The document discusses operating systems and provides details about some examples. It defines an operating system as a collection of software that manages computer hardware resources and provides common services for computer programs. It describes the basic functions of operating systems which include managing resources, providing user interfaces, running applications, and controlling hardware. Some examples of operating systems discussed are Windows, Android, Linux, and Mac OS. Windows is the most widely used operating system on personal computers while Android is the most widely used overall due to its dominance in the mobile market.