This is a comprehensive textbook for B.E./B.Tech. students of Computer Science and Engineering, Information Technology, BCA and MCA. The book discusses the concepts, principles and applications of Operating Systems in an easy-to-understand language. It also incorporates several experiments to be performed in O.S. labs.\n\nDivided into four units, this book describes the history, evolution, functions, types and characteristics of Operating Systems. It provides a detailed account of memory management, virtual memory, processes, CPU scheduling and process synchronization. Moreover, it covers deadlocks, device management and secondary storage structure. Besides the book also explains information management, assembly language programming and protection. The text is supported by several practical examples and case studies.