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.