OPERATING SYSTEM :

An operating system (OS) is the program that, after being initially loaded into the computer by a boot program, manages all of the other application programs in a computer. The application programs make use of the operating system by making requests for services through a defined application program interface (API).

Some Example :

The IT industry largely focuses on the top five OSs, including Apple macOS, Microsoft Windows, Google’s Android OS, Linux Operating System, and Apple iOS. But that’s just the tip of the operating system iceberg. There are numerous free OS options in addition to Linux including Chrome OS, Syllable, and ReactOS, which was initially launched as a Windows95 clone. 

But that’s just in the world of personal computers, mobile devices, and tablets. When you examine server OSs, the number jumps considerably. All told, there are over 63 base proprietary OSs with various versions or updates, in addition to another 26 non-proprietary OSs.

Apple MacOS : macOS is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac computers.

Microsoft Windows : Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft.

Google's Android OS : Google Android OS is Google's Linux-based open-source operating system for mobile devices.

Linux OS : Just like Windows, iOS, and Mac OS, Linux is an operating system. In fact, one of the most popular platforms on the planet, Android, is powered by the Linux operating system. An operating system is software that manages all of the hardware resources associated with your desktop or laptop. To put it simply, the operating system manages the communication between your software and your hardware. Without the operating system (OS), the software wouldn’t function.

Apple iOS : Apple iOS is  a proprietary mobile operating system that runs on mobile devices such as the iPhone, iPad and iPod Touch.It is based on the Mac OS X operating system for desktop and laptop computers. The iOS developer kit provides tools that allow for iOS app development.