Operating system gives life to the system. Without the operating system software, one cannot work with the system at all…But how many of the students are aware of this truth? A lot of standard books are available in the market but my aim in bringing out this book is to make a beginner understand the concept of operating systems, its importance, and its basics in a simple and user friendly manner. This text focuses on the traditional operating systems concepts: Processes, Process Synchronization, CPU Scheduling, deadlocks, and a glance of memory management which is the core of Operating System Concepts –I. The primary intended audience for this book will be the graduate students of computer Science/ Engineering.