isalpha, iswalpha, _isalpha_l, _iswalpha_l

Determines whether an integer represents an alphabetic character.


int isalpha(
   int c
int iswalpha(
   wint_t c
int _isalpha_l(
   int c,
   _locale_t locale
int _iswalpha_l(
   wint_t c,
   _locale_t locale


Integer to test.

The locale to use instead of the current locale.

Return value

Each of these routines returns nonzero if c is a particular representation of an alphabetic character. isalpha returns a nonzero value if c is within the ranges A - Z or a - z. iswalpha returns a nonzero value only for wide characters for which iswupper or iswlower is nonzero; that is, for any wide character that is one of an implementation-defined set for which none of iswcntrl, iswdigit, iswpunct, or iswspace is nonzero. 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 parameter that's passed in instead of the current locale. For more information, see Locale.

The behavior of isalpha and _isalpha_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
_istalpha isalpha _ismbcalpha iswalpha
_istalpha_l _isalpha_l _ismbcalpha_l _iswalpha_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
isalpha <ctype.h>
iswalpha <ctype.h> or <wchar.h>
_isalpha_l <ctype.h>
_iswalpha_l <ctype.h> or <wchar.h>

For more compatibility information, see Compatibility.

See also

Character classification
is, isw routines