The NOR Gate
The NOR gate ("not-or") outputs true only when both its inputs are false, the mirror image of NAND. Like NAND, NOR is functionally complete: copies of NOR alone can build a NOT gate, an OR gate, an AND gate, and every other logic gate, meaning an entire computer can be built from either universal gate on its own. An advanced companion to Meet Norra, naming the real term directly for an older audience instead of the character Norra.
Silence in both switches wakes this gate, and only silence will. One spark from either lamp, and the output falls quiet and still.
This is the NOR gate, not-or, the mirror twin of NAND, dark for every combination but one, both off, exactly as planned.
Round and round the same rule turns: both off is the only door, one lit, both lit, either way, the answer stays at the floor.
Copy this gate alone, and a NOT gate appears inside its frame, copy it twice in careful order, and an OR gate wears its name.
Copy it further, layer by layer, and an AND gate comes to light, every gate a circuit needs can rise from NOR gates stacked in order.
Round and round the same rule turns: both off is the only door, stack enough of this one pattern, and you build a full machine's core.
NAND builds the world from what stays lit. NOR builds it from what stays dim, two mirror rules, two starting points, and both arrive at the same hymn.
A whole computer sleeps inside one gate that answers to the hush, round and round the pattern turns, until the circuit's full and lush.
Key Concepts: The NOR gate outputs true only when both inputs are false, the mirror image of NAND's rule | Like NAND, NOR is functionally complete: copies of NOR alone can build NOT, OR, AND, and every other logic gate | Two different universal gates (NAND and NOR) can each build the identical machine starting from their own single rule | Functional completeness means an entire computer can be constructed from one repeated gate, either NAND or NOR
Key Words: NOR, not-or, universal gate, functionally complete, mirror
Advanced companion note: This is the real-term companion to Norra in meet-norra.md, written for an older audience directly about the NOR gate rather than through the character.