The volume contains the proceedings of the 16th Spring School on Theoretical Computer Science held in Ramatuelle, France, in May 1988. It is a unique combination of research level articles on various aspects of the theory of finite automata and its applications. Advances made in the last five years on the mathematical foundations form the first part of the book. The second part is devoted to the important problems of the theory including star-height, concatenation hierarchies, and connections with logic and word problems. The last part presents a large variety of possible applications: number theory, distributed systems, algorithms on strings, theory of codes, complexity of boolean circuits and others.