字符测试函数

1.1 isxdigit()

1.2 isupper()

1.3 ispunct()

1.4 isspace()

1.5 isprint()

1.6 islower()

1.7 isgraphis()

1.8 isdigit()

1.9 iscntrl()

1.10 isascii()

1.11 isalpha()

1.12 isalnum()