Rational Series and Their Languages

This electronic edition of the English edition is at the date of November 6, 2006, an almost literal transposition of the original text. The modifications concern notation, several proofs, one new statement, and some new exercises. It is planned that the electronic edition will progressively be modified, with inclusion of some new material, but will remain basically of the same size and of the same algebraic style. This book is an introduction to rational formal power series in several noncommutative variables and their relations to formal languages and to the theory of codes.