Logic equivalence: a NOR gate is functionally equivalent to an OR gate followed by which single element?

Introduction / Context:Composite logic functions can be described by combining simpler gates. Recognizing these equivalences helps with circuit minimization and technology mapping. NOR, a universal gate, is defined as the logical negation of OR.

Given Data / Assumptions:

• NOR outputs 1 only when all inputs are 0; otherwise outputs 0.
• We are asked to express NOR as an OR stage followed by one additional element.
• Standard logic gate behavior and naming are assumed.

Concept / Approach:By definition, NOR(X, Y) = NOT(OR(X, Y)). Therefore, implement OR first, then invert its output using a single NOT (inverter). This identity is used widely when decomposing complex gates into primitive cells or CMOS pull-up/pull-down networks.

Step-by-Step Solution:

Verification / Alternative check:Truth table comparison confirms that for inputs (0,0) → OR=0 → NOT=1; for any case with a 1 input → OR=1 → NOT=0, matching NOR behavior exactly.

Why Other Options Are Wrong:

Common Pitfalls:Confusing NOR with NAND (which equals AND followed by NOT). Keep the pairings straight: NOR = OR then NOT; NAND = AND then NOT.

Final Answer:Inverter (NOT)