1. What Are Operating Systems? What Are Their Functions? Describe the Open Systems Interconnection Reference Model (Osi Model) & Its Seven Layers.

An operating system is a set of computer programs that controls the computer hardware and acts as an interface with the application programs. The operating system plays a central role in the functioning of a computer system. It is usually stored on disk, after the computer system is started or booted up portions of operating system are transferred to memory as required. The kernel as the name suggests is the heart of the operating system and controls the most critical processes. Windows by Microsoft, Linux, UNIX, and the Macintosh are the commonly used operating systems.

An operating system performs allocation and assignment of system resources, schedules the use of computer resources, monitors the computer system activities etc. The various functions of an operating system are:

• Performing common computer hardware functions – Getting inputs from the keyboard or any other input devices, retrieving data from disks, storing data on disks and displaying information on a monitor or printer are the common hardware functions and each of these basic functions requires a more detailed set of instructions to complete. Operating system acts as intermediary between the application program and the hardware and it performs hundreds of such functions.

• Providing a user interface – User interface allows individuals to access and command the computer system. The Command based user interface and specific job control language are the commonly used user interfaces. The Graphical User Interface (GUI) uses icons and menus on screen to send commands to the computer; most widely used graphical user interface is Windows of Microsoft.

• Providing a degree of hardware independence – The applications make use of the operating system by making requests for services through a defined application program interface (API) and programmers can use

APIS to crate application software without having to understand the inner workings of the operating system.

• Managing system...