# Boolean

A Boolean has one of two possible values: `true`

or `false`

. Boolean (logical) operators (*and*, *or*, *not*) take Boolean inputs and make another Boolean value. Comparison operators on other types (numbers, strings) create Boolean values.

These blocks represent the `true`

and `false`

Boolean values, which can plug into anyplace a Boolean value is expected:

`let on = true;`

The next three blocks represent the three Boolean (logic) operators:

```
let and = true && false;
let or = true || false;
let not = !true;
```

The next six blocks represent comparison operators that yield a Boolean value. Most comparisons you will do involve numbers:

```
let equality = 42 == 42;
let inequality = 42 != 42;
let lowerThan = 42 < 0;
let greaterThan = 42 > 0;
let lowerOrEqualThan =42 <= 0;
let greaterOrEqualThan = 42 >= 0;
```

Boolean values and operators are often used with an if or while statement to determine which code will execute next. For example:

```
let a = 5
let b = 87
if (a < b) {
a += 1
}
while (a < b) {
a += 1
}
```

## Functions that return a Boolean

Some functions return a Boolean value, which you can store in a Boolean variable. For example, the following code gets the on/off state of `point (1, 2)`

and stores this in the Boolean variable named `on`

. Then the code clears the screen if `on`

is `true`

:

## Boolean operators

Boolean operators take Boolean inputs and evaluate to a Boolean output:

## Conjunction: `A and B`

`A and B`

evaluates to `true`

if-and-only-if both A and B are true:

```
let off = false && false;
let off2 = false && true;
let off3 = true && false;
let on = true && true;
```

## Disjunction: `A or B`

`A or B`

evaluates to `true`

if either `A`

is true or `B`

is true, or if both `A`

and `B`

are true:

```
let off = false || false;
let on = false || true;
let on2 = true || false;
let on3 = true || true;
```

## Negation: `not A`

`not A`

evaluates to the opposite (negation) of A:

```
let on = !false;
let off = !true;
```