Android-Oprating system.

Android is a software stack for mobile devices that includes an operating system, middleware and key applications, that uses a modified version of the Linux kernel. It was initially developed by Android Inc., a firm later purchased by Google, and lately by the Open Handset Alliance. It allows developers to write managed code in the Java language, controlling the device via Google-developed Java libraries.

The unveiling of the Android distribution on November 5, 2007 was announced with the founding of the Open Handset Alliance, a consortium of 65 hardware, software, and telecom companies devoted to advancing open standards for mobile devices. Google released most of the Android code under the Apache License, a free software and open source license.

On Feb 16, 2010 Google announced that 60,000 cell phones with Android are shipping every day. According to a press estimate, the Android platform ranks as the fourth most popular smartphone device-platform as of February 2010

Current features and specifications:
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:The Database Software SQLite is used for data storage purposes
Connectivity Android supports connectivity technologies including GSM/EDGE, IDEN, CDMA, EV-DO, UMTS, Bluetooth, Wi-Fi, and WiMAX.
Messaging:SMS and MMS are available forms of messaging including threaded text messaging.
Web browser:The web browser available in Android is based on the open-source WebKit application framework. The browser scores a 93/100 on the Acid3 Test.
Java support:Software written in Java can be compiled to be executed in the Dalv
ik virtual machine, which is a specialized VM implementation designed for mobile device use, although not technically a standard Java Virtual Machine. Android does not support J2ME, like some other mobile operating systems.
Media support:Android supports the following audio/video/still media formats: 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.[49]
Additional hardware support:Android can use video/still cameras, touchscreens, GPS, accelerometers, magnetometers, 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, and a plugin for the Eclipse IDE.
Market:Like many phone-based application stores, the Android Market is a catalog of applications that can be downloaded and installed to target hardware over-the-air, without the use of a PC. Originally only free applications were supported. Paid-for applications have been available on the Android Market in the United States since 19 February 2009.[50] The Android Market has been expanding rapidly. As of April 15, 2010, it had over 38,000 Android applications for download.[51]
Multi-touch Android:has native support for multi-touch which was initially made available in handsets such as the HTC Hero. The feature was initially disabled at the kernel level (possibly to avoid infringing Apple's patents on touch-screen technology[52]). Google has since released an update for the Nexus One and the Motorola Droid which enables multi-touch natively.[53]
Bluetooth: Support for sending files over bluetooth was added in version 2.0.
Videocalling: Android does not support videocalling. However, it is possible if the phone runs an additional UI. This is proved on the HTC Evo 4G, which runs Sense and can support videocalling.

Hardware running Android:
The first phone to run the Android operating system was the HTC Dream, released on 22 October 2008.
By the end of 2009 there will be at least 18 phone models using Android worldwide, according to Google. In addition to the mobile devices that ship with Android, some users have been able (with some amount of hacking, and with limited functionality) to install it on mobile devices shipped with other operating systems.

Software development :
The early feedback on developing applications for the Android platform was mixed. Issues cited include bugs, lack of documentation, inadequate QA infrastructure, and no public issue-tracking system. (Google announced an issue tracker on 18 January 2008.) In December 2007, MergeLab mobile startup founder Adam MacBeth stated, "Functionality is not there, is poorly documented or just doesn't work... It's clearly not ready for prime time." Despite this, Android-targeted applications began to appear the week after the platform was announced. The first publicly available application was the Snake game. The Android Dev Phone is a SIM-unlocked and hardware-unlocked device that is designed for advanced developers. While developers can use regular consumer devices purchased at retail to test and use their applications, some developers may choose not to use a retail device, preferring an unlocked or no-contract device.

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  Software development kit :
  The Android SDK includes a comprehensive set of development tools. These include a debugger, libraries, a handset emulator (based on QEMU), documentation, sample code, and tutorials. Currently supported development platforms include x86-architecture computers running Linux (any modern desktop Linux distribution), Mac OS X 10.4.8 or later, Windows XP or Vista. Requirements also include Java Development Kit, Apache Ant, and Python 2.2 or later. The officially supported integrated development environment (IDE) is Eclipse (3.2 or later) 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 to create, build and debug Android applications as well as control attached Android devices (e.g., triggering a reboot, installing software package(s) remotely).
  
  A preview release of the Android software development kit (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) has led to widely reported frustration within the Android developer community.
  
  On 18 August 2008 the Android 0.9 SDK beta was released. This release provides 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. On 23 September 2008 the Android 1.0 SDK (Release 1) was released. 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.
  
  On 9 March 2009, Google released version 1.1 for the Android dev phone. While there are a few aesthetic updates, a few crucial updates include support for "search by voice, priced applications, alarm clock fixes, sending gmail freeze fix, fixes mail notifications and refreshing intervals, and now the maps show business reviews". Another important update is that Dev phones can now access paid applications and developers can now see them on the Android Market.
  
  In the middle of May 2009, Google released version 1.5 (Cupcake) of the Android OS and SDK. This update included many new features including video recording, support for the stereo bluetooth profile, a customizable onscreen keyboard system and voice recognition. This release also opened up the AppWidget framework to third party developers allowing anyone to create their own home screen widgets.
  
  In September 2009 the "Donut" version (1.6) was released which featured better search, battery usage indicator and VPN control applet. New platform technologies included Text to Speech engine (not available on all phones), Gestures & Accessibility framework.
  
  Android Applications are packaged in .apk format and stored under /data/app folder on the Android OS. The user can run the command adb root to access this folder as only the root has permissions to access this folder.
  
  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. It ended in early September with the announcement of ten teams that received $275,000 each, and ten teams that received $100,000 each. ADC II was announced on 27 May 2009. The first round of the ADC II closed on 6 October 2009. 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 Doddle!? and WaveSecure being nominated the overall winners of the challenge.
  
  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, Google Translate, Listen for podcasts and My Tracks, a jogging application.
  
  Third party applications:
  With the growing number of Android handsets, there has also been a growing interest by third party developers to port their applications to the Android operating system.
  
  Famous applications that have been converted to the Android operating system include Shazam, Backgrounds, and WeatherBug.
  
  The Android operating system has also been considered important enough by a lot of the most popular internet sites and services to create native android applications. These include MySpace and Facebook.
  
  The release of Mozilla Firefox browser for Android is planned for late 2010. According to an interview with Mozilla's vice president of mobile, Jay Sullivan, conducted by TechRadar on February 17, 2010, part of the delay with the porting of Firefox over to Android has been because Firefox Mobile is built on C and C++ code, but that the new Native Development Kit makes it easier to port Firefox Mobile
  
  
  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 the System.loadLibrary call, which is part of the standard Android Java classes.
  
  Complete applications can be compiled and installed using traditional development tools. 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. Running native code is complicated by the fact that Android uses a non-standard C library (known as Bionic). The underlying graphics device is available as a framebuffer at /dev/graphics/fb0. 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. Skia has backends for both win32 and Cairo, allowing the development of cross-platform applications, and it is the graphics engine underlying the Google Chrome web browser.
  
  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. The community refers to this process as rooting the device. Rooting lets users load modified firmwares allowing users of older phones to use applications available only on newer releases.
  
  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 is one such firmware.
  
  On 24 September 2009, Google issued a cease and desist letter to the modder Cyanogen, citing issues with the re-distribution of Google's closed-source applications within the custom firmware. Even though 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.
  
  Issues for specific applications :
  Unlike other mobile closed platforms like Apple's iPhone OS, Google tracks issues and feature requests at Google Code's site. The following outstanding issues have been highly debated or voted for by the user community:
  


• A source of criticism has been the lack of standards-based iCalendar/CalDAV functionality in the Android calendar client. Currently, the Android calendar is restricted to synchronisation with Google Calendar service.


• As of January 2010[update], the most requested ("starred") feature is the support for Bi-directional text (right-to-left) such as Arabic, Persian and Hebrew.


• Hands free dialing and call answering is not supported. Voice dialing can be used to find/input a number, but selection requires interaction with the screen. This makes it illegal to initiate or answer calls while driving in some areas, and very difficult to use while on a bicycle or motorcycle.


• Bluetooth voice dialing is also not supported. This feature in particular has caused some surprise; many older phones have had this feature for several years.


• Android does not support animated GIF files. It only shows the first frame.


• Android does not support encrypted sending (SMTP+TLS) and receiving (IMAP+SSL) of e-mail over self-signed certificates.


• Because of potential security issues, Android does not officially allow applications to be installed on, nor run from, an SD card. Current Android products such as the HTC Dream and Magic have limited onboard memory and many users feel restricted by this lack of functionality. However, several unsupported modifications exist, to give the user this capability.