Operating Systems is aimed at developing an understanding of the fundamental concepts and techniques of operating systems. This book discusses concepts, structure and techniques of operating systems encompassing everything from low-level device drivers to concurrency, etc. The text is presented in a lucid language, which sustains the readers interest and also makes the understanding of the concepts very easy. Each chapter in the text is supplemented with chapter-end exercises , points to be remembered and assistance for section exercises after each section, thus making it even more reader-friendly. The organization of the learning material differs greatly from the organization of a book; the main idea being to help the reader understand the concepts involved in operating systems very easily. This learning material will be very useful to students opting for BE/BTech (Computer Science) and MCA programmes, as well as to practicing engineers. It will go a long way in helping students understand the concepts of operating systems not only in academic exams but also in competitive exams.