Part II, The Prolog Language, has been modified to be compatible with the new Prolog standard, and the chapter on program development has been significantly modified: predicates defined have been moved to a more appropriate chapter, section on efficiency has moved into a very expanded chapter on cuts and negation, and a new section was added to a gradual improvement - a systematic way to build Prolog programs developed by Leon Sterling. Chapters on the transformation program and a completely new chapter on logic grammars adds new material to recognize simple language, showing how grammars apply to more computer science examples.