Computer Science
Grade 2
20 min
Debugging Instructions: Finding the Mistake
Students identify errors in a set of instructions (e.g., an algorithm for making a sandwich that's missing a step).
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1
Introduction & Learning Objectives
Learning Objectives
Identify a 'bug' or mistake in a short sequence of instructions.
Explain why the order of instructions is important.
Test a sequence of instructions step-by-step.
Correct a simple mistake in an algorithm.
Use the term 'debugging' to mean finding and fixing mistakes.
Create a correct sequence of 3-4 instructions for a simple task.
Oh no! 😟 Your robot friend is trying to make a sandwich and put the bread on last! How can we help?
We will learn how to find and fix mistakes in instructions. This is called debugging! It helps make sure our instructions work perfectly.
Real-World Applications
Fixing a step in a recipe 🥪
Correcting directions to a friend's house 🗺️
Finding a mistake when building with blocks 🧱
Figuring out...
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Key Concepts & Vocabulary
TermDefinitionExample
InstructionA single step in a list of things to do. ➡️An instruction is 'pick up the blue crayon'.
SequenceA list of instructions in a special order. 🔢1. Get paper. 2. Get crayon. 3. Draw a sun.
AlgorithmA list of steps to finish a task. 📝The algorithm for brushing your teeth has many steps.
BugA mistake in the instructions that causes a problem. 🐞A bug is telling your robot to go left instead of right.
DebuggingThe process of finding and fixing bugs. 🕵️♀️Debugging is when we find the 'go left' bug and change it to 'go right'.
ProgramA set of instructions for a computer or robot. 💻We write a program to tell a character to jump in a game.
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Core Syntax & Patterns
One Step at a Time
Check each instruction one by one, in order. 1️⃣ 2️⃣ 3️⃣
Don't skip ahead! Go through the list from the start to find the bug.
Act It Out
Pretend you are the robot and follow the steps. 🤖
Acting out the instructions helps you see where things go wrong.
Find and Fix
When you find the bug, change it to the right instruction. ✅
After you find the mistake, you must fix it so the program works.
4 more steps in this tutorial
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Challenging
A robot's code to build a wall is `Repeat 5 times: [Get Brick, Move Right, Place Brick]`. A bug deletes the `Move Right` block. What will the robot build now?
A.short wall with 5 bricks
B.single brick placed on the ground
C.Nothing, the code will have an error
D.tall tower of 5 bricks
Challenging
A robot's job is to clean up by putting toys in a box. Its only instruction is: `If toy is on the floor, pick it up`. The robot finishes, but there is still a toy left on the table. Why wasn't the room cleaned perfectly?
A.The instruction was too specific; it didn't mention the table
B.The robot ran out of battery
C.The toy box was full
D.The robot can't see toys on tables
Challenging
To move a robot forward 3 spaces, a coder writes: `Move Forward, Move Forward, Move Forward`. A friend says there is a 'bug' because there is a better way. What 'bug' are they talking about?
A.The code has too many blocks
B.The code is inefficient and could use a loop
C.The robot will move 4 spaces by mistake
D.The code is too hard to read
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