5. Structure as in claim 4, wherein each of said shift registers is capable of storing a plurality of K bits, where K is a positive integer, and the data stored within said N shift registers indicates which textual characters have been decoded and the relative position of said textual characters within said textual material.
5. Structure as in claim 4, wherein each of said shift registers is capable of storing a plurality of K bits, where K is a positive integer, and the data stored within said N shift registers indicates which textual characters have been decoded and the relative position of said textual characters within said textual material. 7. Structure as in claim 5 wherein said means for comparing comprises a plurality of logical gates, each said logical gate corresponding to one character string to be decoded and wherein each said logical gate comprises: a plurality of K input leads corresponding to an equal plurality of K characters comprising a desired character string, said input lead corresponding to the kth character (where kth is an integer given by 1.ltoreq./.ltoreq.K) from the end of said desired character string being connected to the kth least significant bit of said shift register associated with said kth character.