' c-char ' | (1) | |
u ' c-char ' (since C11) | (2) | |
U ' c-char ' (since C11) | (3) | |
L ' c-char ' | (4) | |
' c-char-sequence ' | (5) |
where.
'), backslash (\), or the newline character. \' \" \? \\ \a \b \f \n \r \t \v, hex escapes \x... or octal escapes \... as defined in escape sequences.
| (since C99) |
'a' or '\n' or '\13'. Such constant has type int and a value equal to the representation of c-char in the execution character set as a value of type char mapped to int. If c-char is not representable as a single byte in the execution character set, the value is implementation-defined.u'่ฒ', but not u'๐' (u'\U0001f34c'). Such constant has type char16_t and a value equal to the value of c-char in the 16-bit encoding produced by mbrtoc16 (normally UTF-16). If c-char is not representable or maps to more than one 16-bit character, the behavior is implementation-defined.U'่ฒ' or U'๐'. Such constant has type char32_t and a value equal to the value of c-char in in the 32-bit encoding produced by mbrtoc32 (normally UTF-32). If c-char is not representable or maps to more than one 32-bit character, the behavior is implementation-defined.L'ฮฒ' or L'่ฒ. Such constant has type wchar_t and a value equal to the value of c-char in the execution wide character set (that is, the value that would be produced by mbtowc). If c-char is not representable or maps to more than one wide character (e.g. a non-BMP value on Windows where wchar_t is 16-bit), the behavior is implementation-defined .'AB', has type int and implementation-defined value.Many implementations of multicharacter constants use the values of each char in the constant to initialize successive bytes of the resulting integer, in big-endian order, e.g. the value of '\1\2\3\4' is 0x01020304.
In C++, ordinary character constants have type char, rather than int.
Unlike integer constants, a character constant may have a negative value if char is signed: on such implementations '\xFF' is an int with the value -1.
When used in a controlling expression of #if or #elif, character constants may be interpreted in terms of the source character set, the execution character set, or some other implementation-defined character set.
#include <stddef.h>
#include <stdio.h>
#include <uchar.h>
int main (void)
{
printf("constant value \n");
printf("-------- ----------\n");
// integer character constants,
int c1='a'; printf("'a': %#010x\n", c1);
int c2='๐'; printf("'๐': %#010x\n\n", c2); // implementation-defined
// multicharacter constant
int c3='ab'; printf("'ab': %#010x\n\n", c3); // implementation-defined
// 16-bit wide character constants
char16_t uc1 = u'a'; printf("'a': %#010x\n", (int)uc1);
char16_t uc2 = u'ยข'; printf("'ยข': %#010x\n", (int)uc2);
char16_t uc3 = u'็ซ'; printf("'็ซ': %#010x\n", (int)uc3);
// implementation-defined (๐ maps to two 16-bit characters)
char16_t uc4 = u'๐'; printf("'๐': %#010x\n\n", (int)uc4);
// 32-bit wide character constants
char32_t Uc1 = U'a'; printf("'a': %#010x\n", (int)Uc1);
char32_t Uc2 = U'ยข'; printf("'ยข': %#010x\n", (int)Uc2);
char32_t Uc3 = U'็ซ'; printf("'็ซ': %#010x\n", (int)Uc3);
char32_t Uc4 = U'๐'; printf("'๐': %#010x\n\n", (int)Uc4);
// wide character constants
wchar_t wc1 = L'a'; printf("'a': %#010x\n", (int)wc1);
wchar_t wc2 = L'ยข'; printf("'ยข': %#010x\n", (int)wc2);
wchar_t wc3 = L'็ซ'; printf("'็ซ': %#010x\n", (int)wc3);
wchar_t wc4 = L'๐'; printf("'๐': %#010x\n\n", (int)wc4);
}Possible output:
constant value -------- ---------- 'a': 0x00000061 '๐': 0xf09f8d8c 'ab': 0x00006162 'a': 0x00000061 'ยข': 0x000000a2 '็ซ': 0x0000732b '๐': 0x0000df4c 'a': 0x00000061 'ยข': 0x000000a2 '็ซ': 0x0000732b '๐': 0x0001f34c 'a': 0x00000061 'ยข': 0x000000a2 '็ซ': 0x0000732b '๐': 0x0001f34c
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