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ANDROID APPLICATION FUNDAMENTALS

Android apps are written in the Java programming language.

The Android SDK tools compile

your code—along with any data and resource files—into an APK.(Android package)

APK file contains all the contents

of an Android app.Android-powered devices use to install the app.

Once installed on a device, each Android app lives in its own security sandbox:

The Android operating system is a multi-user Linux system in which each app is a

different user.

By default, the system assigns each app a unique Linux user ID (the ID is used only by

the system and is unknown to the app). The system sets permissions for all the files in an

app so that only the user ID assigned to that app can access them.

Each process has its own virtual machine (VM), so an app's code runs in isolation from

other apps.

By default, every app runs in its own Linux process. Android starts the process when any

of the app's components need to be executed, then shuts down the process when it's no longer

needed or when the system must recover memory for other apps.

Principle of Least Privilege:

Each app, by default, has access only to the components that it requires to do its work and

no more. This creates a very secure environment in which an app cannot access parts of

the system for which it is not given permission.

There are ways for an app to share data with other apps and for an

app to access system services:

It's possible to arrange for two apps to share the same Linux user ID, in which case

they are able to access each other's files. To conserve system resources, apps with the

same user ID can also arrange to run in the same Linux process and share the same VM (the

apps must also be signed with the same certificate).

An app can request permission to access device data such as the user's

contacts, SMS messages, the mountable storage (SD card), camera, Bluetooth, and more. All

app permissions must be granted by the user at install time.

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Android Software Stack

Android software stack (also known as android architecture) includes

linux kernel, native libraries (middleware), Android Runtime,

Application Framework and Applications.

History of Android

The history and versions of android are interesting to know. The code names of android ranges from A to J currently, such as Aestro, Blender, Cupcake, Donut, Eclair, Froyo, Gingerbread, Honeycomb, Ice Cream Sandwitch,Jelly Bean and KitKat. Let's understand the android history pointy:

Initially, Andy Rubin founded Android Incorporation in Palo Alto, California, United States in October, 2003.

In 17th August 2005, Google acquired android Incorporation. Since then, it is in the subsidiary of Google Incorporation.

The key employees of Android Incorporation are Andy Rubin, Rich Miner, Chris White and Nick Sears.

Originally intended for camera but shifted to smart phones later because of low market for camera only.

Android is the nick name of Andy Rubin given by coworkers because of his love to robots.

In 2007, Google announces the development of android OS.

In 2008, HTC launched the first android mobile.

Android Versions, Codename and API

Let's see the android versions codename and API provided by Google.

VersionCodenameAPI1.5Cupcake31.6Donut42.1Eclair72.2Froyo82.3Gingerbread9 and 103.1 and 3.3Honeycomb12 and 134.0Ice Cream Sandwitch154.1, 4.2 and 4.3Jelly Bean16, 17 and 184.4KitKat19

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