Android is developed in clandestine by Google until the latest changes and updates are accessible to be released, at which point the antecedent cipher is fabricated accessible publicly.[87] This antecedent cipher will alone run afterwards modification on baddest devices, usually the Nexus alternation of devices. The antecedent cipher is, in turn, acclimatized by OEMs to run on their hardware.[88] Android's antecedent cipher does not accommodate the generally proprietary accessory drivers that are bare for assertive accouterments components.[89]
The blooming Android logo was advised for Google in 2007 by clear artist Irina Blok. The architectonics aggregation was tasked with a activity to actualize a universally identifiable amount with the specific admittance of a apprentice in the final design. Afterwards abundant architectonics developments based on science-fiction and amplitude movies, the aggregation eventually approved afflatus from the animal attribute on bathroom doors and adapted the amount into a apprentice shape. As Android is open-sourced, it was agreed that the logo should be likewise, and aback its barrage the blooming logo has been reinterpreted into endless variations on the aboriginal design.[90]
Update schedule
See also: Android adaptation history
Google provides above upgrades, incremental in nature, to Android every six to nine months, which a lot of accessories are able of accepting over the air.[91] The latest above absolution is Android 4.4 "KitKat".[5]
Compared to its arch battling adaptable operating system, namely iOS, Android updates are about apathetic to adeptness absolute devices. For accessories not beneath the Nexus brand, updates generally admission months from the time the accustomed adaptation is clearly released.[92] This is partly due to the all-encompassing aberration in accouterments of Android devices, to which anniversary advancement accept to be accurately tailored, as the official Google antecedent cipher alone runs on their flagship Nexus devices. Porting Android to specific accouterments is a time- and resource-consuming action for accessory manufacturers, who accent their newest accessories and generally leave earlier ones behind.[92] Hence, earlier smartphones are frequently not adapted if the architect decides it is not account their time, behindhand of whether the buzz is able of alive the update. This botheration is circuitous if manufacturers adapt Android with their own interface and apps, which accept to be reapplied to anniversary new release. Additional delays can be alien by wireless carriers who, afterwards accepting updates from manufacturers, added adapt and cast Android to their needs and conduct all-encompassing testing on their networks afore sending the advancement out to users.[92]
The abridgement of after-sale abutment from manufacturers and carriers has been broadly criticized by customer groups and the technology media.[93][94] Some commentators accept acclaimed that the industry has a banking allurement not to advancement their devices, as the abridgement of updates for absolute accessories fuels the acquirement of newer ones,[95] an attitude declared as "insulting".[94] The Guardian has complained that the adjustment of administration for updates is complicated alone because manufacturers and carriers accept advised it that way.[94] In 2011, Google partnered with a amount of industry players to advertise an "Android Amend Alliance", accord to bear appropriate updates for every accessory for 18 months afterwards its release;[96] however, there has not been addition official chat about that alliance.[92][97]
In 2012, Google began decoupling assertive aspects of the operating arrangement (particularly amount applications) so they could be adapted through Google Play Store, apart of Android itself. One of these components, Google Play Services, is a closed-source system-level action accouterment APIs for Google services, installed automatically on about all accessories alive Android adaptation 2.2 and higher. With these changes, Google can add new operating arrangement functionality through Play Casework and appliance updates afterwards accepting to deliver an advancement to the operating arrangement itself. As a result, Android 4.2 and 4.3 independent almost beneath user-facing changes, absorption added on accessory changes and belvedere improvements.[3][98]
Linux kernel
Android consists of a atom based on the Linux atom abiding abutment (LTS) branch. As of January 2014, accepted Android versions are congenital aloft Linux atom 3.4 or newer,[99][100] but the specific atom adaptation amount depends on the absolute Android accessory and chipset.[101][102][103] Android has acclimated assorted kernels aback its aboriginal 2.6.25.[40]
Android's Linux atom has added architectural changes that are implemented by Google alfresco the archetypal Linux atom development cycle, such as the admittance of apparatus like Binder, ashmem, pmem, logger, wakelocks, and altered out-of-memory (OOM) handling.[104][105][106] Assertive appearance that Google contributed aback to the Linux kernel, conspicuously a adeptness administration affection alleged "wakelocks", were alone by mainline atom developers partly because they acquainted that Google did not appearance any absorbed to advance its own code.[107][108][109] Google appear in April 2010 that they would appoint two advisers to plan with the Linux atom community,[110] but Greg Kroah-Hartman, the accepted Linux atom maintainer for the abiding branch, said in December 2010 that he was anxious that Google was no best aggravating to get their cipher changes included in boilerplate Linux.[108] Some Google Android developers hinted that "the Android aggregation was accepting fed up with the process," because they were a baby aggregation and had added burning plan to do on Android.[111]
In August 2011, Linus Torvalds said that "eventually Android and Linux would appear aback to a accepted kernel, but it will apparently not be for four to 5 years".[112] In December 2011, Greg Kroah-Hartman appear the alpha of Android Mainlining Project, which aims to put some Android drivers, patches and appearance aback into the Linux kernel, starting in Linux 3.3.[113] Linux included the autosleep and wakelocks capabilities in the 3.5 kernel, afterwards abounding antecedent attempts at merger. The interfaces are the aforementioned but the upstream Linux accomplishing allows for two altered append modes: to anamnesis (the acceptable append that Android uses), and to deejay (hibernate, as it is accepted on the desktop).[114] Google maintains a accessible cipher athenaeum that contains their beginning plan to re-base Android off the latest abiding Linux versions.[115][116]
The beam accumulator on Android accessories is breach into several partitions, such as /system for the operating arrangement itself, and /data for user abstracts and appliance installations.[117] In adverse to desktop Linux distributions, Android accessory owners are not accustomed basis admission to the operating arrangement and acute partitions such as /system are read-only. However, basis admission can be acquired by base aegis flaws in Android, which is acclimated frequently by the open-source association to enhance the capabilities of their devices,[118] but aswell by awful parties to install bacilli and malware.[119]
Android is a Linux administration according to the Linux Foundation,[120] Google's open-source arch Chris DiBona,[121] and several journalists.[122][123] Others, such as Google architect Patrick Brady, say that Android is not Linux in the acceptable Unix-like Linux administration sense; Android does not cover the GNU C Library and some of added apparatus about begin in Linux distributions.[124]
Software stack
Android's architectonics diagram
[icon] This area requires expansion. (December 2013)
On top of the Linux kernel, there are the middleware, libraries and APIs accounting in C, and appliance software alive on an appliance framework which includes Java-compatible libraries based on Apache Harmony. Android uses the Dalvik basic apparatus with just-in-time accumulation to run Dalvik "dex-code" (Dalvik Executable), which is usually translated from the Java bytecode.[125][126] Android 4.4 aswell supports new beginning runtime basic machine, ART, which is not enabled by default.[127]
Android's accepted C library, Bionic, was developed by Google accurately for Android, as a ancestry of the BSD's accepted C library code. Bionic has several above appearance specific to the Linux kernel, and its development continues apart of added Android's antecedent cipher bases. The capital allowances of appliance Bionic instead of the GNU C Library (glibc) or uClibc are its altered licensing model, abate runtime footprint, and enhancement for low-frequency CPUs.[126]
Aiming for a added acceptable licensing model, against the end of 2012 Google switched the Bluetooth assemblage in Android from the GPL-licensed BlueZ to the Apache-licensed BlueDroid.[128]
Android does not accept a built-in X Window Arrangement by default, nor does it abutment the abounding set of accepted GNU libraries. This fabricated it difficult to anchorage absolute Linux applications or libraries to Android,[124] until adaptation r5 of the Android Built-in Development Kit brought abutment for applications accounting absolutely in C or C++.[129] Libraries accounting in C may aswell be acclimated in Java appliance by bang of a baby Java bushing and accepting of the JNI.[130]
Open-source community
Android has an alive association of developers and enthusiasts who use the Android Open Antecedent Activity (AOSP) antecedent cipher to advance and deliver their own adapted versions of the operating system.[131] These community-developed releases generally accompany new appearance and updates to accessories faster than through the official manufacturer/carrier channels, admitting afterwards as all-encompassing testing or superior assurance;[24] accommodate connected abutment for earlier accessories that no best accept official updates; or accompany Android to accessories that were clearly appear alive added operating systems, such as the HP TouchPad. Association releases generally appear pre-rooted and accommodate modifications clashing for non-technical users, such as the adeptness to overclock or over/undervolt the device's processor.[132] CyanogenMod is the a lot of broadly acclimated association firmware,[133] and acts as a foundation for abundant others.
Historically, accessory manufacturers and adaptable carriers accept about been unsupportive of third-party firmware development. Manufacturers accurate affair about abnormal activity of accessories alive actionable software and the abutment costs consistent from this.[134] Moreover, adapted firmwares such as CyanogenMod sometimes action features, such as tethering, for which carriers would contrarily allegation a premium. As a result, abstruse obstacles including bound bootloaders and belted admission to basis permissions are accepted in abounding devices. However, as community-developed software has developed added popular, and afterward a account by the Librarian of Congress in the United States that permits the "jailbreaking" of adaptable devices,[135] manufacturers and carriers accept ashen their position apropos third affair development, with some, including HTC,[134] Motorola,[136] Samsung[137][138] and Sony,[139] accouterment abutment and auspicious development. As a aftereffect of this, over time the charge to avoid accouterments restrictions to install actionable firmware has lessened as an accretion amount of accessories are alien with apart or unlockable bootloaders, agnate to Nexus alternation of phones, although usually acute that users abandon their devices' warranties to do so.[134] However, admitting architect acceptance, some carriers in the US still crave that phones are bound down, arresting developers and customers
The blooming Android logo was advised for Google in 2007 by clear artist Irina Blok. The architectonics aggregation was tasked with a activity to actualize a universally identifiable amount with the specific admittance of a apprentice in the final design. Afterwards abundant architectonics developments based on science-fiction and amplitude movies, the aggregation eventually approved afflatus from the animal attribute on bathroom doors and adapted the amount into a apprentice shape. As Android is open-sourced, it was agreed that the logo should be likewise, and aback its barrage the blooming logo has been reinterpreted into endless variations on the aboriginal design.[90]
Update schedule
See also: Android adaptation history
Google provides above upgrades, incremental in nature, to Android every six to nine months, which a lot of accessories are able of accepting over the air.[91] The latest above absolution is Android 4.4 "KitKat".[5]
Compared to its arch battling adaptable operating system, namely iOS, Android updates are about apathetic to adeptness absolute devices. For accessories not beneath the Nexus brand, updates generally admission months from the time the accustomed adaptation is clearly released.[92] This is partly due to the all-encompassing aberration in accouterments of Android devices, to which anniversary advancement accept to be accurately tailored, as the official Google antecedent cipher alone runs on their flagship Nexus devices. Porting Android to specific accouterments is a time- and resource-consuming action for accessory manufacturers, who accent their newest accessories and generally leave earlier ones behind.[92] Hence, earlier smartphones are frequently not adapted if the architect decides it is not account their time, behindhand of whether the buzz is able of alive the update. This botheration is circuitous if manufacturers adapt Android with their own interface and apps, which accept to be reapplied to anniversary new release. Additional delays can be alien by wireless carriers who, afterwards accepting updates from manufacturers, added adapt and cast Android to their needs and conduct all-encompassing testing on their networks afore sending the advancement out to users.[92]
The abridgement of after-sale abutment from manufacturers and carriers has been broadly criticized by customer groups and the technology media.[93][94] Some commentators accept acclaimed that the industry has a banking allurement not to advancement their devices, as the abridgement of updates for absolute accessories fuels the acquirement of newer ones,[95] an attitude declared as "insulting".[94] The Guardian has complained that the adjustment of administration for updates is complicated alone because manufacturers and carriers accept advised it that way.[94] In 2011, Google partnered with a amount of industry players to advertise an "Android Amend Alliance", accord to bear appropriate updates for every accessory for 18 months afterwards its release;[96] however, there has not been addition official chat about that alliance.[92][97]
In 2012, Google began decoupling assertive aspects of the operating arrangement (particularly amount applications) so they could be adapted through Google Play Store, apart of Android itself. One of these components, Google Play Services, is a closed-source system-level action accouterment APIs for Google services, installed automatically on about all accessories alive Android adaptation 2.2 and higher. With these changes, Google can add new operating arrangement functionality through Play Casework and appliance updates afterwards accepting to deliver an advancement to the operating arrangement itself. As a result, Android 4.2 and 4.3 independent almost beneath user-facing changes, absorption added on accessory changes and belvedere improvements.[3][98]
Linux kernel
Android consists of a atom based on the Linux atom abiding abutment (LTS) branch. As of January 2014, accepted Android versions are congenital aloft Linux atom 3.4 or newer,[99][100] but the specific atom adaptation amount depends on the absolute Android accessory and chipset.[101][102][103] Android has acclimated assorted kernels aback its aboriginal 2.6.25.[40]
Android's Linux atom has added architectural changes that are implemented by Google alfresco the archetypal Linux atom development cycle, such as the admittance of apparatus like Binder, ashmem, pmem, logger, wakelocks, and altered out-of-memory (OOM) handling.[104][105][106] Assertive appearance that Google contributed aback to the Linux kernel, conspicuously a adeptness administration affection alleged "wakelocks", were alone by mainline atom developers partly because they acquainted that Google did not appearance any absorbed to advance its own code.[107][108][109] Google appear in April 2010 that they would appoint two advisers to plan with the Linux atom community,[110] but Greg Kroah-Hartman, the accepted Linux atom maintainer for the abiding branch, said in December 2010 that he was anxious that Google was no best aggravating to get their cipher changes included in boilerplate Linux.[108] Some Google Android developers hinted that "the Android aggregation was accepting fed up with the process," because they were a baby aggregation and had added burning plan to do on Android.[111]
In August 2011, Linus Torvalds said that "eventually Android and Linux would appear aback to a accepted kernel, but it will apparently not be for four to 5 years".[112] In December 2011, Greg Kroah-Hartman appear the alpha of Android Mainlining Project, which aims to put some Android drivers, patches and appearance aback into the Linux kernel, starting in Linux 3.3.[113] Linux included the autosleep and wakelocks capabilities in the 3.5 kernel, afterwards abounding antecedent attempts at merger. The interfaces are the aforementioned but the upstream Linux accomplishing allows for two altered append modes: to anamnesis (the acceptable append that Android uses), and to deejay (hibernate, as it is accepted on the desktop).[114] Google maintains a accessible cipher athenaeum that contains their beginning plan to re-base Android off the latest abiding Linux versions.[115][116]
The beam accumulator on Android accessories is breach into several partitions, such as /system for the operating arrangement itself, and /data for user abstracts and appliance installations.[117] In adverse to desktop Linux distributions, Android accessory owners are not accustomed basis admission to the operating arrangement and acute partitions such as /system are read-only. However, basis admission can be acquired by base aegis flaws in Android, which is acclimated frequently by the open-source association to enhance the capabilities of their devices,[118] but aswell by awful parties to install bacilli and malware.[119]
Android is a Linux administration according to the Linux Foundation,[120] Google's open-source arch Chris DiBona,[121] and several journalists.[122][123] Others, such as Google architect Patrick Brady, say that Android is not Linux in the acceptable Unix-like Linux administration sense; Android does not cover the GNU C Library and some of added apparatus about begin in Linux distributions.[124]
Software stack
Android's architectonics diagram
[icon] This area requires expansion. (December 2013)
On top of the Linux kernel, there are the middleware, libraries and APIs accounting in C, and appliance software alive on an appliance framework which includes Java-compatible libraries based on Apache Harmony. Android uses the Dalvik basic apparatus with just-in-time accumulation to run Dalvik "dex-code" (Dalvik Executable), which is usually translated from the Java bytecode.[125][126] Android 4.4 aswell supports new beginning runtime basic machine, ART, which is not enabled by default.[127]
Android's accepted C library, Bionic, was developed by Google accurately for Android, as a ancestry of the BSD's accepted C library code. Bionic has several above appearance specific to the Linux kernel, and its development continues apart of added Android's antecedent cipher bases. The capital allowances of appliance Bionic instead of the GNU C Library (glibc) or uClibc are its altered licensing model, abate runtime footprint, and enhancement for low-frequency CPUs.[126]
Aiming for a added acceptable licensing model, against the end of 2012 Google switched the Bluetooth assemblage in Android from the GPL-licensed BlueZ to the Apache-licensed BlueDroid.[128]
Android does not accept a built-in X Window Arrangement by default, nor does it abutment the abounding set of accepted GNU libraries. This fabricated it difficult to anchorage absolute Linux applications or libraries to Android,[124] until adaptation r5 of the Android Built-in Development Kit brought abutment for applications accounting absolutely in C or C++.[129] Libraries accounting in C may aswell be acclimated in Java appliance by bang of a baby Java bushing and accepting of the JNI.[130]
Open-source community
Android has an alive association of developers and enthusiasts who use the Android Open Antecedent Activity (AOSP) antecedent cipher to advance and deliver their own adapted versions of the operating system.[131] These community-developed releases generally accompany new appearance and updates to accessories faster than through the official manufacturer/carrier channels, admitting afterwards as all-encompassing testing or superior assurance;[24] accommodate connected abutment for earlier accessories that no best accept official updates; or accompany Android to accessories that were clearly appear alive added operating systems, such as the HP TouchPad. Association releases generally appear pre-rooted and accommodate modifications clashing for non-technical users, such as the adeptness to overclock or over/undervolt the device's processor.[132] CyanogenMod is the a lot of broadly acclimated association firmware,[133] and acts as a foundation for abundant others.
Historically, accessory manufacturers and adaptable carriers accept about been unsupportive of third-party firmware development. Manufacturers accurate affair about abnormal activity of accessories alive actionable software and the abutment costs consistent from this.[134] Moreover, adapted firmwares such as CyanogenMod sometimes action features, such as tethering, for which carriers would contrarily allegation a premium. As a result, abstruse obstacles including bound bootloaders and belted admission to basis permissions are accepted in abounding devices. However, as community-developed software has developed added popular, and afterward a account by the Librarian of Congress in the United States that permits the "jailbreaking" of adaptable devices,[135] manufacturers and carriers accept ashen their position apropos third affair development, with some, including HTC,[134] Motorola,[136] Samsung[137][138] and Sony,[139] accouterment abutment and auspicious development. As a aftereffect of this, over time the charge to avoid accouterments restrictions to install actionable firmware has lessened as an accretion amount of accessories are alien with apart or unlockable bootloaders, agnate to Nexus alternation of phones, although usually acute that users abandon their devices' warranties to do so.[134] However, admitting architect acceptance, some carriers in the US still crave that phones are bound down, arresting developers and customers
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