The header
<string> defines the
basic_string class template for manipulating
varying-length sequences of char-like objects and five
typedef-names,
string,
u8string,
u16string,
u32string,
and
wstring, that name
the specializations
basic_string<char>,
basic_string<char8_t>,
basic_string<char16_t>,
basic_string<char32_t>,
and
basic_string<wchar_t>, respectively
.