# 2. NOT

There are a number of logical operations that the CPU can carry out either singly or as a combination. The hardware which carries out the logical operations are called 'logic gates' and they reside inside the CPU and some other digital chips on the motherboard.

Each gate has one or more inputs and one output. Every logic gate follows a particular rule.

The most basic are NOT, AND, and OR.

The first of these gates, NOT, is the simplest. The rule that NOT follows is "*the output is the opposite of its input*".

So if you input 1, NOT will output 0.

If you input 0, NOT will output 1.

Input | Output |
---|---|

1 | 0 |

0 | 1 |

The table above is called a **truth table**. It shows the outcomes of every possible input. The NOT truth table is quite simple. But truth tables can get very complex when you start combining multiple logic gates.

Another name for the NOT gate is **inverter**.

**Challenge** see if you can find out one extra fact on this topic that we haven't
already told you

Click on this link: What is a NOT logic gate