C++ - Unsigned integers

Question

I have the following program written in C++:

The problem with this program is that if the user inputs a negative number, it is NOT caught by the line if(!cin). I thought that unsigned integers can NOT accept negative numbers. Then why if I enter a negative number to size, it is NOT caught by if(!cin) and the program continues execution with no error messages?

I cannot make use of if(size < 0). I want to show how unsigned integers can solve the problem of negative input.

Answer 1

The difference between unsigned and signed integers on most platforms is a sign-bit ... other than that, the actual binary value is the same, it's just interpreted two different ways depending on the sign-ness of the type that the binary value represents. So you can definitely "represent" a negative value input as a unsigned value ... it won't be re-interpreted as that value, but it can definitely be input as that value without an error being set on the stream.