pxt-calliope/docs/reference/out-of-bounds.md

# out of bounds

The behavior of functions whose parameter values are out of bounds.

Many of the BBC micro:bit functions have parameters. If a parameter is an unexpected value, the parameter is considered *out of bounds*.

For example, the [plot](/reference/led/plot) function has two parameters:

### syntax

```
export function plot(x: number, y: number)
```

### parameters

* x - the *x coordinate* or horizontal position (0, 1, 2, 3, 4)
* y - the *y coordinate* or vertical position (0, 1, 2, 3, 4)

### out of bounds

here's an example of code with an out of bounds parameter (the *x* and *y* parameters are outside the expected range of 0-4):

```
led.plot(9, -21)
```

### what happens?

Typically, when a parameter supplied to a function is out of bounds that function does nothing (as if the function never executed). So, in the above case, the LED screen will not change.

### return value

If you call the `point` function with an out of bounds parameter, the function returns `false`:

```
let on = led.point(5, -5)
```

### see also

For more information on the out-of-bounds behavior of a function, see the documentation for that [function](/js/contents).