Reads a sequence of 8-bit extended ASCII characters over the alphabet { A, C, T, G } from standard input; compresses them using two bits per character; and writes the results to standard output.

Reads a binary sequence from standard input; converts each two bits to an 8-bit extended ASCII character over the alphabet { A, C, T, G }; and writes the results to standard output.

Sample client that calls compress() if the command-line argument is "-" an expand() if it is "+".