Propagation delay is the time required for a gate to change its state

Noise immunity is the amount of noise which can be applied to the input of a gate without causing the gate to change state

Fan-in of a gate is always equal to fan-out of the same gate

Operating speed is the maximum frequency at which digital data can be applied to a gate

X NAND X

X NOR X

X NAND 1

X NOR 1

NOT

AND

OR

XOR

OR

AND

NAND

XOR

1 bit

2 bits

4 bits

8 bits