Basic logical operators are the logic functions AND, OR, NOT and they operate on binary values and binary variables. Logic gates implement logic functions.

**The three basic logical operations are:**AND- Denoted by a dot (.)

For example, Y = A . B is read as Y is equal to A AND B.

OR- Denoted by a plus (+)

For example, Z = X + Y is read as Z is equal to X OR Y.

NOT- Denoted by a single quote mark ( ' ) or ($\sim$) before the variable.

For example, X = A' is read as X is equal to NOT A.

Digital systems are constructed using logic gates. The basic gates are described below:

__AND gate__The AND gate is an electronic circuit that gives a high output (1) only if all its inputs are high. Sometimes dot is omitted and it is written as AB instead of A . B.

__OR gate__The OR gate is an electronic circuit that gives a high output (1) if one or more of its inputs are high.

__NOT gate__The NOT gate is an electronic circuit which gives an inverted version of the input at its output. It is also known as an Inverter.