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So let's have a look at Android software stack, because it's composed of several different layers.

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So each layer defines interfaces and offers specific services.

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So let's briefly examine Android's architecture from the bottom up.

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As you can see in the figure, Android is built on top of the Linux kernel.

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As in any unique system, the colonel provides drivers for hardware networking file system access as

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well as process management.

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Now, on top of the colonel, the hardware abstraction layer defines a standard interface for interacting

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with built in hardware components.

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So this is the basis for allowing applications to interact with the devices hardware, for example,

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it allows a stock phone application to use device's microphone and speaker.

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Android runtime, also known as Art.

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So this is an application runtime environment replacing Dalvik, which was the process virtual machine

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that was originally used by Android, so outperforms the translation the applications bytecode into

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native instructions are later executed by the devices runtime environment.

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I'll explain this process in much more detail in the next lecture.

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How many core Android system components and services such as art and hell are built from native code

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that requires native libraries written in C and C++?

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The Android platform provides Java framework APIs to expose the functionality of some of these native

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libraries to apps.

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Android's core Java libraries are originally derived from the Apache Harmony Project and just happened

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to be the next layer on our stack.

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Now, on top of native libraries and Android runtime, there is an Android framework.

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So Android framework includes Android APIs such as user interface telephony, resources, locations,

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content providers and package managers.

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It provides a lot of classes and interfaces for Android application development.

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Now, on top of the Android framework, there are applications.

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All applications, such as browser camera, calendar, home contact and settings are using the Android

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framework that uses Android runtime and libraries.

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Android runtime and native libraries are using Linux kernel.