cout prints "-0" instead of "0"

Question

#include <iostream>
using namespace std;

int main()
{
    double u = 0;
    double w = -u;
    cout << w << endl;
    return 0;
}

Why does this great piece of code output -0 and not 0, as one would expect?

Answer 1

The IEEE 754 standard for floating-point numbers has the sign bit separate from the mantissa, which allows for zero to be negative. Wikipedia should be able to help explain this.