The fourth edition of Introduction to Languages and Theory of Computation has been substantially rewritten, and the number of chapters has been reduced from fourteen to eleven. Like its predecessors, the fourth edition takes advantage of the clarity and efficiency of mathematical language, but it focuses on readability and removing obstacles to student understanding. Technical details are provided where they help to illuminate the arguments and minimized when all they add is completeness. Informal language makes the mathematical notation more approachable, but the author is careful not to erect barriers in the form of paragraphs of prose. Examples are modified and reorganized so that each builds on previous ones; complications that turn out to be peripheral to the subject are eliminated. Many exercises have been reworked, and the selection varies from elementary to challenging. The exposition is streamlined and improved, and result is a shorter book that retains the rigor and topic selection of previous editions. //ir
