why NAND or NOR gates are called universal gate?
The repeated use of NAND (or NOR) gates can produce all the three basic gates i.e., OR, AND and NOT gates ; whose various combinations provide us large no. of complicated digital circiuts.
Any circuit can be implemented using NAND or NOR gate(one at a time).
Any circuit can be implemented using NAND or NOR gate(one at a time).