Android is a Linux-based operating system designed primarily for touchscreen mobile devices such as smartphones and tablet computers. It is currently developed by Google in conjunction with the Open Handset Alliance. Initially developed by Android Inc, whom Google financially backed and later purchased in 2005, Android was unveiled in 2007 along with the founding of the Open Handset Alliance, a consortium of 86 hardware,software, and telecommunication companies devoted to advancing open standards for mobile devices.
Google releases the Android code as open source, under the Apache License. The Android Open Source Project (AOSP), led by Google, is tasked with the maintenance and further development of Android. Additionally, Android has a large community of developers writing applications ("apps") that extend the functionality of devices, written primarily in a customized version of Java. They are available for download through Google Play or third-party sites. In October 2012, there were approximately 700,000 apps available for Android, and the estimated number of applications downloaded from Google Play (and the now-defunct Android Market) was 25 billion.
The first Android-powered phone was sold in October 2008, and by the end of 2010 Android had become the world's leading smartphone platform, overtaking Symbian which held the record previously. It had a worldwide smartphone market share of 75% during the third quarter of 2012, with 500 million devices activated and 1.3 million activations per day. Application of the operating system has also moved beyond mobile phones and tablets, currently televisions, netbooks and cameras are some of the types of devices Android is featured in.
Android has a growing selection of third party applications, which can be acquired by users either through an app store such asGoogle Play or the Amazon Appstore, or by downloading and installing the application's APK file from a third-party site. The Play Store application allows users to browse, download and update apps published by Google and third-party developers, and is pre-installed on devices that comply with Google's compatibility requirements. The app filters the list of available applications to those that are compatible with the user's device, and developers may restrict their applications to particular carriers or countries for business reasons. Purchases of unwanted applications can be refunded within 15 minutes of the time of download, and some carriers offer direct carrier billing for Google Play application purchases, where the cost of the application is added to the user's monthly bill. As of September 2012, there were more than 675,000 apps available for Android, and the estimated number of applications downloaded from the Play Store was 25 billion.
Applications are developed in the Java language using the Android software development kit (SDK). The SDK includes a comprehensive set of development tools,including a debugger, software libraries, a handset emulator based on QEMU, documentation, sample code, and tutorials. The officially supported integrated development environment (IDE) is Eclipse using the Android Development Tools (ADT) plugin. Other development tools are available, including a Native Development Kit for applications or extensions in C or C++, Google App Inventor, a visual environment for novice programmers, and various cross platform mobile web applications frameworks.
In order to work around limitations on reaching Google services due to Internet censorship in the People's Republic of China, Android devices sold in the PRC are generally customized to use state approved services instead.
The version history of the Android mobile operating system began with the release of the Android beta in November 2007. The first commercial version, Android 1.0, was released in September 2008. Android is under ongoing development by Google and the Open Handset Alliance, and has seen a number of updates to its base operating system since its original release. These updates typically fixbugs and add new features. Since April 2009, Android versions have been developed under a codename and released in alphabetical order: Cupcake, Donut, Eclair, Froyo, Gingerbread, Honeycomb, Ice Cream Sandwich, and Jelly Bean. As of 2012, over 400 million active devices use the Android OS worldwide. The most recent major Android update was Jelly Bean 4.2, which was announced in October 2012, and was released on commercial devices in November.