39 lines
2.7 KiB
Markdown
39 lines
2.7 KiB
Markdown
# Blocks - Variables
|
||
|
||
An introduction to variables for the Block Editor. #docs
|
||
|
||
## What is a variable?
|
||
|
||
Variables are things that are remembered by the BBC micro:bit. Variables can take a few formats and can have functions applied to them. For example, we could create a string, which is text. Or we could create a calculator that stores whichever number the user inputs as an integer, or whole number.
|
||
|
||
We can modify variables but they must first be defined. Open the ‘Variables’ drawer to the left of your code.
|
||
|
||
In the variables section you will see two blocks: `set item` and `item`. The set item block allows you to set a variable to another value or create a new variable.
|
||
|
||
Drag the `set item` block into your code. Click the little arrow next to the word `item` and select **New Variable**, enter **value** as the name. You have now created a new variable called value, however you must set an initial value. Go to the **Maths** drawer and drag a `0` block, connecting it to the empty socket in the `set` value block. Your code should look like this:
|
||
|
||
|
||
|
||
## Using Variables
|
||
|
||
We can also set value to something else using this line. For example, we could use the functions in the **Maths** drawer to set value to a new value. If we combine this with the `forever` loop and if statements from the previous page then we can create a counter:
|
||
|
||
|
||
|
||
Drag a `forever` block from the **Basic** drawer and add an `if` block from the **If** drawer. Attach the ‘button pressed’ block from the ‘Input’ drawer.
|
||
|
||
Drag another `set item` block from the **Variables** draw and click the **down arrow** next to item, however this time select **value**, we don’t have to declare it again as we have already created it. Open the **Maths** drawer and drag a `+` block before clicking it into place in the `set` value block. Drag an `item` block from the **Variables** drawer and again click the **down arrow** before selecting **value**. Add a `0` from the **Maths** drawer and change the value from **0** to **1**.
|
||
|
||
Finally, beneath that line, drag a `show number` block from the **Basic** drawer, and drag out the `0`. Drag another variable block from the **Variables** drawer, change it to `value`, and drop this into the space.
|
||
|
||
### What does this code do?
|
||
|
||
* We create a new variable called value and set it to 0
|
||
* The code runs forever and waits for the user to press the A button
|
||
* When the user does, value will be set to value + 1 (value will be incremented by 1)
|
||
* Value will then be displayed on the BBC micro:bit's LEDS
|
||
* This effectively creates a counter
|
||
|
||
Variables can also be used for conditions with loops. See the 'Loops' section to learn about this.
|
||
|