Origin: This OS was first build by a small company which then bought by Google. Now it can be said that Android is the gift from Google. Till date many versions of Android is available as Google continously updated it. It first released on November 5th 2007.

Some salient features of Android OS:

• The current Android version is 4.0.
  
• All the releases of Android are nicknamed after sweets or dessert items.
• Cupcake (1.5), Frozen Yogurt (2.2), Honeycomb (3.0), and Ice Cream Sandwich (4.0).
  
• Since the HTC Dream (mobile model) was introduced, top manufacturer of mobiles now adopting Android for their smartphones.
  
•  On 15 November 2011, Android reached 52.5% of the global smartphone market share.

Features of Android 4.0 (Ice cream sandwitch)

Android 4.0 have things which people love most about Android — easy multitasking, rich notifications, customizable home screens, resizable widgets, and improved interactivity — and adds powerful ways of communicating and sharing the content with outer world.

It has following new attractive features

1. Multitasking better than iOS (an iPhone OS)
That Recent Apps button is really attractive, displaying thumbnails of open apps in a vertical coloumn that you can easily scroll up and down. You just need to swipe an app off the screen to close it. This approach is more easy than the iPhone, which forces you to double tap the home button and then press and hold an app icon before closing it.

2. Face unlock for your device
Just guess keeping your device in front of your face makes it unlock. It is really a waooo feature. This feature of face unlock is present in android 4.0. Just make sure you have enough ambient light for the front-facing camera, Sometime if it not recognize your face due to poor light condition,we had to enter a pin as a backup. Also keep in mind that you can fool the OS by holding up a picture of yourself. it is more of a convenience feature than a security feature. 

3. Improved camera app
Android 4.0 "Ice Cream Sandwich" makes a Panorama mode standard with its camera app. You just swivel your phone to left to right and the software takes care of the rest. The OS also includes robust editing capabilities, from auto-fix and cropping to a wide range of special effects.

4. Resizable widgets

Ice Cream Sandwich wants to put widgets more front and center, that is why you see a Widgets tab when you open the Apps menu. You can resize widgets just by pressing and holding on them and then dragging any one of the corners.

5. New look for contacts
A new People app in Ice Cream Sandwich is more elaborating than your typical address book, providing a large profile along with social networking addition. It is being able to swipe to the right while viewing a contact to see Google+ updates and Twitter updates from that person in a single stream. But sorry to say that google hasn’t added Facebook yet.

6. Android Beam for NFC based sharing
The idea is really appriciating one. Provided your Ice Cream Sandwich phone has an NFC (near field communications) chip inside, you can transmit info to other phones running the latest Android OS just by touching the two together. You can share anything from contacts and Web pages to apps and YouTube videos.

7. Improved Web browsing
The new browser in Ice Cream Sandwich is not only faster than its predecessor, it helps you to open up, up to 16 browser tabs at once. You can also sync bookmarks from your Google Chrome account. Offline reading helps users to save specific web pages for reading them offline.

8. Respond to calls with a text
Android Ice Cream Sandwich makes it easy to ignore incoming calls without leting other end anoy. If you are too busy to answer the call, just swipe up and you’ll see a list of stored text messages you can tab for select. Choices include “Can’t talk right now and “I’ll call you right back.” You can also create a custom message on your own.

9. Swipe to dismiss notifications, tasks, and browser tabs
While we like that Android phones let you see notifications with a swipe down from the screen. Ice Cream Sandwich makes it easier to manage them. You can dismiss individual notifications by just swiping them off the screen, as opposed to needing to clear them all at once. You can also dive into settings from this menu with a tap.

10. Powerful voice input engine

Android 4.0 introduces a powerful new voice input engine that offers a continuous open microphone experience and streaming voice recognition. The new voice input engine lets users to dictate the text he want, for as long as he want, using the language he want. Users can speak continously for a long time, even pausing for intervals if he wish, and dictate punctuation to create correct sentences. As the voice input engine enters text, it underlines possible dictation errors in gray. After dictating, users can correct the words with suitable suggestions by tab them.