<istream>
Defines the template class basic_istream, which mediates extractions for the iostreams, and the template class basic_iostream, which mediates both insertions and extractions. The header also defines a related manipulator. This header file is typically included for you by another iostreams header; you rarely have to include it directly.
For a list of all members of this header, see <istream> Members.
#include <istream>
See Also
Reference
Thread Safety in the Standard C++ Library