NAND and NOR gates are the two universal logic gates. By wiring multiple gates of just one of these types together, an engineer can build inverters, AND gates, OR gates, flip-flops, and eventually an entire microprocessor. This property simplifies manufacturing, as a fabricator can stamp out thousands of identical gates to create any desired digital circuit.
We ran out of inverters, so just tie the inputs of a spare NAND together to make a universal logic gate act as a NOT.
Related terms
NAND gate
A fundamental digital logic gate that outputs low only when all its inputs are high.
NOR gate
A digital logic gate that outputs true only when all of its inputs are false.
NOT gate
A digital logic gate that outputs the inverse of its input state.
Flip-flop
A bistable logic circuit that stores a single bit of binary data.