C++ In a Nutshell

<cwchar>

The <cwchar> header is the C++ version of the C standard <wchar.h> header, which declares types and functions for working with wide characters. Many of these functions are wide versions of functions found in <cstdio> and <cstring> plus improved versions of the multibyte functions from <cstdlib>.

You can use narrow (byte-oriented) I/O functions, as declared in <cstdio>, or wide I/O functions, as declared in <cwchar>, but you cannot mix wide and narrow functions on a single stream without explicitly changing the stream’s orientation (see the fwide function in this section for details).

Wide I/O treats a file as a sequence of multibyte characters. When reading, multibyte characters are converted to wide characters, and when writing, wide characters are converted to multibyte characters. The conversion depends on the C locale (set with setlocale in <clocale>).

See Chapter 1 for information about character sets, Chapter 8 for information about multibyte characters and shift states, and Chapter 9 for information about wide characters and I/O.

When working with wide characters, consider using the C++ I/O streams and wstring class instead of the C functions. (See <string> later in this chapter for the wstring class and the char_traits class template.) The <locale> header provides additional support for converting between narrow and wide characters (the codecvt and related facets).