Computer Science
Grade 3
20 min
Debugging Review: Recap and Strategies
Students will review the concepts learned in the chapter and discuss effective debugging strategies.
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Introduction & Learning Objectives
Learning Objectives
Identify when a program has a bug.
Describe a bug by comparing what was expected to what actually happened.
Use the 'One Step at a Time' strategy to trace through code.
Find and fix bugs in simple event-based programs.
Find and fix bugs in simple conditional (if/then) statements.
Explain in their own words why a bug was happening.
Have you ever tried to build a LEGO tower and it fell over because one block was in the wrong spot? 🧐 Finding that one block is just like debugging!
Today, we're going to be 'Debugging Detectives'! We will review what bugs are and learn super strategies to find and fix them in our code. Being a good bug detective makes you a great coder!
Real-World Applications
Fixing a video game that isn't w...
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Key Concepts & Vocabulary
TermDefinitionExample
BugA mistake or error in a computer program that makes it do something unexpected.You code a cat to say 'Meow!' when you click it, but instead it jumps. The jump is the bug.
DebuggingThe process of finding and fixing bugs in your code. It's like being a detective for your program!You look at your code blocks and realize you used a 'jump' block instead of a 'say' block, so you swap them. That's debugging!
EventAn action that causes something to happen in a program.Clicking the green flag, pressing the spacebar, or a sprite touching another sprite are all events.
ConditionalAn instruction that tells the computer to do something ONLY IF a certain condition is true. It's an 'if... then...' statement.IF the score is g...
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Core Syntax & Patterns
Strategy 1: One Step at a Time
Read your code one block at a time, from top to bottom, and say what each block does.
Use this when your program is doing something, but you're not sure where it goes wrong. Slowing down helps you spot the mistake.
Strategy 2: Talk it Out
Explain your code out loud to a friend, a teacher, or even a rubber duck.
Use this when you are stuck. Saying the code's purpose out loud can help you hear the mistake in your own logic.
Strategy 3: Compare and Contrast
Ask yourself: 'What did I EXPECT to happen?' and 'What ACTUALLY happened?'
Use this to clearly identify the problem. Knowing exactly what's wrong is the first step to figuring out how to fix it.
4 more steps in this tutorial
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Challenging
A game has a `lives` variable that starts at 3. The code says `if <touching lava> then <change lives by -1>`. You touch the lava for just a moment, but your `lives` variable instantly becomes 0. What is the most likely cause?
A.The `lives` variable can only be 3 or 0
B.The `if` statement is inside a 'forever' loop, and it ran many times before your character moved away
C.The computer miscounted
D.Touching lava always ends the game immediately
Challenging
In a quiz game, the code is: `ask 'What is 2+2?' and wait`. Then, `if <answer = 4> then <say 'Correct!'> else <say 'Try Again!'>`. A player types '4 ' (a 4 with a space after it) and the game says 'Try Again!'. Why?
A.The computer can't do math
B.The player was too slow to answer
C.The computer sees the text '4' and the text '4 ' as two different things
D.The 'say' block is broken
Challenging
You have a very long script with a bug somewhere in the middle. What is the FASTEST and most efficient strategy to find the bug's general location?
A.Read the entire script from top to bottom over and over
B.Delete the second half of the script and see if the bug is still in the first half
C.Rewrite the entire script from memory
D.Ask a friend to read the whole script for you
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