WHAT IS ANDROID

Android is a software stack for mobile device that includes an operating system, middleware and key application.

THE ARCHITECTURE OF ANDROID

Several component of android are design as a stack which ranges form “Application” to “linux kernel.” Application is the upper layer of the stack while linux kernel forms the lowest layer.

 Application: All application is written using a java program. The set of application in android include home, contact, phone, browser, e.t.c.

Application Frame Work: There are no differences between the frame work application interface used by the developers and the one used by the core applications.

          The Application infrastructure has been made so simple that it allows the re-use of component. Publishing and re-using of existing application capabilities by other application is always allowed. Replacements of components by the user are allowed.

Application frame work includes:  

1.Activity manager.  2. Window Manager. 3. Content Provider. 4. View System. 5. Notification Manager.  6. Package Manager. 7. Telephony Manager. 8. Resource Manager. Location Manager. 10.XMPP Service.

Libraries

Various components of Android system make use of set of c/c++. These capabilities can be accessed by the developer by going through the android application frame work.

Android Runtime

Android comprises of:

1.     Core Libraries

2.     Dalvick Virtual Machine

Most of the functionality available in the java programming language core libraries is also available in the core library of android. Application of android runs uniquely with its own process, with its own type of Dalvik virtual machine. One of the advantage of using dalvik is that, it allows a device to run effective multiple VMs.

“VM is registered based , and runs classes compiled by a java language compiler that has been transferred into the .dex  format by the included dx tools.” [http://developer.android.com/guide/basics/what-is-android.html]

Linux Kernel

Linux kernel comprises of :

1.     Display Driver.  2. Camera Driver. 3. Blue tooth Driver. 4. M-System Driver. 5. Binder (IPC) driver. 6. USB Driver. 7. Key Pad Driver. 8. Wi Fi Driver. 9. Audio Driver. 10. Power Management.

Core system service like security , memory management , network stack and driver model in android uses linux 2.6.

“The kernel also acts as an abstraction layer between the hardware and rest of the software.” (www.linux.com).