Defined in header <cwchar>
std::wint_t btowc( int c );

Widens a single-byte character c to its wide character equivalent.

Most multibyte character encodings use single-byte codes to represent the characters from the ASCII character set. This function may be used to convert such characters to wchar_t.


c - single-byte character to widen

Return value

WEOF if c is EOF.

Wide character representation of c if (unsigned char)c is a valid single-byte character in the initial shift state, WEOF otherwise.


#include <clocale>
#include <cwchar>
#include <iostream>
void try_widen(char c)
    std::wint_t w = std::btowc(c);
    if (w != WEOF)
        std::cout << "The single-byte character " << +(unsigned char)c
                  << " widens to " << +w << '\n';
        std::cout << "The single-byte character " << +(unsigned char)c
                  << " failed to widen\n";
int main()
    std::setlocale(LC_ALL, "lt_LT.iso88594");
    std::cout << std::hex << std::showbase << "In Lithuanian ISO-8859-4 locale:\n";
    try_widen('\xdf'); // German letter ß (U+00df) in ISO-8859-4
    try_widen('\xf9'); // Lithuanian letter ų (U+0173) in ISO-8859-4
    std::setlocale(LC_ALL, "lt_LT.utf8");
    std::cout << "In Lithuanian UTF-8 locale:\n";

Possible output:

In Lithuanian ISO-8859-4 locale:
The single-byte character 0x41 widens to 0x41
The single-byte character 0xdf widens to 0xdf
The single-byte character 0xf9 widens to 0x173
In Lithuanian UTF-8 locale:
The single-byte character 0x41 widens to 0x41
The single-byte character 0xdf failed to widen
The single-byte character 0xf9 failed to widen

See also

narrows a wide character to a single-byte narrow character, if possible
converts a character or characters from char to CharT
(virtual protected member function of std::ctype<CharT>)
C documentation for btowc

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