# Boolean

A Boolean has one of two possible values: `true`; `false`. Boolean (logical) operators (and, or, not) take Boolean inputs and yields a Boolean value. Comparison operators on other types (numbers, strings yields a Boolean value.

The following blocks represent the true and false Boolean values, which can be plugged in anywhere 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:

## 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-and-only-if either A is true or B is 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;``````