An operating system manages computer hardware and software resources and allows applications to run. It performs basic functions like managing devices, files, memory, and providing an interface for other programs. Common operating systems include Ubuntu, Android, Windows, and Mac OS. Android has the largest market share in smartphones. Operating systems have evolved from early batch systems to today's multi-tasking, distributed, and real-time systems. An operating system is essential software that enables a computer to function and run other programs.