8. A system according to claim 1, wherein each possible character in the stream of characters is classified into one of a plurality of Types and the followset means includes means for storing, accessing and updating a followset table, for each of a plurality of ordered character groups, each group including a last character therein and the Type of the character immediately preceding the last character, i.e., the Type of the next-to-last character, such table listing candidates for the character which may follow, in the stream, the character group with which the table is associated.
8. A system according to claim 1, wherein each possible character in the stream of characters is classified into one of a plurality of Types and the followset means includes means for storing, accessing and updating a followset table, for each of a plurality of ordered character groups, each group including a last character therein and the Type of the character immediately preceding the last character, i.e., the Type of the next-to-last character, such table listing candidates for the character which may follow, in the stream, the character group with which the table is associated. 9. A system according to claim 8, wherein the character group consists of the last character therein, the Type of the next-to-last character, and the Type of the character immediately preceding the next-to-last character.