The derived template class describes an object that can serve as a ctype facet of a given locale, enabling the classification of characters and conversion of characters between case and native and locale specified character sets.
template<class _Elem>
class ctype_byname : public ctype<_Elem>
{
public:
    explicit ctype_byname(
        const char *_Locname,
        size_t _Refs = 0
    );
    explicit ctype_byname(
        const string& _Locname,
        size_t _Refs = 0
    );
protected:
    virtual __CLR_OR_THIS_CALL ~ctype_byname();
};
Remarks
Its behavior is determined by the named locale _Locname. Each constructor initializes its base object with ctype<CharType>(_Refs) or the equivalent for base class ctype<char>.
Requirements
Header: <locale>
Namespace: std
See Also
Reference
Thread Safety in the Standard C++ Library