The present book, designed fora wide circle of readers (familiarity with math­ ematics up to high school level suffices for comprehension of all of its contents), makes, of course, no claim to serve even as an elementary introduction to the scientific information theory. We can give here only a preliminary idea of import­ ant practical applications of this theory. Similarly, it shall not be possible to deal here with the deeper purely mathematical problems connected with the in­ formation theory. The main aim of the authors is much simpler : it consists of acquainting the reader with certain, though not complex but highly important, new mathematical ideas, and leading him through these ideas to an understand­ ing of one of the possible means of employing mathematical methods of modern engineering.