Question

What are universal gates? How can AND gate be realized using an appropriate combination of NOR gates?

Answer 1

A NOR gate is a logic gate which gives a positive output only when both inputs are negative. Like NAND gates, NOR gates are so-called "universal gates" that can be combined to form any other kind of logic gate.

NAND gates are one of the two basic logic gates (the other being NOR logic) from which any other logic gates can be built. Due to this property, NAND and NOR gates are sometimes called "universal gates". However, modern integrated circuits are not constructed exclusively from a single type of gate.

Answer 2

A universal gate is a gate which can implement any Boolean function without need to use any other gate type.

NAND gate and NOR gates are called as Universal gates.

Any logical gate an be constructed using only NAND gates or only NOR gates.

How can AND gate be realized using an appropriate combination of NOR gates :

The AND gate is replaced by a NOR gate with all its inputs complemented by NOR gate inverters.