Operating System

An operating system (OS) is best thought of as a resource manager: it manages all the resources of a computer — the hardware, including the CPU, RAM, disk, network and the other input-output devices — so that each is used well. Beyond the hardware, it also:

• controls the various application software and device drivers,
• manages system security, and
• handles access by different users.

It is the most important system software on any machine. Popular examples: Windows, Linux, Android, Macintosh, and so on.

The two primary objectives of an operating system

1. Provide services for building and running application programs

When an application program needs to run, it is the operating system that loads the program into memory and allocates it to the CPU for execution. And when multiple application programs need to run, the operating system decides the order of their execution. Every program you launch is, behind the scenes, being scheduled and placed by the OS.

2. Provide an interface between the user and the computer

The OS gives the user a way to interact with the machine. A user interface is a software component that is part of the operating system, whose job is to take commands or inputs from the user for the operating system to process. Whether you type commands, click icons, touch a screen or speak, you are talking to the OS through one of its user interfaces.

The two sub-sections that follow expand each objective in turn: …