<ostream>
Defines the template class basic_ostream, which mediates insertions for the iostreams. The header also defines several related manipulators. (This header is typically included for you by another of the iostreams headers. You rarely need to include it directly.)
For a list of all members of this header, see <ostream> Members.
#include <ostream>
See Also
Reference
Thread Safety in the Standard C++ Library