Application Fundamentals

Android applications are written in java programming language. After writing the code we can compile the code and build the entire application into Android package with an .apk suffix. Once the application is signed and is packed to apk, it can be installed in any android device.

Once apk is installed in android, each Android application lives in its own security sandbox:
> The Android operating system is a multi-user Linux system in which each
application is a different user.
> By default, the system assigns each application a unique Linux user ID (the ID
is used only by the system and is unknown to the application). The system sets
permissions for all the files in an application so that only the user ID
assigned
to that application can access them.
> Each process has its own virtual machine (VM), so an application's code runs in
isolation from other applications
> By default, every application runs in its own Linux process. Android starts the
process when any of the application'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 applications

What is Android?

Android is a platform for applications to run on mobile devices. Android provides a more user friendly environment for mobile users, to work around using mobiles, when compared to other mobile operating systems. This software stack gives users a more attractive touch experience, which makes it more popular.

Android is an open source software, which uses Linux as its core. The feature that makes android more common among smartphone operating systems is licensing. Window operating system is another operating system used among smartphone, for which the hardware manufacturers need to pay for. Another factor that makes android stand forward, when compared to windows mobile is the cost of the device. The windows mobile devices are very expensive. But android provides smart phone devices for very less rates, which makes it common among common customers.