 | |
|---|---|
 Android 2.3 "Gingerbread" | |
| Company / developer | Google Inc., Open Handset Alliance |
| Programmed in | C (core),[1] C++ (some third party libraries), Java (UI) |
| Working state | Current |
| Source model | Free and open source software |
| Initial release | 21 October 2008 |
| Latest stable release | 2.3.2 (Gingerbread) Build: GRH78C[2] / 21 January 2011[2] |
| Supported platforms | ARM, MIPS, Power Architecture, x86[citation needed] |
| Kernel type | Monolithic (modified Linux kernel) |
| Default user interface | Graphical |
| License | Apache 2.0 (Linux kernel patches are licensed under GPL v2[3]) |
| Official website | android.com |
Android has a large community of developers writing application programs ("apps") that extend the functionality of the devices. There are currently over 200,000 apps available for Android.[12]Android Market is the online app store run by Google, though apps can be downloaded from third-party sites (AT&T permits third-party apps only on their Aria phone [13]). Developers write primarily in the Java language, controlling the device via Google-developed Java libraries.[14] Python, Ruby and other languages are also available for Android development via the Android Scripting Environment.
The unveiling of the Android distribution on 5 November 2007 was announced with the founding of the Open Handset Alliance, a consortium of 79 hardware, software, and telecom companies devoted to advancing open standards for mobile devices.[15][16] Google released most of the Android code under the Apache License, a free software and open source license.[17]
The Android operating system software stack consists of Java applications running on a Java-based, object-oriented application framework on top of Java core libraries running on a Dalvik virtual machine featuring JIT compilation. Libraries written in C include the surface manager, OpenCore[18] media framework, SQLite relational database management system, OpenGL ES 2.0 3D graphics API, WebKit layout engine, SGL graphics engine, SSL, and Bionic libc. The Android operating system consists of 12 million lines of code including 3 million lines of XML, 2.8 million lines of C, 2.1 million lines of Java, and 1.75 million lines of C++.[19]
History
Acquisition by Google
In July 2005, Google acquired Android Inc., a small startup company based in Palo Alto, California, USA.[20] Android's co-founders who went to work at Google included Andy Rubin (co-founder of Danger),[21] Rich Miner (co-founder of Wildfire Communications, Inc.),[22] Nick Sears (once VP at T-Mobile),[23] and Chris White (headed design and interface development at WebTV).[24] At the time, little was known about the functions of Android, Inc. other than that they made software for mobile phones.[20] This began rumors that Google was planning to enter the mobile phone market.At Google, the team led by Rubin developed a mobile device platform powered by the Linux kernel which they marketed to handset makers and carriers on the premise of providing a flexible, upgradable system. It was reported that Google had already 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 part.[25][26][27] More speculation that Google's Android would be entering the mobile-phone market came in December 2006.[28] 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.[29] More speculation followed reporting 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 telephony.[30][31]
Open Handset Alliance
Main article: Open Handset Alliance
"Today's announcement is more ambitious than any single 'Google Phone' that the press has been speculating about over the past few weeks. Our vision is that the powerful platform we're unveiling will power thousands of different phone models."
Eric Schmidt, former Google Chairman/CEO[5]
On 9 December 2008, it was announced that 14 new members would be joining the Android Project, including PacketVideo, ARM Holdings, Atheros Communications, Asustek Computer Inc, Garmin Ltd, Softbank, Sony Ericsson, Toshiba Corp, and Vodafone Group Plc.[32][33]
Licensing
With the exception of brief update periods, Android has been available under a free software / open source license since 21 October 2008. Google published the entire source code (including network and telephony stacks)[34] under an Apache License.[35] Google also keeps the reviewed issues list publicly open for anyone to see and comment.[36]Update history
Android has seen a number of updates since its original release. These updates to the base operating system typically fix bugs and add new features. Generally each update to the Android operating system is developed under a code name based on a dessert item. The code names are in alphabetical order.| 1.0 | Released 23 September 2008[37] |
|---|---|
| 1.1 | On 9 February 2009, Android 1.1 update for Android was released for T-Mobile G1 Only. Included in the update were:[38]
|
| 1.5 (Cupcake) Based on Linux Kernel 2.6.27 | On 30 April 2009, the official 1.5 (Cupcake) update for Android was released.[39][40] There were several new features and UI updates included in the 1.5 update:[41]
|
| 1.6 (Donut) Based on Linux Kernel 2.6.29[42] | On 15 September 2009, the 1.6 (Donut) SDK was released.[43][44] Included in the update were:[42]
|
| 2.0 / 2.1 (Eclair) Based on Linux Kernel 2.6.29[45] | On 26 October 2009, the 2.0 (Eclair) SDK was released.[46] Changes include:[47]
The 2.1 SDK was released on 12 January 2010.[50] |
| 2.2 (Froyo)[51] Based on Linux Kernel 2.6.32 [52] (2.2.2 latest release) | On 20 May 2010, the 2.2 (Froyo) SDK was released.[51] Changes included:[52]
|
| 2.3 (Gingerbread)[58] Based on Linux Kernel 2.6.35[59] | On 6 December 2010, the 2.3 (Gingerbread) SDK was released.[58] Changes included:[59]
|
| 3.0 (Honeycomb)[61] | On 26 January 2011, a preview of the 3.0 (Honeycomb) SDK was released. Changes include:[62]
|
| Ice Cream Sandwich[63] | Possible mid-2011 release.[63] |
Features
Current features and specifications:[64][65][66]
| Handset layouts | The platform is adaptable to larger, VGA, 2D graphics library, 3D graphics library based on OpenGL ES 2.0 specifications, and traditional smartphone layouts. |
|---|---|
| Storage | SQLite, a lightweight relational database, is used for data storage purposes |
| Connectivity | Android supports connectivity technologies including GSM/EDGE, IDEN, CDMA, EV-DO, UMTS, Bluetooth, Wi-Fi, LTE, and WiMAX. |
| Messaging | SMS and MMS are available forms of messaging, including threaded text messaging and now Android Cloud to Device Messaging Framework (C2DM) is also a part of Android Push Messaging service. |
| Web browser | The web browser available in Android is based on the open-source WebKit layout engine, coupled with Chrome's V8 JavaScript engine. The browser scores a 93/100 on the Acid3 Test. |
| Java support | 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 the Dalvik virtual machine. Dalvik is 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. |
| Media support | 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, WAV, JPEG, PNG, GIF, BMP.[66] |
| 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 10.1 plugin.[67] Apple HTTP Live Streaming is supported by RealPlayer for Mobile[68] and planned to be supported by the operating system in Android 3.0 (Honeycomb).[62] Microsoft Smooth Streaming is planned to be supported through the awaited port of Silverlight plugin to Android. |
| Additional hardware support | Android can use video/still cameras, touchscreens, GPS, accelerometers, gyroscopes, magnetometers, proximity and pressure sensors, thermometers, accelerated 2D bit blits (with hardware orientation, scaling, pixel format conversion) and accelerated 3D graphics. |
| Development environment | Includes a device emulator, tools for debugging, memory and performance profiling. The integrated development environment (IDE) is Eclipse (currently 3.4 or greater) using the Android Development Tools (ADT) Plugin. The programming languages are Java and C/C++. |
| Market | The Android Market is a catalog of applications that can be downloaded and installed to Android devices over-the-air, without the use of a PC. |
| Multi-touch | 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).[69] Google has since released an update for the Nexus One and the Motorola Droid which enables multi-touch natively.[70] |
| Bluetooth | 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 through manufacturer customizations and third-party applications. Full HID support is planned for Android 3.0 (Honeycomb).[62] |
| Video calling | The mainstream Android version does not support video calling, but some handsets have a customized version of the operating system which supports it, either via UMTS network (like the Samsung Galaxy S) or over IP. Video calling through Google Talk is planned for Android 3.0 (Honeycomb). |
| Multitasking | Multitasking of applications is available.[71] |
| Voice based features | Google search through Voice has been available since initial release.[72] Voice actions for calling, texting, navigation etc. are supported on Android 2.2 onwards.[73] |
| Tethering | Android supports tethering, which allows a phone to be used as a wireless/wired hotspot. Prior to Android 2.2 this was supported by third-party applications or manufacturer customizations.[74] |
Hardware running Android
Main article: List of Android devices
The Android OS can be used as an operating system for cellphones, netbooks and tablets, including the Dell Streak, Samsung Galaxy Tab and other devices.[75][76]The world's first TV running Android, called Scandinavia, has also been launched by the company People of Lava.[77]
The first commercially available phone to run the Android operating system was the HTC Dream, released on 22 October 2008.[78]
[edit] Google's flagship smartphones
A list of Android phones that are marketed by Google and contain the "Pure Google" Android experience.Software development
Software development kit
The Android software development kit (SDK) includes a comprehensive set of development tools.[84] These include a debugger, libraries, a handset emulator (based on QEMU), documentation, sample code, and tutorials. Currently supported development platforms include computers running Linux (any modern desktop Linux distribution), Mac OS X 10.4.9 or later, Windows XP or later. The officially supported integrated development environment (IDE) is Eclipse (currently 3.4, 3.5 or 3.6) using the Android Development Tools (ADT) Plugin, though developers may use any text editor to edit Java and XML files then use command line tools (Java Development Kit and Apache Ant are required) to create, build and debug Android applications as well as control attached Android devices (e.g., triggering a reboot, installing software package(s) remotely).[85]A preview release of the Android SDK was released on 12 November 2007. On 15 July 2008, the Android Developer Challenge Team accidentally sent an email to all entrants in the Android Developer Challenge announcing that a new release of the SDK was available in a "private" download area. The email was intended for winners of the first round of the Android Developer Challenge. The revelation that Google was supplying new SDK releases to some developers and not others (and keeping this arrangement private) led to widely reported frustration within the Android developer community at the time.[86]
On 18 August 2008 the Android 0.9 SDK beta was released. This release provided an updated and extended API, improved development tools and an updated design for the home screen. Detailed instructions for upgrading are available to those already working with an earlier release.[87] On 23 September 2008 the Android 1.0 SDK (Release 1) was released.[88] According to the release notes, it included "mainly bug fixes, although some smaller features were added". It also included several API changes from the 0.9 version. Multiple versions have been released since.[89]
Enhancements to Android's SDK go hand in hand with the overall Android platform development. The SDK also supports older versions of the Android platform in case developers wish to target their applications at older devices. Development tools are downloadable components, so after one has downloaded the latest version and platform, older platforms and tools can also be downloaded for compatibility testing.[90]
Android applications are packaged in .apk format and stored under
/data/app folder on the Android OS (the folder is accessible to root user only for security reasons). APK package contains .dex files[91] (compiled byte code files called Dalvik executable), resource files, etc.Android Market
Main article: Android Market
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 December 2010[update] there were about 200,000 games, applications and widgets available on the Android Market, with an estimated 2.5 billion total downloads.[92]Only devices that comply with Google's compatibility requirements are allowed to preinstall Google's closed-source Android Market app and access the Market.[93] 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 reasons. [94]
Google announced the Android Market on 28 August 2008, and it was available to users on 22 October 2008. Support for paid applications was available from 13 February 2009 for US and UK developers,[95] with additional support from 29 countries on 30 September 2010.[96]
Since apps can be installed using "apk"-files, alternatives, such as GetJar, coexist with the official Android Market.
App Inventor for Android
Main article: Google App Inventor
On 12 July 2010 Google announced the availability of App Inventor for Android, a Web-based visual development environment for novice programmers, based on MIT's Open Blocks Java library and providing access to Android devices' GPS, accelerometer and orientation data, phone functions, text messaging, speech-to-text conversion, contact data, persistent storage, and Web services, initially including Amazon and Twitter.[97] "We could only have done this because Android’s architecture is so open," said the project director, MIT's Hal Abelson.[98] Under development for over a year,[99] the block-editing tool has been taught to non-majors in computer science at Harvard, MIT, Wellesley, and the University of San Francisco, where Professor David Wolber developed an introductory computer science course and tutorial book for non-computer science students based on App Inventor for Android.[100][101]Android Developer Challenge
Main article: Android Developer Challenge
The Android Developer Challenge was a competition for the most innovative application for Android. Google offered prizes totaling 10 million US dollars, distributed between ADC I and ADC II. ADC I accepted submissions from 2 January to 14 April 2008. The 50 most promising entries, announced on 12 May 2008, each received a $25,000 award to fund further development.[102][103] It ended in early September with the announcement of ten teams that received $275,000 each, and ten teams that received $100,000 each.[104] ADC II was announced on 27 May 2009.[105] The first round of the ADC II closed on 6 October 2009.[106] The first-round winners of ADC II comprising the top 200 applications were announced on 5 November 2009. Voting for the second round also opened on the same day and ended on November 25. Google announced the top winners of ADC II on November 30, with SweetDreams, What the Doodle!? and WaveSecure being nominated the overall winners of the challenge.[107][108]Google applications
Google has also participated in the Android Market by offering several applications for its services. These applications include 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",[109] which allows users to search, write messages, and initiate calls by voice.
Third party applications
With the growing number of Android handsets, there has also been an increased interest by third party developers to port their applications to the Android operating system.As of December 2010, the Android Marketplace had over 200,000 applications,[92] with over 1 billion downloads. This is up from 70,000 in July 2010.[110][111]
Obstacles to development include the fact that Android does not use established Java standards, i.e. Java SE and ME. This prevents compatibility among Java applications written for those platforms and those for the Android platform. Android only reuses the Java language syntax, but does not provide the full-class libraries and APIs bundled with Java SE or ME.[112] However, there are multiple tools in the market that provide J2ME to Android conversion services, which enable the developer to convert Java into Android. Companies like Myriad Group and UpOnTek provide these services.[113][114][115]
Developers have reported that it is difficult to maintain applications on multiple versions of Android, owing to compatibility issues between versions 1.5 and 1.6,[116] especially the different resolution ratios in use among various Android phones.[117] Such problems were pointedly brought into focus as they were encountered during the ADC2 contest.[118] Further, the rapid growth in the number of Android-based phone models with differing hardware capabilities also makes it difficult to develop applications that work on all Android-based phones.[119][120][121][122] As of August 2010, 83% of Android phones run the 2.x versions, and 17% still run the 1.5 and 1.6 versions[123]
Native code
Libraries written in C and other languages can be compiled to ARM native code and installed using the Android Native Development Kit. Native classes can be called from Java code running under the Dalvik VM using theSystem.loadLibrary call, which is part of the standard Android Java classes.[124][125]Complete applications can be compiled and installed using traditional development tools.[126] The ADB debugger gives a root shell under the Android Emulator which allows native ARM code to be uploaded and executed. ARM code can be compiled using GCC on a standard PC.[126] Running native code is complicated by the fact that Android uses a non-standard C library (libc, known as Bionic). The underlying graphics device is available as a framebuffer at /dev/graphics/fb0.[127] The graphics library that Android uses to arbitrate and control access to this device is called the Skia Graphics Library (SGL), and it has been released under an open source license.[128] Skia has backends for both win32 and Unix, allowing the development of cross-platform applications, and it is the graphics engine underlying the Google Chrome web browser.[129]
Community-based firmware
There is a community of open-source enthusiasts that build and share Android-based firmware with a number of customizations and additional features, such as FLAC lossless audio support and the ability to store downloaded applications on the microSD card.[130] This usually involves rooting the device. Rooting allows users root access to the operating system, giving more control over their environment variables. In order to use custom firmwares the devices bootloader must be unlocked. Rooting alone does not allow the flashing of custom firmware. Modified firmwares allow users of older phones to use applications available only on newer releases.[131]Those firmware packages are updated frequently, incorporate elements of Android functionality that haven't yet been officially released within a carrier-sanctioned firmware, and tend to have fewer limitations. CyanogenMod and VillainROM are two examples of such firmware.
On 24 September 2009, Google issued a cease and desist letter[132] to the modder Cyanogen, citing issues with the re-distribution of Google's closed-source applications[133] within the custom firmware. Even though most of Android OS is open source, phones come packaged with closed-source Google applications for functionality such as the application store and GPS navigation. Google has asserted that these applications can only be provided through approved distribution channels by licensed distributors. Cyanogen has complied with Google's wishes and is continuing to distribute this mod without the proprietary software. He has provided a method to back up licensed Google applications during the mod's install process and restore them when it is complete.[134]
[edit] Marketing
Logos
The Android logo was designed with the Droid font family made by Ascender Corporation.[135]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.[136]
Typeface
The custom typeface of Android is called Norad, only used in the text logo.[137]Research company Canalys estimated that by Q2 2009, Android had a 2.8% share of the worldwide smartphone market.[138]
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.[139] By the end of Q3 2010 Android's U.S. market share had grown to 21.4 percent.[140]
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.[8] Furthermore, analysts pointed to advantages that Android has as a multi-channel, multi-carrier OS, which allowed it to duplicate the quick success of Microsoft's Windows Mobile.[141]
In early October 2010, Google added 20 countries to its list of approved submitters. By mid-October, purchasing apps will be available in a total of 32 countries.[142] For a complete list of countries that are allowed to sell apps and those able to buy them see Android Market.
As of December 2010[update] Google said over 300,000 Android phones were being activated daily,[143] up from 100,000 per day in May 2010.[144]
Other: 0.1% of devices running obsolete versions[145]
Platform | API Level | Distribution |
| Android 2.3 (Gingerbread) | 9 | 0.4% |
| Android 2.2 (Froyo) | 8 | 51.8% |
| Android 2.0/2.1 (Eclair) | 7 | 35.2% |
| Android 1.6 (Donut) | 4 | 7.9% |
| Android 1.5 (Cupcake) | 3 | 4.7% |
Linux compatibility
Android's kernel was derived from Linux but has been tweaked by Google outside the main Linux kernel tree.[146] 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 GNU/Linux applications or libraries to Android.[147] However, support for the X Window System is possible.[148] Google no longer maintains the code they previously contributed to the Linux kernel as part of their Android effort, creating a separate version or fork of Linux.[149][150] This was due to a disagreement about new features Google felt were necessary (some related to security of mobile applications).[151] The code which is no longer maintained was deleted in January 2010 from the Linux codebase.[152]Google announced in April 2010 that they will hire two employees to work with the Linux kernel community.[153]
However, as of January 2011, points of contention still exist between Google and the Linux kernel team: Google tried to push upstream some Android-specific power management code in 2009, which is still rejected today.[154]
Furthermore, 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[155] Some Google Android developers hinted that "the Android team were getting fed up with the process", because they were a small team and had more urgent work to do on Android.[156]
Claimed infringement of copyrights and patents
On 12 August 2010, Oracle, owner of Java since it acquired Sun Microsystems in April 2009, sued Google over claimed infringement of copyrights and patents. The lawsuit claims that, "In developing Android, Google knowingly, directly and repeatedly infringed Oracle's Java-related intellectual property."[157]Specifically the patent infringement claim references seven patents including United States Patent No. 5,966,702, entitled "Method And Apparatus For Preprocessing And Packaging Class Files", and United States Patent No. 6,910,205, entitled "Interpreting Functions Utilizing A Hybrid Of Virtual And Native Machine Instructions".[158] It also references United States Patent No. RE38,104, ("the '104 patent") entitled “Method And Apparatus For Resolving Data References In Generated Code” authored by James Gosling, best known as the father of the Java programming language.[159]
In response Google submitted multiple lines of defense, saying 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.[160][161][162]
The Free Software Foundation has said that Google could have avoided this suit by building Android on top of IcedTea whose GPL license provides some protection against patents, instead of implementing it independently under the Apache License. It has also called the suit a "clear attack against someone's freedom to use, share, modify, and redistribute software".[163] However, the FSF also criticized Google, writing that "It's sad to see that Google apparently shunned those protections in order to make proprietary software development easier on Android.", and remarking that Google had not taken any clear position or action against software patents.
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