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A wide character constant represents characters with more than 8 bits of character code. This is an obscure feature that we need to document but that you probably won’t ever use. If you’re just learning C, you may as well skip this section.
The original C wide character constant looks like ‘L’ (upper
case!) followed immediately by an ordinary character constant (with no
intervening space). Its data type is wchar_t, which is an
alias defined in stddef.h for one of the standard integer
types. Depending on the platform, it could be 16 bits or 32 bits. If
it is 16 bits, these character constants use the UTF-16 form of
Unicode; if 32 bits, UTF-32.
There are also Unicode wide character constants which explicitly
specify the width. These constants start with ‘u’ or ‘U’
instead of ‘L’. ‘u’ specifies a 16-bit Unicode wide
character constant, and ‘U’ a 32-bit Unicode wide character
constant. Their types are, respectively, char16_t and
char32_t; they are declared in the header file
uchar.h. These character constants are valid even if
uchar.h is not included, but some uses of them may be
inconvenient without including it to declare those type names.
The character represented in a wide character constant can be an
ordinary ASCII character. L'a', u'a' and U'a'
are all valid, and they are all equal to 'a'.
In all three kinds of wide character constants, you can write a non-ASCII Unicode character in the constant itself; the constant’s value is the character’s Unicode character code. Or you can specify the Unicode character with an escape sequence (see Unicode Character Codes).
Next: Wide String Constants, Previous: Unicode Character Codes, Up: Constants [Contents][Index]