The book Operating System is an insightful work that elaborates on fundamentals as well as advanced topics of the discipline. Keeping the needs of the students in mind, this book offers an in-depth coverage of concepts, design and functions of an operating system irrespective of the hardware used. With neat illustrations and examples and presentation of difficult concepts in the simplest form, the aim is to make the subject crystal clear to the students, and the book extremely student-friendly. The book caters to undergraduate students of most Indian universities, who would find the introductory and advanced discussions highly informative and enriching. Tailored as a guide for self-paced learning the book equips budding system programmers with the right knowledge and expertise. The topics covered include: Organization of the computer system; communication between processes; threads and multithreading models; scheduling criteria and algorithms; synchronization among cooperating processes; deadlock situation; memory management; virtual memory; I/O system; disk scheduling algorithms, disk management, swap-space management and RAID; file types, attributes and access methods; managing files, directories and disc space; security and protection in computers; UNIX and Linux operating systems; implementation of various OS concepts in Windows 2000; multiprocessor and distributed systems.