Android Architecture

In order to develop applications in android it is necessary to understand the architecture of android so given below content  will help you to understand it's structure

                         Android Architecture

1Applications

            Android will ship with a set of core applications including an email client, SMS program, calendar, maps, browser, contacts, and others. All applications are written using the Java programming language.

2 Application Framework

       These frameworks are used to create the applications in Android.By providing an open development platform, Android offers developers the ability to build extremely rich and innovative applications. Developers are free to take advantage of the device hardware, access location information, run background services, set alarms, add notifications to the status bar, and much, much more.Developers have full access to the same framework APIs used by the core applications.

3 Libraries

            Android includes a set of C/C++ libraries used by various components of the Android system. These capabilities are exposed to developers through the Android application framework. Some of the core libraries are listed below 

·         System C library - a BSD-derived implementation of the standard C system library (libc), tuned for embedded Linux-based devices

·         Media Libraries - based on Packet Video’sOpenCORE; the libraries support playback and recording of many popular audio and video formats, as well as static image files, including MPEG4, H.264, MP3, AAC, AMR, JPG, and PNG

·         Surface Manager - manages access to the display subsystem and seamlessly composites 2D and 3D graphic layers from multiple applications

·         LibWebCore - a modern web browser engine which powers both the Android browser and an embeddable web view

·         SGL - the underlying 2D graphics engine

·         3D libraries - an implementation based on OpenGL ES 1.0 APIs; the libraries use either hardware 3D acceleration (where available) or the included, highly optimized 3D software rasterizer

·         Free Type - bitmap and vector font rendering

·         SQLite - a powerful and lightweight relational database engine available to all applications

4 Android Runtime     

            Android includes a set of core libraries that provides most of the functionality available in the core libraries of the Java programming language.Every Android application runs in its own process, with its own instance of the Dalvik virtual machine. Dalvik has been written so that a device can run multiple VMs efficiently. The Dalvik VM executes files in the Dalvik Executable (.dex) format which is optimized for minimal memory footprint. The VM is register-based, and runs classes compiled by a Java language compiler that have been transformed into the .dex format by the included "dx" tool.

The Dalvik VM relies on the Linux kernel for underlying functionality such as threading and low-level memory management.

5 Linux Kernel

            Android relies on Linux version 2.6 for core system services such as security, memory management, process management, network stack, and driver model. The kernel also acts as an abstraction layer between the hardware and the rest of the software stack.