isdigit, iswdigit, _isdigit_l, _iswdigit_l

Determines whether an integer represents a decimal-digit character.


int isdigit(
   int c
int iswdigit(
   wint_t c
int _isdigit_l(
   int c,
   _locale_t locale
int _iswdigit_l(
   wint_t c,
   _locale_t locale


Integer to test.

The locale to use.

Return value

Each of these routines returns nonzero if c is a particular representation of a decimal-digit character. isdigit returns a nonzero value if c is a decimal digit (0 - 9). iswdigit returns a nonzero value if c is a wide character that corresponds to a decimal-digit character. Each of these routines returns 0 if c doesn't satisfy the test condition.

The versions of these functions that have the _l suffix use the locale that's passed in instead of the current locale for their locale-dependent behavior. For more information, see Locale.

The behavior of isdigit and _isdigit_l is undefined if c isn't EOF or in the range 0 through 0xFF, inclusive. When a debug CRT library is used and c isn't one of these values, the functions raise an assertion.

Generic-text routine mappings

TCHAR.H routine _UNICODE and _MBCS not defined _MBCS defined _UNICODE defined
_istdigit isdigit _ismbcdigit iswdigit
_istdigit_l _isdigit_l _ismbcdigit_l _iswdigit_l


By default, this function's global state is scoped to the application. To change this behavior, see Global state in the CRT.


Routine Required header
isdigit <ctype.h>
iswdigit <ctype.h> or <wchar.h>
_isdigit_l <ctype.h>
_iswdigit_l <ctype.h> or <wchar.h>

For more compatibility information, see Compatibility.

See also

Character classification
is, isw routines