Which of the following is an example of an operating system that is used by smart phones?

Types of mobile operating systems

There are numerous mobile device operating systems available today, and two of the most widely adopted are the iPhone's OS, Apple iOS, and Google's open source OS, Google Android. These two mobile OSes take different approaches to the mobile operating system.

Apple distributes the only devices that natively support iOS, and it takes a "walled garden" approach, in which Apple regulates all mobile apps and services that can run on the iOS devices. Apple developed iOS to run on its own XNU kernel. Apple has also released several device-specific mobile operating systems such as watchOS for the Apple Watch and iPadOS for the iPad tablets.

Google takes a different approach with Android, which is open source. This means that mobile device OEMs (original equipment manufacturers) can customize the Android source code and customize it to fit their devices. Android runs on the Linux kernel.

There are other mobile operating systems available, but their adoption rates are well below those of iOS and Android. These other operating systems include KaiOS, Sailfish OS and Huawei's Harmony OS.

KaiOS, based on the discontinued Mozilla Firefox OS, runs mostly on dumb phones -- also known as feature phones. These mobile devices have very limited computing power, but the latest version of KaiOS can bring more comprehensive feature sets to these devices such as an app store and the Google Assistant.

Sailfish OS is based on multiple open source projects and runs mostly on smartphones and tablet computers from Jolla, which developed the operating system, and Sony mobile devices. Sailfish OS and KaiOS both run on the Linux kernel.

Huawei's Harmony OS, initially released in August 2019, can also run on IoT devices. Huawei's devices typically run Android operating system, but Harmony OS may replace Android on these devices in the future. Harmony OS runs on a microkernel that Huawei developed.

There are numerous mobile operating systems that are no longer commonly supported. The BlackBerry 10 operating system, which succeeded BlackBerry OS in 2013, has extended support available but for a small install base. Nokia's Symbian operating system received its last update in 2013 and is no longer supported.

LG webOS -- formerly Palm webOS and HP webOS -- transitioned from a smartphone and tablet operating system to a smart TV operating system after LG acquired the OS from Hewlett-Packard in 2013. The Microsoft's Windows Phone operating system was discontinued by Microsoft in 2017. Windows 8 and Windows 8.1 function as both traditional desktop operating systems and mobile operating systems, but mainstream support for these OSes is no longer available for Windows mobile devices or desktops.

Features of mobile operating systems

Mobile operating systems deliver various features to users, and the distinguishing feature that mobile operating systems offer is the ability to connect to the internet via the smartphone's built-in modem and a wireless service provider such as Verizon or AT&T. This is a major difference between mobile operating systems and most desktop operating systems, which rely on a Wi-Fi network or Ethernet connection to access the internet.

Many mobile OSes offer a native web browser application, which allows users to search the internet and visit webpages. Mobile operating systems also offer application stores, which allow users to download and interface with mobile applications. Several mobile operating systems also have native GPS (global positioning system) applications that allow users to search for locations, follow step-by-step directions and, in some cases, share location with different devices. The GPS feature, of course, relies on the mobile device's hardware and can't run without that support.

While some native applications come with mobile operating systems such as iOS and Android, the mobile app stores open up new possibilities for users. In some cases, the applications add new features and improved user interface (UI) for websites that are accessible via a web browser, but other applications bring new functionality to the mobile devices.

Other common mobile operating system features include native email applications that allow users to link their work and personal email accounts, a calendar application that users can keep track of tasks, meetings and events, and a contacts library to organize and search for contact information.

Most mobile operating systems -- other than Android -- are tied to specific hardware with little flexibility. Users can jailbreak or root devices, however, which allows them to install another mobile OS or unlock restricted applications.