A successful text for the upper level undergraduate operating systems course, or a supplement for real-time systems and systems programming courses. The book is known for its emphasis on design and its careful evolution from theory to practice, making it an excellent text for those courses with a lab component. The book contains a complete kernel of a multiprocess operating system (KMOS) directly usable in a PC environment or portable to other machines. The KMOS provides students and instructors with the core of a ready-made real time operating system to put theory into practice. The instructions and applications of KMOS are at the end of the text so instructors who teach a primarily theoretical course will not be hampered by it. Consistency in chapters and a topical organization provides a common thread and reference point. For example, all appropriate synchronization mechanisms are applied to the same general problem, and the same structure and outline is followed in presenting different memory-management schemes. Hardware foundation and support for operating systems is discussed throughout, establishing a link between computer architecture and operating systems. This enable students to assess the advantages and/or limitations of a given hardware for operating systems support. A clear, detailed explanation of input/output programming illustrates the intricacies of interrupt programming and the techniques and timing relationships leading to multiprogramming. Case studies allow students to relate their theoretical knowledge and design experiences to widely used contemporary operating systems such as UNIX, DOS, and OS/2. This edition contains examples from commercial operating systems added throughout to illustrate operating systems principles. Three new chapters have been added - security (chapter 9), multiprocessors (chapter 100, and distributed systems (chapetr 11). KBOS is now written in object-oriented TurboPascal to satisfy market needs.