1.Selected Answer: An operating system has three main functions: 1) manage the computer's resources, such as the central processing unit, memory, disk drives, and printers, 2) establish a user interface, 3) execute and provide services for applications software. 2.Selected Answer: Multitasking, in an operating system, is allowing a user to perform more than one computer task (such as the operation of an application program) at a time. The operating system is able to keep track of where you are in these tasks and go from one to the other without losing information. 3.Selected Answer: File management is one of the basic and important features of operating systems. Operating system is used to manage files of a computer system. All the files with different extensions are managed by the operating system. A file is a collection of specific information stored in the memory of a computer system.