Andy Wellings is Professor of Real-Time Systems in the Department of Computer Science, University of York, U.K. His research interests are focused on two related areas of computing: the design, use and implementation of real-time programming languages and operating systems; and the design and use of general purpose distributed operating systems. Professor Wellings has published over 100 technical papers and reports, including five textbooks. He teaches courses in Operating Systems, Real-Time Systems and Networks and Distributed Systems. He was a primary contributor to the Asynchrony chapter, and part of the team for the scheduling and threads chapters.