toupper, _toupper, towupper, _toupper_l, _towupper_l

Convert character to uppercase.

int toupper(
   int c 
int _toupper(
   int c 
int towupper(
   wint_t c 
int _toupper_l(
   int c ,
   _locale_t locale
int _towupper_l(
   wint_t c ,
   _locale_t locale


  • c
    Character to convert.

  • locale
    Locale to use.

Return Value

Each of these routines converts a copy of c, if possible, and returns the result.

If c is a wide character for which iswlower is nonzero and there is a corresponding wide character for which iswupper is nonzero, towupper returns the corresponding wide character; otherwise, towupper returns c unchanged.

There is no return value reserved to indicate an error.

In order for toupper to give the expected results, __isascii and islower must both return nonzero.


Each of these routines converts a given lowercase letter to an uppercase letter if possible and appropriate. The case conversion of towupper is locale-specific. Only the characters relevant to the current locale are changed in case. The functions without the _l suffix use the currently set locale. The versions of these functions with the _l suffix take the locale as a parameter and use that instead of the currently set locale. For more information, see Locale.

In order for toupper to give the expected results, __isascii and isupper must both return nonzero.

Data Conversion Routines

Generic-Text Routine Mappings

TCHAR.H routine

_UNICODE & _MBCS not defined

_MBCS defined

_UNICODE defined










_toupper_l and _towupper_l have no locale dependence and are not meant to be called directly. They are provided for internal use by _totupper_l.



Required header






<ctype.h> or <wchar.h>

For additional compatibility information, see Compatibility in the Introduction.


See the example in to Functions.

.NET Framework Equivalent


See Also


is, isw Routines

to Functions


Interpretation of Multibyte-Character Sequences