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Important This document may not represent best practices for current development, links to downloads and other resources may no longer be valid. Current recommended version can be found here.

isdigit, iswdigit, _isdigit_l, _iswdigit_l

Determines if a particular character is a decimal-digit character.

int isdigit( 
   int c 
);
int iswdigit( 
   wint_t c 
);
int _isdigit_l( 
   int c,
   _locale_t locale
);
int _iswdigit_l( 
   wint_t c,
   _locale_t locale
);

c

Integer to test.

locale

The locale to use.

Each of these routines returns nonzero if c is a particular representation of a decimal-digit character. isdigit returns a nonzero value if c is a decimal digit (0 – 9). iswdigit returns a nonzero value if c is a wide character corresponding to a decimal-digit character. Each of these routines returns 0 if c does not satisfy the test condition.

When used with a debug CRT library, isdigit will display a CRT assert if passed a parameter that is not EOF or in the range of 0 through 0xFF. When used with a debug CRT library, isdigit will use the parameter as an index into an array, with undefined results if the parameter is not EOF or in the range of 0 through 0xFF.

The versions of these functions with the _l suffix are identical except that they use the locale passed in instead of the current locale for their locale-dependent behavior. For more information, see Locale.

Generic-Text Routine Mappings

TCHAR.H routine

_UNICODE & _MBCS not defined

_MBCS defined

_UNICODE defined

_istdigit

isdigit

_ismbcdigit

iswdigit

_istdigit_l

_isdigit_l

_ismbcdigit_l

_iswdigit_l

Routine

Required header

isdigit

<ctype.h>

iswdigit

<ctype.h> or <wchar.h>

_isdigit_l

<ctype.h>

_iswdigit_l

<ctype.h> or <wchar.h>

For additional compatibility information, see Compatibility in the Introduction.

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