# isalnum, iswalnum, _isalnum_l, _iswalnum_l

Visual Studio 2005

Determines if a particular character is an alphanumeric character.

```
int isalnum(
int c
);
int iswalnum(
wint_t c
);
int _isalnum_l(
int c,
_locale_t locale
);
int _iswalnum_l(
wint_t c,
_locale_t locale
);
```

#### Parameters

c

Integer to test.

locale

The locale to use.

## Return Value

Each of these routines returns nonzero if c is a particular representation of an alphanumeric character. isalnum returns a nonzero value if either isalpha or isdigit is nonzero for c, that is, if c is within the ranges A – Z, a – z, or 0 – 9. iswalnum returns a nonzero value if either iswalpha or iswdigit is nonzero for c. Each of these routines returns 0 if c does not satisfy the test condition.

When used with a debug CRT library, isalnum will display a CRT assert if passed a parameter that is not EOF or in the range of 0 through 0xFF. isalnum 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 parameter passed in instead of the current locale.

Generic-Text Routine Mappings
TCHAR.H routine _UNICODE & _MBCS not defined _MBCS defined _UNICODE defined

_istalnum

isalnum

iswalnum

_istalnum_l

_isalnum_l

_ismbcalnum_l

_iswalnum_l

## Requirements

isalnum

<ctype.h>

ANSI, Windows 95, Windows 98, Windows 98 Second Edition, Windows Millennium Edition, Windows NT 4.0, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003

iswalnum

<ctype.h> or <wchar.h>

ANSI, Windows 95, Windows 98, Windows 98 Second Edition, Windows Millennium Edition, Windows NT 4.0, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003

_isalnum_l

<ctype.h>

Windows 95, Windows 98, Windows 98 Second Edition, Windows Millennium Edition, Windows NT 4.0, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003

_iswalnum_l

<ctype.h> or <wchar.h>

Windows 95, Windows 98, Windows 98 Second Edition, Windows Millennium Edition, Windows NT 4.0, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003

For additional compatibility information, see Compatibility in the Introduction.