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.
22.214.171.124.1 Uppercase Characters
126.96.36.199.2 Lowercase Characters
188.8.131.52.3 Corresponding Characters in the Other Case
184.108.40.206.4 Case of Implementation-Defined Characters