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Advanced Scratch · Week 2

Calculator

Step 1 of 4

Scratch 2 - Lesson 2: Calculator

What You'll Learn

In this lesson, you will create a simple calculator in Scratch. By the end of this project, you'll have a functioning calculator that can perform basic math operations (addition, subtraction, multiplication, and division).

Interactive Calculator Demo

Check out the final Scratch project below!

Key Concepts: Variables, User Input, Conditional Statements, Mathematical Operations

1. Ask Function & Conditional Logic

Try It: Conditional Logic

Type your math operation

The Ask and Wait Block

The ask [ ] and wait block in Scratch is crucial for getting user input. It's like asking a question and waiting for an answer.

The light blue Sensing block reading "ask What's your name? and wait", with the oval answer block beneath it that stores whatever the user types in.

The "ask and wait" block, and the "answer" block that holds the reply

1 Drag the ask [ ] and wait block from the "Sensing" category.

2 Type your question in the block, e.g., "What operation do you want to perform?"

3 The user's answer is stored in the answer block.

Conditional Logic with If-Then Blocks

We use conditional logic to decide what operation to perform based on the user's input.

1 Drag an if [ ] then block from the "Control" category.

2 Use the = block from "Operators" to check the answer.

3 Add blocks inside the if-then to perform the chosen operation.

Pro Tip: Use multiple if-then blocks to handle different operations in your calculator.

2. Coding the Subtraction Operation

Try It: Subtraction

Getting the Numbers

Before we can subtract, we need to get two numbers from the user.

1 Use two ask [ ] and wait blocks to get both numbers.

2 Store each answer in a variable (e.g., 'number1' and 'number2').

Performing the Subtraction

Now let's subtract the numbers and show the result.

1 Use the - block from the "Operators" category.

2 Place your 'number1' and 'number2' variables in the subtraction block.

3 Use a say [ ] block to display the result.

Challenge: Can you modify this code to handle addition, multiplication, and division as well?

Homework and Exercises

Exercise 1: Complete Calculator

Extend your calculator to handle all four basic operations: addition, subtraction, multiplication, and division.

1 Add if-then blocks for each operation.

2 Use appropriate operator blocks for each calculation.

3 Test your calculator with different inputs.

Exercise 2: Advanced Operations

Add more advanced operations to your calculator.

1 Implement a square root function.

2 Add a power function (x to the power of y).

3 Include a modulo operation (remainder after division).

Practice: Advanced Calculator

Remember: The key to becoming a great programmer is practice and creativity. Keep experimenting and building new things!

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