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Saturday, December 17, 2011

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
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

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