NNOR

NNOR is a shorthand sometimes used in digital electronics to denote an N-input NOR gate, a generalization of the standard two-input NOR gate. In many textbooks and diagrams, NNOR may be written as N-NOR or simply NNOR to indicate a gate with N input terminals.

The NNOR gate outputs a logic high (1) only when all of its inputs are low (0). For a two-input example, the output is 1 only when both inputs are 0; if any input is 1, the output is 0. In Boolean terms, Y = NOT(A1 OR A2 OR ... OR AN), often written Y = NOR(A1, A2, ..., AN). The NNOR gate is functionally complete, meaning that using NNOR gates alone you can implement any Boolean function.

In hardware design, the N-input NOR is typically implemented using standard NOR primitives; for large N, designers may cascade or fan-in-limit with a limited number of inputs per gate, depending on the target fabrication process. The choice of N affects propagation delay and fan-in characteristics, and physical implementations may favor smaller-N variants for speed or reliability.

Despite its straightforward definition, the term NNOR is not always used consistently; in some contexts, designers may refer simply to a “multi-input NOR” instead of NNOR. See also NOR gate, logic gates, Boolean algebra.