The header <iostream>
declares objects that associate objects with the
standard C streams provided for by the functions declared in
<cstdio>, and includes all the headers necessary to use these objects.
The objects are constructed and the associations are established at some
time prior to or during the first time an object of class
ios_base::Init is constructed, and in any case before the body
of main ([basic.start.main]) begins execution.
The objects are not destroyed during program execution.273