The problem is that programmers tend to confuse the concept of unsigned integers and non-negative integers. They think that just because a number can never be n

The problem is that programmers tend to confuse the concept of unsigned integers and non-negative integers. They think that just because a number can never be negative it is OK to use an unsigned integer to represent it. This leads to lots of mixed arithmetic of unsigned and signed types which leads to subtle bugs because neither is a subset of the other.