#### Answer

If the memory unit is a two-dimensional grid $1,024\left(2^{10}\right)$ by $1,024\left(2^{10}\right)$
then it contains a total of $1,048,576\left(2^{20}\right)$ memory cells. We need a total
of 20 bits to represent all the possible memory addresses, which range
from 0 to $2^{20}-1 .$