pxt-calliope/docs/lessons/counter/activity.md
2016-03-25 16:47:20 -07:00

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# counter activity
Display a number with a variable.
### ~avatar avatar
### @video td/videos/counter-0
Welcome! This tutorial will teach you how to make a counter that increments when button A is pressed. Let's get started!
### ~
Let's start by creating a **local variable** `count` to keep track of the current count.
```blocks
let count = 0
```
The code under ``on button pressed("A")`` will run each time the user presses A. Let's add a line of code that increments `count` by `1`.
```blocks
let count = 0
input.onButtonPressed(Button.A, () => {
count = count + 1
})
```
Since the count has changed, it's time to refresh the screen display. Let's add a line of code to display the count on screen.
```blocks
let count = 0
input.onButtonPressed(Button.A, () => {
count = count + 1
basic.showNumber(count)
})
```
### ~avatar avatar
Excellent, you're ready to continue with the [challenges](/microbit/lessons/counter/challenges)
### ~