Show that a binary alphabet suffices. That is, given Turing Machine M with alphabet A, create a new Turing Machine Mo with a binary alphabet that carries out the same computation as M.
Furthermore, x E L(M) exactly if 6(x) € L(Mb), where b(x) denotes the encoding of x in binary.
Hint. Encode each character of A using [log A] binary symbols, and make Mb's finite control sufficiently larger than that of M so that it can "read" and "write" a character of M.