<wctype.h>

The <wctype.h> include file declares functions used to classify wide characters:

iswalnum iswctype iswprint iswxdigit
iswalpha iswdigit iswpunct towlower
iswblank iswgraph iswspace towupper
iswcntrl islower iswupper wctype

<wctype.h> also defines the types wint_t and wctype_t, and the macro WEOF, which expands to a constant expression of type wint_t whose value does not correspond to any member of the extended character set and indicates EOF.