practice for complex conditionals?

Prefer deeply nested IFs
Use EVALUATE TRUE for clarity and include WHEN OTHER
Use GO TO statements
Avoid comments and documentation

Frequently Asked Questions

Related Concepts

Conditional Execution

Patterns for IF and EVALUATE.

EVALUATE

Multi-branch decision structures.

Condition Names (88)

Using condition-names as flags.

TRAILING-SIGN TYPE