islower, iswlower, _islower_l, _iswlower_l

Determines whether an integer represents a lowercase character.


int islower(
   int c
int iswlower(
   wint_t c
int islower_l(
   int c,
   _locale_t locale
int _iswlower_l(
   wint_t c,
   _locale_t locale


Integer to test.

Locale to use.

Return value

Each of these routines returns nonzero if c is a particular representation of a lowercase character. islower returns a nonzero value if c is a lowercase character (a - z). iswlower returns a nonzero value if c is a wide character that corresponds to a lowercase letter, or if c is one of an implementation-defined set of wide characters 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 that's passed in instead of the current locale for their locale-dependent behavior. For more information, see Locale.

The behavior of islower and _islower_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
_istlower islower _ismbclower iswlower
_istlower_l _islower _l _ismbclower_l _liswlower_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
islower <ctype.h>
iswlower <ctype.h> or <wchar.h>
_islower_l <ctype.h>
_swlower_l <ctype.h> or <wchar.h>

For more compatibility information, see Compatibility.

See also

Character classification
is, isw routines