Collaboration diagram for I/O:

Classes
class	std::basic_filebuf< _CharT, _Traits >

class	std::basic_fstream< _CharT, _Traits >

class	std::basic_ifstream< _CharT, _Traits >

class	std::basic_ios< _CharT, _Traits >

class	std::basic_iostream< _CharT, _Traits >

class	std::basic_istream< _CharT, _Traits >

class	std::basic_istringstream< _CharT, _Traits, _Alloc >

class	std::basic_ofstream< _CharT, _Traits >

class	std::basic_ostream< _CharT, _Traits >

class	std::basic_ostringstream< _CharT, _Traits, _Alloc >

class	std::basic_streambuf< _CharT, _Traits >

class	std::basic_stringbuf< _CharT, _Traits, _Alloc >

class	std::basic_stringstream< _CharT, _Traits, _Alloc >

class	std::ios_base::failure

class	std::ios_base

class	std::istreambuf_iterator< _CharT, _Traits >

class	std::ostreambuf_iterator< _CharT, _Traits >

class	__gnu_cxx::stdio_filebuf< _CharT, _Traits >

class	__gnu_cxx::stdio_sync_filebuf< _CharT, _Traits >

Typedefs
typedef basic_filebuf< char >	std::filebuf

typedef basic_fstream< char >	std::fstream

typedef basic_ifstream< char >	std::ifstream

typedef basic_ios< char >	std::ios

typedef basic_iostream< char >	std::iostream

typedef basic_istream< char >	std::istream

typedef basic_istringstream< char >	std::istringstream

typedef basic_ofstream< char >	std::ofstream

typedef basic_ostream< char >	std::ostream

typedef basic_ostringstream< char >	std::ostringstream

typedef basic_streambuf< char >	std::streambuf

typedef basic_stringbuf< char >	std::stringbuf

typedef basic_stringstream< char >	std::stringstream

typedef basic_filebuf< wchar_t >	std::wfilebuf

typedef basic_fstream< wchar_t >	std::wfstream

typedef basic_ifstream< wchar_t >	std::wifstream

typedef basic_ios< wchar_t >	std::wios

typedef basic_iostream< wchar_t >	std::wiostream

typedef basic_istream< wchar_t >	std::wistream

typedef basic_istringstream< wchar_t >	std::wistringstream

typedef basic_ofstream< wchar_t >	std::wofstream

typedef basic_ostream< wchar_t >	std::wostream

typedef basic_ostringstream< wchar_t >	std::wostringstream

typedef basic_streambuf< wchar_t >	std::wstreambuf

typedef basic_stringbuf< wchar_t >	std::wstringbuf

typedef basic_stringstream< wchar_t >	std::wstringstream

Detailed Description

Nearly all of the I/O classes are parameterized on the type of characters they read and write. (The major exception is ios_base at the top of the hierarchy.) This is a change from pre-Standard streams, which were not templates.

For ease of use and compatibility, all of the basic_* I/O-related classes are given typedef names for both of the builtin character widths (wide and narrow). The typedefs are the same as the pre-Standard names, for example:

typedef basic_ifstream<char> ifstream;

Because properly forward-declaring these classes can be difficult, you should not do it yourself. Instead, include the <iosfwd> header, which contains only declarations of all the I/O classes as well as the typedefs. Trying to forward-declare the typedefs themselves (e.g., class ostream;) is not valid ISO C++.

For more specific declarations, see https://gcc.gnu.org/onlinedocs/libstdc++/manual/io.html#std.io.objects