Robert Baber's original approach to the semantics of computer programs will familiarize software designers and developers with applicable results of research in the theory of proving programs correct. Throughout the book, the mathematical treatment is rigorous. A body of fundamental principles underlying computing science has been developed in recent years: these provide guidelines for the design process, and enable the software engineer to verify systematically and precisely important characteristics of proposed designs. The software engineer is thus in a position to develop error-free programs just as engineers in other fields are able to verify their designs.