# IsNull()

Checks whether the specified expression has a null value. This function takes an expression argument of any type and returns a Boolean value. If the expression is null, the function returns the Boolean value `TRUE`

. If the expression has a value, it returns the Boolean value `FALSE`

.

# Syntax

`IsNull(<expression>)`

# Input

**expression**

expression

The expression to check.

# Output

Boolean

# Examples

Assume that you have a form in which there is a number question with the reference name number_of_cars.

- If this question is not answered, the expression
`IsNull($number_of_cars)`

returns`TRUE`

because the answer is null, meaning that it does not contain a value of any type. - If the question is instead answered 2, the expression
`IsNull($number_of_cars)`

returns`FALSE`

because the answer contains a value.