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 releases 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.
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 billion.
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 day.
Version history
Main article: 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 dessert.- Recent releases
- 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 Communication.
- 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 2011.
- 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 version
- 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, 2011.
Design
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.
Linux
Android's kernel is based on the Linux kernel 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 Android.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 Android.
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 years".
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.
Features
- 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, NFC and WiMAX.
- Messaging
- 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.
- 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 100/100 on the Acid3 test on Android 4.0.
- 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 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.
- 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, FLAC, WAV, JPEG, PNG, GIF, BMP.
- 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.
- 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 at the time). Google has since released an update for the Nexus One and the Motorola Droid which enables multi-touch natively.
- 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 in Android 3.1+, and in earlier versions through manufacturer customizations and third-party applications.
- Video calling
- 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
- 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 onwards.
- Tethering
- 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 customizations.
- Screen capture
- 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.
- External storage
- 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 exFAT.
Uses
See also: List of Android devices
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 iDroid.
In December 2011 it was announced the Pentagon has officially approved Android for use by its personnel.
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
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 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 devices.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 reasons.
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 Appstore.
Application security
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. Overprivileged applications expose users to unnecessary permission warnings and increase the impact of a bug or vulnerability." The authors then go on to survey overprivileged 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 ones."
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.AndroidOS.FakePlayer.a, 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.
Privacy
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 ads.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 servers.
Marketing
The Android logo was designed along with the Droid font family made by Ascender Corporation.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 logo.
- Version
| 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% |
No comments:
Post a Comment