De Morgan's laws

DeMorgan's Law, named for nineteenth century logician and mathematician Augustus DeMorgan, is an interesting and powerfull observation of boolean logic. It can be expressed as a pair of equations:

P and Q = not((not P) or (not Q))

P or Q = not((not P) and (not Q))

This simple fact is used extensively in digital circuit design for manipulating the types of logic gates used by the circuit.