isalnum, iswalnum, _isalnum_l, _iswalnum_l

Determines whether an integer represents an alphanumeric character.


int isalnum( int c );
int iswalnum( wint_t c );
int _isalnum_l( int c,  _locale_t locale );
int _iswalnum_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 an alphanumeric character. isalnum returns a nonzero value if either isalpha or isdigit is nonzero for c, that is, if c is within the ranges A - Z, a - z, or 0 - 9. iswalnum returns a nonzero value if either iswalpha or iswdigit is nonzero for c. Each of these routines returns 0 if c does not satisfy the test condition.

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

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

Generic-Text Routine Mappings

TCHAR.H routine _UNICODE & _MBCS not defined _MBCS defined _UNICODE defined
_istalnum isalnum _ismbcalnum iswalnum
_istalnum_l _isalnum_l _ismbcalnum_l _iswalnum_l


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


Routine Required header
isalnum <ctype.h>
iswalnum <ctype.h> or <wchar.h>
_isalnum_l <ctype.h>
_iswalnum_l <ctype.h> or <wchar.h>

For additional compatibility information, see Compatibility.

See also

Character Classification
is, isw Routines