Computer Science
Grade 2
20 min
Algorithm Debugging: Spot the Error!
Students are given faulty algorithms and must identify and correct the errors.
Tutorial Preview
1
Introduction & Learning Objectives
Learning Objectives
Define an algorithm and a bug.
Identify a 'bug' or error in a simple sequence of steps.
Explain why a bug causes a problem.
Correct an error in a given algorithm.
Follow an algorithm one step at a time to check for mistakes.
Trace a simple loop and find an error inside it.
Oh no! 🤖 Robot Robby is making a sandwich all wrong! Can you help fix his instructions?
We will learn about instructions called algorithms. Sometimes, they have mistakes called bugs! We will be bug detectives 🕵️♀️ and learn how to spot and fix them.
Real-World Applications
Fixing the steps to build a LEGO set
Following a recipe to bake cookies 🍪
Giving a friend directions to your desk
Playing a board game with the correct rules
2
Key Concepts & Vocabulary
TermDefinitionExample
AlgorithmA list of steps to finish a task. Like a recipe! 📜The algorithm for brushing your teeth is: 1. Get toothbrush. 2. Put on toothpaste. 3. Brush teeth. 4. Rinse.
Bug 🐛A mistake or error in an algorithm. It makes things go wrong!A bug is putting your sock on *after* your shoe. Oops! 👟
DebuggingThe process of finding and fixing bugs. You become a bug detective! 🕵️♂️You see the sock is on the shoe. Debugging is taking the shoe off and putting the sock on first.
SequenceThe order that steps happen in. One thing comes after another.In the morning sequence, you wake up first, then you eat breakfast.
LoopAn instruction that tells you to repeat steps over and over. 🔁A loop in a song is singing the chorus 3 times.
3
Core Syntax & Patterns
The One-Step-at-a-Time Rule
Read and do only one instruction at a time.
Use this rule to slow down and check every single step. Don't skip ahead! This helps you find the exact spot where the bug is hiding.
The What's Next? Rule
Ask yourself: 'Does this step make sense right now?'
After you read a step, think about what should happen. If it seems silly, like pouring milk on the table, you might have found a bug!
4 more steps in this tutorial
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Challenging
The goal is to pat your head and rub your tummy at the same time, three times. The code is: 'Repeat 3 times: [Pat Head], [Stomp Foot]'. What is the bug inside the loop?
A.The repeat count is wrong
B.It should only be one action, not two
C.It's missing a 'Rub Tummy' action
D.'Stomp Foot' should be 'Rub Tummy'
Challenging
A child's morning algorithm has two bugs: 1. Put on shoes. 2. Eat breakfast. 3. Put on socks. 4. Brush teeth. What are the two bugs?
A.Eating breakfast and brushing teeth are in the wrong order
B.Putting on shoes before socks, and they are in the wrong place in the list
C.The child should get dressed before eating
D.There is only one bug
Challenging
A robot starts facing North (↑). It runs the code: 'Repeat 2 times: [Move Forward], [Turn Left]'. Which way is the robot facing at the end?
A.North (↑)
B.East (→)
C.South (↓)
D.West (←)
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