Version History of Android

 Android 1.0 (API level 1)

Android 1.0, the first commercial version of the software, was released on 23 September 2008. The first Android device, the HTC Dream, incorporated the following Android 1.0 features:

Android 1.1 (API level 2)

On 9 February 2009, the Android 1.1 update was released, initially for the HTC Dream only. Android 1.1 was known as "Petit Four" internally, though this name was not used officially. The update resolved bugs, changed the Android API and added a number of features:

Android 1.5 Cupcake (API level 3) 

On 30 April 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 dessert item ("Cupcake"), a theme which would be used for all releases henceforth. The update included several new features and UI amendments:

Android 1.6 Donut (API level 4) 

On 15 September 2009, the Android 1.6 SDK – dubbed Donut – was released, based on Linux kernel 2.6.29

Android 2.0 Eclair (API level 5)

On 26 October 2009, the Android 2.0 SDK – codenamed Eclair – was released, based on Linux kernel 2.6.29. Changes included

Android 2.0.1 Eclair (API level 6)

Android 2.1 Eclair (API level 7)

Android 2.2–2.2.3 Froyo (API level 8)

On 20 May 2010, the SDK for Android 2.2 (Froyo, short for frozen yogurt) was released, based on Linux kernel 2.6.32.

Android 2.3–2.3.2 Gingerbread (API level 9)

On 6 December 2010, the Android 2.3 (Gingerbread) SDK was released, based on Linux kernel 2.6.35.

Android 2.3.3–2.3.7 Gingerbread (API level 10)

Android 3.0 Honeycomb (API level 11)

On 22 February 2011, the Android 3.0 (Honeycomb) SDK – the first tablet-only Android update – was released, based on Linux kernel 2.6.36. The first device featuring this version, the Motorola Xoom tablet, was released on 24 February 2011.

Android 3.1 Honeycomb (API level 12)

Android 3.2 Honeycomb (API level 13)

Most first -and second-generation Google TV-enabled devices utilize Honeycomb 3.2.A

Android 4.0–4.0.2 Ice Cream Sandwich (API level 14)

The SDK for Android 4.0.1 (Ice Cream Sandwich), based on Linux kernel 3.0.1 was publicly released on 19 October 2011. Google's Gabe Cohen stated that Android 4.0 was "theoretically compatible" with any Android 2.3.x device in production at that time. The source code for Android 4.0 became available on 14 November 2011. The update introduced numerous new features, including:

Android 4.0.3–4.0.4 Ice Cream Sandwich (API level 15)

Support for Adobe Systems' Flash player ended with Ice Cream Sandwich.

Android 4.1 Jelly Bean (API level 16)

Google announced Android 4.1 (Jelly Bean) at the Google I/O conference on 27 June 2012. Based on Linux kernel 3.0.31, Jelly Bean was an incremental update with the primary aim of improving the functionality and performance of the user interface. The performance improvement involved "Project Butter", which uses touch anticipation, triple buffering, extended  vsync timing and a fixed frame rate of 60 fps to create a fluid and "buttery-smooth" UI. Android 4.1 Jelly Bean was released to the Android Open Source Project on 9 July 2012, and the Nexus 7 tablet, the first device to run Jelly Bean, was released on 13 July 2012.

Android 4.2 Jelly Bean (API level 17)

Google was expected to announce Jelly Bean 4.2 at an event in New York City on 29 October 2012, but the event was cancelled due to Hurricane Sandy. Instead of rescheduling the live event, Google announced the new version with a press release, under the slogan "A new flavor of Jelly Bean". The first devices to run Android 4.2 were LG's Nexus 4 and Samsung's Nexus 10, which were released on 13 November 2012.

Android 5.0 Key Lime Pie (API level 18)

On 3 December 2012, it was reported that Google was working on Android 5.0, the successor to Jelly Bean, and confirmed by a Google employee that the OS version will sport the name of Key Lime Pie.^[  In February 2013, a leaked Qualcomm document revealed that Key Lime Pie would be released in the second quarter of 2013.

What is API Level?

API Levels generally mean that as a programmer, you can communicate with the devices' built in functions and functionality. As the API level increases, functionality adds up (although some of it can get deprecated).

Choosing an API level for an application development should take at least two things into account:

1.       Current distribution(see picture) - How many devices can actually support my application, if it was developed for API level 9, it cannot run on API level 8 and below, then "only" around 60% of devices can run it (true to the date this post was made).

2.       Choosing a lower API level may support more devices but gain less functionality for your app. you may also work harder to achieve features you could've easily gained if you chose higher API level.

Android API levels can be divided to three main groups (not scientific, but what the heck):

1.       Android 1.5 - 2.3 (API levels 3-10) - Android made specifically for Smart phones.

2.       Android 3.0 - 3.2 (API levels 11-13) - Honeycomb, Android made for tablets.

3.       Android 4 (API levels 14-) - Ice Cream Sandwich - Current generation, a big merge with tons of additional functionality, totally revamped Android version, for both phone and tablets.