Android

Android is an open-source software stack for mobile devices that includes an operating system, middleware and key applications.Google Inc. purchased the initial developer of the software, Android Inc., in 2005. Android's mobile operating system is based upon a modified version of the Linux kernel. Google and other members of the Open Handset Alliance collaborated on Android's development and release. The Android Open Source Project (AOSP) is tasked with the maintenance and further development of Android.

The most recent released versions of Android are:

• 1.1 Platform
• 1.5 Cupcake)
• 1.6 (Donut)
• 2.0 Platform
• 2.0.1 Platform
• 2.0/2.1 (Eclair), which revamped the user interface and introduced HTML5 and Exchange ActiveSync 2.5 support

• 2.2 (Froyo), which introduced speed improvements with JIT optimization and the Chrome V8 JavaScript engine, and added Wi-Fi hotspot tethering and Adobe Flash support

• 2.3 (Gingerbread), which refined the user interface, improved the soft keyboard and copy/paste features, and added support for Near Field Communication

• 3.0 (Honeycomb), a tablet-oriented release which supports larger screen devices and introduces many new user interface features, and supports multicore processors and hardware acceleration for graphics. The Honeycomb SDK has been released and the first device featuring this version, the Motorola Xoom tablet, went on sale in February 2011.

• 4.0 (Ice-cream sandwich) is the upcoming version of Android, a combination of Gingerbread and Honeycomb into a "cohesive whole," with a possible release in mid-2011.
• 4.1.x (Jelly bean)
• 4.2.x (Jelly bean)
• 4.3 (Jelly bean) 
• 4.4.x (Kit kat)
• 5.x (Key lime pie) 

Source: Wikipedia