How to record system screen in Ubuntu Desktop OS ?

 Screen Recording in Ubuntu is very easy.

Follow below steps.

If you want to start screen recording.

Use the shortcut : Ctrl + Alt + Shift + R

After that you will see a yellow bubble in upper left corner (somewhere nearby network, volume and battery icon area). If it is visible meaning is that system is started recording your current screen.

Once you want to stop screen recording- Use the same shortcut: Ctrl + Alt + Shift + R.

To get the recorded screen file, you can go to the video folder in folders.

What is mean by an open source OS ?

Open Source operating system, also called free software is software that can be used, and modified without restriction,and which can be copied and redistributed in modified or unmodified form either without restriction, or with restrictions only to ensure that further recipients can also do these things. To make these acts possible, the human readable form of the program (called the source code)  must to made available. The source code may be either accompanied by a software license saying that the copyright holder permits these acts (a free software licence), or be released into public domain, so that these rights automatically hold.
Linux is a well known open source OS. Linux has wide verity of distributions.Such as fedora, Red Hat, Linux mint etc..

Different Types of Operating Systems

         This post explains the different types of operating systems that are used in PCs, category is based on the types of computers they control and the sort of applications they support.

• Single-user, single task - As the name implies, this operating system is designed to manage the computer so that one user can effectively do one thing at a time. DOS is a good example of a single-user, single-task operating system.

• Single-user, multi-tasking - This is the type of operating system most people use on their desktop and laptop computers today. Windows 98 and the MacOS are both examples of an operating system that will let a single user have several programs in operation at the same time. For eg. it's entirely possible for a Windows user to be writing a note in a word processor while downloading a file from the Internet while printing the text of an e-mail message.

• Multi-user - A multi-user operating system allows many different users to take advantage of the computer's resources simultaneously. The operating system must make sure that the requirements of the various users are balanced, and that each of the programs they are using has sufficient and separate resources so that a problem with one user doesn't affect the entire community of users. Unix, Windows 2000, Linux and mainframe operating systems, are examples of multi-user operating systems.