18. The decompressing means of claim 17, wherein: each of said code characters are selected from a set of code characters shared by said relative alphabets.
17. The decompressing means of claim 14, further comprising: means for storing a table relating said text and code characters and said contexts and responsive to said selecting means for providing said corresponding text characters, said table including, for each context of the language of said text, an associated relative alphabet containing said text characters occurring in association with said contexts of said language, and wherein each of said text characters of each of said relative alphabets is associated with a said corresponding code character.