This book is designed for a one-semester operating-systems course for advanced undergraduates and beginning graduate students. Prerequisites for the course generally include an introductory course on computer architecture and an advanced programming course. The goal of this book is to bring together and explain current practice in operating systems. This includes much of what is traditionally covered in operating-system textbooks: concurrency, scheduling, linking and loading, storage management (both real and virtual), file systems, and security. However, the book also covers issues that come up every day in operating-systems design and implementation but are not often taught in undergraduate courses. For example, the text includes: Deferred work, which includes deferred and asynchronous procedure calls in Windows, tasklets in Linux, and interrupt threads in Solaris. The intricacies of thread switching, on both uniprocessor and multiprocessor systems. Modern file systems, such as ZFS and WAFL. Distributed file systems, including CIFS and NFS version 4. The book and its accompanying significant programming projects make students come to grips with current operating systems and their major operating-system components and to attain an intimate understanding of how they work.