Now in paperback, this classic book is addressed to all lovers of number theory. On the one hand, it gives a comprehensive introduction to constructive algebraic number theory, and is therefore especially suited as a textbook for a course on that subject. On the other hand many parts go beyond an introduction and make the user familiar with recent research in the field. New methods which have been developed for experimental number theoreticians are included along with new and important results. Both computer scientists interested in higher arithmetic and those teaching algebraic number theory will find the book of value.