文字操作 <ctype.h>
Name		Standards	Author
-----------------------------------------------------------
isalnum		ISO C89		Yume
isalpha		ISO C89		Yume
isascii		BSD		Yume
isblank		ISO C99		Yume
iscntrl		ISO C89		Yume
isdigit		ISO C89		Yume
isgraph		ISO C89		Yume
islower		ISO C89		Yume
isprint		ISO C89		Yume
ispunct		ISO C89		Yume
isspace		ISO C89		Yume
isupper		ISO C89		Yume
isxdigit	ISO C89		Yume
tolower		ISO C89		Yume
toupper		ISO C89		Yume
