xor, xnor, and binary adders
An XOR gate is an exclusive OR gate. It outputs a logic 1 if only one of the inputs is a logic 1, but not if both are logic 1's.
An XNOR gate is an inverted XOR gate. It outputs a logic 1 only if all outputs are the same.
A binary adder is a circuit that adds binary numbers. It takes the corresponding bits from each number and adds them individually while carrying output from previous bits. It then outputs the new number.