About Android
Android
is an operating system based on the Linux kernel with a user interface
based on direct manipulation, designed primarily for touchscreen mobile
devices such as smartphones and tablet computers,
using touch inputs, that loosely correspond to real-world actions, like
swiping, tapping, pinching, and reverse pinching to manipulate
on-screen objects, and a virtual keyboard. Despite being primarily
designed for touchscreen input, it also has been used in televisions,
games consoles, digital cameras, and other electronics
Android
powers hundreds of millions of mobile devices in more than 190
countries around the world. It's the largest installed base of any
mobile platform and growing fast—every day another million users power
up their Android devices for the first time and start looking for apps,
games, and other digital content.
Android gives you a
world-class platform for creating apps and games for Android users
everywhere, as well as an open marketplace for distributing to them
instantly.
Features
Interface
Android's default user interface 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, and a virtual keyboard. The response to user input is designed to be immediate and provides a
fluid touch interface, often using the vibration capabilities of the
device to provide haptic feedback to the user. 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, or allowing the user to steer a vehicle in a
racing game by rotating the device, simulating control of a steering
wheel. Android devices boot to the homescreen, the primary navigation
and information point on the device, which is similar to the desktop
found on PCs. Android homescreens are typically made up of app icons and
widgets;
app icons launch the associated app, whereas widgets display live,
auto-updating content such as the weather forecast, the user's email
inbox, or a news ticker directly on the homescreen. A homescreen may be
made up of several pages that the user can swipe
back and forth between, though Android's homescreen interface is heavily
customisable, allowing the user to adjust the look and feel of the
device to their tastes.
Third-party apps available on Google
Play and other app stores can extensively re-theme the homescreen, and
even mimic the look of other operating systems, such as Windows Phone.
Most manufacturers, and some wireless carriers, customise the look and
feel of their Android devices to differentiate themselves from their
competitors.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 display
important information or updates, such as a newly received email or SMS
text, in a way that does not immediately interrupt or inconvenience the
user.
Notifications are persistent until read (by tapping, which opens the
relevant app) or dismissed by sliding it off the screen. Beginning on
Android 4.1, "expanded notifications" can display expanded details or
additional functionality; for instance, a music player can display
playback controls, and a "missed call" notification provides buttons for
calling back or sending the caller an SMS message.
Android provides the ability to run applications which change the
default launcher and hence the appearance and externally visible
behaviour of Android. These appearance changes include a multi-page dock
or no dock, and many more changes to fundamental features of the user
interface.
Applications
See also: Android software development and Google Play
Android
has a growing selection of third party applications, which can be
acquired by users either through an app store such as Google Play or the
Amazon Appstore, or by downloading and installing the application's APK
file from a third-party site.
Google Play Store allows users to browse, download and update
applications published by Google and third-party developers, and the
Play Store client application is pre-installed on devices that comply
with Google's compatibility requirements and license the Google Mobile
Services software.
The client application filters the list of available applications down
to those compatible with the user's device, and developers may restrict
their applications to particular carriers or countries for business
reasons.
Purchases of unwanted applications can be refunded within 15 minutes of the time of download,
and some carriers offer direct carrier billing for Google Play
application purchases, where the cost of the application is added to the
user's monthly bill.
As of July 2013, there are more than one million applications available for Android in Play Store.
As of May 2013, 48 billion apps have been installed from Google Play store.
Applications ("apps"), that extend the functionality of devices, are developed primarily in the Java programming language language using the Android software development kit (SDK). The SDK includes a comprehensive set of development tools,
including a debugger, software libraries, a handset emulator based on
QEMU, documentation, sample code, and tutorials. The officially
supported integrated development environment (IDE) is Eclipse using the
Android Development Tools (ADT) plugin. 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.
It was announced in January 2014 that Chrome HTML5 web
applications should become available, using a compatibility layer from
the open source Apache Cordova framework to allow such applications to
be wrapped in a native application shell, enabling their distribution
over Google Play.
Memory management
Since Android devices are usually battery-powered, Android is designed to manage memory (RAM)
to keep power consumption at a minimum, in contrast to desktop
operating systems which generally assume they are connected to unlimited
mains electricity.
When an Android app is no longer in use, the system will automatically
suspend it in memory – while the app is still technically "open",
suspended apps consume no resources (for example, battery power or
processing power) and sit idly in the background until needed again.
This has the dual benefit of increasing the general responsiveness of
Android devices, since applications do not need to be closed and
reopened from scratch each time, and also ensuring that background
applications do not consume power needlessly.
Android manages the apps stored in memory automatically: when memory
is low, the system will begin killing apps and processes that have been
inactive for a while, in reverse order since they were last used (oldest
first). This process is designed to be invisible to the user, such that
users do not need to manage memory or the killing of apps themselves.
However, confusion over Android memory management has resulted in
third-party task killers becoming popular on Google Play store; these
third-party task killers are generally regarded as doing more harm than
good.
