While loop help

[kenken]

Would someone please help me understand why the following codes produce different outcomes for the variable sum when the variable number's type is changed to unsigned int. In addition, the second while loop doesn't terminate with a negative number. Thanks.

  int number, sum = 0;
	
	while (cin >> number && number > 0)
		sum += number;
	cout << sum;


unsigned int number, sum = 0;
	
	while (cin >> number && number > 0)
		sum += number;
	cout << sum;

[deleted account xyzzy]

the second while loop doesn't terminate with a negative number.

An unsigned int can NEVER be negative, it wraps around to a large positive number. Both of your while loops should end when 0 is entered.

[kenken]

@Furry Guy

I understand that unsigned can't be negative and the wrap-around effect of int, but that doesn't explain the result when the the following input is entered.
1 2 3 -1 a. With this input, a terminates the loop rather than -1 and the sum is 6 rather than 5.

int main()
{
	unsigned int number, sum = 0;

	cout << "Enter numbers: ";

	while (cin >> number && number > 0)
	{
		sum += number;
	}
	cout << sum;
	
	return 0;
}

[deleted account xyzzy]

Both sum AND number wrap around when entering -1. std::cin goes into an error state when 'a' is entered, 'a' is not an integer so the comparison is invalid, and the loop terminates.