The addition problem on the left did not require any bits to be carried, since the sum of bits in

each column was either 1 or 0, not 10 or 11. In the other two problems, there definitely were bits to

be carried, but the process of addition is still quite simple.

As we'll see later, there are ways that electronic circuits can be built to perform this very task of

addition, by representing each bit of each binary number as a voltage signal (either "high," for a 1;

or "low" for a 0). This is the very foundation of all the arithmetic which modern digital computers

perform.