Specifies that integer variables shall appear in base 16 notation.
A reference to an object of type ios_base, or to a type that inherits from ios_base.
A reference to the object from which _Str is derived.
By default, integer variables are displayed in base 10 notation. dec and oct also change the way integer variables appear.
The manipulator effectively calls _Str.setf(ios_base::hex, ios_base::basefield), and then returns _Str.
See dec for an example of how to use hex.