User:RANA Abilasha

Our world, geographically have not changed for millions of years, but if we talk about technology it definitely has undergone massive transformation which lead to the contraction of what we perceive our global as. In other words, we are controlling this planet in our own hands. By relating physical and technical components, I just want to acknowledge how powerful we have become due to advancement in technology. It changes so rapidly that sometimes it is hard to keep up with. Speaking of technology, we carry it with us that fits on our pockets; smartphones. Also widely known as 'Mini Computer'. As the number of users is multiplying every day, facilities are also expanding. Starting with simple regular handset which were used only for making phone calls, mobiles have changed our lives and have become part of it. The application of mobile now does not limit with only phone calls, they have innumerable uses such as camera, music player, t.v, browser, calculator, reminder etc. And with the new technologies, new software and operating systems are required.

Background One of the most commonly used mobile operating system these days is ANDROID. Android is a software bunch comprising not only operating system but also middle-ware and key applications. Android Inc was founded in Palo Alto of California, U.S. by Andy Rubin, Rich Miner, Nick Sears and Chris White in 2003. Later Android Inc. was acquired by Google in 2005.

Introduction Android is a Linux based operating system, it is designed primarily for touch screen mobile devices such as smart phones, tablet and computers. Android applications are written in Java Programming Language. The operating system have developed a lot in last 15 years starting from black and white phones to recent smart phones. Especially for smart phones, mobile OS has significantly evolved from Palm OS in 1996 to Windows Pocket PC in 2000 then to Blackberry OS and Android. The android is a powerful operating system and it supports large number of applications in Smartphones. These applications more comfortable and advanced for the users. The hardware that supports android software is based on ARM architecture platform. The android is an open source operating system means that it's free and any one can use it. The android has got millions of apps available in low cost that helps you manage your life which is why android is gaining its popularity. Version

The version history of the Android mobile operating system began with the first commercial Android Device in September 2008, and has gone through multiple major releases, with the current version being 8.0 "Oreo", released in August 2017.

The android is a operating system and is a stack of software components which is divided into five sections and four main layers that is:

- Linux Kernel

- Libraries

- Android Runtime

- Application Framework

- Application

Linux Kernel Positioned at the bottom of the Android software stack, the android uses the powerful Linux kernel and it supports wide range of hardware drivers. The kernel is the heart of the operating system that manages input and output requests from software. This provides basic system functionalities like process management, memory management, device management like camera, keypad, display etc. The kernel itself does not interact directly with the user but rather interacts with the shell and other programs as well as with the hard ware devices on the system.

Libraries Above a Linux kernel there is a set of libraries including open source web browser such as webkit, library libc. These libraries are used to play and record audio and video. The SQLite is a data base which is useful for storage and sharing of application data. The SSL libraries are responsible for internet security etc.

Android Runtime The android runtime provides a key component called Dalvik Virtual Machine which is a kind of java virtual machine. It is specially designed and optimized for android. The Dalvik VM is the process virtual machine in the android operating system. It is a software that runs apps on android devices. The Dalvik VM makes use of Linux core features like memory management and multi threading which is in a java language. The Dalvik VM enables every android application to run it's own process. The Dalvik VM executes the files in the .dex format.

Applications Framework The Application Framework is a set of services that collectively form the environment in which Android applications run and are managed. This framework implements the concept that Android applications are constructed from reusable, interchangeable and replaceable components. This layer provides many higher level services to applications such as windows manager, view system, package manager, notification manager, resource manager etc. The application developers are allowed to make use of these services in their application.

Applications Located at the top of the Android software stack are the applications. These comprise both the native applications provided with the particular Android implementation (for example web browser and email applications) and the third party applications installed by the user after purchasing the device.

Conclusion A good Android development knowledge foundation requires an understanding of the overall architecture of Android. Android is implemented in the form of a software stack architecture consisting of a Linux kernel, a runtime environment and corresponding libraries, an application framework and a set of applications. Applications are predominantly written in Java and run within individual instances of the Dalvik virtual machine.