Operating System

What Is an Operating System?

An operating system (OS) is a core set of programs that control and supervise the hardware resources of a computer and provide services to other system software, application software, programmers, and users of a computer.

The OS gives the computer the instructions it needs to operate, telling it how to interact with hardware, other software, and the user.

The OS establishes a standard interface, or means of communication, between users and their computer systems.
When you power up a computer, you boot the system.
The booting procedure is so named because the computer "pulls itself up by its own bootstraps" (without the assistance of humans).
When booting the system,

First, a program in read-only memory (ROM) initializes the system and runs a system check to verify that the electronic components are operational and readies the computer for processing.
Next, the operating system is loaded to RAM, takes control of the system, and presents the user with a system prompt or a GUI screen full of options.

Operating System Parts

Operating systems are composed of two major parts:

control programs, and
service program.

Control programs manage computer hardware and resources.
The main program in most operating systems is the supervisor program.

A supervisor program is a control program that is known in some operating systems as the monitor, executive, or kernel.
The supervisor program is responsible for controlling all other OS programs as well as other system and application programs.
The supervisor program controls the activities of all of the hardware components of a computer.


Service programs are external OS programs that provides a service to the user or programmer of a computer.
They must be loaded separately because they are not automatically loaded when the operating system is loaded.
They perform routine but essential functions, such as formatting a disk for use and copying files from one location to another.