As we embrace the world of personal portable and perplexingly complex digital systems it falls to the bewildered designer to take advantage of the available transistors to produce a system which is small fast cheap and correct yet possesses increased functionality. Increasingly these systems must consume little energy. This book examines the many ways in which processor based systems are designed to allow low power devices. It looks at processor design methods memory optimization dynamic voltage scaling methods compiler methods and multi processor methods. Each section has an introductory chapter to give a broad view and have a few specialist chapters in the area to give a deeper perspective. The book provides a good starting point to engineers in the area and to research students embarking upon the exciting area of embedded systems and architectures.