There are several theories of programming. The first usable theory, often called "Hoare's Logic," is still probably the most widely known. In it, a specification is a pair of predicates: a precondition and postcondition (these and all technical terms will be defined in due course). Another popular and closely related theory by Dijkstra uses the weakest precondition predicate transformer, which is a function from programs and postconditions to preconditions. lones's Vienna Development Method has been used to advantage in some industries; in it, a specification is a pair of predicates (as in Hoare's Logic), but the second predicate is a relation. Temporal Logic is yet another formalism that introduces some special operators and quantifiers to describe some aspects of computation. The theory in this book is simpler than any of those just mentioned. In it, a specification is just a boolean expression. Refinement is just ordinary implication. This theory is also more general than those just mentioned, applying to both terminating and nonterminating computation, to both sequential and parallel computation, to both stand-alone and interactive computation. And it includes time bounds, both for algorithm classification and for tightly constrained real-time applications.

Understanding programming and programming languages requires knowledge of the underlying theoretical model. This book explores aspects of programming that are amenable to mathematical proof. The author describes a programming theory which is much simpler and more comprehensive than the current theories to date. In the theoretical model, a specification is just a boolean expression and refinement is just an ordinary implication. The author develops a practical and broad method for writing precise specifications and designing programs whose executions probably satisfy the specifications. Beginning with preparatory material in logic, numbers, sets, lists, functions and relations, the book advances further into program theory, the heart of the book. Subsequent chapters may be selected or omitted according to course emphasis. The text will be useful to students in courses on programming methodology or verification at the advanced undergraduate or beginning graduate level, as well as for software engineers in the field. All technical terms are explained and then demonstrated in the book wherever possible. No advanced mathematical knowledge or programming language is assumed.The book contains numerous exercises and worked-out solutions for specific exercises. Transparency masters and solutions for the remaining exercises are available from the author.