Operating System:

1. An operating system is the most important software that runs on a computer.

2. It manages the computer's memory and processes, as well as all of its software and hardware.

3. It also allows to communicate with the computer without knowing how to speak the computer's language.

4. Without an operating system, a computer is useless.

Job of Operating System:

1. Your computer's operating system (OS) manages all of the software and hardware on the computer.

2. Most of the time, there are several different computer programs running at the same time, and they all need to access your computer's central processing unit (CPU), memory, and storage.

3. The operating system coordinates all of this to make sure each program gets what it needs.

Types of Operating System:

1. Operating systems usually come pre-loaded on any computer you buy.

2. Most people use the operating system that comes with their computer, but it's possible to upgrade or even change operating systems.

The three most common operating systems for personal computers are Microsoft Windows, macOS, and Linux.

1. Modern operating systems use a graphical user interface, or GUI

2. A GUI lets you use your mouse to click icons, buttons, and menus, and everything is clearly displayed on the screen using a combination of graphics and text.

3. Each operating system's GUI has a different look and feel, so if you switch to a different operating system it may seem unfamiliar at first.

4. However, modern operating systems are designed to be easy to use, and most of the basic principles are the same.

Microsoft Windows:

1. Microsoft created the Windows operating system in the mid-1980s.

2. There have been many different versions of Windows, but the most recent ones are Windows 10 (released in 2015), Windows 8 (2012), Windows 7 (2009), and Windows Vista (2007).

3. Windows comes pre-loaded on most new PCs, which helps to make it the most popular operating system in the world.

macOS:

1. macOS (previously called OS X) is a line of operating systems created by Apple.

2. It comes preloaded on all Macintosh computers, or Macs.

3. Some of the specific versions include Mojave (released in 2018), High Sierra (2017), and Sierra (2016).

Linux:

1. Linux is a family of open-source operating systems, which means they can be modified and distributed by anyone around the world.

2. This is different from proprietary software like Windows, which can only be modified by the company that owns it.

3. The advantages of Linux are that it is free, and there are many different distributions—or versions—you can choose from.