Discontinued mobile operating systems  :

Symbian :

Main article: Symbian

Symbian was originally developed by Psion as EPOC32. It was the world's most widely used smartphone operating system until Q4 2010, though the platform never gained popularity or widespread awareness in the U.S., as it did in Europe and Asia. The first Symbian phone, the touchscreen Ericsson R380 Smartphone, was released in 2000, and was the first device marketed as a "smartphone". It combined a PDA with a mobile phone. Variants of Symbian OS began to emerge, most notably Symbian UIQ, MOAP and S60, each supported by different manufacturers. With the creation of Symbian Foundation in 2008, Symbian OS was unified under one variant under the stewardship of Nokia. In February 2011, Nokia announced that it would replace Symbian with Windows Phone as the operating system on all of its future smartphones, with the platform getting abandoned throughout the following few years.

Windows Mobile :

Main article: Windows Mobile

Windows Mobile was based on the Windows CE kernel and first appeared as the Pocket PC 2000 operating system. Throughout its lifespan, the operating system was available in both touchscreen and non-touchscreen formats. It was supplied with a suite of applications developed with the Microsoft Windows API and was designed to have features and appearance somewhat similar to desktop versions of Windows. Third parties could develop software for Windows Mobile with no restrictions imposed by Microsoft. Software applications were eventually purchasable from Windows Marketplace for Mobile during the service's brief lifespan. Windows Mobile was phased out in favor of Windows Phone.

Bada :

Main article: Bada

The Bada operating system for smartphones was announced by Samsung in November 2009. The first Bada-based phone was the Samsung Wave S8500, released in June 2010. Samsung shipped 4.5 million phones running Bada in Q2 of 2011. In 2013, Bada merged with a similar platform called Tizen.

Firefox OS :

Main article: Firefox OS

Firefox OS was demonstrated by Mozilla in February 2012. It was designed to have a complete community based alternative system for mobile devices, using open standards and HTML5 applications. The first commercially available Firefox OS phones were ZTE Open and Alcatel One Touch Fire. As of 2014 more companies have partnered with Mozilla including Panasonic (which is making a smart TV with Firefox OS) and Sony.

In December 2015, Mozilla announced that it would phase out development of Firefox OS for smartphones, and would reposition the project to focus on other forms of internet-connected devices.

Palm OS :

Main article: Palm OS

In late 2001, Handspring launched the Springboard GSM phone module with limited success. In May 2002, Handspring released the Palm OS Treo 270smartphone, that did not support Springboard, with both a touchscreen and a full keyboard. The Treo had wireless web browsing, email, calendar, a contact organizer and mobile third-party applications that could be downloaded or synced with a computer. Handspring was purchased by Palm, Inc which released theTreo 600 and continued releasing Treo devices with a few Treo devices using Windows Mobile. After buying Palm in 2011, Hewlett-Packard (HP) discontinued its webOS smartphone and tablet production.

webOS :

Main article: webOS

webOS is a proprietary mobile operating system running on the Linux kernel, initially developed by Palm, which launched with the Palm Pre. After being acquired by HP, two phones (the Veer and the Pre 3) and a tablet (the TouchPad) running webOS were introduced in 2011. On August 18, 2011, HP announced that webOS hardware was to be discontinued but would continue to support and update webOS software and develop the webOS ecosystem. HP released webOS as open source under the name Open webOS, and plans to update it with additional features. On February 25, 2013 HP announced the sale of WebOS to LG Electronics, who used the operating system for its current "smart" or Internet-connected TVs, but not smartphones. In January 2014, Qualcomm has announced that it has acquired technology patents from HP, which includes all the WebOS patents.

Maemo / MeeGo :

Main article: MeeGo

MeeGo is an operating system created from the source code of Moblin (produced by Intel) and Maemo (produced by Nokia). Before that, Nokia used Maemo on some of its smartphones and internet tablets (such as Nokia N810 and N900). MeeGo was originally envisioned to power a variety of devices from netbooks, tablets to smartphones and smart TVs. However, the only smartphones which used MeeGo was the Nokia N9 and Nokia N950 (MeeGo v1.2 Harmattan). Following Nokia's decision to move to Windows Phone OS in 2011 and to cease MeeGo development, the Linux Foundation canceled MeeGo in September 2011 in favor of the development of Tizen.

Application stores :

Main article: List of digital distribution platforms for mobile devices

The introduction of Apple's App Store for the iPhone and iPod Touch in July 2008 popularized manufacturer-hosted online distribution for third-party applications (software, computer programs) focused on a single platform. Up until that point, smartphone application distribution depended on third-party sources providing applications for multiple platforms, such as GetJar, Handango, Handmark, and PocketGear.

Following the success of the App Store, other smartphone manufacturers launched application stores, such as Google's Android Market (now Google Play Store) and RIM's BlackBerry App World in April 2009. In February 2014, 93% of mobile developers were targeting smartphones first for mobile app development.

Display :

Main article: Display device

Samsung Galaxy S6(5.1 inches), S6 Edge(5.1 inches), S6 Edge+(5.7 inches)

One of the main characteristics of smartphones is their screen. It usually fills most of the phone's front surface (about 70%); screen size usually defines the size of a smartphone. Many have an aspect ratio of 16:9; some are 4:3 or other ratios.

They are measured in diagonal inches, starting from 2.45 inches. Phones with screens larger than 5.2 inches are often called "phablets". Smartphones with screens over 4.5 inches commonly are shifted while using a single hand, since most thumbs cannot reach the entire screen surface, or used in place with both hands. Liquid-crystal displays are the most common; others are IPS, LED, OLED, AMOLED and E Ink displays.

An upcoming development is a Braille screen, using microfluidics technology.