isalpha, iswalpha, _isalpha_l, _iswalpha_l

Determines whether an integer represents an alphabetic character.

Syntax

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
);

Parameters

c
Integer to test.

locale
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 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 isalpha and _isalpha_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
_istalpha isalpha _ismbcalpha iswalpha
_istalpha_l _isalpha_l _ismbcalpha_l _iswalpha_l

Requirements

Routine Required header
isalpha <ctype.h>
iswalpha <ctype.h> or <wchar.h>
_isalpha_l <ctype.h>
_iswalpha_l <ctype.h> or <wchar.h>

For additional compatibility information, see Compatibility.

See also

Character Classification
Locale
is, isw Routines