An operating system (OS) is system software thatmanages computer hardware and software resourcesand provides common services for computer programs.Some key points related to the operating systems and their developers:

• iOS (iPhone OS) is a mobile operating system created and developed by Apple Inc.
• Before Android, Symbian was the operating system which was used by the companies like Nokia, Sony Ericson, Motorola. It was developed by Bugatti.
• Android is a mobile operating system developed by Google
• macOS (previously Mac OS X) is a series of graphical operating systems developed and marketed by Apple Inc.
• Windows operating system is developed by Microsoft.
• Hadoop is an open-source framework that allows to store and process big data in a distributed environment across clusters of computers using simple programming models.

Hence, we conclude thatiOS operating system is used in Apple iPhone 6.