This well-organized and comprehensive book, written in an easy-to-understand language, provides a deep insight into the working of an operating system, which is essentially a concurrent program, and strikes a fine balance between theory and practice. The text provides the program design illustration and guidance along with new concepts. It gives an in-depth analysis of the fundamental concepts of an OS as an interrupt driven program whose basic constituents are the processes giving rise to a concurrent program. Further, the book gives a comprehensive coverage of such topics as CPU scheduling, device scheduling, deadlocks, memory management, file system, and the considerations of the security of the whole system. The programs discussed in the text are in C language and have been successfully run and tested in the Linux operating system.