Logic Gates:

Logic gates are electronic circuits in computer, which perform all operation in computer. Logic gates have one or more input signals and only one output signal. It is basic circuits for all major circuits in computer.

Types of Gates:

1. AND GATE: This type of gate may have two or more than two input and have only one output. If all inputs are high then only output will be high. If any one input will be low then output will be low. Table given below shows AND operation.

I	J	K=I*J I AND J
0	0	0
0	1	0
1	0	0
1	1	1

In AND operation both input are multiplied and then give output. So if there is any low input in AND gate then output will be low (0). To take a high output all input must be high (1).

2. OR GATE: This type of gate may have two or more than two input signal and give one output. Such type of gate gives high (1) output when any one input is high. If all inputs are low then output will be low. Table below shows OR operation.

I	J	K=I+J I OR J
0	0	0
0	1	1
1	0	1
1	1	1

Above table shows that in OR gate when value of I and J is 0 then value of K is 0 because of OR operation. Means in OR gate if all inputs will be low then output will be low. To take high output from OR gate any one of the inputs must be high.

3. NOT GATE: It has one input and one output. In NOT gate if input signal is high then output will be low. If input signal is low then output will be high. Means in this gate inverse of input signal will be received on output. To take complement of input this gate is used. Always opposite of the input signal will be received at the output. Table below shows NOT operation.

I	~I NOT I
0	1
1	0