Computer Science
Grade 6
20 min
8. Debugging Strategies: Finding and Fixing Errors
Introduce common debugging techniques and strategies for identifying and fixing errors in code.
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Introduction & Learning Objectives
Learning Objectives
Define the terms 'bug' and 'debugging' in the context of programming.
Differentiate between a syntax error and a logic error.
Read a basic error message to identify the line number and type of error.
Apply the 'print debugging' strategy to check the value of a variable at a specific point in a program.
Systematically test and correct a simple program with one or two errors.
Explain the 'Rubber Duck Debugging' method as a problem-solving technique.
Ever followed a recipe perfectly, but the cookies came out weird? Finding the mistake is like debugging code! 🍪🕵️
In this lesson, you'll become a code detective! We will learn about different types of errors, called 'bugs,' and discover powerful strategies...
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Key Concepts & Vocabulary
TermDefinitionExample
BugAn error or mistake in a computer program that causes it to produce an incorrect or unexpected result, or to behave in unintended ways.If you write code to add 2 + 2 but the program shows the answer 5, there is a bug in your code.
DebuggingThe process of finding and fixing bugs in a program's code. It's like being a detective for your program.Reading your code line-by-line to find out why 2 + 2 resulted in 5 is the process of debugging.
Syntax ErrorA mistake in the code that breaks the rules of the programming language, like a spelling or grammar error. The program usually won't run at all.Typing `prnt("Hello")` instead of `print("Hello")`. The computer doesn't understand the word 'prnt'.
Logic ErrorA mistake in th...
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Core Syntax & Patterns
Read the Error Message
Error messages often tell you the file name, the line number, and the type of error.
When your program crashes, don't panic! The computer is trying to help. Look for the line number it points to and read the description of the error (e.g., `NameError`, `SyntaxError`). This is your first and best clue.
One Change at a Time
Make one small change to your code, then run it again to see what happens.
Don't try to fix five things at once. If you change one thing and it fixes the problem, you know exactly what the bug was. If it doesn't fix it, you can easily change it back and try something else.
Rubber Duck Debugging
Explain your code, line by line, out loud to someone or something (like a rubber duck).
This forces you to slow down an...
4 more steps in this tutorial
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Challenging
You are debugging a long program by adding `print()` statements to check a variable's value. A `print()` on line 20 shows the correct value. A `print()` on line 40 shows the correct value. A `print()` on line 60 shows an incorrect value. What does this tell you?
A.The error that changes the variable happens somewhere between line 40 and line 60
B.The error must be on line 20
C.The `print()` command is broken
D.The entire program is wrong and must be deleted
Challenging
Your program has a complex logic error where the final score is calculated incorrectly, but it's not obvious why. Which of these debugging strategies would be the LEAST effective way to find the problem?
A.Explaining the code line-by-line to a friend (Rubber Ducking)
B.Randomly changing numbers and operators until the output looks correct
C.Adding print statements to check the value of variables at each step of the calculation
D.Using a piece of paper to trace the variables and calculate the result by hand
Challenging
In a game, pressing the 'up' arrow is supposed to increase the player's `y` coordinate. Instead, it increases the `x` coordinate, moving the player right. The game doesn't crash. What is the most logical first step to debug this?
A.Check if the computer's keyboard is plugged in correctly
B.Rewrite all the code for player movement from scratch
C.Change the player's starting position to see if that fixes it
D.Find the section of code that handles the 'up' arrow press and check which variable it changes
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