1. abi - This folder contains a sub folder called cpp which actually contains many C++ files linked to many places.
2. android Remember this?
Code:
repo init -u git://github.com/CyanogenMod/android.git
Have a look at this also.
3. art - Yeah, it is the folder that deals with the compilation of the latest android ART runtime. If you're looking into source directories of some other androidversions, you won't fins it obviously.
4. bionic - Bionic is mainly a port of the BSD C library to our Linux kernel with the following additions/changes:
- No support for locales.
- No support for wide chars (i.e. multi-byte characters).
- its own smallish implementation of pthreads based on Linux futexes.
- Support for x86, ARM and ARM thumb CPU instruction sets and kernel interfaces.
5. bootable - Boot and startup related code. Some of it is legacy, the fastboot protocol info could be interesting since it is implemented by boot loaders in a number of devices such as the Nexus ones.
6. build - The main entry point of the build system resides here - envsetup.sh, if you follow the instruction in source.android.com you will see that the first step before you do anything to build Android is to use the command source build/envsetup.sh
The script will check few things to make sure all the needed application available in the local machine. It also setup the devices that can be built, which is extracted from the directory device.
7. cts - the compatability tests. The test suite to ensure that a build complies with the Android specification.
8. dalvik - This is the folder responsible for the compilation of the Dalvik runtime for the Android devices.
*Have a look at the difference between the two(art and dalvik) folders and you'll have an idea of how things work in that case*
9. Development - This directory contains application that are not part of the deployed app in the OS. There are some useful application such as widgetbuilder, etc
10. Device - It contains the device specific configurations for many devices.
Note - Many people ask me what, the folders like 'common' and 'generic are for, so here -
> common - This directory contains gps information and also a script that allows you to extract proprietary binary files from your phone to be part of the build process.(You can try to have a look at your device's device tree and then the cm.mk file, where you could find relations of these files. In my case, it shows like this:
Code:
# Include GSM stuff $(call inherit-product, vendor/cm/config/gsm.mk) -and- # Inherit some common cyanogenmod stuff. $(call inherit-product, device/common/gps/gps_eu_supl.mk)
> Google - This directory contains the Android Accessories Kit code. It contains a demokit Android app that allows you to control the ADK board. The ADK firmware can be check out here http://code.google.com/p/microbridge/. There is a good article about this here.
> sample - This directory contains a full example of writing your own Android platform shared library, without changing the Android framework. It also shows how to write JNI code for incorporating native code into the library, and a client application that uses the library. This example is ONLY for people working with the open source platform to create a system image that will be delivered on a device which will include a custom library as shown here. It can not be used to create a third party shared library, which is not currently supported in Android.
11. docs - I contains an important sub-folder called source.android.com. Contains tutorials, references, and miscellaneous information relating to the AndroidOpen Source Project (AOSP). The current iteration of this site is fully static HTML (notably lacking in javascript and doxygen content), and is and/or was maintained by skyler (illustrious intern under Dan Morrill and assistant to the almighty JBQ).
12. external - This directory contains source code for all external open source projects such as SQLite, Freetype, webkit and webview.
13. frameworks - Ah, one of the most important directories. it contains the sources for the framework. Here you will find the implementation of key services such as the System Server with the Package- and Activity managers. A lot of the mapping between the java application APIs and the native libraries is also done here.
A special note on this one - I'd recommend new users to not to play with any file/folder inside the frameworks folder, maybe your ROM doesn't boots then.
14. hardware - Hardware related source code such as the Android hardware abstraction layer specification and implementation. This folder also contains the reference Radio Interface Layer(RIL - To communicate with the modem side) implementation.
15. Kernel - It's not a default folder in the source code, but it's a part of device configuration set-up. It contains the kernel source of your device.
16. libcore - I'll explain this one with the important folders inside this, since every folder performs a different function.
- dalvik - DalvikVM runtime for Android
- dom - Java test classes for DOM
- expectations - Contains information about the test cases
- include - Some C/C++ include files that used for Array and String handling
- json - JSON based Java implementation
- luni - Contains test source code for loading .jar and .dex files
- support - Contains support class file for testing Dalvik
- xml - XML pull and push implementation
18. ndk - Contains build scripts and helper files for building the NDK
19. out(Everyone's favorite directory
) - The build output will be placed here after you run make. The folder structure is out/target/product/. In the default build for the emulator the output will be placed in out/target/product/generic. This is where you will find the images used by the emulator to start (or to be downloaded and flashed to a device if you are building for a hardware target).20. packages - Standard Android application that are available as part of the AOSP - Camera, SMS, Dialer, Launcher, etc
21. pdk - I believe that 'pdk' is the Platform Development Kit, it's basically an SDK/set of tools that Google sends to OEMs to evaluate their framework ahead of each major Android upgrade since Android 4.1.
(Thanks to @yowanvista
)22. prebuilt - Contains files that are distributed in binary form for convenience. Examples include the cross compilations toolchains for different development machines.
23. sdk - This directory contains lots of apps that are not part of operating system. There are quite useful apps that developers can leverage on and can be enhanced further as part of the operating system.
24. system - Source code files for the core Android system. That is the minimal Linux system that is started before the Dalvik VM and any java based services are enabled. This includes the source code for the init process and the default init.rc script that provide the dynamic configuration of the platform.
25. tools - Some external important tools that help in compiling. Not sure though. :/
26. vendor - This directory contains vendors specific libraries. Most of the proprietary binary libraries from non-open source projects are stored here when building AOSP.
One thing - Beyond the above you also have the hidden .repo directory that contains the source for the repo utility. It also holds the manifest specifying what git repositories you want to track for this Android source project. If you have your own additions you could automatically track them by adding a local manifest here. For modifications of the platform framework there are some instructions available in the device/sample folder of the source code tree. That will show you how to add APIs to Android without having to modify the core framework.
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