Why is the maximum value of an unsigned n-bit integer 2^n-1 and not 2^n?

Question

The maximum value of an n-bit integer is 2ⁿ-1. Why do we have the \"minus 1\"? Why isn\'t the maximum just 2ⁿ?

Answer 1

It's because in computing, numbers start at 0. So if you have, for example, 32 address lines (2³² addressable bytes), they will be in the range [0, 2^32).