B2.1.4 Constructing and Using Common Debugging Techniques Notes

The Importance of Debugging

1. Debugging is the process of identifying and fixing errors in your code.
2. It ensures that your program behaves as expected and is a critical skill for any programmer.

Common Debugging Techniques

1. Trace Tables
2. Breakpoint Debugging
3. Print Statements
4. Step-by-Step Code Execution

Trace Tables

1. Trace tables are used to manually track the values of variables as an algorithm executes.
2. They help identify logic errors by showing how data changes over time.

Breakpoint Debugging

1. Breakpoints are markers set in your code that pause execution at specific points.
2. This allows you to inspect variable values and program flow.

How to Use Breakpoints

1. Set a Breakpoint: Place a breakpoint at a line of code where you want to pause execution.
2. Run the Program: Execute the program in a debugger. It will pause at the breakpoint.
3. Inspect Variables: Check the values of variables and the program state.
4. Continue Execution: Step through the code line by line or resume normal execution.

Print Statements

Print statements are a simple yet effective way to debug by displaying variable values and program flow in the console.

for i in range(5):
    print("Iteration:", i)   # Debug print

for (int i = 0; i < 5; i++) {
    System.out.println("Iteration: " + i);   // Debug print
}

Iteration: 0
Iteration: 1
Iteration: 2
Iteration: 3
Iteration: 4

Step-by-Step Code Execution

1. A debugging technique that allows programmers to run code one line at a time. It is typically done using an Integrated Development Environment (IDE) with built-in debugging tools.
2. This method helps track program flow, verify logic, and inspect variable values in real time.

Key Features

1. Step In
   1. Enters a function or method call to trace its execution line by line.
   2. Useful for debugging nested functions or identifying issues inside a specific method.
   3. Example: If code calls calculateTotal(), stepping in shows what happens inside that method.
2. Step Over:
   1. Executes the current line as a whole, then moves to the next line of code.
   2. If the line calls a function, the debugger runs the function without showing its internal steps.
   3. Example: total = calculateTotal() executes fully, then moves to the next line.
3. Step Out:
   1. Completes execution of the current function and returns to the calling code.
   2. Useful when you accidentally step too deep into a function or once you’ve finished debugging it.

Choosing the Right Debugging Technique

1. Trace Tables: Use for logic errors and understanding algorithm flow.
2. Breakpoints: Ideal for inspecting specific code sections in large programs.
3. Print Statements: Quick checks for variable values and program flow.
4. Step-by-Step Execution: Best for detailed analysis of complex logic.