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.
126.96.36.199.1 Uppercase Characters
188.8.131.52.2 Lowercase Characters
184.108.40.206.3 Corresponding Characters in the Other Case
220.127.116.11.4 Case of Implementation-Defined Characters