Introduction To Android – Googles another Avatar

When we talk about the high-end mobile we mostly come across a general term and that would be “ANDROID”. Knowingly or unknowingly we have been using this term ,So what is this ANDROID , what features of this make it an widely used OS, and that too for mobile?

So, here is an overview of what it is:

WHAT IS ANDROID?

Android is a software stack for mobile devices that includes an operating system, middleware and key applications. The Android SDK provides the tools and APIs necessary to begin developing applications on the Android platform using the Java programming language. Android does a software bunch comprise not only operating system but also middleware and key applications. Below is the architecture of Android.

Android Architecture

android-architecture

We can clearly see that architecture can be broken into following categories:

1. Application and widgets
2. Application framework
3. Libraries
4. Linux kernel

Let us discuss them one by one

Application Framework

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. The application architecture is designed to simplify the reuse of components; any application can publish its capabilities and any other application may then make use of those capabilities. This same mechanism allows components to be replaced by the user.

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’s Open CORE; 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 or the included,
• Free Type – bitmap and vector font rendering
• SQLite – a powerful and lightweight relational database engine available to all applications

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.

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.

Applications:

These are the basics of Android applications.

• Android applications are composed of one or more application components (activities, services, content providers, and broadcast receivers)
• Each component performs a different role in the overall application behavior, and each one can be activated individually (even by other applications)
• The manifest file must declare all components in the application and should also declare all application requirements, such as the minimum version of Android required and any hardware configurations required
• Non-code application resources (images, strings, layout files, etc.) should include alternatives for different device configurations (such as different strings for different languages)