isleadbyte, _isleadbyte_l
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isleadbyte, _isleadbyte_l

Determine if a character is the lead byte of a multibyte character.

Important note Important

This API cannot be used in applications that execute in the Windows Runtime. For more information, see CRT functions not supported with /ZW.

int isleadbyte(
   int c 
int _isleadbyte_l(
   int c 


Integer to test.

isleadbyte returns a nonzero value if the argument satisfies the test condition or 0 if it does not. In the "C" locale and in single-byte character set (SBCS) locales, isleadbyte always returns 0.

The isleadbyte macro returns a nonzero value if its argument is the first byte of a multibyte character. isleadbyte produces a meaningful result for any integer argument from –1 (EOF) to UCHAR_MAX (0xFF), inclusive.

The expected argument type of isleadbyte is int; if a signed character is passed, the compiler may convert it to an integer by sign extension, yielding unpredictable results.

The version of this function with the _l suffix is identical except that it uses the locale passed in instead of the current locale for its locale-dependent behavior.

Generic-Text Routine Mappings

TCHAR.H routine

_UNICODE & _MBCS not defined

_MBCS defined

_UNICODE defined


Always returns false

_ isleadbyte

Always returns false


Required header





For additional compatibility information, see Compatibility in the Introduction.

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