What Is Operating System: (Definition, Importance, Functions & Examples)

Operating System

An operating system or OS is a software program that enables the computer hardware to communicate and operate with the computer software. Without a computer operating system, a computer and software programs would be useless. The picture is an example of Microsoft Windows XP, a popular operating system and what the box may look like if you were to visit a local retail store to purchase it.

When computers were first introduced, the user interacted with them using a command line interface, which required commands. Today, almost every computer is using a GUI (Graphical User Interface) operating system that is much easier to use and operate.


  • Microsoft Windows 10 - PC and IBM compatible operating system. Microsoft Windows is the most common and used operating system.
  • Apple mac-OS - Apple Mac operating system. Today, the only Apple computer operating system is mac-OS. 
  • Ubuntu Linux - A popular variant of Linux used with PC and IBM compatible computers.
  • Google Android - Operating system used with Android compatible phones and tablets.
  • iOS - Operating system used with the Apple iPhone and i Pads.
  • Chromium - G

N/B:   Note that we said that an operating system is a set of programs. The most important program in the operating system, the program that manages the operating system, is the supervisor program, most of which remains in memory and is thus referred to as resident. The supervisor controls the entire operating system and loads into memory other operating system programs (called nonresident) from disk storage only as needed.

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, and (3) execute and provide services for applications software. Keep in mind, however, that much of the work of an operating system is hidden from the user; many necessary tasks are performed behind the scenes. In particular, the first listed function, managing the computer's resources, is taken care of without the user being aware of the details. Furthermore, all input and output operations, although invoked by an applications program, are actually carried out by the operating system. Although much of the operating system functions are hidden from view, you will know when you are using an applications software package, and this requires that you invoke-call into action-the operating system. Thus you both establish a user interface and execute software. 


  • Boots or starts the computer operation.
  • Provides human-computer operation.
  • Schedules jobs.
  • Passes control from one program to the next.
  • Job queuing.
  • Manages interrupt handling.
  • Controls input and output operations.
  • Controls program execution.
  • Loads programs and routines into the main memory for execution and processing.
  • Manages data and file storage.
  • Supports various file organization methods.
  • Assigns different tasks to the CPU.
  • Provides security and control.
  • Keeps details of the resources such as number of files stored, where they are kept, how much storage space is free etc.
  • Monitors fault or errors in a program and displays suitable error messages which help the user to find the source of fault.


Following are the points that justify the need and importance of an operating system
  1. Operating system behaves as a resource manager. It utilizes the computer in a cost effective manner. It keeps account of different jobs and the where about of their results and locations in the memory.
  2. It schedules jobs according to their priority passing control from one program to the next. The overall function of job control is especially important where there are several users (a multi user environment).
  3. Operating system makes a communication link between user and the system and
    helps the user to run application programs properly and get the required output.
  4. Operating system has the ability to fetch the programs in the memory when required and not all the operating system to be loaded in the memory at the same time. Thus giving the user the space to work in the required package more conveniently and easily.
  5. Operating system helps the user in file management, making of directions, and saving files in them, is a very good feature provided by the operating system to organize data according to the needs of the user.
  6. Multi programming is a very important feature of operating system. It schedules and controls the running of several programs at once.
  7. It provides program editors that help the user to modify and update the program lines.
  8. Debugging aids provided by the operating system help the user to detect and rename errors in programs
  9. Disk maintenance ability of operating system checks the validity of data stored on diskettes and perhaps make corrections to erroneous data.
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