Source Code
Directory Structure
art
ART (Android Runtime) operating environment is located in the art/ directory.
It also includes dex complier, JVM, JIT, Dalvik VM etc.
bionic
This directory contains the C library (libc) used by Android.
It includes low-level system components like the standard C library, dynamic linker, and other essential runtime components.
bootable
This directory contains the bootloader (which is responsible for loading the Android kernel and initiating the system boot process), recovery image, and other low-level system software that is typically loaded before the kernel.
build
Directory contains the build system for Android.
It includes tools and scripts for building the entire Android system, managing dependencies, and generating the final system images.
Contains :
envsetup.shscript that initializes the build environment.Android.mkfile that defines the build rules for the entire Android system.make and soong build systems.
cts
Contains the Compatibility Test Suite (CTS) for Android.
CTS is used to check for incompatibilities with Android OS during device development.
dalvik
It contains the Dalvik Virtual Machine related code.
Even though ART is the default runtime environment for Android, android still uses Dalvik VM for running apps that are not compiled with ART.
Since Android uses ART, why is the Dalvik folder still present in the AOSP source code?
Android originally used the Dalvik Virtual Machine as its runtime environment up to Android 4.4 (KitKat). With Android 5.0 (Lollipop), ART (Android Runtime) officially replaced Dalvik to improve performance through ahead-of-time (AOT) compilation, better garbage collection, and improved debugging tools.
However, the dalvik/ folder still exists in the AOSP source tree for a few key reasons: Some internal components and tools, especially in ART, still reuse or depend on code and class structures originally written under the Dalvik namespace. Removing it would break backward compatibility or require substantial refactoring.
developers
Contains demo and sample android projects.
development
It includes tools for debugging, profiling, and testing Android applications.
device
It contains device specific files and configurations.
It includes supporting configuration and driver files required for Development boards like linaro, hikey etc.
external
Includes external projects and libraries that Android uses but are not part of the core AOSP.
These could be open-source projects or third-party libraries.
For example, Dagger2
frameworks
Contains the core Android system framework.
We can find all the System service (ActivityManagerService.java, PackageManagerService.java), libraries, and APIsthat are used by the Android system.
hardware
Contains the hardware abstraction layer (HAL) for Android.
It consists of HAL for audio, video, TV, camera, USB, and other hardware components.
Contains hardware-specific code, including drivers for various hardware components like sensors, cameras, and audio devices.
kernel
It contains the kernel configuration and prebuilts.
libcore
The /libcore directory includes core libraries used by the Android system.
These libraries provide fundamental functionality for Java applications on Android, such as I/O operations, utilities, and networking.
libnativehelper
This directory contains helper code for native development.
It provides support for integrating native (C/C++) code with the Java-based Android framework.
out
After the build is complete, the output is placed in the /out directory.
The /out directory is where the build system places the output artifacts, including compiled binaries, libraries, and system images.
packages
The /packages directory includes various Android applications and system packages.
It contains source code for apps like the Android Browser, Calculator, Calendar, and others.
pdk
The Platform Development Kit (PDK) includes tools and documentation for building Android devices.
It provides resources for device manufacturers to create Android-compatible hardware.
It includes only necessary components for developing HAL.
platform_testing
Consists of platform tests modules.
prebuilts
The /prebuilts directory contains prebuilt binaries and tools that are used in the Android build process.
It includes toolchains like asuite, android emulator, bazel etc.
sdk
It contains instructions and tools for building the Android SDK, for a specific build.
system
It contains low level file system libraries, applications and components.
Folders for SELinux, Logging and many low level configuration files.
test
It contains test suits like csuite, vts(vendor test suite), mts(mainline test suite) etc.
toolchain
It contains files related to benchmark and pgoprofiles.
tools
It contains tools like apksig, asuite, trade federation etc.