isupper, _isupper_l, iswupper, _iswupper_l

Determines whether an integer represents an uppercase character.

int isupper(
   int c 
int _isupper_l (
   int c,
   _locale_t locale
int iswupper(
   wint_t c 
int _iwsupper_l(
   wint_t c,
   _locale_t locale 


  • c
    Integer to test.

  • locale
    Locale to use.

Return Value

Each of these routines returns nonzero if c is a particular representation of an uppercase letter. isupper returns a nonzero value if c is an uppercase character (A – Z). iswupper returns a nonzero value if c is a wide character that corresponds to an uppercase 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 does not 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 isupper and _isupper_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







_ismbclower, _ismbclower_l, _ismbcupper, _ismbcupper_l




Required header






<ctype.h> or <wchar.h>



For additional compatibility information, see Compatibility.

.NET Framework Equivalent


See Also


Character Classification


is, isw Routines