This book is based on the Open University course units on concurrency and is a presentation of the techniques of concurrency and sequential programming. The authors introduce the Open Development Method, which provides a progression from a specification in CSP (Communication Sequential Processes)through refinement to code in Occam. The book is divided into four sections: Part 1 introduces concurrent processes and process networks, Part 2 gradually presents the elements of CSP notation. Parts 3 and 4 use these techniques to apply the full development method to several realistic case studies.