Logic Gates: NOR

The NOR (= "not or") logic gate takes two bits as an input. Its output follows the rule: "if both bits are $0$, output $1$; otherwise, output $0$." You can implement it in your code as follows: given the Boolean variables x and y, then !(x || y) means "x nor y". Below is the black-box representation of the NOR gate and its truth table.

Bonus question: How can we build a NOR gate if we know how to build NOT, AND, OR, XOR, and NAND gates?

NOR Gate: black-box representation.

NOR Gate: black-box representation. Miriam Briskman, CC BY-NC 4.0.

Input Output
x y (x + y)'
$0$ $0$ $1$
$0$ $1$ $0$
$1$ $0$ $0$
$1$ $1$ $0$
NOR truth table