The header wchar.h includes specific definitions for use with wide character sets.

Defines	Definitions
WCHAR_MIN	Minimum value of a wide char
WCHAR_MAX	Maximum value of a wide char
WEOF	A value that differs from any member of the wide-character set and is used to denote end of file
EILSEQ	Value stored in errno to report a wide char sequence error
wctrans_t	Scalar type for locale-specific wide char mappings