Floating-point example

    #include <iostream>
    using namespace std;
    int main()
    {
        const double PI = 3.1415926;
        cout.precision( 7 );
        cout << fixed << "fixed format: " << PI << '\n';
        cout << scientific << "scientific format: " << PI << '\n';
        // back to default format:
        cout.unsetf( ios_base::fixed );
        cout.unsetf( ios_base::scientific );
        cout << "default format: " << PI << '\n';
        return 0;
    }
    /*
    Output:
    fixed format: 3.1415926
    scientific format: 3.1415926e+000
    default format: 3.141593
    */