1. In a computer system including input and output devices and a dictionary of terms each of which has a code indicating the way in which the term may be associated to form compound words, a process for isolating the unknown components of an input compound word which is misspelled or for which the dictionary of terms does not contain all of its components, comprising: identifying all dictionary terms which have a code indicating that they can be initial substrings of compound words and which are initial substrings of said input compound word; for each said initial substring, identifying in turn the remaining substring of the input compound word by retaining the portion of the compound word succeeding the initial substring; identifying the unknown components of the input compound word to be the set of said remaining substrings truncated at a point where any terminal substring starts.