namespace std {
  template <class charT, class traits = char_traits<charT>>
  class basic_iostream
    : public basic_istream<charT, traits>,
      public basic_ostream<charT, traits> {
  public:
    using char_type   = charT;
    using int_type    = typename traits::int_type;
    using pos_type    = typename traits::pos_type;
    using off_type    = typename traits::off_type;
    using traits_type = traits;
    // [iostream.cons], constructor
    explicit basic_iostream(basic_streambuf<charT, traits>* sb);
    // [iostream.dest], destructor
    virtual ~basic_iostream();
  protected:
    // [iostream.cons], constructor
    basic_iostream(const basic_iostream& rhs) = delete;
    basic_iostream(basic_iostream&& rhs);
    // [iostream.assign], assign and swap
    basic_iostream& operator=(const basic_iostream& rhs) = delete;
    basic_iostream& operator=(basic_iostream&& rhs);
    void swap(basic_iostream& rhs);
  };
}The class template basic_iostream inherits a number of functions that allow reading input and writing output to sequences controlled by a stream buffer.
explicit basic_iostream(basic_streambuf<charT, traits>* sb);
Effects: Constructs an object of class basic_iostream, initializing the base class subobjects with basic_istream<charT, traits>(sb) and basic_ostream<charT, traits>(sb).
basic_iostream(basic_iostream&& rhs);
virtual ~basic_iostream();
basic_iostream& operator=(basic_iostream&& rhs);
void swap(basic_iostream& rhs);