Character Classification

Each of these routines tests a specified single-byte character, wide character, or multibyte character for satisfaction of a condition. (By definition, the ASCII character set is a subset of all multibyte-character sets. For example, Japanese katakana includes ASCII as well as non-ASCII characters.) Generally these routines execute faster than tests you might write. For example, the following code executes slower than a call to isalpha(c):

if ((c >= 'A') && (c <= 'Z')) || ((c >= 'a') && (c <= 'z'))
    return TRUE;

Character-Classification Routines

Routine	Character Test Condition
isalnum, iswalnum, _ismbcalnum	Alphanumeric
isalpha, iswalpha, _ismbcalpha	Alphabetic
__isascii, iswascii	ASCII
iscntrl, iswcntrl	Control
__iscsym	Letter, underscore, or digit
__iscsymf	Letter or underscore
isdigit, iswdigit, _ismbcdigit	Decimal digit
isgraph, iswgraph, _ismbcgraph	Printable other than space
islower, iswlower, _ismbclower	Lowercase
_ismbchira	Hiragana
_ismbckata	Katakana
_ismbclegal	Legal multibyte character
_ismbcl0	Japan-level 0 multibyte character
_ismbcl1	Japan-level 1 multibyte character
_ismbcl2	Japan-level 2 multibyte character
_ismbcsymbol	Non-alphanumeric multibyte character
isprint, iswprint, _ismbcprint	Printable
ispunct, iswpunct, _ismbcpunct	Punctuation
isspace, iswspace, _ismbcspace	White-space
isupper, iswupper, _ismbcupper	Uppercase
iswctype	Property specified by desc argument
isxdigit, iswxdigit	Hexadecimal digit
mblen	Return length of valid multibyte character; result depends on LC_CTYPE category setting of current locale