Android is a Linux-based operating system for mobile devices such as smartphones and tablet computers. It is developed by the Open Handset Alliance led by
Google purchased the initial developer of the software, Android Inc., in
2005. The unveiling of the Android distribution in 2007 was announced 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 released the Android code as open-source, under the Apache
License. The Android Open Source Project (AOSP) is tasked with the maintenance and further development of
Android - Smartphone: Galaxy Nexus
Android has a large community of developers writing applications ("apps") that extend the functionality of the devices. Developers write primarily in a customized version of
Java. Apps can be downloaded from third-party sites or through online stores such as Android Market, the app store run by Google. As of October 2011 there were more than 400,000 apps available for Android, and the estimated number of applications downloaded from the Android Market as of December 2011 exceeded 10
Android was listed as the best-selling smartphone platform worldwide in Q4 2010 by
Canalys with over 200 million Android devices in use by November 2011. According to Google's Andy Rubin, as of December 2011 there are over 700,000 Android devices activated every
Android, Inc. was founded in Palo Alto, California, United States in October, 2003 by Andy Rubin (co-founder of
Danger), Rich Miner (co-founder of Wildfire Communications, Inc.), Nick Sears (once VP at
T-Mobile), and Chris White (headed design and interface development at WebTV) to develop, in Rubin's words "...smarter mobile devices that are more aware of its owner's location and
preferences". Despite the obvious past accomplishments of the founders and early employees, Android Inc. operated secretly, revealing only that it was working on software for mobile phones. That same year, Rubin ran out of money. Steve Perlman, a close friend of Rubin, brought him $10,000 in cash in an envelope and refused a stake in the
Acquisition by Google
Google acquired Android Inc. on August 17, 2005, making Android Inc. a wholly owned subsidiary of Google Inc. Key employees of Android Inc., including Andy Rubin, Rich Miner and Chris White, stayed at the company after the
acquisition. Not much was known about Android Inc. at the time of the acquisition, but many assumed that Google was planning to enter the mobile phone market with this
At Google, the team led by Rubin developed a mobile device platform powered by the Linux kernel. Google marketed the platform to handset makers and carriers on the promise of providing a flexible, upgradable system. Google had lined up a series of hardware component and software partners and signaled to carriers that it was open to various degrees of cooperation on their
Speculation about Google's intention to enter the mobile communications market continued to build through December
2006. Reports from the BBC and The Wall Street Journal noted that Google wanted its search and applications on mobile phones and it was working hard to deliver that. Print and online media outlets soon reported rumors that Google was developing a Google-branded handset. Some speculated that as Google was defining technical specifications, it was showing prototypes to cell phone manufacturers and network operators.
In September 2007, InformationWeek covered an Evalueserve study reporting that Google had filed several patent applications in the area of mobile
Open Handset Alliance
On November 5, 2007, the Open Handset Alliance, a consortium of several companies which include Broadcom Corporation, Google, HTC, Intel, LG, Marvell Technology Group, Motorola, Nvidia, Qualcomm, Samsung Electronics, Sprint Nextel, T-Mobile and Texas Instruments unveiled itself. The goal of the Open Handset Alliance is to develop open standards for mobile
devices. On the same day, the Open Handset Alliance also unveiled their first product, Android, a mobile device platform built on the Linux kernel version
On December 9, 2008, 14 new members joined, including ARM Holdings, Atheros Communications, Asustek Computer Inc, Garmin Ltd, Huawei Technologies, PacketVideo, Softbank, Sony Ericsson, Toshiba Corp, and Vodafone Group
ndroid Open Source ProjectThe Android Open Source Project (AOSP) is led by Google, and is tasked with the maintenance and development of
Android. According to the project "The goal of the Android Open Source Project is to create a successful real-world product that improves the mobile experience for end
users." AOSP also maintains the Android Compatibility Program, defining an "Android compatible" device "as one that can run any application written by third-party developers using the Android SDK and NDK", to prevent incompatible Android
implementations. The compatibility program is also optional and free of charge, with the Compatibility Test Suite also free and
Android version history
Android has seen a number of updates since its original release, each fixing bugs and adding new features. Each version is named, in alphabetical order, after a
2.3 Gingerbread refined the user interface, improved the soft keyboard and copy/paste features, improved gaming performance, added SIP support (VoIP calls), and added support for Near Field
3.0 Honeycomb was a tablet-oriented release which supports larger screen devices and introduces many new user interface features, support for multi-core processors, hardware acceleration for
graphics and full system encryption. The first device featuring this version, the Motorola Xoom tablet, went on sale in February
3.1 Honeycomb, released in May 2011, added support for extra input devices, USB host mode for transferring information directly from cameras and other devices, and the Google Movies and Books
3.2 Honeycomb, released in July 2011, added optimization for a broader range of screen sizes, new "zoom-to-fill" screen compatibility mode, loading media files directly from SD card, and an extended screen support
API. Huawei MediaPad is the first 7 inch tablet to use this
4.0 Ice Cream Sandwich, announced on October 19, 2011, brought Honeycomb features to smartphones and added new features including facial recognition unlock, network data usage monitoring and control, unified social networking contacts, photography enhancements, offline email searching, app folders, and information sharing using NFC. Android 4.0.3 Ice Cream Sandwich is the latest Android version that is available to phones. The source code of Android 4.0.1 was released on November 14,
Android consists of a kernel based on the Linux kernel, with middleware, libraries and APIs written in C and application software running on an application framework which includes Java-compatible libraries based on Apache Harmony. Android uses the Dalvik virtual machine with just-in-time compilation to run Dalvik dex-code (Dalvik Executable), which is usually translated from Java
The main hardware platform for Android is the ARM architecture. There is support for x86 from the Android x86
project, and Google TV uses a special x86 version of Android.
Android's kernel is based on the Linux
and has further architecture changes by Google outside the typical Linux kernel development
cycle. Android does not have a native X Window System nor does it support the full set of standard GNU libraries, and this makes it difficult to port existing Linux applications or libraries to
Certain features that Google contributed back to the Linux kernel, notably a power management feature called wakelocks, were rejected by mainline kernel developers, partly because kernel maintainers felt that Google did not show any intent to maintain their own
code. Even though Google announced in April 2010 that they would hire two employees to work with the Linux kernel
community, Greg Kroah-Hartman, the current Linux kernel maintainer for the -stable branch, said in December 2010 that he was concerned that Google was no longer trying to get their code changes included in mainstream
Linux. Some Google Android developers hinted that "the Android team was getting fed up with the process", because they were a small team and had more urgent work to do on
However, in September 2010, Linux kernel developer Rafael J. Wysocki added a patch that improved the mainline Linux wakeup events framework. He said that Android device drivers that use wakelocks can now be easily merged into mainline Linux, but that Android's opportunistic suspend features should not be included in the mainline
kernel. In 2011 Linus Torvalds said that "eventually Android and Linux would come back to a common kernel, but it will probably not be for four to five
In December 2011, Greg Kroah-Hartman announced the start of the Android Mainlining Project, which aims to put some Android drivers, patches and features back into the Linux kernel, starting in Linux
3.3. further integration being expected for Linux Kernel 3.4.
The Android Emulator default home screen (v1.5)Current features and
The platform is adaptable to larger, VGA, 2D graphics library, 3D graphics library based on OpenGL ES 2.0 specifications, and traditional smartphone layouts.
SQLite, a lightweight relational database, is used for data storage purposes.
Android supports connectivity technologies including GSM/EDGE, IDEN, CDMA, EV-DO, UMTS, Bluetooth, Wi-Fi, LTE, NFC and WiMAX.
SMS and MMS are available forms of messaging, including threaded text messaging and now Android Cloud To Device Messaging (C2DM) is also a part of Android Push Messaging service.
Multiple language support
Android supports multiple languages.
While most Android applications are written in Java, there is no Java Virtual Machine in the platform and Java byte code is not executed. Java classes are compiled into Dalvik executables and run on Dalvik, a specialized virtual machine designed specifically for Android and optimized for battery-powered mobile devices with limited memory and CPU. J2ME support can be provided via third-party applications.
Android supports the following audio/video/still media formats: WebM, H.263, H.264 (in 3GP or MP4 container), MPEG-4 SP, AMR, AMR-WB (in 3GP container), AAC, HE-AAC (in MP4 or 3GP container), MP3, MIDI, Ogg Vorbis, FLAC, WAV, JPEG, PNG, GIF,
Streaming media support
RTP/RTSP streaming (3GPP PSS, ISMA), HTML progressive download (HTML5 <video> tag). Adobe Flash Streaming (RTMP) and HTTP Dynamic Streaming are supported by the Flash
plugin. Apple HTTP Live Streaming is supported by RealPlayer for
Android, and by the operating system in Android 3.0 (Honeycomb).
Additional hardware support
Android can use video/still cameras, touchscreens, GPS, accelerometers, gyroscopes, barometers, magnetometers, dedicated gaming controls, proximity and pressure sensors, thermometers, accelerated 2D bit blits (with hardware orientation, scaling, pixel format conversion) and accelerated 3D graphics.
Android has native support for multi-touch which was initially made available in handsets such as the HTC Hero. The feature was originally disabled at the kernel level (possibly to avoid infringing Apple's patents on touch-screen technology at the
time). Google has since released an update for the Nexus One and the Motorola Droid which enables multi-touch
Supports A2DP, AVRCP, sending files (OPP), accessing the phone book (PBAP), voice dialing and sending contacts between phones. Keyboard, mouse and joystick (HID) support is available in Android 3.1+, and in earlier versions through manufacturer customizations and third-party
Android does not support native video calling, but some handsets have a customized version of the operating system that supports it, either via the UMTS network (like the Samsung Galaxy S) or over IP. Video calling through Google Talk is available in Android 2.3.4 and later. Gingerbread allows Nexus S to place Internet calls with a SIP account. This allows for enhanced VoIP dialing to other SIP accounts and even phone numbers. Skype 2.1 offers video calling in Android 2.3, including front camera support.
Multitasking of applications is available.
Voice based features
Google search through voice has been available since initial release. Voice actions for calling, texting, navigation, etc. are supported on Android 2.2
Android supports tethering, which allows a phone to be used as a wireless/wired Wi-Fi hotspot. Before Android 2.2 this was supported by third-party applications or manufacturer
Android supports capturing a screenshot by pressing the power and volume-down buttons at the same
time. Prior to Android 4.0, the only methods of capturing a screenshot were through manufacturer and third-party customizations or otherwise by using a PC connection (DDMS developer's tool). These alternative methods are still available with the latest Android.
Most Android devices include microSD slot and can read microSD cards formatted with FAT32, Ext3fs or Ext4fs file system. To allow use of high-capacity storage media such as USB flash drives and USB HDDs, many Android tablets also include USB 'A' receptacle. Storage formatted with FAT32 is handled by Linux Kernel VFAT driver, while 3rd party solutions are required to handle other popular file systems such as NTFS, HFS Plus and
List of Android devices
Galaxy Nexus, the latest "Google phone"
Google TV Home ScreenWhile Android is designed primarily for smartphones and tablets, the open and customizable nature of the operating system allows it to be used on other electronics, including laptops and
netbooks, smartbooks, and ebook readers. Further, Google intends to bring Android to televisions with Google TV, and the OS has seen niche applications on
wristwatches, headphones, car CD and DVD players, digital cameras,
portable media players and landlines.
The first commercially available phone to run Android was the HTC Dream, released on 22 October
2008. In early 2010 Google collaborated with HTC to launch its flagship Android device, the Nexus One. This was followed later in 2010 with the Samsung-made Nexus S and in 2011 with the Galaxy Nexus.
iOS and Android 2.3.3 'Gingerbread' may be set up to dual boot on a jailbroken iPhone or iPod Touch with the help of OpeniBoot and
In December 2011 it was announced the Pentagon has officially approved Android for use by its
Android software development and List of open source Android applications
Applications are usually developed in the Java language using the Android Software Development Kit, but 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.
Android Market is the online software store developed by Google for Android devices. An application program ("app") called "Market" is preinstalled on most Android devices and allows users to browse and download apps published by third-party developers, hosted on Android Market. As of October 2011 there were more than 300,000 apps available for Android, and the estimated number of applications downloaded from the Android Market as of December 2011 exceeded 10
billion. The operating system itself is installed on 130 million total
Only devices that comply with Google's compatibility requirements are allowed to preinstall Google's closed-source Android Market app and access the
Market. The Market filters the list of applications presented by the Market app to those that are compatible with the user's device, and developers may restrict their applications to particular carriers or countries for business
Google has participated in the Android Market by offering several applications themselves, including Google Voice (for the Google Voice service), Sky Map (for watching stars), Finance (for their finance service), Maps Editor (for their MyMaps service), Places Directory (for their Local Search), Google Goggles that searches by image, Gesture Search (for using finger-written letters and numbers to search the contents of the phone), Google Translate, Google Shopper, Listen for podcasts and My Tracks, a jogging application. In August 2010, Google launched "Voice Actions for
Android", which allows users to search, write messages, and initiate calls by voice.
Alternatively, users can install apps directly onto the device if they have the application's APK file or from third party app stores such as the Amazon
Android applications run in a sandbox, an isolated area of the operating system that does not have access to the rest of the system's resources, unless access permissions are granted by the user when the application is installed. Before installing an application, Android Market displays all required permissions. A game may need to enable vibration, for example, but should not need to read messages or access the phonebook. After reviewing these permissions, the user can decide whether to install the
Android has been criticized for providing an ineffective and too coarse grained permission
system. In Android Permissions Demystified, Felt, Chin, Hanna, Song, and Wagner observe "... an install-time permission system is ineffective if developers routinely request more permissions than they require.
Over-privileged applications expose users to unnecessary permission warnings and increase the impact of a bug or vulnerability." The authors then go on to survey
over-privileged applications, including a Google authored reference implementations, using their Stowaway
tool. In Dr. Android and Mr. Hide: Fine-grained security policies on unmodified Android, Jeon, Micinski, Vaughan, et. al. comment on the coarse grained permissions, stating "[the] deviation from least privilege increases the threat from vulnerabilities and malware. To address this issue, we present a novel system that can replace existing platform permissions with finer-grained
Some Android malware incidents have been reported involving rogue applications on Android Market. In August 2010, Kaspersky Lab reported detection of the first malicious program for Android, named
Trojan-SMS, an SMS trojan which had already infected a number of
devices. In some cases applications which contained Trojans were hidden in pirated versions of legitimate
apps. Google has responded by removing malicious apps from the Android Market, remotely disabling them on infected devices, and scanning newly-uploaded apps for potentially malicious
software. Several security firms have released antivirus software for Android devices, in particular, AVG
Technologies, Avast!, F-Secure, Kaspersky, McAfee and Symantec.
Android smartphones have the ability to report the location of Wi-Fi access points, encountered as phone users move around, to build vast databases containing the physical locations of hundreds of millions of such access points. These databases form electronic maps to locate smartphones, allowing them to run apps like Foursquare, Latitude, Places, and to deliver location-based
Third party monitoring software such as TaintDroid, an academic research-funded project, can, in some cases, detect when personal information is being sent from applications to remote
The Android logo was designed along with the Droid font family made by Ascender
Android Green is the color of the Android Robot that represents the Android operating system. The print color is PMS 376C and the RGB color value in hexadecimal is #A4C639, as specified by the Android Brand
Guidelines. The custom typeface of Android is called Norad (cf. NORAD). It is only used in the text
Research company Canalys estimated in Q2 2009 that Android had a 2.8% share of worldwide smartphone
shipments. By Q4 2010 this had grown to 33% of the market, becoming the top-selling smartphone platform. This estimate includes the Tapas and OMS variants of
Android. By Q3 2011 Gartner estimates more than half (52.5%) of the smartphone market belongs to
In February 2010 ComScore said the Android platform had 9.0% of the U.S. smartphone market, as measured by current mobile subscribers. This figure was up from an earlier estimate of 5.2% in November
2009. By the end of Q3 2010 Android's U.S. market share had grown to
In May 2010, Android's first quarter U.S. sales surpassed that of the rival iPhone platform. According to a report by the NPD group, Android achieved 25% smartphone sales in the US market, up 8% from the December quarter. In the second quarter, Apple's iOS was up by 11%, indicating that Android is taking market share mainly from RIM, and still has to compete with heavy consumer demand for new competitor
offerings. Furthermore, analysts pointed to advantages that Android has as a multi-channel, multi-carrier
OS. In Q4 2010 Android had 59% of the total installed user base of Apple's iOS in the U.S. and 46% of the total installed user base of iOS in
As of June 2011, Google said that 550,000 new Android devices were being activated every day — up from 400,000 per day a month earlier — and more than 100 million devices had been
activated. Android hit 300,000 activations per day back in December 2010. By July 14, 2011, 550,000 Android devices were being activated by Google each day, with 4.4% growth per
week. On 1 August 2011, Canalys estimated that Android had about 48% of the smartphone market
share. On October 13, 2011, Google announced that there were 190 million Android devices in the
market. As of November 16, 2011, during the Google Music announcement "These Go to Eleven", 200 million Android devices had been
activated. Based on this number, with 1.9% of Android devices being tablets, approximately 3.8 million Android Honeycomb Tablets have been
sold. On December 20, 2011. Andy Rubin announced that Google was activating 700,000 new Android devices
Usage share of the different versions, by February 1, 2012Usage share of the different versions, by February 1,
Distribution API level %
4.0.x Ice Cream Sandwich 14-15 1.0%
3.x.x Honeycomb 11-13 3.4%
2.3.x Gingerbread 9-10 58.6%
2.2 Froyo 8 27.8%
2.0, 2.1 Eclair 7 7.6%
1.6 Donut 4 1.0%
1.5 Cupcake 3 0.6%
There were two more internal releases, called "Astro" and "Bender". The code names are in alphabetical order, and were allegedly changed from robots to desserts to avoid trademark
The carrier Telstra opened the world's first Android store, Androidland, on Bourke Street, Melbourne in December
TrademarksIn order to use the Android trademark, device manufacturers must ensure that the device complies with the Compatibility Definition Document (CDD) and then get permission from Google. Devices must also meet this definition to be eligible to license Google's closed-source applications, including the Android
Market. Participation in the compatibility program is free of charge.
In September 2010, Skyhook Wireless filed a lawsuit against Google in which they alleged that Google had used the compatibility document to block Skyhook's mobile positioning service (XPS) from Motorola's Android mobile
devices. In December 2010 a judge denied Skyhook's motion for preliminary injunction, saying that Google had not closed off the possibility of accepting a revised version of Skyhook's XPS service, and that Motorola had terminated their contract with Skyhook because Skyhook wanted to disable Google's location data collection functions on Motorola's devices, which would have violated Motorola's obligations to Google and its
The source code for Android is available under free and open source software licenses. Google published their Linux kernel changes under the GNU General Public License version 2, and the rest of the code (including network and telephony
stacks) under the Apache License version 2.0.
The Open Handset Alliance develops the GPL-licensed part of Android, that is their changes to the Linux kernel, in public, with source code publicly available at all times. The rest of Android is developed in private, with source code released publicly when a major new version is released. Typically Google collaborates with a hardware manufacturer to produce a flagship device (part of the Google Nexus series) featuring the new version of Android, then makes the source code available after that device has been
In early 2011, Google chose to temporarily withhold the Android source code to the tablet-only Honeycomb release, creating doubts over Google's commitment to open source with
Android. The reason, according to Andy Rubin in an official Android blog post, was because Honeycomb was rushed for production of the Motorola
Xoom, and they did not want third parties creating a "really bad user experience" by attempting to put onto smartphones a version of Android intended for
tablets. The source code was once again made available in November 2011 with the release of Android
Both Android and Android phone manufacturers have been the target of numerous patent lawsuits. On 12 August 2010, Oracle sued Google over claimed infringement of copyrights and patents related to the Java programming
language. Specifically, the patent infringement claim references seven United States patents including US 5966702 "Method and apparatus for pre-processing and packaging class files", and US 6910205 "Interpreting functions utilizing a hybrid of virtual and native machine
In response, Google submitted multiple lines of defense, counterclaiming that Android did not infringe on Oracle's patents or copyright, that Oracle's patents were invalid, and several other defenses. They said that Android is based on Apache Harmony, a clean room implementation of the Java class libraries, and an independently developed virtual machine called Dalvik.
Microsoft has also sued several manufacturers of Android devices for patent infringement, and collects patent licensing fees from others. In October 2011 Microsoft said they had signed license agreements with ten Android device manufacturers, accounting for 55% of worldwide revenue for Android
devices. These include Samsung and HTC.
Google has publicly expressed its dislike for the current patent landscape in the United States, accusing Apple, Oracle and Microsoft of trying to take down Android through patent litigation, rather than innovating and competing with better products and
services. In August 2011, Google started the process of purchasing Motorola Mobility for US$12.5 billion, which was viewed in part as a defensive measure to protect Android, since Motorola Mobility holds more than 17,000
patents. In December 2011 Google acquired in the region of a thousand patents from
IBM, which may aid in defense against Oracle. In February 2012, the U.S. Department of Justice and the European Union approved Google's aquisition of Motorola
devices at Google.com
(operating system) at the Open Directory Project
Brin introduces the Android platform on YouTube
Building a Mobile Platform to Change the Industry: lecture by Google
Mobile Platforms Manager, Richard Miner at Stanford University
Internals: Fragment of a course detailing the architecture of Android
and interaction of its components
of Android internals
Wireless Application Development Volume I: Android Essentials, 3rd
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