Chapter 3- Logic Circuits

Logic Gates :

Logic circuits are very small electronic decision-making hardware devices that are fed one or more inputs and give back one output. Logic gates are just like binary. They are only fed ones and zeros  and they only give ones and zeros. 

There are 3 types of logic gates:

• The NOT gate
• The OR gate 
• The AND gate

Truth Tables :

A truth table is used to define the output of a logic gate or a logic circuit for all possible combinations of inputs. 
The truth tables are actually used to calculate the output for given inputs at each point along the logic circuit. 

NOT GATE -> The NOT gate accepts only 1 input and gives its inverse as output. If a 1 is input ,then 0 is given as an output, but if 0 is an input, then 1 is the output. So basically, in the truth table of the NOT gate, the inputs and outputs are always opposite. The NOT gate is also known as an inverter.

AND gate -> The AND gate accepts 2 or more inputs, and gives only one output. In the AND gate, the output is only 1 if all the inputs are 1 as well. 

OR gate -> The OR gate accepts 2 or more inputs and gives only one output, which will be 1 when either one or all of the inputs are 1. So, the OR gate always gives a 1 as an output, unless they're all 0. 

The NOT gate can have only one input, but the AND and OR gate can have two, three and even four inputs.