Lesson 3: Variables (Teacher Notes)

This is the teacher guide for Lesson 3. It includes the lesson flow, strategies, and example code.

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Learning Objectives

• Students understand what variables are.
• Students can change a variable using button inputs.
• Students can show changing values on the Micro:bit screen.
• Students can build a simple counter program.

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Suggested Lesson Flow

1. Introduction (5 mins)

• Ask: “What if we want to remember a number?” → introduce variables.
• Show an example: press A to increase a number on your Micro:bit.

2. Demonstration (5 mins)

• Show how to:

  • Create a variable
  • Set its starting value
  • Change it with buttons
  • Display it

• Emphasize that a variable is stored information.

3. Student Activity (15–20 mins)

• Students follow their instructions.
• Build the counter → then add decreasing → then reset.
• Optional challenges for early finishers.

4. Wrap-Up (5 mins)

• Ask reflective questions:

  • “How could we use variables in a game?”
  • “What happens if we decrease below 0?”

• Remind students to save their project.

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Common Issues & Fixes

Problem	Solution
Number doesn’t change	Ensure the student added change count by inside the right button block.
Screen doesn’t update	Add show number count after changing the variable.
Reset doesn’t work	Make sure set count to 0 is inside A+B event.

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Demo Code Example (JavaScript)

let count = 0
basic.showNumber(count)

input.onButtonPressed(Button.A, function () {
    count += 1
    basic.showNumber(count)
})

input.onButtonPressed(Button.B, function () {
    count += -1
    basic.showNumber(count)
})

input.onButtonPressed(Button.AB, function () {
    count = 0
    basic.showNumber(count)
})

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Extension Examples

Score Keeper

let score = 0
input.onButtonPressed(Button.A, function () {
    score += 5
    basic.showNumber(score)
})
input.onButtonPressed(Button.B, function () {
    score += 1
    basic.showNumber(score)
})

Shake to Multiply

let value = 1
input.onGesture(Gesture.Shake, function () {
    value = value * 2
    basic.showNumber(value)
})

Temperature in a Variable

let temp = 0
input.onButtonPressed(Button.A, function () {
    temp = input.temperature()
    basic.showNumber(temp)
})