Single-byte to wide-character conversion.
Standard Library (libc.a)
#include <stdio.h>
#include <wchar.h>
wint_t btowc (intc);
The btowc function determines whether c constitutes a valid (one-byte) character in the initial shift state.
The behavior of this function is affected by the LC_CTYPE category of the current locale.
The btowc function returns WEOF if c has the value EOF or if (unsigned char) c does not constitute a valid (one-byte) character in the initial shift state. Otherwise, it returns the wide-character representation of that character.