1. A method of compacting characters for storage, comprising: generating a sequence of four-bit characters in which some characters are of a first character set and other characters are taken from a second character set; inserting a given four-bit shift character not taken from either character set in said sequence of characters every time a character of either set is followed by a character of the other set; and storing said sequence of characters and said shift character in a memory means in which each memory address represents at least one pair of stored characters, each character of said at least one pair being selected from said first character set said second character set and said given shift character.