The version history of the Android mobile operating system began with the release of the Android beta in November 2007. The first commercial version, Android 1.0, was released in September 2008. Android is under ongoing development by Google and the Open Handset Alliance (OHA), and has seen a number of updates to its base operating system since its initial release.
Since April 2009, Android versions have been developed under a confectionery-themed code name and released according to alphabetical order: Cupcake (1.5), Donut (1.6), Eclair (2.0–2.1), Froyo (2.2–2.2.3), Gingerbread (2.3–2.3.7), Honeycomb (3.0–3.2.6), Ice Cream Sandwich (4.0–4.0.4), Jelly Bean (4.1–4.3), and KitKat (4.4). On 3 September 2013, Google announced that 1 billion activated devices now use the Android OS worldwide. The most recent major Android update was KitKat 4.4, which was released to commercial devices on 22 November 2013, via an OTA update.
Reference: http://en.wikipedia.org/wiki/Android_version_history
