COBOL Tutorial

COBOL DEBUG-LINE Clause - Quick Reference

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Overview

The DEBUG-LINE clause is used to define debugging data items that track the current line number being executed during program debugging. This clause is part of COBOL's debugging facility and provides essential line-by-line execution tracking for program analysis and troubleshooting.

Purpose and Usage

Line number tracking - Track current execution line
Program flow analysis - Monitor execution path
Debugging support - Identify execution location
Error location - Pinpoint where errors occur
Development aid - Support program development

Line Tracking Concept

Program Execution: [Line 1] → [Line 2] → [Line 3] → ...

DEBUG-LINE: [Current Line Number]

Debugging Info: [Line 1: Variable A = 10]

Tracks exact line being executed

DEBUG-LINE provides real-time tracking of the current execution line.

Syntax

The DEBUG-LINE clause follows specific syntax patterns and is typically used at the 77 level for independent debugging data items.

Basic Syntax

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* Basic DEBUG-LINE clause syntax
77 debug-line-name DEBUG-LINE.
 
* Examples
77 DEBUG-CURRENT-LINE DEBUG-LINE.
77 DEBUG-LINE-NUMBER DEBUG-LINE.
77 DEBUG-EXEC-LINE DEBUG-LINE.
 
* Complete example with data description
77 DEBUG-CURRENT-LINE DEBUG-LINE PIC 9(5).
77 DEBUG-LINE-NUMBER DEBUG-LINE PIC 9(6).
77 DEBUG-EXEC-LINE DEBUG-LINE COMP.
 
* Usage in program
PROCEDURE DIVISION.
    * Display current line number
    DISPLAY "Executing line: " DEBUG-CURRENT-LINE
    
    * Store line number for later use
    MOVE DEBUG-CURRENT-LINE TO SAVED-LINE-NUMBER
    
    * Check if at specific line
    IF DEBUG-CURRENT-LINE = 100
        DISPLAY "Reached line 100"
    END-IF

DEBUG-LINE is typically used at the 77 level for independent debugging items.

Data Type Considerations

Data Type	Size	Use Case
PIC 9(5)	5 digits	Programs up to 99,999 lines
PIC 9(6)	6 digits	Large programs up to 999,999 lines
COMP	Binary	Efficient storage and processing
COMP-3	Packed decimal	Mainframe compatibility

Debugging Mode Requirements

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* Enabling debugging mode for DEBUG-LINE
* Compiler option
* Example: cobc -fdebug program.cob
 
* Runtime debugging activation
* Set environment variable
* Example: COBOL_DEBUG=1 ./program
 
* Program-level debugging declaration
PROGRAM-ID. DEBUG-PROGRAM.
ENVIRONMENT DIVISION.
CONFIGURATION SECTION.
SPECIAL-NAMES.
    DEBUGGING MODE IS ON.
 
DATA DIVISION.
WORKING-STORAGE SECTION.
77 DEBUG-CURRENT-LINE DEBUG-LINE PIC 9(5).

DEBUG-LINE requires debugging mode to be enabled for line tracking functionality.

Common Use Cases

DEBUG-LINE is commonly used in specific debugging scenarios where line-by-line execution tracking is needed for program analysis.

Program Flow Tracking

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* Tracking program execution flow
77 DEBUG-CURRENT-LINE DEBUG-LINE PIC 9(5).
 
PROCEDURE DIVISION.
    DISPLAY "Starting at line: " DEBUG-CURRENT-LINE
    
    PERFORM PROCESS-DATA
    DISPLAY "After PROCESS-DATA at line: " DEBUG-CURRENT-LINE
    
    PERFORM VALIDATE-DATA
    DISPLAY "After VALIDATE-DATA at line: " DEBUG-CURRENT-LINE
    
    PERFORM WRITE-RESULTS
    DISPLAY "After WRITE-RESULTS at line: " DEBUG-CURRENT-LINE
    
    DISPLAY "Program completed at line: " DEBUG-CURRENT-LINE

Track which sections of the program are being executed.

Error Location Identification

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* Identifying where errors occur
77 DEBUG-CURRENT-LINE DEBUG-LINE PIC 9(5).
77 ERROR-LINE-NUMBER PIC 9(5).
 
PROCEDURE DIVISION.
    * File processing with error tracking
    OPEN INPUT CUSTOMER-FILE
    IF FILE-STATUS NOT = "00"
        MOVE DEBUG-CURRENT-LINE TO ERROR-LINE-NUMBER
        DISPLAY "File open error at line: " ERROR-LINE-NUMBER
        DISPLAY "File status: " FILE-STATUS
    END-IF
    
    * Read processing with error tracking
    READ CUSTOMER-FILE
    IF FILE-STATUS NOT = "00"
        MOVE DEBUG-CURRENT-LINE TO ERROR-LINE-NUMBER
        DISPLAY "Read error at line: " ERROR-LINE-NUMBER
        DISPLAY "File status: " FILE-STATUS
    END-IF

Identify the exact line where errors occur for easier debugging.

Conditional Debugging

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* Conditional debugging based on line numbers
77 DEBUG-CURRENT-LINE DEBUG-LINE PIC 9(5).
 
PROCEDURE DIVISION.
    * Only show debugging info for specific line ranges
    IF DEBUG-CURRENT-LINE >= 100 AND DEBUG-CURRENT-LINE <= 200
        DISPLAY "Debug info at line: " DEBUG-CURRENT-LINE
        DISPLAY "Variable A = " VARIABLE-A
        DISPLAY "Variable B = " VARIABLE-B
    END-IF
    
    * Break execution at specific line
    IF DEBUG-CURRENT-LINE = 150
        DISPLAY "Breakpoint reached at line 150"
        * Add breakpoint logic here
    END-IF
    
    * Track execution frequency
    IF DEBUG-CURRENT-LINE = 75
        ADD 1 TO EXECUTION-COUNT
        DISPLAY "Line 75 executed " EXECUTION-COUNT " times"
    END-IF

Use line numbers to implement conditional debugging logic.

Best Practices and Tips

Following these best practices ensures effective use of the DEBUG-LINE clause for program debugging and line tracking.

DEBUG-LINE Design Principles

Choose appropriate size - Select data type that accommodates your program size
Use meaningful names - Choose descriptive names for debugging line items
Minimize overhead - Don\'t overuse line tracking to avoid performance impact
Document line ranges - Document which line ranges are important for debugging
Consider production impact - Remember that line tracking can affect performance
Test debugging functionality - Verify that line tracking works correctly

Common Pitfalls to Avoid

Pitfall	Problem	Solution
Insufficient field size	Line numbers overflow	Choose appropriate PIC size for program
Overuse in production	Performance degradation	Use conditional compilation or separate versions
Not enabling debug mode	No line tracking information	Ensure debugging mode is properly enabled
Poor naming conventions	Confusing debugging output	Use clear, descriptive names
Not documenting usage	Difficult to understand line tracking	Document all line tracking items and their purpose

Performance Considerations

Line tracking overhead - DEBUG-LINE adds runtime overhead when active
Memory usage - Line tracking items consume additional memory
I/O impact - Line tracking output may affect I/O performance
Production considerations - Disable line tracking in production environments
Selective tracking - Use conditional logic for selective line tracking
Debugging levels - Consider different levels of line tracking detail

When to Use DEBUG-LINE

Use Case	DEBUG-LINE Suitability	Reasoning
Development debugging	Excellent	Essential for line-by-line debugging
Complex program logic	Good	Helps track complex execution paths
Error investigation	Good	Provides exact error location
Production monitoring	Poor	Performance impact outweighs benefits
Simple programs	Poor	Unnecessary overhead for simple logic

DEBUG-LINE Clause Quick Reference

Usage	Syntax	Example
Basic line tracking	77 debug-line-name DEBUG-LINE	77 DEBUG-LINE DEBUG-LINE
With data description	77 debug-line-name DEBUG-LINE PIC...	77 DEBUG-LINE DEBUG-LINE PIC 9(5)
Multiple line trackers	Multiple 77 items with DEBUG-LINE	77 DEBUG1 DEBUG-LINE 77 DEBUG2 DEBUG-LINE
Numeric line tracking	77 debug-line-name DEBUG-LINE PIC 9(n)	77 DEBUG-LINE DEBUG-LINE PIC 9(6)
Binary line tracking	77 debug-line-name DEBUG-LINE COMP	77 DEBUG-LINE DEBUG-LINE COMP

Test Your Knowledge

1. What is the primary purpose of the DEBUG-LINE clause in COBOL?

To define data types
To track program execution line numbers during debugging
To control file operations
To perform calculations

2. At what level is the DEBUG-LINE clause typically used?

01 level only
88 level only
77 level only
Any level except 01

3. What information does DEBUG-LINE provide during debugging?

Only variable names
Only program flow
Current line number being executed
Only error messages

4. When is DEBUG-LINE most useful?

During production runs
During program development and debugging
Only during compilation
Only during program termination

5. How does DEBUG-LINE relate to program debugging?

They are completely independent
DEBUG-LINE provides essential line tracking for debugging
DEBUG-LINE overrides other debugging features
They serve the same purpose

COBOL Tutorial

COBOL DEBUG-LINE Clause - Quick Reference

Overview

Purpose and Usage

Line Tracking Concept

Syntax

Basic Syntax

Data Type Considerations

Debugging Mode Requirements

Common Use Cases

Program Flow Tracking

Error Location Identification

Conditional Debugging

Best Practices and Tips

DEBUG-LINE Design Principles

Common Pitfalls to Avoid

Performance Considerations

When to Use DEBUG-LINE

DEBUG-LINE Clause Quick Reference

Test Your Knowledge

Frequently Asked Questions

Related Concepts

DEBUG-ITEM Clause

DEBUGGING MODE

Data Description Entries

Working-Storage Section

Error Handling

Related Pages

COBOL Tutorial

COBOL DEBUG-LINE Clause - Quick Reference

Overview

Purpose and Usage

Line Tracking Concept

Syntax

Basic Syntax

Data Type Considerations

Debugging Mode Requirements

Common Use Cases

Program Flow Tracking

Error Location Identification

Conditional Debugging

Best Practices and Tips

DEBUG-LINE Design Principles

Common Pitfalls to Avoid

Performance Considerations

When to Use DEBUG-LINE

DEBUG-LINE Clause Quick Reference

Test Your Knowledge

Frequently Asked Questions

What is the difference between DEBUG-LINE and DEBUG-ITEM?

Can DEBUG-LINE be used in production programs?

How do you access the line number information from DEBUG-LINE?

What data type should be used for DEBUG-LINE?

Are there performance implications when using DEBUG-LINE?

Related Concepts

DEBUG-ITEM Clause

DEBUGGING MODE

Data Description Entries

Working-Storage Section

Error Handling

Related Pages