The fifth edition address the important changes that have occurred in the construction of real-time systems since the publising of the fourth edition in 2011. Some of the important innovations and developments include: safety critical systems, internet of things, mobile computing, software security, and the virtualization of small real-time systems. It is an introductory text about real-time systems -- systems where timeliness is a crucial part of the correctness of the system. Real-time software designers must be familiar with computer architecture and organization, operating systems, software engineering, programming languages, and compiler theory. The text provides a pragmatic overview of these subjects from the perspective of the real-time systems designer. The book is organized into chapters that are essentially self-contained. Thus, the material can be rearranged or omitted depending on the background and interests of the reader or instructor.