ANDROID 3.0 PLATFORM SDK
Android is a mobile operating system initially developed by Android Inc. Android was bought by Google in 2005.Android 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.
Android has a large community of developers writing application programs that extend the functionality of the devices. There are currently over 200,000 apps available for Android. Android Market is the online app store run by Google, though apps can also be downloaded from third-party sites. Developers write primarily in the Java language, controlling the device via Google.
SOFTWARE DEVELOPMENT KIT
The Android software development kit (SDK) includes a comprehensive set of development tools. These include a debugger, libraries, a handset emulator, documentation, sample code, and tutorials. Currently supported development platforms include computers running Linux any modern desktop Linux Distribution, MAC OS X10.4.9 or later, Windows XP or later. The officially supported Integrated Development Environment (IDE) is Eclipse currently 3.4, 3.5 or 3.6 using the Android Development Tools (ADT) Plugin, though developers may use any text editor to edit Java and XML files then use command line tools Java Development Kit and Apache Ant are required to create, build and debug Android applications as well as control attached Android devices e.g., triggering a reboot, installing software package(s) remotely.
A preview release of the Android SDK was released on 12 November 2007. On 15 July 2008, the Android Developer Challenge Team accidentally sent an email to all entrants in the Android Developer Challenge announcing that a new release of the SDK was available in a "private" download area. The email was intended for winners of the first round of the Android Developer Challenge. The revelation that Google was supplying new SDK releases to some developers and not others and keeping this arrangement private led to widely reported frustration within the Android developer community at the time.
On 18 August 2008 the Android 0.9 SDK beta was released. This release provided an updated and extended API, improved development tools and an updated design for the home screen. Detailed instructions for upgrading are available to those already working with an earlier release. On 23 September 2008 the Android 1.0 SDK Release 1 was released. According to the release notes, it included "mainly bug fixes, although some smaller features were added". It also included several API changes from the 0.9 version. Enhancements to Android's SDK go hand in hand with the overall Android platform development. The SDK also supports older versions of the Android platform in case developers wish to target their applications at older devices. Development tools are downloadable components, so after one has downloaded the latest version and platform, older platforms and tools can also be downloaded for compatibility testing.
Android applications are packaged in .apk format and stored under data app folder on the Android OS the folder is accessible to root user only for security reasons. APK package contains .dex files, resource files, etc.