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.
188.8.131.52.1 Uppercase Characters
184.108.40.206.2 Lowercase Characters
220.127.116.11.3 Corresponding Characters in the Other Case
18.104.22.168.4 Case of Implementation-Defined Characters