A mobile operating system, also known as a mobile OS, a mobile platform, or a handheld operating system, is the operating system that controls a mobile device or information appliance—similar in principle to an operating system such as Windows, Mac OS, or Linux that controls a desktop computer or laptop. However, they are currently somewhat simpler, and deal more with the wireless versions of broadband and local connectivity, mobile multimedia formats, and different input methods. Most of these operating systems are made for ARM processors even though versions for x86 and x86-64 might exist.

The increasing importance of mobile devices has triggered intense competition among technology giants, like Google, Microsoft, Apple, and Nokia in a bid to capture the bigger market share pre-emptively. Palm, Research In Motion and Ericsson are also significant firms in the mobile platform sector. In November 2007, Google formed a Linux-based open source alliance to make inroads into this mobile platform market, raising consumer awareness of the growing mobile platform frenzy.

The most common operating systems (OS) used in smartphones are:

* The Symbian OS/Symbian platform from the Symbian Foundation (36.6%)(open public license)
Symbian has the largest share in most markets worldwide, but lags behind other companies in the relatively small but highly visible North American market.  It has been used by many major handset manufacturers, including BenQ, Fujitsu, LG, Mitsubishi, Motorola, Nokia, Samsung, Sharp, and Sony Ericsson. Current Symbian-based devices are being made by Fujitsu, Nokia, Samsung, Sharp, and Sony Ericsson. As part of the formation of the Symbian platform in 2009 three UIs were merged into a single platform which is now fully open source. Recently, though shipments of Symbian devices have increased, the operating system's worldwide market share has declined from over 50% to just over 40% from 2009 to 2010.

* Android from Google Inc. (25.5%)(open source, Apache)
Android works on Linux kernel with custom utilities made by Google Inc. Android was developed by a small startup company that was purchased by Google Inc., and Google continues to update the software. Android is an open source, Linux-derived platform backed by Google, along with major hardware and software developers (such as Intel, HTC, ARM, Samsung, Motorola and eBay, to name a few), that form the Open Handset Alliance. Released on November 5th 2007, the OS has a following among programmers. There have been seven releases of Android- Android 1.0, 1.5, 1.6, 2.0, 2.1, 2.2 and 2.3. All are nicknamed after a dessert item like Cupcake (1.5) or Frozen Yogurt (2.2). Most major mobile service providers carry an Android device.

Since the HTC Dream (T-Mobile G1) was introduced, there has been an explosion in the number of devices that carry Android OS. From Q2 of 2009 to the second quarter of 2010, Android's worldwide market share rose 850% from 1.8% to 17.2%.

* iOS from Apple Inc. (16.7%)(closed source, proprietary)
The Apple iPhone, iPod Touch and iPad all use an operating system called iOS, which is derived from Mac OS X. Third party applications were not officially supported until the release of iOS 2.0 on July 11th 2008. Before this, "jailbreaking" allowed third party applications to be installed, and this method is still available. Currently all iOS devices are developed by Apple and manufactured by Foxconn or another of Apple's partners.

* RIM BlackBerry OS (14.8%)(closed source, proprietary)
This OS is focused on easy operation and was originally designed for business. Recently it has seen a surge in third-party applications and has been improved to offer full multimedia support. Currently Blackberry's App World has over 15,000 downloadable applications.

* Windows Mobile from Microsoft (2.8%)(closed source, proprietary)
The Windows CE operating system and Windows Mobile middleware are widely spread in Asia. The two improved variants of this operating system, Windows Mobile 6 Professional (for touch screen devices) and Windows Mobile 6 Standard, were unveiled in February 2007. It has been criticized for having a user interface which is not optimized for touch input by fingers; instead, it is more usable with a stylus. However, unlike iPhone OS, it does support both touch screen and physical keyboard configurations.

Windows Mobile's market share has sharply declined in recent years to just 5% in Q2 of 2010. Microsoft is phasing out the Windows Mobile OS to specialized markets and is instead focusing on it's new platform, Windows Phone.

* Windows Phone from Microsoft (negligible)(closed source, proprietary)
On February 15th, 2010 Microsoft unveiled its next-generation mobile OS, Windows Phone 7. The new mobile OS includes a completely new over-hauled UI inspired by Microsoft's "Metro Design Language". It includes full integration of Microsoft services such as Windows Live, Zune, Xbox Live and Bing, but also integrates with many other non-Microsoft services such as Facebook and Google accounts. The new OS platform has received some positive reception from the technology press.[12][13][14] As Windows Phone 7 is a new platform, there is no backwards compatibility with Windows Mobile applications and some power-user features that were in Windows Mobile will not be present until near-future updates.

* Palm webOS from HP (certain parts open sourced) and Palm OS/Garnet OS from Access Co. (closed source, proprietary)
Palm webOS is Palm's next generation operating system. PalmSource traditionally used its own platform developed by Palm Inc. Access Linux Platform (ALP) is an improvement that was planned to be launched in the first half of 2007. It will use technical specifications from the Linux Phone Standards Forum. The Access Linux Platform will include an emulation layer to support applications developed for Palm-based devices.

* bada from Samsung Electronics (closed source, proprietary)
This is a mobile operating system being developed by Samsung Electronics. Samsung claims that bada will rapidly replace its proprietary feature phone platform, converting feature phones to smartphones.The name 'bada' is derived from 바다, the Korean word for ocean or sea. The first device to run bada is called 'Wave' and was unveiled to the public at Mobile World Congress 2010. The Wave is a fully touchscreen phone running the new mobile operating system. With the phone, Samsung also released an app store, called Samsung Apps, to the public. It has close to 3000[21] mobile applications.

Samsung has said that they don't see Bada as a smartphone platform, but as a platform with a kernel configurable architecture, which allows the use of either proprietary Real-time operating system (RTOS) kernel, or the Linux kernel. Though Samsung plans to install bada on many phones, the company still has a large lineup of Android phones.

* MeeGo from Nokia and Intel (open source, GPL)
At the 2010 Mobile World Congress in Barcelona, Nokia and Intel both unveiled 'MeeGo' a brand new mobile operating system which would combine the best of Moblin and the best of Maemo to create a truly open-sourced experience for users across all devices.

* Maemo from Nokia (open source, GPL)
Maemo is a software platform developed by Nokia for smartphones and Internet Tablets. It is based on the Debian operating system.

Maemo is mostly based on open source code, and has been developed by Maemo Devices within Nokia in collaboration with many open source projects such as the Linux kernel, Debian and GNOME.

Maemo is based on Debian GNU/Linux and draws much of its GUI, frameworks and libraries from the GNOME project. It uses the Matchbox window manager and the GTK-based Hildon as its GUI and application framework.