Android (operating system)
(Most of the Links Given are From Wikipedia)
  | |
|---|---|
 Home screen displayed by Samsung Galaxy Nexus, running Android 4.1 "Jelly Bean" | |
| Company / developer | Google, Open Handset Alliance,Android Open Source Project |
| Programmed in | C, C++, Java[1] |
| OS family | Unix-like, Linux |
| Working state | Current |
| Source model | Open source[2] |
| Initial release | September 23, 2008[3] |
| Latest stable release | 4.1 Jelly Bean[4] / July 10, 2012[5] |
| Marketing target | Smartphones andTablet computers |
| Available language(s) | Multi-lingual |
| Package manager | Google Play / APK |
| Supported platforms | ARM, MIPS,[6] x86[7] |
| Kernel type | Monolithic (modified Linux kernel) |
| Default user interface | Graphical (Multi-touch) |
| License | Apache License 2.0 Linux kernel patches under GNU GPL v2[8] |
| Official website | www.android.com |
Android is a Linux-based operating system designed primarily for touchscreen mobile devices such as smartphones and tablet computers, developed by Google in conjunction with the Open Handset Alliance.[2] Initially developed by Android Inc, whom Google financially backed and later purchased in 2005,[9] Android was unveiled in 2007 along with the founding of the Open Handset Alliance, a consortium of 86 hardware, software, andtelecommunication companies devoted to advancing open standards for mobile devices.[10]
Google releases the Android code as open-source, under the Apache License.[11] The Android Open Source Project (AOSP), lead by Google, is tasked with the maintenance and further development of Android.[12] Additionally, Android has a large community of developers writing applications ("apps") that extend the functionality of devices. Developers write primarily in a customized version of Java,[13] and apps can be downloaded from online stores such as Google Play (formerly Android Market), the app store run by Google, or third-party sites. In June 2012, there were more than 600,000 apps available for Android, and the estimated number of applications downloaded from Google Play was 20 billion.[14]
The first Android-powered phone was sold in October 2008,[15] and by the end of 2010 Android had become the world's leading smartphone platform.[16] It had a worldwide smartphone market share of 59% at the beginning of 2012,[17] and as of third quarter 2012, there were 500 million devices activated and 1.3 million activations per day.[18][19]
[edit]
Android, Inc. was founded in Palo Alto, California, United States in October 2003 by Andy Rubin (co-founder of Danger),[20] Rich Miner (co-founder of Wildfire Communications, Inc.),[21] Nick Sears[22] (once VP at T-Mobile),[23] and Chris White (headed design and interface development at WebTV)[9]to develop, in Rubin's words "...smarter mobile devices that are more aware of its owner's location and preferences."[9] 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.[9] 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 company.[24]History
Google acquired Android Inc. on August 17, 2005, making Android Inc. a wholly owned subsidiary of Google. Key employees of Android Inc., including Andy Rubin, Rich Miner and Chris White, stayed at the company after the acquisition.[9] 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 move.[9]
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 part.[25][26][27]
Speculation about Google's intention to enter the mobile communications market continued to build through December 2006.[28] Reports from theBBC 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 telephony.[29][30]
On November 5, 2007, the Open Handset Alliance, a consortium of technology companies including Google, device manufacturers such as HTC andSamsung, wireless carriers such as Sprint Nextel and T-Mobile, and chipset makers such as Qualcomm and Texas Instruments, unveiled itself. The goal of the Open Handset Alliance is to develop open standards for mobile devices.[10] On the same day, the Open Handset Alliance unveiled Android as its first product, a mobile device platform built on the Linux kernel version 2.6.[10]
The first commercially available phone to run Android was the HTC Dream, released on October 22, 2008.[31] In early 2010 Google collaborated with HTC to launch its flagship[32] Android device, the Nexus One. This was followed later in 2010 with the Samsung-made Nexus S and in 2011 with the Galaxy Nexus.
[edit]Description
See also: List of features in Android
The user interface in Android is based on the concept of direct manipulation,[33] using single- and multi-touch inputs like swiping, tapping, pinching and reverse pinching to manipulate on-screen objects.[33] The response to user input is designed to be immediate and provides a fluid touch interface. Internal hardware such as accelerometers, gyroscopes and proximity sensors are used by some applications to respond to additional user actions, for example adjusting the screen from portrait to landscape depending on how the device is orientated, or allowing the user to steer a vechicle in a racing game by rotating the device, simulating control of a steering wheel.[34]
Android devices boot to the homescreen, which is similar to the desktop found on PCs, and is the primary navigation and information point on the device. Android homescreens are typically made up of app icons, which launch the associated app, and widgets, which display live, auto-updating content such as the weather forecast, the user's email inbox, or a news ticker directly on the homescreen.[35] A homescreen may be made up of several pages that the user can swipe back and forth between.
Always present along the top of the screen is a status bar, showing information about the device and its connectivity. This status bar can be 'pulled' down to reveal a notification screen where apps may display important information or updates, such as a newly received email or SMS text, in a way that doesn't immediately interrupt or inconvenience the user.[36] In early versions of Android these notifications could be tapped to open the relevant app, but recent updates have provided enhanced functionality, such as the ability to call a number back directly from the missed call notification, without having to open the dialer app first.[37] Notifications are persistent until read or dismissed by the user.
While 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 andnetbooks, smartbooks,[38] ebook readers,[39] and smart TVs (Google TV). Further, the OS has seen niche applications on wristwatches,[40] headphones,[41] car CD and DVD players,[42] smart glasses (Project Glass), refrigerators, vehicle satnav systems, home automation systems, games consoles, mirrors,[43] cameras,[44][45] portable media players[46] landlines,[47] and treadmills.[48]
The Android logotype was designed along with the Droid font family by Ascender Corporation,[49] the robot icon was designed by Irina Blok.[50] 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.[51] The custom typeface of Android is called Norad (cf. NORAD). It is only used in the text logo.[51]
[edit]Linux
Android consists of a kernel based on the Linux kernel 2.6 and Linux Kernel 3.x (Android 4.0 onwards), with middleware, libraries and APIs written in Cand application software running on an application framework which includes Java-compatible libraries based on Apache Harmony. Android uses theDalvik virtual machine with just-in-time compilation to run Dalvik dex-code (Dalvik Executable), which is usually translated from Java bytecode.[52] The main hardware platform for Android is the ARM architecture. There is support for x86 from the Android x86 project,[7] and Google TV uses a special x86 version of Android.
Android's linux kernel has further architecture changes by Google outside the typical Linux kernel development cycle.[53] Android does not have a nativeX Window System by default nor does it support the full set of standard GNU libraries, and this makes it difficult to port existing Linux applications or libraries to Android.[54] But the support of simple C and SDL applications is possible by injection of a small java shim and usage of the JNI[55] like e.g. in the Jagged Alliance 2 port for Android.[56]
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.[57][58][59] Even though Google announced in April 2010 that they would hire two employees to work with the Linux kernel community,[60] 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.[58] 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 Android.[61]
Linux included the autosleep and wakelocks capabilities in the 3.5 kernel, after many previous attempts at merger. The interfaces are the same but the upstream Linux implementation allows for two different suspend modes: to memory (the traditional suspend that android uses), and to disk (hibernate, as it is known on the desktop). [62] In August 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 years".[63] 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.[64] further integration being expected for Linux Kernel 3.4.[65]
The flash storage on Android devices is split into several partitions, such as "/system" for the operating system itself and "/data" for user data and app installations.[66] In contrast to desktop Linux distributions, Android device owners are not given root access to the operating system for security reasons, and sensitive partitions such as /system are read-only. However, root access on the device can be obtained by exploiting security flaws in within Android, which is used frequently by the open source community to enhance the capabilities of their devices, but also by malicious parties to install viruses and malware.[67]
[edit]Android Open Source Project
The Android Open Source Project is led by Google, and tasked with the maintenance and development of Android.[68] 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."[69] 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.[69] The compatibility program is optional and free of charge, with the Compatibility Test Suite also free and open-source.[70]
[edit]Updates
Main article: Android version history
Android has a rapid release cycle, with new major versions being released every six to nine months.[71] Updates are typically incremental in nature, gradually improving the software on a regular schedule, rather than completely overhauling the system every two to three years which is common for desktop operating systems such as Windows. Between each major release, minor interim releases are made available as often as necessary to fix security issues and other software bugs. Most Android smartphones and tablets are capable of receiving updates "over-the-air" which allows the device to download and install updates without having to be connected to a PC.
Compared to rival mobile operating systems such as iOS, Android updates are typically very slow in reaching devices, often taking many months from the official Google release date to actually being distributed to phones and tablets.[72] In 2011, Google partnered with a number of manufacturers and carriers to announce an "Android Update Alliance", pledging to deliver timely updates for every device for 18 months after its release.[73] As of 2012, this alliance has never been mentioned since.[72]
Update delays are caused partly due to the extensive variation in hardware which makes up the Android ecosystem: each update must be tailored to the specific hardware in each device, which varies greatly from device to device, as the official Google source code only runs on their current flagship Nexus phone. Porting Android to specific hardware is a time- and resource-consuming process for device manufacturers, who prioritize their newest devices and often leave older ones behind.[72] Hence, older smartphones are frequently not updated to the latest release of Android if the manufacturer decides it's not worth their time, even if the phone is capable of running the update. This problem is compounded when manufacturers customize Android with their own unique interface and apps, as these modifications must be reapplied to each new release of the operating system. Some commentators have noted that manufacturers have a financial incentive not to update their devices, as lack of updates for existing devices fuels the purchase of newer ones.[74]
Further delays can be introduced by wireless carriers who, after receiving updates from manufacturers, customize and brand Android to their needs and conduct extensive testing on their networks before sending the update out to users.[72]
[edit]Applications
See also: Android software development
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.
Applications can be acquired by end-users either through a store such as Google Play or the Amazon Appstore, or by downloading and installing the application's APK file from a third-party site.[75]
[edit]Google Play
Main article: Google Play
Google Play is an online software store developed by Google for Android devices. An application program ("app") called "Play Store" is preinstalled on most Android devices and allows users to browse and download apps published by third-party developers, hosted on Google Play. As of June 2012, there were more than 600,000 apps available for Android, and the estimated number of applications downloaded from the Play Store exceeded 20 billion.[14] The operating system itself is installed on 400 million total devices.[76]
Only devices that comply with Google's compatibility requirements are allowed to preinstall and access the Play Store.[77] 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.[78]
Google offers many free applications in the Play Store including Google Voice, Google Goggles, Gesture Search, Google Translate, Google Shopper, Listen and My Tracks. In August 2010, Google launched "Voice Actions for Android",[79] which allows users to search, write messages, and initiate calls by voice.
[edit]Security
See also: Mobile security
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, the Play Store 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 application.[80] The sandboxing and permissions system weakens the impact of vulnerabilities and bugs in applications, but developer confusion and limited documentation has resulted in applications routinely requesting unnecessary permissions, reducing its effectiveness.[81] The complexity of inter-application communication implies Android may have opportunities to run unauthorized code.[82]
Several security firms have released antivirus software for Android devices, in particular, Lookout Mobile Security,[83] AVG Technologies,[84] Avast!,[85] F-Secure,[86] Kaspersky,[87] McAfee[88] and Symantec.[89] This software is ineffective as sandboxing also applies to such applications, limiting their ability to scan the deeper system for threats.[90]
[edit]Privacy
Android smartphones have the ability to report the location of Wi-Fi access points, encountered as phone users move around, to build 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 likeFoursquare, Latitude, Places, and to deliver location-based ads.[91]
Third party monitoring software such as TaintDroid,[92] an academic research-funded project, can, in some cases, detect when personal information is being sent from applications to remote servers.[93]
In March 2012, it was revealed that Android Apps can copy photos without explicit user permission,[94] Google responded they "originally designed the Android photos file system similar to those of other computing platforms like Windows and Mac OS. [...] we're taking another look at this and considering adding a permission for apps to access images. We've always had policies in place to remove any apps [on Google Play] that improperly access your data."[95]
[edit]Licensing
The source code for Android is available under free and open source software licenses. Google publishes most of the code (including network and telephony stacks)[96] under the Apache Licenseversion 2.0,[97][8][98] and the rest, Linux kernel changes, under the GNU General Public License version 2.
The Open Handset Alliance develops the 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 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 released.[99]
In early 2011, Google chose to temporarily withhold the Android source code to the tablet-only Honeycomb release, the reason, according to Andy Rubin in an official Android blog post, was because Honeycomb was rushed for production of the Motorola Xoom,[100] 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.[101] The source code was once again made available in November 2011 with the release of Android 4.0.[102]
As Android is not completely released under a GPL compatible license, e.g. Google's code is under the Apache license,[8] and also the Android Market allows proprietary software, Richard Stallman and the FSF are critical against Android and recommending the usage of alternatives as Replicant.[103][104]
[edit]Reception
Research company Canalys estimated in Q2 2009 that Android had a 2.8% share of worldwide smartphone shipments.[105] 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.[16] By Q3 2011 Gartner estimates more than half (52.5%) of the smartphone market belongs to Android.[106] By Q2 2012 according to the research firm IDC, Android has a 68% share of the global smartphone market.[107]
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.[108] By the end of Q3 2010 Android's U.S. market share had grown to 21.4%.[109]
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.[110] Furthermore, analysts pointed to advantages that Android has as a multi-channel, multi-carrier OS.[111] 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 Europe.[112][113]
As of June 2011, Google said that 550,000 new Android devices were being activated every day[114] — up from 400,000 per day a month earlier — and more than 100 million devices had been activated.[115] 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.[116] On August 1, 2011, Canalys estimated that Android had about 48% of the smartphone market share.[117] On October 13, 2011, Google announced that there were 190 million Android devices in the market.[118] As of November 16, 2011, during the Google Music announcement "These Go to Eleven", 200 million Android devices had been activated.[119] Based on this number, with 1.9% of Android devices being tablets, approximately 3.8 million Android Honeycomb Tablets have been sold.[120] On February 27, 2012, Andy Rubin announced that Google was activating over 850,000 Android smartphones and tablets daily.
In December 2011 it was announced the Pentagon has officially approved Android for use by its personnel.[121][122][123]
There has been some concern about the ease at which paid Android apps can be pirated - i.e. downloaded for free without the developer's permission.[124] Unlike the app store on iOS devices, which is the only place where iOS apps may be downloaded and installed from, Android apps can be downloaded and installed from anywhere, which makes it trivial to install unauthorized copies of apps from file sharing networks. In an interview with Eurogamer, the developers of Football Manager 2009 stated that the ratio of pirated players vs legitimate players was 5:1 for their game Football Manager 2009.[125] In 2010, Google released a tool for validating authorised purchases for use within apps, but developers complained that this was insufficient and trivial to crack. Google responded that the tool, especially its initial release, was intended as a sample framework for developers to modify and build upon depending on their needs, not as a finished security solution.[126] Piracy on Android remains an ongoing concern.
[edit]
Usage share of the different versions as of September 4, 2012.[127] Most Android devices to date still run the older OS version 2.3.x Gingerbread that was released on December 6, 2010.
| Version | Release date | API level | Distribution (September 4, 2012) |
|---|---|---|---|
| 4.1.x Jelly Bean | July 9, 2012 | 16 | 1.2% |
| 4.0.x Ice Cream Sandwich | October 19, 2011 | 14-15 | 20.9% |
| 3.x.x Honeycomb | February 22, 2011 | 11-13 | 2.1% |
| 2.3.x Gingerbread | December 6, 2010 | 9-10 | 57.5% |
| 2.2 Froyo | May 20, 2010 | 8 | 14% |
| 2.0, 2.1 Eclair | October 26, 2009 | 7 | 3.7% |
| 1.6 Donut | September 15, 2009 | 4 | 0.4% |
| 1.5 Cupcake | April 30, 2009 | 3 | 0.2% |
[edit]Open source community
Android has an active community of developers and enthusiasts who use the Android source code to develop and distribute their own modified versions of the operating system.[128] These community-developed releases, the most widely used of which being CyanogenMod,[129] often bring new features and updates to devices faster than through the official manufacturer/carrier channels, albeit without as extensive testing or quality assurance.[130] Community releases often come pre-rooted and contain modifications unsuitable for non-technical users, such as the ability to overclock or over/undervolt the device's processor.[131]
Historically, the early responses of tablet and smartphone manufacturers and mobile carriers were typically unsupportive of third-party firmware development. Manufacturers expressed concern about improper functioning of devices running unofficial software and the support costs resulting from this.[132] Moreover, modified firmwares such as CyanogenMod sometimes offer features for which carriers would otherwise charge a premium (e.g., tethering). As a result, technical obstacles including locked bootloaders and restricted access to root permissions were common in many devices. However, as community-developed software has grown more popular, and following a statement by the Librarian of Congress in the United States that permits the "jailbreaking" of mobile devices,[133] manufacturers and carriers have softened their position regarding third party development, with some, including HTC,[132] Motorola,[134] Samsung[135][136] and Sony Ericsson,[137]providing support and encouraging development. As a result of this, over time the need to circumvent hardware restrictions to install unofficial firmware has lessened as an increasing number of devices are shipped with unlocked or unlockable bootloaders, similar to the Nexus series of phones, although usually requiring that users waive their devices' warranties to do so.[132]
[edit]Copyrights and patents
Further information: Oracle v. Google
Both Android and Android phone manufacturers have been the target of numerous patent lawsuits. On August 12, 2010, Oracle sued Google over claimed infringement of copyrights and patents related to the Java programming language.[138] Oracle originally sought damages up to $6.1 billion,[139] but this valuation was rejected by a federal judge who asked Oracle to revise the estimate.[140] 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.[141] In May 2012 the jury in this case found that Google did not infringe on Oracle's patents, and the trial judge ruled that the structure of the Java APIs used by Google was not copyrightable.[142][143]
In addition to lawsuits against Google directly, various proxy wars have been waged against Android indirectly by targeting manufacturers of Android devices, with the effect of discouraging manufacturers from adopting the platform by increasing the costs of bringing an Android device to market.[144] Both Apple and Microsoft have sued several manufacturers for patent infringement, with Apple's ongoing legal action against Samsung being a particularly high-profile case. In October 2011 Microsoft said they had signed patent license agreements with ten Android device manufacturers, whose products account for 55% of the worldwide revenue for Android devices.[145] These include Samsung and HTC.[146] Samsung's patent settlement with Microsoft includes an agreement that Samsung will allocate more resources to developing and marketing phones running Microsoft's Windows Phone operating system.[144]
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.[147] In 2011-2, Google purchased Motorola Mobility for US$12.5 billion, which was viewed in part as a defensive measure to protect Android, since Motorola Mobility held more than 17,000 patents.[148] In December 2011 Google bought over a thousand patents from IBM.
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