Lesson 3: Variables

In this lesson, you’ll learn how to use variables on the Micro:bit to store and change information. By the end, you’ll build a working counter app that increases, decreases, and resets numbers.

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What You’ll Learn

• What a variable is.
• How to create a variable.
• How to increase and decrease a value.
• How to show changing numbers on the Micro:bit.
• How to make a counter, score keeper, or number changer.

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Steps

1. Open MakeCode

Go to MakeCode for Micro:bit: https://makecode.microbit.org/

2. Start a New Project

• Click New Project
• Name it: Variables

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3. Make a Variable

• Open the Variables menu.
• Click Make a variable.
• Name it: count.
• Drag set count to 0 into the on start block.
• Add a show number block and set it to show count.

Test it:

• The Micro:bit should show 0 when it starts.

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4. Button A: Increase the Number

• From Input, drag on button A pressed.
• From Variables, drag change count by 1.
• Add show number count.

Test it:

• Press A → the number goes up.

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5. Button B: Decrease the Number

• From Input, drag on button B pressed.
• Add change count by -1.
• Add show number count.

Test it:

• Press B → the number goes down.

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6. Reset the Counter

• Use on button A+B pressed.
• Add set count to 0.
• Add show number count.

Test it:

• Press A+B → resets back to 0.

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7. Extra Challenges (Optional)

Try one of these:

• Shake the Micro:bit to double the count.
• Stop the counter from going below 0 or above 20.
  • If count < 0, set it to 0.
  • If count > 20, set it to 20.
• Make A+B set the count to a random number between 0 and 100.
• Add milestones:
  • When count reaches 10 → ⭐ icon
  • When count reaches 20 → 🎉

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Reflection

• Why is it useful to store numbers in variables?
• How could a counter or score system be used in a game?
• What else could you store in a variable?