Logic Gates

Logic gates are physical electronic devices which control the flow of signals in a circuit. They take in one or greater than one binary inputs, perform a logical operation, and give a single binary output.

All computers have logic gates. Complex structures of logic gates can often serve a purpose or solve a particular problem.

In logic gates, '1' as an input usually refers to an 'on', or 'true' state. A '0' can refer to an 'off', or 'false' state.

The main and most commonly occurring logic gates:

- OR

- AND

- NOT

- NOR

- NAND

All of the above logic gates take one or two binary values as input, outputting a single binary output.

OR gates:

The output value of an OR gate is 1, if either one of or both of the input values are 1. Otherwise, it has an output of 0.

INPUT: | OUTPUT:

0 0 | 0

0 1 | 1

1 0 | 1

1 1 | 1

AND gates:

The output value of an AND gate is 1, if both of the input values are 1. Otherwise, it has an output of 0.

INPUT: | OUTPUT:

0 0 | 0

0 1 | 0

1 0 | 0

1 1 | 1

NOT gate:

A NOT gate takes in one binary input, and changes it to the other binary value.

INPUT: | OUTPUT:

1 | 0

0 | 1

NOR and NAND gates do the opposite to OR and AND gates respectively. Below are images of how the logic gates are represented when drawing them.

AND: NAND:

NOT:

OR: NOR:

There are several more different logic gates.

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