56 lines
1.3 KiB
Markdown
56 lines
1.3 KiB
Markdown
# In Background
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Run code in the background as a separate process or thread; for more information on this advanced construct, see [the micro:bit - a reactive system](/device/reactive).
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```sig
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control.inBackground(() => {
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})
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```
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### Example
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The example below shows how a background process can be used to display the current value of the global variable `num`, while code (like the `on button pressed` handler) can change the value of the variable.
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```blocks
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let num = 0
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control.inBackground(() => {
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while (true) {
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basic.showNumber(num, 150)
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basic.pause(100)
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}
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})
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input.onButtonPressed(Button.A, () => {
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num++;
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})
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```
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The code below using the `forever` loop is equivalent to the code above
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```blocks
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let num = 0
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basic.forever(() => {
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basic.showNumber(num, 150)
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})
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input.onButtonPressed(Button.A, () => {
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num++;
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})
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```
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### Contention for the LED display
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If you have multiple processes that each show something on the LED screen, you may get unexpected results. Try, for example:
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```blocks
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basic.forever(() => {
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basic.showNumber(6789, 150)
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})
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input.onButtonPressed(Button.A, () => {
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basic.showNumber(2, 150)
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})
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```
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### See also
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[while](/blocks/loops/while), [forever](/reference/basic/forever), [on button pressed](/reference/input/on-button-pressed)
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