Android Architecture

Android operating system consists of different software components arranged in stack. Following are the different components of android operating system-

1. Libraries

2. Android Runtime

3. Application Framework

4. Linux kernel

5. Applications

    Linux kernel

• Bottom layer of android operating system is Linux kernel. Android is built on top of Linux 2.6 kernel and few architectural changes made by Google.
• Linux kernel provides device drivers drivers like camera, keypad, display etc. which make our task easier while interfacing the android with peripheral devices .
• It also provides basic system functionality such as process management, memory management and device management.

Libraries

• On the top of Linux Kernel another layer called libraries is present.
• Their a set of libraries including open-source Web browser engine uch as WebKit, OpenGL, FreeType, SQLite, Media, C runtime library (libc) etc.
• Libraries are java libraries build specific for android operating system 

SQLite: It is used to access data published by content providers and it includes SQLite                   database management classes.

Webkit: It is the browser engine used to display internet content or HTML content.

OpenGL: It is used to provide java interface to the OpenGL/ES 3D graphics rendering                    API

SSL:It is used to provide internet  security

   Android Runtime

• It is the third components of the android architecture and placed in the second layer from bottom.
• There are core libraries and DVM (Dalvik Virtual Machine) which is responsible to run android application. DVM is like JVM but it is optimized for mobile devices. It consumes less memory and provides fast performance.

   Application Framework

• It is the second topmost components in android operating system.
• It provides higher level services to the applications in the form of Java classes.
• Application framework manages basic functions of android devices such as resources management, voice call management etc.
• Following are the some important blocks of Application Framework-

Activity Manager: it is used to manage activity life cycle of the applications.

Content Providers: it is used to manage the data sharing between two application.

Resource Manager:it is used to manage the different types of resources used in                                               android app.

Telephony Manager: it is used to manages all voice calls.

     Applications

         On the top of the application framework there is an Applications.Applications are created by             the third party user or developer will be installed on application layer