The wide-character functions use two headers: and .
The header defines the types wint_t, wctrans_t, and wctype_t.
The wide-character functions operate on characters of type wchar_t, which are 16 bits.
The types wctrans_t and wctype_t are used to represent a character mapping (character translation) and the classification of a character, respectively.
The wide-character EOF is defined as WEOF.
The mbstate_t type describes the state of conversion from a multibyte to wide-character .
The header also defines the macros NULL, WEOF, WCHAR_MAX, and WCHAR_MIN. The last two define the maximum and minimum value that can be held in an object of type wchar_t.