An Operating System (OS) is an interface between a computer user and computer hardware. An operating system is a software which performs all the basic tasks like file management, memory management, process management, handling input and output, and controlling peripheral devices such as disk drives and printers. An operating system is the most important software that runs on a computer. It manages the computer’s memory and processes, as well as all of its software and hardware. It also allows you to communicate with the computer without knowing how to speak the computer’s language. Without an operating system, a computer is useless. There are many functions those are performed by the operating system. But the main goal of operating system is to provide the interface between the user and the hardware. The development of operating systems is ruled both by the evolution of hardware architectures and evolving application requirements. Furthermore, the rapid growth development of smartphones and tablets has changed the software distribution ecosystem. This book explores the operating computer and mobiles devices systems. With regard to operating systems, the specifics advances discussed in this book include the boot process method, the improvement of global system performance for reliable starting, design method of managing shared resources and services. Method, design and implementation of security mechanism tool for countering the attack of the operating system are also discussed in this book. Other studies were explored in this literature to develop a new structure to better manage software games, to improve human machine interaction and development of embedded system.