The operating system (English; Operating System, referred to as OS) is a program that manages computer hardware and software resources. It is also the core and cornerstone of the computer system. The operating system is responsible for basic tasks such as managing and configuring memory, prioritizing the supply and demand of system resources, controlling input and output devices, operating networks, and managing file systems. The operating system manages all hardware resources of the computer system, including software resources and data resources; controls the operation of programs; improves the human-machine interface; provides support for other application software, etc., so that all resources of the computer system can maximize their use and provide users with convenient , effective and friendly service interface. The operating system is a huge management control program, which roughly includes five aspects of management functions: process and processor management, job management, storage management, device management, and file management. At present, common operating systems on microcomputers include DOS, OS/2, UNIX, XENIX, LINUX, Windows, Netware, etc. But all operating systems have four basic characteristics: concurrency, enjoyment, virtuality and uncertainty.

There are many types of operating systems. The OS installed on different machines can range from simple to complex, from embedded systems in mobile phones to large-scale operating systems in supercomputers. Many operating system manufacturers also have inconsistent definitions of OS. For example, some OSs integrate a graphical user interface, while some OSs only use text interfaces and regard graphical interfaces as a non-essential application.

Operating system theory is a long-standing and active branch of computer science, and the design and implementation of operating systems are the foundation and core of the software industry.