Introduction to Operating Systems

Before you start

Objectives: learn what is operating system, why do we need it, what are the most important components, and what types of user interfaces are available.

Prerequisites: no prerequisites.

Key terms: system, hardware, applications, interface, kernel, utilities, platform


The operating system serves as an interface between the applications that are running on the computer and the computer’s hardware itself. Operating systems performs actions such as managing the file system, receiving user input from input hardware devices such as the keyboard or mouse, controlling the use of processing devices by applications, serving as a platform for applications, moderating hardware and sending user output to output hardware devices such as the monitor or a printer.


The computer hardware and the operating system are modular. That means that we could take a PC with Windows, remove Windows off of it and install a different operating system on top of it. For example, we can install Windows, Linux or NetWare on the same hardware. The same is with Macintosh hardware. We could take Mac OS off of a Macintosh PC and install Linux on top of it. The thing is, the hardware and the operating system are not tied together.

Application Platform

Operating system provides a platform for our applications. Applications need a place to run and are designed for specific operating systems. The applications themselves cannot run directly on the PC hardware. There has to be an operating system sitting in between. The OS is installed and runs on top of the PC hardware. On top of the operating system we install many different applications.

Hardware Access

Operating system also provides means for the applications to access the hardware in the PC. OS contains special routines that allow the programmer who’s writing an application to access a certain piece of hardware in the PC. Because of that, the programmer does not have to know how specific hardware actually works. Operating system takes care of that. So, OS provides an application platform and moderates the hardware for the applications, as well.


Operating system also provides security. In the old days, for example, there was no login and everything just worked without authentication. Today that’s not the case. Any operating system that we are going to use, such as Windows XP, Mac OS or Linux, is going to require us to provide some kind of credentials to use the PC.

File System

Operating system also manages our file system. The file system encompasses all the different storage devices that are installed on the computer. In this case, we’re talking about working with specific pieces of hardware, such as the hard disk drive, the floppy disk drive, a CD or DVD drive, or a flash ROM drive. The operating system is responsible for organizing and storing the data that we are working on, on storage devices.

Parts of the OS

The OS itself is composed of different parts. The first part of the operating system is the Kernel.


The kernel is the core of the operating system. It is loaded into memory when the system boots up and it does most of the critical operating system jobs. It’s responsible for managing the file system, managing security, working with the hardware and providing a platform for applications to run on. The kernel is running behind the scenes and we, as a user, don’t work with it. Most of the time we work with utilities.


Utilities are another component of a typical operating system. Most operating systems come with lots of utilities. For example, when we are working with files on our computer, we are actually using utilities that are interacting with the kernel to do a particular job.

User Interface

Every operating system comes with an interface of some sort. The interface is what allows us to interact in some way with the kernel and the utilities. There’s two different basic types of user interfaces. The first is the Command Line Interface or CLI.


For example. DOS used a command line. In command line we have to type in the commands for something to happen. The command line is more popular in Linux operating systems. Command line interfaces are really powerful but they can be very difficult for end users to use. That’s why we have a Graphical User Interface or GUI.


With a GUI, instead of using a command line, we represent things graphically on the screen. GUI is used a lot in Windows OS. Linux itself also includes a Graphical User Interface that isn’t quite as advanced as perhaps the GUI used by Windows or the Mac OS, but it is getting very close. Both interfaces are good for different purposes. CLI provides great flexibility, but in a day-to-day work GUI is more practical.


The operating system serves as an interface between the applications that are running on the computer and the computer’s hardware itself. The hardware and the operating system are not tied together, which means that computers are modular in general. Operating system also provides security and manages our file system. Parts of the OS are Kernel and Utilities. User interface can be Command Line Interface (CLI) or Graphical User Interface (GUI).