1.Operating system is the system software that manages computer hardware and software resources, and provides public services for computer programs. For hardware functions such as input-output and memory allocation, the operating system acts as a mediator between program and computer hardware and provides an operating interface for users to interact with the system.

2.Familiar Operating System:①Windows is the most common computer operating system. It is the operating software developed by Microsoft. The Windows operating system has the characteristics of good man-machine interaction, many supporting applications and strong hardware adaptability.②IOS is a mobile operating system developed by apple. IOS, like apple's macOS, is a unix-like commercial operating system.③Android is a free and open source operating system based on Linux, mainly used in mobile devices, such as smartphones and tablets, led and developed by Google and the open handset alliance. The platform consists of operating system, middleware, user interface and application software.④Linux is a POSIX and unix-based multi-user, multi-task, multi-threaded, multi-cpu operating system. It can run major UNIX tools, applications, and network protocols. It supports 32-bit and 64-bit hardware. Linux is a stable multi-user network operating system, which inherits the network core design idea of Unix. It is primarily used on computers based on Intel x86 family cpus.