NOR versus OR – do they operate in exactly the same way?

Introduction / Context:
OR and NOR are related but distinct logic operations. Recognizing the inversion bubble on NOR is vital for correct reading of schematics and active-LOW signal conventions.

Given Data / Assumptions:

• Standard two-input (extendable to N input) gates.
• Active-HIGH logic convention.
• Ideal Boolean behavior.

Concept / Approach:
NOR is the logical negation of OR: NOR(A,B) = NOT(OR(A,B)). Their truth tables are complements. Therefore, they do not operate in the same way; NOR only outputs 1 when all inputs are 0, while OR outputs 1 if any input is 1.

Step-by-Step Solution:

Verification / Alternative check:
Draw symbols: NOR shows an inversion bubble at the output, signaling logical negation. Truth tables confirm complementarity. De Morgan's laws also express relationships: NOR equals AND of inverted inputs: NOR(A,B) = NOT(A + B) = (NOT A) * (NOT B).

Why Other Options Are Wrong:
“Correct” is false by definition. “Only with wired-OR lines” and “Only with tri-state outputs” confuse hardware interconnects with logical functions. “Only when inputs are all LOW” cherry-picks a single row and ignores other combinations.

Common Pitfalls:
Ignoring inversion bubbles in schematic symbols; that bubble changes the function dramatically. Always check polarity indicators.

Final Answer:
Incorrect