Sunday, February 23, 2014
ANDROID is an operating
system based on the Linux kernel, and designed primarily for touchscreen mobile devices such as smartphones and tablet
computers. Initially developed by Android, Inc., which Google backed financially and later bought in
2005, Android was unveiled in 2007 along
with the founding of the Open
Handset Alliance: a consortium of hardware,
software, and telecommunication companies devoted to advancing open standards for mobile devices. The first publicly available
smartphone running Android, the HTC
Dream, was released on October 22, 2008.
The user interface of Android is based on direct manipulation, using touch
inputs that loosely correspond to real-world actions, like swiping, tapping,
pinching and reverse pinching to manipulate on-screen objects. 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 oriented.
Android allows users to customize their home screens with shortcuts to
applications and widgets, which
allow users to display live content, such as emails and weather information,
directly on the home screen. Applications can further send notifications to the
user to inform them of relevant information, such as new emails and text
messages.
Android's source code is released by Google under the Apache License; this permissive licensing allows the
software to be freely modified and distributed by device manufacturers,
wireless carriers and enthusiast developers. Most Android devices ship with a
combination of open source and proprietary software. As of July 2013, Android has the
largest number of applications ("apps"), available for download in Google Play store which has had over 1 million
apps published, and over 50 billion downloads. A developer survey conducted in
April–May 2013 found that Android is the most used platform among developers:
it is used by 71% of the mobile developers population.
Android
is popular with technology companies which require a ready-made, low-cost and
customizable operating system for high-tech devices. Despite being primarily designed
for phones and tablets, it also has been used in televisions, games consoles, digital cameras and other electronics. Android's open
nature has encouraged a large community of developers and enthusiasts to use
the open-source code as a foundation for community-driven projects, which add
new features for advanced users or bring Android to devices which were
officially released running other operating systems.
As of May
2012, Android became the most popular mobile
OS, having the largest installed base, and is a market leader in most countries including the United States; there it
has had the highest installed base of mobile phones for years. In the third quarter of 2013,
Android's share of the global smartphone shipment market—led by Samsung
products—was 81.3%, the highest ever. In most markets Android-powered phones
are the most popular comprising more than half of the overall smartphone sales,
including the United States market starting with the September–November 2013
period. The operating system's success has
made it a target for patent litigation as part of the so-called "smartphone
wars" between technology companies. As of September 2013, one billion
Android devices have been activated.
General Features
Messaging
SMS and MMS are available forms of messaging, including threaded text messaging and Android
Cloud To Device Messaging (C2DM) and now
enhanced version of C2DM, Android Google Cloud Messaging (GCM) is also a part of Android Push Messaging service.
Web browser
The web browser available in Android is based on the open-source Blink (previously WebKit) layout engine, coupled
with Chrome's V8 JavaScript engine. The browser scores 100/100 on the Acid3 test on Android 4.0.
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. As of Android 4.1, Google has expanded Voice Actions with
the ability to talk back and read answers from Google's Knowledge Graph when
queried with specific commands. The ability to
control hardware has not yet been implemented.
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.
Multitasking
Multitasking of applications, with unique handling of memory
allocation, is available.
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.
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. Users with the Google+ Android app can video chat with other google+ users
through hangouts.
Multiple language
support
Android supports multiple languages.
Accessibility
Built in text to speech is provided by Talk back for
people with low or no vision. Enhancements for people with hearing disabilities
is available as is other aids.
Connectivity
Connectivity
Android supports connectivity technologies including GSM/EDGE, Wi-Fi, Bluetooth, LTE, CDMA, EV-DO, UMTS, NFC, IDEN and WiMAX.
Bluetooth
Supports voice dialing and sending contacts between phones,
sending files (OPP), accessing the phone book (PBAP), A2DP and AVRCP. Keyboard, mouse and
joystick (HID) support is available in Android 3.1+, and in
earlier versions through manufacturer customizations and third-party
applications.
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.
Media
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 since Android 3.0 (Honeycomb).
Media support
Android supports the following audio/video/still media formats: WebM, H.263, H.264, AAC, HE-AAC (in 3GP or MP4 container), MPEG-4 SP, AMR, AMR-WB (in 3GP container), MP3, MIDI,Ogg Vorbis, FLAC, WAV, JPEG, PNG, GIF, BMP, WebP.
External storage
Most Android devices include microSD slot and can read microSD
cards formatted with FAT32, Ext3 or Ext4 file system. To allow use of high-capacity storage media
such as USB flash drivesand 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.
Hardware support
Android devices can include still/video 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.
Other
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.
Handset layouts
The platform works for various screen sizes from smartphone sizes
and to tablet size, and can potentially connect to an external screen, eg.
through HDMI, or wirelessly with Miracast. Portrait and landscape orientations are supported and usually
switching between by turning. A 2D graphics library, 3D graphics library based on OpenGL ES 2.0 specifications
is used.
Storage
SQLite, a lightweight relational database, is used for data storage purposes.
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