The characters with case are a subset of the alphabetic characters. A character with case has the property of being either uppercase or lowercase. Every character with case is in one-to-one correspondence with some other character with the opposite case.
18.104.22.168.1 Uppercase Characters
22.214.171.124.2 Lowercase Characters
126.96.36.199.3 Corresponding Characters in the Other Case
188.8.131.52.4 Case of Implementation-Defined Characters