A computer "nibble" consists of four "bits," each bit being either a 0 or a 1. If characters are represented using a code that uses a nibble for each character, how many different characters can be represented?

16.

Explanation:

A Nibble has four bits. These are binary bits that consists of 0 and 1 only. So the different codes it can represent are started from 0000 and to 1111. Each code corresponds to a single character only. The number of characters it can represent are 2*2*2*2=16. So the number of different characters represented are 16.