# Keyword Reference

# Null

Keyword value to use in function call.

$var = Null

## Remarks

Use this keyword to trigger specific operations of functions that accept it as parameter.
Null evaluates only to Null, still in mathematical operations this keyword has value of 0, and as string it has no value (empty string).
The evaluation is only done during mathematical operations. For comparison operation "if $v = Null" will succeed
provided $v = Null.
COM method will receive Null as VT_NULL VARIANT. DllCall's wstr and str types will be set to NULL (pointers).

## Related

Default, IsKeyword

## Example

    ; Message box with an "Error" title.

    DllCall("user32.dll", "int", "MessageBoxW", "hwnd", 0, "wstr", "Some text", "wstr", Null, "dword", 0)