Determine if an integer represents character that is a hex digit.
int isxdigit(
   int c 
);
int iswxdigit(
   wint_t c 
);
int _isxdigit_l(
   int c,
   _locale_t locale
);
int _iswxdigit_l(
   wint_t c,
   _locale_t locale
);
Parameters
- c 
 Integer to test.
- locale 
 Locale to use.
Return Value
Each of these routines returns nonzero if c is a particular representation of a hexadecimal digit. isxdigit returns a nonzero value if c is a hexadecimal digit (A – F, a – f, or 0 – 9). iswxdigit returns a nonzero value if c is a wide character that corresponds to a hexadecimal digit character. Each of these routines returns 0 if c does not satisfy the test condition.
For the "C" locale, the iswxdigitfunction does not provide support for Unicode full width hexadecimal characters.
When used with a debug CRT library, isxdigit will display a CRT assert if passed a parameter that is not EOF or in the range of 0 through 0xFF. When used with a debug CRT library, isxdigit will use the parameter as an index into an array, with undefined results if the parameter is not EOF or in the range of 0 through 0xFF.
The versions of these functions with the _l suffix are identical except that they use the locale passed in instead of the current locale for their locale-dependent behavior. For more information, see Locale.
Generic-Text Routine Mappings
| TCHAR.H routine | _UNICODE & _MBCS not defined | _MBCS defined | _UNICODE defined | 
|---|---|---|---|
| _istxdigit | isxdigit | isxdigit | iswxdigit | 
Requirements
| Routine | Required header | 
|---|---|
| isxdigit | <ctype.h> | 
| iswxdigit | <ctype.h> or <wchar.h> | 
| _isxdigit_l | <ctype.h> | 
| _iswxdigit_l | <ctype.h> or <wchar.h> | 
For additional compatibility information, see Compatibility in the Introduction.