1.What is Operating System? 

The operating system is the computer program which manages the computer hardware and software resources, and also the kernel and cornerstone of the computer system. Operating systems handle such basic tasks as managing and configuring memory, prioritizing system resource supply and demand, controlling input and output devices, operating networks, and managing file systems. The operating system also provides an interface for users to interact with the system.

2.Write sevral your familiar operating systems in details.

2.1 macOS

macOS (formerly "Mac OS X" and later "OS X") is a line of open core graphical operating systems developed, marketed, and sold by Apple Inc., the latest of which is pre-loaded on all currently shipping Macintosh computers. Mac system is a graphical operating system based on Unix kernel. An operating system that cannot normally be installed on a regular PC. Developed by apple itself. The Mac's operating system has gone to OS 10, code-named Mac OS X(Roman numeral for X 10), the biggest change in the Mac's 15-year history. The new system is very reliable; Many of its features and services embody apple's philosophy,for example,the full screen window mode.

2.2 Linux

Linux is a set of free use and free dissemination of unix-like operating system, is a POSIX and unix-based multi-user, multi-task, support multi-threading and multi-cpu operating system. It is not only stable, but also open source. Its core firewall components have high performance and simple configuration, which guarantees the security of the system. Compared with other operating systems, Linux has the characteristics of open source, no copyright, and large number of users in the technical community. Open source enables users to tailor freely, with high flexibility, powerful functions and low cost.

2.3 Windows

Windows operating system is an operating system launched by Microsoft of America. The system was born in 1985 to now, after years of development and improvement, relatively mature and stable, is the current mainstream operating system of personal computers. Software has experienced many years of development, the current launch of the win10 system is quite mature. The Windows operating system has the characteristics of good man-machine interaction, many supporting applications and strong hardware adaptability.

In windows10,the new feature Cortana can be used to search for files on your hard drive, system Settings, installed applications, and even other information on the Internet. As a personal assistant, Cortana can also help you set reminders based on time and place, as it does on mobile platforms.