The operating systems used for telephones, cell phones or smartphones are many, but there are 2 that are the main ones and that occupied almost the entire mobile telephony market: Android and iOS. Followed, but by far, they would be on Symbian, Blackberry OS and Windows Phone.
An Operating System (OS) is a program or set of programs of a computer system, which manages the physical resources (hardware), the execution protocols of the rest of the content (software), as well as the user interface. For example: Ubuntu, MacOS, Windows, Haiku.