Introduction

Android story began with joint venture of Google and open handset alliance in 2007. Later Google purchased open hand alliance and it is now Google alone owing the Android. Android is an operating system and is most widely used in the smartphones, tablets and such communication devices. Presently one single version of Android “KitKat 4.4”is the most used Android version. 39 percent of Android based smartphones run on this version. However Jelly Bean (4.1-4.3.1) has even a bigger share by running 46 percent of Android devices. Prior to this iOS was the most dominant operating system.

The Android story began in November 2007with the release of Android Beta. Later Android 1.0 was released for commercial used in September 2008. On 3^rd September Google declared that one billion devices were running Android and now 62% of US smartphone, 82.7% of Chinese market and 73.3% of European market has Android based mobiles.

The Android operating system was developed by Android inc. Which later Google purchased in 2005. Before releasing the beta version in 2007 two versions of the operating system were released and later beta version of this operating system was released in November 2007. Although the software development kit was released on 12^th November 2007 but the birthday of Android is celebrated on 5^th November (from November 12^th 2007 to September 23^rd 2008, 8 software development kits were released). First to appear in the market was Android 1.0 as commercial version and the date of release was September 23^rd 2008 and the first Android Mobile was HTC dream. This version had the following features; Android Market application, Web browser to show, zoom and pan full HTML and XHTML web pages, Camera support  this version lacked the option to change the camera's resolution, white balance, quality, Folders allowing the grouping of a number of application icons into a single folder icon on the Home screen, Access to web email servers, supporting POP3, IMAP4, and SMTP, Gmail synchronization with the Gmail application, Google Contacts synchronization with the People application, Google Calendar synchronization with the Calendar application, Google Maps with Street View to view maps and satellite imagery, Google Sync, allowing management of over-the-air synchronization of Gmail, People, and Calendar Google Search, allowing users to search the Internet and phone applications, contacts, calendar, Google Talk instant messaging, Instant messaging, text messaging, and MMS, Media Player, enabling management, importing, and playback of media files – however, this version lacked video and stereo Bluetooth support, Notifications appear in the Status bar, with options to set ringtone, LED or vibration alerts, Voice Dialer allows dialing and placing of phone calls without typing a name or number, Wallpaper allows the user to set the background image or photo behind the Home screen icons and widgets, YouTube video player, Other applications include: Alarm Clock, Calculator, Dialer (Phone), Home screen (Launcher), Pictures (Gallery), and Settings, Wi-Fi and Bluetooth support, Android 1.0 Screenshot.png, Android 1.0 on the old Android SDK emulator, Android 1.1 (API level 2).

Cupcake

On February 9^th 2009, the Android 1.1 update was released, specifically for the HTC Dream with the name "Petit Four" the purpose of this update was to update resolved bugs, changed the Android API and added a number of features. Yet later On April 27, 2009, the Android 1.5 update was released, based on Linux kernel 2.6.27. This was the first release to officially use a codename based on a sweet treat as "Cupcake", it added new feature like; Support for third-party virtual keyboards with text prediction and user dictionary for custom words, Support for Widgets miniature application views that can be embedded in other applications such as the Home screen and receive periodic updates, Video recording and playback in MPEG-4 and 3GP formats, Auto-pairing and stereo support for Bluetooth (A2DP and AVRCP profiles), Copy and paste features in web browser, User pictures shown for Favorites in Contacts, Specific date/time stamp shown for events in call log, and one-touch access to a contact card from call log event, Animated screen transitions, Auto-rotation option, New stock boot animation, Ability to upload videos to YouTube, Ability to upload photos to Picasa, Android 1.5 Cupcake Screenshot.png, Android 1.5 on the Android SDK emulator, Android 1.6 Donut (API level 4) and after that On September 15, 2009, the Android 1.6 SDK – dubbed Donut – was released, based on Linux kernel 2.6.29, this update had also has the bunch of improved features.

Android 2.0 Éclair

The next version of the operating system is Android 2.0 Éclair (API level 5) was released on October 26^th 2009 with the improved features of Expanded Account sync, allowing users to add multiple accounts to the mobile for synchronization of email and contacts, Microsoft Exchange email support, with combined inbox to browse email from multiple accounts in one page, Bluetooth 2.1 support, Ability to tap a Contacts photo and select to call, SMS, or email the person, Ability to search all saved SMS and MMS messages, with delete oldest messages in a conversation automatically deleted when a defined limit is reached, new camera features, including flash support, digital zoom, scene mode, white balance, color effect and macro focus, Improved typing speed on virtual keyboard, with smarter dictionary that learns from word usage and includes contact names as suggestions.

Android 2.2 Froyo (Frozen Yogurt)

The next version of Android 2.2 Froyo (Frozen Yogurt) was released in January 2011 for bug fixes, security updates and performance improvements.

Ginger Bread

 The next update of t he next version with the name “Ginger Bread” was Android 2.3.3 to 2.3.7 in April 2011 and carried many improvements and features. An important update, 2.3.5 was released in on July 25^th 2011 with following improvements; improved network performance for the Nexus S 4G, among other fixes and improvements, Fixed Bluetooth bug on Samsung Galaxy S, Improved Gmail application, Shadow animations for list scrolling, Camera software enhancements and Improved battery efficiency.

Android 3.0 Honeycomb

During the same duration on February 22^nd 2011 Android 3.0 (Honeycomb) was released with many new features such as; Optimized tablet support with a new “holographic” user interface, Added System Bar, featuring quick access to notifications, status, and soft navigation buttons, available at the bottom of the screen, Added Action Bar, giving access to contextual options, navigation, widgets, or other types of content at the top of the screen, Simplified multitasking – tapping Recent Applications in the System Bar allows users to see snapshots of the tasks underway and quickly jump from one application to another, Redesigned keyboard, making typing fast, efficient and accurate on larger screen sizes, Simplified, more intuitive copy/paste interface, Multiple browser tabs replacing browser windows, plus form auto-fill and a new “incognito” mode allowing anonymous browsing, Quick access to camera exposure, focus, flash, zoom, front-facing camera, time-lapse, and other camera features, Ability to view albums and other collections in full-screen mode in Gallery, with easy access to thumbnails for other photos, New two-pane Contacts UI and Fast Scroll to let users easily organize and locate contacts, New two-pane Email UI to make viewing and organizing messages more efficient, allowing users to select one or more messages, Hardware acceleration, Support for multi-core processors, Ability to encrypt all user data, ,HTTPS stack improved with Server Name Indication (SNI)File system in User space (FUSE; kernel module), Applications' write access to secondary storage (memory cards on devices with internal primary storage) is disabled outside of designated, app-specific directories, while full access to internal primary storage is still allowed through a separate application-level permission. The most first- and second-generation Google TV-enabled devices utilize Honeycomb 3.2.

Next came Version 3.2 was released on July 15, 2011with features like improved hardware support, increased ability of applications to access files on the SD card. On September 20^th 2011 version 3.2.1 was released for Bug fixes and minor security, stability and Wi-Fi improvements, update to Google Books, improved Adobe Flash support in browser and improved Chinese handwriting prediction.

Ice Cream Sandwich

Next came the most well known updated version Android 4.0 and 4.02 with the name Ice cream sandwich this is Linux kernel 32.01 based and was released on 19^th October 2011 it has Major refinements to the "Holo" interface with new Roboto font family, Soft buttons from Android 3.x are now available for use on phones, Separation of widgets in a new tab, listed in a similar manner to applications, Easier-to-create folders, with a drag-and-drop style, Improved visual voicemail with the ability to speed up or slow down voicemail messages, Improved error correction on the keyboard, Face Unlock, a feature that allows users to unlock handsets using facial recognition software, Ability to shut down applications from the recent apps list with a swipe, New gallery layout, organized by location and person, Refreshed "People" application with social network integration, status updates and hi-res images, Android Beam, a near-field communication feature allowing the rapid short-range exchange of web bookmarks, contact info, directions, YouTube videos and other data and Android VPN Framework (AVF), and TUN (but not TAP) kernel module. Prior to 4.0, VPN software required rooted Android.

Jelly Bean

The very famous update Android 4.1 Jelly Bean was announced and issued on July 9^th 2012. It reformed almost entire system with latest features like Smoother user interface, Triple buffering in the graphics pipeline, Enhanced accessibility, Bi-directional text and other language support, User-installable keyboard maps, Expandable notifications, Ability to turn off notifications on an application-specific basis, Shortcuts and widgets can automatically be re-arranged or re-sized to allow new items to fit on home screens, Bluetooth data transfer for Android Beam, Tablets with smaller screens now use an expanded version of the interface layout and home screen used by phones, Improved camera application, Multichannel audio. The Fraunhofer FDK AAC codec becomes standard in Android, adding AAC 5.1 channel encoding/decoding. USB audio (for external sound DACs), Audio chaining, Ability for other launchers to add widgets from the application drawer without requiring root access.

The other versions of Jelly Bean are 4.1.1 which was issued on July 11^th 2012 for fixing the bug on Nexus 7and 4.1.2 was issued on October 9^th 2012 for Lock/home screen rotation support for the Nexus 7, One-finger gestures to expand/collapse notifications and bug fixes for The next Jelly Beans version 4.2 was released on November 13, 2012 with major features of Lock screen improvements, to swipe directly to camera, Notification power controls ("Quick Settings"), "Daydream" screensavers, showing information when idle or docked, Multiple user accounts (tablets only), Accessibility improvements: triple-tap to magnify the entire screen, pan and zoom with two fingers. Speech output and Gesture Mode navigation for blind users. New clock application with built-in world clock, stop watch and timer.

KitKat

On September 3^rd 2013 Google announced Android KitKat and it was released on October 31^st 2013 it has the features like Refreshed interface with white elements instead of blue, Clock no longer shows bold hours; all digits are thin. The H, M, and S markings for the stopwatch and timer have been removed, leaving just the numbers. Ability for applications to trigger translucency in the navigation and status bars, Ability for applications to use "immersive mode" to keep the navigation and status bars hidden while maintaining user interaction, Action overflow menu buttons are always visible, even on devices with a "Menu" key, which was officially deprecated by Android 4.0., Restriction for applications when accessing external storage, except for their own directories, Optimizations for performance on devices with lower specifications, including zRAM support and "low RAM" device API, Wireless printing capability, NFC host card emulation, enabling a device to replace smart cards, WebViews now based on Chromium engine (feature parity with Chrome for Android 30), Expanded functionality for notification listener services, Public API for developing and managing text messaging clients, Storage Access Framework, an API allowing apps to retrieve files in a consistent manner. As part of the framework, a new system file picker allows users to access files from various sources (including those exposed by apps, such as online storage services). New framework for UI transitions, Sensor batching, step detector and counter APIs, Settings application now makes it possible to select default text messaging and home (launcher) application, Audio tunneling, audio monitoring and loudness enhancer, Built-in screen recording feature (primarily for developers, as usage of ADB is required), Native infrared blaster API, Expanded accessibility APIs and system-level closed captioning settings, Android Runtime (ART) introduced as a new experimental application runtime environment, not enabled by default, as a replacement for the Dalvik virtual machine, Bluetooth Message Access Profile (MAP) support, Disabled access to battery statistics by third-party applications, Settings application no longer uses a multi-pane layout on devices with larger screens, Wi-Fi and mobile data activity (TX/RX) indicators are moved to quick settings, Browser text wrap is disabled. Android 4.4.2.png, Android 4.4.2 (OmniROM, AOSP-based).

Android 4.4 KitKat has more updates like 4.4.1 released on December 5^th 2013 for Improvements to auto focus, white balance and HDR+ for the Nexus 5 camera, Better application compatibility for the experimental Android Runtime (ART), Camera application now loads Google+ Photos instead of Gallery when swiping away from the camera view, Miscellaneous improvements and bug fixes. This KitKat 4.4 goes up to 4.4.4 and than 4.4w1, 4.4w2 for different improvements.

Android 5.0 Lollipop

This new updated version of Android operating system named Lollipop was announced on 25^th June 2014 in Google IO. However it was released for selected devices on November 12^th 2014. Lollipop redesigned user interface for responsive design language referred to as "material design". Other changes include improvements to the notifications which can be accessed from the lock screen and displayed within applications as top-of-the-screen banners. Furthermore, Google made internal changes to the platform, with the Android Runtime (ART) officially replacing Dalvik for improved application performance, and with changes intended to improve and optimize battery usage, known internally as Project Volta.

The major characteristic includes: Vector drawables, which scale without losing definition support for print previews Material design, bringing a restyled user interface refreshed lock screen, no longer supporting widgets refreshed notification tray and quick settings pull-down project Volta, for battery life improvements searches can be performed within the system settings for quicker access to particular settings lock screen provides shortcuts to application and notification settings, Guest logins and multiple user accounts are available on more devices, such as phones. Audio input and output through USB devices, Third-party applications regain the ability to read and modify data located anywhere on external storage, such as on SD cards. Pinning of an application's screen for restricted user activity. Recently used applications are remembered even after restarting the device. WebViews receive updates independently through Google Play for security reasons, instead of relying on system-wide vendor updates , Addition of 15 new languages: Basque, Bengali, Burmese, Chinese (Hong Kong), Galician, Icelandic, Kannada, Kyrgyz, Macedonian, Malayalam, Marathi, Nepali, Sinhala, Tamil and Telugu, Tap and Go allows users to quickly migrate to a new Android device, using NFC and Bluetooth to transfer Google Account details, configuration settings, user data and installed applications. A flashlight-style application is included, working on supported devices with a camera flash. User-customizable priorities for application notifications. Smart lock feature, Android 5.0-en.png, Android 5.0 "Lollipop" homescreen.

The next version of Lollipop is 5.1 released on 9^th March 2015 with features like: Ability to join Wi-Fi networks and control paired Bluetooth devices from quick settings support for multiple SIM cards, Device protection: if a device is lost or stolen it will remain locked until the owner signs into their Google account, even if the device is reset to factory settings. High-definition voice calls, available between compatible devices running Android 5.1 Hardware requirements.  

This Android has a very fast moving history of success and developed the mobile operating system from elementary level to very highly advance and sophisticated level of performance. To run latest Android there are some hardware requirements and latest hardware equipment like X86 and MIPS architecture. The Android needs to be having minimum 32MB of RAM but 128 MB is preferable. The first mobile phone using Android HTC Dream had 192 MB RAM and 32 MB flash memory and 200 MHz ARM architecture (ARMv5) processor. The latest Android 5.1 Lollipop at least 512MB of RAM because the minimum requirement of Android of 4.4 is 340 MB. Any device less than 512 MB RAM will not be qualified for Android operating system. Google has done wonderful job by developing this operating system that is running the entire world of communication.