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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