A D218: Boolean function $f : \{ 0, 1 \} \times \{ 0, 1 \} \to \{ 0, 1 \}$ is a NOR boolean logic gate if and only if
(1) | \begin{equation} f(0, 0) = 1 \end{equation} |
(2) | \begin{equation} f(1, 0) = 0 \end{equation} |
(3) | \begin{equation} f(0, 1) = 0 \end{equation} |
(4) | \begin{equation} f(1, 1) = 0 \end{equation} |