multibytewidecharacter

Multibyte wide character is a term used to describe how a single character can be represented in two related forms in some programming environments: as a multibyte sequence of bytes in a character encoding, and as a wide character in a wide-character type. It is not a formal standard type itself, but rather a concept that arises when dealing with international text in languages such as C and C++. The idea is to bridge processing of encoded text (multibyte characters) with processing of wide characters in code points.

In C and C++, the wide-character type is wchar_t, while multibyte characters are sequences of char. The size and encoding of wchar_t are implementation-defined and can differ between platforms (for example, 2 bytes on many Windows environments and 4 bytes on many Unix-like systems). Conversions between multibyte sequences and wide characters are performed with standard library facilities, including functions such as mblen, mbtowc, wcrtomb, and the pair mbstowcs / wcstombs, aided by the mbstate_t object that preserves conversion state.

The active locale influences how multibyte sequences map to wide characters. Programs can set the locale with setlocale, which affects character classification, encoding rules, and conversion behavior. In modern software design, UTF-8 is a common multibyte encoding, while wide-character usage varies by platform. When portability is important, developers must account for differences in wchar_t size and encoding, and may prefer using UTF-8 with char-based APIs or carefully managed conversions between multibyte and wide representations. Potential pitfalls include differences in surrogate handling, endianness, and locale-dependent behavior.