2. Android is the step in the vision of creating a better mobile phone.
Introduction
Android is the step in the vision of creating a better mobile phone.
It is a complete open mobile platform software stack release by Google.
Android can be run on mobile devices from companies that have come together to form the Open Handset Alliance.

3. Android is a mobile operating system (OS) developed by Google, based on the Linux kernel and designed primarily for touchscreen mobile devices such as smartphones and tablets.
Android's user interface is mainly based on direct manipulation, using touch gestures that loosely correspond to real-world actions, such as swiping, tapping and pinching, to manipulate on-screen objects, along with a virtual keyboard for text input.
As of 2015, Android has the largest installed base of all operating systems.

4. Initially developed by Android, Inc
Initially developed by Android, Inc., which Google 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.
As of July 2013, the Google Play store has had over one million Android applications ("apps") published, and over 50 billion applications downloaded.
At Google I/O 2014, the company revealed that there were over one billion active monthly Android users, up from 538 million in June 2013.

5. Applications in Android
Android initially came into existence with the sure fire idea that developments are given the power and freedom to create enthralling Mobile applications while taking advantage of everything that the mobile handset has to offer.
This particular software for Mobile Application is made to be open source, thereby giving the opportunity to the developers to introduce and incorporate any technological advancement.

6. Developer
Google
Open Handset Alliance
Written in
C (core), C++, Java (UI)
OS family
Unix-like
Source model
Open source and in most devices with proprietary components
Initial release
September 23, 2008; 7 years ago
Latest release
6.0 "Marshmallow" / October 5, 2015; 3 months ago
Marketing target
Smartphones, tablet computers,TVs, cars and wearable devices
Available in
70 languages
Package manager
Google Play
Platforms
32- and 64-bit: ARM architectures, x86, x86-64,MIPS and MIPS64
Kernel type
Monolithic (modified Linux kernel)
Default user interface
Graphical (Multi-touch)
License
Apache License 2.0 GNU GPL v2 for the Linux kernel modifications
Official website

7. Hardware
The main hardware platform for Android is the ARM architecture (ARMv7 and ARMv8-A architectures), with x86 and MIPS architectures also officially supported in later versions of Android.
Since Android 5.0 "Lollipop", 64-bit variants of all platforms are supported in addition to the 32-bit variants.
Since 2012, Android devices with Intel processors began to appear, including phones and tablets.
Requirements for the minimum amount of RAM for devices running Android 5.1 range from 512 MB of RAM for normal-density screens, to about 1.8 GB for high-density screens.

8. Hardware…
The recommendation for Android 4.4 is to have at least 512 MB of RAM, while for "low RAM" devices 340 MB is the required minimum amount that does not include memory dedicated to various hardware components such as the baseband processor.
Android 4.4 requires a 32-bit ARMv7, MIPS or x86 architecture processor (latter two through unofficial ports),together with an OpenGL ES 2.0 compatible graphics processing unit (GPU).
Android devices incorporate many optional hardware components, including still or video cameras, GPS, orientation sensors, dedicated gaming controls, accelerometers, gyroscopes, barometers, magnetometers, proximity sensors, pressure sensors, thermometers, and touchscreens.

9. Hardware…
In addition to running on smartphones and tablets, several vendors run Android natively on regular PC hardware with a keyboard and mouse.
In addition to their availability on commercially available hardware, similar PC hardware–friendly versions of Android are freely available from the Android-x86 project, including customized Android 4.4.
Chinese companies are building a PC and mobile operating system, based on Android, to "compete directly with Microsoft Windows and Google Android".

10. Software stack
On top of the Linux kernel, there are the middleware, libraries and APIs written in C, and application software running on an application framework which includes Java-compatible libraries based on Apache Harmony (next version of Android uses OpenJDK instead).
Development of the Linux kernel continues independently of other Android's source code bases.
Until version 5.0, Android used Dalvik as a process virtual machine with trace-based just-in-time (JIT) compilation to run Dalvik "dex-code" (Dalvik Executable), which is usually translated from the Java bytecode.

11. Software stack
Android 4.4 introduced Android Runtime (ART) as a new runtime environment, which usesahead-of-time (AOT) compilation to entirely compile the application bytecode into machine code upon the installation of an application.
In December 2015, Google announced that the next version of Android would switch to a Java implementation based on OpenJDK.
Android's standard C library, Bionic, was developed by Google specifically for Android, as a derivation of the BSD's standard C library code.

12. Software stack…
The main benefits of using Bionic instead of the GNU C Library (glibc) or uClibc are its smaller runtime footprint, and optimization for low-frequency CPUs.
Aiming for a different licensing model, toward the end of 2012 Google switched the Bluetooth stack in Android from the GPL-licensed BlueZ to the Apache-licensed BlueDroid.
Android does not have a native X Window System by default, nor does it support the full set of standard GNU libraries. This made it difficult to port existing Linux applications or libraries to Android, until version r5 of the Android Native Development Kit brought support for applications written completely in C or C++.

14. Advantages Android can Run Multiple Apps at the Same Time.
Android keeps information visible on your home screen.
Android has is a customizable home screen which keeps active widgets right at your fingertips, always accessible and always visible – without having to launch an application first.
Android has a better application market compare to  Apple’s App .
Android is Hardware independent.

15.   Disadvantages
Connected to the Internet: Android can be said is in need of an active internet connection.
At least there should be a GPRS internet connection in your area, so that the device is ready to go online to suit our needs.
Sometimes there are ads: because it is easy and free, sometimes often a lot of advertising.
Wasteful Batteries, This is because the OS is a lot of "process" in the background causing the battery quickly drains.

16. Thanks….