An operating system is a software controlling the operation of a computer system and its resources. Major functions of operating systems may include: Managing memory and other system resources.Imposing security and access policies.Scheduling and multiplexing processes and threads.Launching and closing user programs, and providing basic system services for them.Providing a basic user interface and application programmer interface.Not all operating systems provide all of these functions. Single-tasking systems like MS-DOS would not schedule processes, while embedded systems like eCOS may not have a user interface. The opearting system which I fimilar with such as macos、windows、Chrome OS, BlackBerry Tablet OS, and flavors of the open source operating system Linux