字符测试函数

isalnum(测试字符是否为英文字母或数字)

isalpha(测试字符是否为英文字母)

isascii(测试字符是否为ASCII码字符)

isblank(测试字符是否为空格字符)

iscntrl(测试字符是否为ASCII码的控制字符)

isdigit(测试字符是否为阿拉伯数字)

isgraph(测试字符是否为可打印字符)

islower(测试字符是否为小写英文字母)

isprint(测试字符是否为可打印字符)

isspace(测试字符是否为空格字符)

ispunct(测试字符是否为标点符号或特殊符号)

isupper(测试字符是否为大写英文字母)

isxdigit(测试字符是否为16进制数字)-Character test function isalnum (test whether the characters in English letters or numbers) isalpha (test whether the letters of the alphabet characters) isascii (test characters are characters in ASCII code) isblank (test characters for space characters) iscntrl (test whether the ASCII characters control character code) isdigit (test characters for Arabic numerals) isgraph (test characters are printable characters) islower (test characters are lowercase letters of the alphabet) isprint (test characters are printable characters) isspace (test whether the characters space character) ispunct (test characters for punctuation or special symbols) isupper (test characters are capitalized letters of the alphabet) isxdigit (test whether the 16 hexadecimal characters figures)