pxt-calliope/docs/reference/js/lessons/counter.md

# counter lesson

Learn how to create a counter with with on button pressed.

### @video td/videos/counter-0

## Topic

Variables

## Quick Links

* [activity](/lessons/counter/activity)
* [challenges](/lessons/counter/challenges)
* [quiz](/lessons/counter/quiz)
* [quiz answers](/lessons/counter/quiz-answers)
* [tutorial](/lessons/counter/tutorial)

## Class

Year 7

## Prior learning/place of lesson in scheme of work

Learn how to creating a **variable** to keep track of the current count. We will be learning how to create a counter app using a variable as well as simple commands, such as on button pressed, and show number.

## Documentation

* **variable**: [read more...](/reference/variables/var)
* **arithmetic operators**: [read more...](/reference/types/number)
* **on button pressed** : [read more...](/reference/input/on-button-pressed)
* **show number** : [read more...](/reference/basic/show-number)

## Objectives

* learn how to create a variable as a place where you can store data so that you can use it later in your code, accessible across all functions, and in nested code blocks
* learn how arithmetic operators operate on numbers and return a number
* learn how to run code when an input button is pressed
* learn how to show a number on the LED screen, one digit at a time (scrolling from left to right)

## Progression Pathways / Computational Thinking Framework

#### Algorithms

* Understands that iteration is the repetition of a process such as a loop. (AL)
* Represents solutions using a structured notation. (AL) (AB)

#### Programming & Development

* Creates programs that implement algorithms to achieve given goals. (AL)
* Declares and assigns variables.(AB)

#### Data & Data Representation

* Understands the difference between data and information. (AB)
* Defines data types: real numbers and Boolean. (AB)

#### Information Technology

*  Collects, organises and presents data and information in digital content. (AB)
* Makes appropriate improvements to solutions based on feedback received, and can comment on the success of the solution. (EV)

Computational Thinking Concept: AB = Abstraction; DE = Decomposition; AL = Algorithmic Thinking; EV = Evaluation; GE = Generalisation

## Activity

* time: 20 min.
* [activity](/lessons/counter/activity)
* [tutorial](/lessons/counter/tutorial)
* [quiz](/lessons/counter/quiz)

## Extended Activity

* time: 20 min.
* [challenges](/lessons/counter/challenges)

## Homework

* Extended Activity: [challenges](/lessons/counter/challenges)