> For the complete documentation index, see [llms.txt](https://cs.brash.ca/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://cs.brash.ca/unit-2/variables/booleans.md).

# Booleans

By now you probably know what a [boolean value](https://en.wikipedia.org/wiki/Boolean_data_type) is and you may have heard about [boolean algebra](https://en.wikipedia.org/wiki/Boolean_algebra) or [George Boole](https://en.wikipedia.org/wiki/George_Boole). Together, they are the bread and butter that makes programming work.\
\
We can compare two or more values, utilize a boolean for situations with only two states, or combine values using boolean algebra in order to control our code.

In Javascript, anything with a value is considered to be true (see [truthiness](/unit-2/variables/booleans/truthiness.md)). We can use [comparison operators](/unit-2/variables/numbers.md#comparison) to return a `true` or `false` value. For example:  `(10 < 6)   // false`. \
Strongly typed languages such as C++ and Java have a boolean primitive type. JS also has a boolean type but it is loosely (or dynamically) typed, so it can take on other values as well.

Later in our programming adventure, we will even create our own functions that return a boolean value in order to state if something happened or not.

## Boolean Logic

You may have seen boolean logic for [logic gates](/unit-1/binary-and-logic/logic-gates.md). This same process can be applied to boolean values in code.

| Operator | Symbol      | Example(s)                                                                               |   |                                            |   |                            |
| -------- | ----------- | ---------------------------------------------------------------------------------------- | - | ------------------------------------------ | - | -------------------------- |
| Not      | !           | `!(4 < 10)` = false                                                                      |   |                                            |   |                            |
| And      | &&          | <p><code>(true && false)</code> = false</p><p><code>(3 < 5 && 7 > 1)</code> = true</p>   |   |                                            |   |                            |
| Or       | \|\|        | <p><code>(true                                                                           |   | false)</code> = true</p><p><code>(5 > 10   |   | 1 == 1)</code> true</p>    |
| Nand     | !(x && y)   | <p><code>!(true && false)</code> = true</p><p><code>!(3 < 5 && 7 > 1)</code> = false</p> |   |                                            |   |                            |
| Nor      | !(x \|\| y) | <p><code>!(true                                                                          |   | false)</code> = false</p><p><code>!(5 > 10 |   | 1 == 1)</code> = false</p> |


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