What is an Operating system?

It is like a mediator between computer hardware and computer user.Computer cannot understand high-level language like English. It can understand only digital data that is 0's and 1's. Also called as Binary language. When you type something from your I/O devices it can convert it into binary form.Operating system converts these instructions into machine readable form.
One can't communicate with computer directly without operating system. Simply it is said that "Interface between computer and User".
examples:

1. Windows
2. Linux
3. Macintosh ( simply Mac) 

Then coming to mobile OS we have

1. Android ( Google )
2. IOS ( Apple )
3. J2MEE ( Java based )
4. Tizen ( Recently Samsung launched ).

Windows is the famous operating system,90% of the PCs Has been running with Windows.

It was created by Microsoft.It is a GUI ( Graphical User Interface ) based system.It is not an open-source OS. We need to pay some amount money for this OS. 

Examples are:

MS-DOS (Microsoft Disk Operating System) 

It is fully based on Commands.We can manage the files with the help of commands. Like moving files,deleting,copying,etc.

Windows-XP 

Windows-7

Windows-8

Windows-10 (Coming soon)

We have three different versions in windows. They are

1. Basic
2. Professional
3. Ultimate.

2.Linux

It is an open-source operating source. You don't need to pay anything for this OS. It can be modified by anyone. Now-a-days 90% of the super computers are working based on this Linux. We have been using this in servers,mobile devices,vehicles,industries,etc. we can find Linux everywhere. It is an omnipresent.

In Linux we have different version based on user requirement.\