This book thoroughly reviews the history of the development of embedded Operating Systems, covers the technical characteristics, historic facts, as well as background business stories of mainstream embedded Operating Systems, and analyzes the technical evolution, market development, and new opportunities of embedded Operating Systems in the age of the Internet of Things. From the perspective of time, the book examines the evolution of critical technical aspects, including real-time and Power Management of embedded Operating Systems and Linux, Internet of Things security, communication, and cloud computing. The book looks into applications of embedded Operating Systems with important markets of mobile phones, communication equipment, automobile, and wearable devices, and also discusses business model and the issue of intellectual property of embedded Operating Systems. In addition, the book walks through the status quo, technical features, product evaluation and background of the Internet of Things Operating Systems in the second half of the book.