2. Android is a Linux-based operating
system designed primarily
for touchscreen mobile devices such
as smartphones and tablet computers.
3.
4. Android is open source and Google releases the
code under the Apache License.[12] This open
source code and permissive licensing allows the
software to be freely modified and distributed
by device manufacturers, wireless carriers and
enthusiast developers.
5.
6. Android's user interface is based on direct
manipulation,[35] using touch inputs that
loosely correspond to real-world actions, like
swiping, tapping, pinching and reverse
pinching to manipulate on-screen objects.
7. Android devices boot to the homescreen, the
primary navigation and information point on
the device, which is similar to
the desktop found on PCs.
8. 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.
9. Android is developed in private by Google until the
latest changes and updates are ready to be released, at
which point the source code is made available publicly.
10. This source code will only run without
modification on select devices, usually
the Nexus series of devices. With many
devices, there are proprietary components
which have to be provided by the
manufacturer, in order for Android to work.
11. 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.
12. Applications are developed in the Java language
using the Android software development
kit (SDK). The SDK includes a comprehensive
set of development tools,[47]including
a debugger, software libraries, a
handset emulator based
on QEMU, documentation, sample code, and
tutorials.
13. In order to work around limitations on
reaching Google services due to Internet
censorship in the People's Republic of China,
Android devices sold in the PRC are
generally customized to use state approved
services instead.
14. Android consists of a kernel based on Linux kernel version 2.6
and, from Android 4.0 Ice Cream Sandwich onwards, version
3.x, with middleware,libraries and APIs written
in C, and application software running on an application
framework which includes Java-compatible libraries based
on Apache Harmony.
15. Android's linux kernel has further architecture changes
by Google outside the typical Linux kernel development
cycle. Android does not have a nativeX Window
System by default 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.
16. 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.
17. 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 (i.e. oldest first).
18. Google provides major
updates, incremental in nature, to
Android every six to nine months, which
most devices are capable of receiving over
the air.[71] The latest major update is
Android 4.2 Jelly Bean.
19. Research company Canalys estimated in the second
quarter of 2009 that Android had a 2.8% share of
worldwide smartphone shipments.[126] By the
fourth quarter of 2010 this had grown to 33% of the
market, becoming the top-selling smartphone
platform.