Appendix A: Key Files Reference

This appendix provides a quick-reference table of the most important source files in AOSP, organized by subsystem and cross-referenced to the chapter where each file is discussed. Paths are relative to the AOSP root ($AOSP/).

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Build System (Chapter 2)

File Path	Purpose
build/make/core/main.mk	Top-level build entry point; includes all other makefiles
build/make/core/Makefile	Legacy build rules for images, OTA, packaging
build/make/core/definitions.mk	Common macro definitions used across the build
build/make/core/envsetup.mk	Environment variable setup for build configuration
build/make/core/product.mk	Product-level build variable definitions
build/make/core/product_config.mk	Product configuration loading and validation
build/make/core/board_config.mk	Board-level hardware configuration
build/make/core/binary.mk	Shared rules for building native binaries
build/make/core/tasks/berberis_test.mk	Build configuration for native bridge testing
build/make/envsetup.sh	Shell environment setup; defines lunch, m, mm, mmm
build/soong/cmd/soong_build/main.go	Soong build system entry point
build/soong/android/module.go	Base module type definitions for Soong
build/soong/android/androidmk.go	Android.mk to Soong conversion logic
build/soong/cc/cc.go	C/C++ module build rules for Soong
build/soong/cc/library.go	Shared/static library build rules
build/soong/cc/binary.go	Native binary build rules
build/soong/cc/config/riscv64_device.go	RISC-V 64-bit device configuration
build/soong/java/java.go	Java module build rules for Soong
build/soong/java/app.go	Android application build rules
build/soong/apex/apex.go	APEX module build rules
build/blueprint/context.go	Blueprint core context and dependency resolution
build/blueprint/module_ctx.go	Module context interface for Blueprint
device/generic/goldfish/board/BoardConfigCommon.mk	Emulator board configuration (common)
device/google/cuttlefish/vsoc_x86_64/BoardConfig.mk	Cuttlefish virtual device board config (x86_64)

Boot and Init (Chapter 4)

File Path	Purpose
system/core/init/init.cpp	PID-1 init process main entry point
system/core/init/service.cpp	Service lifecycle management (start/stop/restart)
system/core/init/service_parser.cpp	Parsing of service definitions in .rc files
system/core/init/action.cpp	Action and trigger execution engine
system/core/init/action_parser.cpp	Parsing of action blocks in .rc files
system/core/init/property_service.cpp	System property daemon and persistence
system/core/init/first_stage_init.cpp	First-stage init before mounting partitions
system/core/init/first_stage_mount.cpp	Early partition mounting logic
system/core/init/selinux.cpp	SELinux policy loading during init
system/core/init/ueventd.cpp	Device node creation daemon
system/core/init/reboot.cpp	Shutdown and reboot sequencing
system/core/rootdir/init.rc	Root init script; defines core services and triggers
system/core/rootdir/init.zygote64_32.rc	Zygote startup configuration (64+32-bit)
system/core/fastboot/fastboot.cpp	Fastboot protocol host-side implementation
bootable/recovery/recovery.cpp	Recovery mode main entry point

Kernel (Chapter 5)

File Path	Purpose
kernel/common/Makefile	Top-level kernel Makefile
kernel/common/arch/arm64/configs/gki_defconfig	GKI default kernel configuration
kernel/common/drivers/android/binder.c	Binder kernel driver implementation
kernel/common/drivers/android/binder_alloc.c	Binder memory allocation
kernel/common/drivers/staging/android/ion/	ION memory allocator (legacy)
kernel/common/drivers/dma-buf/	DMA-BUF framework for buffer sharing
kernel/common/drivers/gpu/drm/	DRM/KMS graphics driver framework
kernel/common/include/uapi/linux/android/binder.h	Binder UAPI header
kernel/common/fs/fuse/dev.c	FUSE device implementation (for scoped storage)
kernel/build/build.sh	Kernel build wrapper script
kernel/build/kleaf/	Kleaf (Bazel-based) kernel build system

HAL -- Hardware Abstraction Layer (Chapter 10)

File Path	Purpose
hardware/interfaces/	Top-level HIDL/AIDL HAL interface directory
hardware/interfaces/audio/aidl/	Audio HAL AIDL interface definitions
hardware/interfaces/camera/provider/aidl/	Camera provider HAL interface
hardware/interfaces/graphics/composer/aidl/	HWC (Hardware Composer) HAL interface
hardware/interfaces/graphics/allocator/aidl/	Gralloc allocator HAL interface
hardware/interfaces/graphics/mapper/stable-c/	Gralloc mapper stable-C HAL interface
hardware/interfaces/health/aidl/	Battery/health HAL interface
hardware/interfaces/sensors/aidl/	Sensors HAL interface
hardware/interfaces/neuralnetworks/aidl/	NNAPI HAL interface
hardware/interfaces/power/aidl/	Power HAL interface
hardware/interfaces/thermal/aidl/	Thermal HAL interface
hardware/interfaces/bluetooth/aidl/	Bluetooth HAL interface
hardware/interfaces/wifi/aidl/	Wi-Fi HAL interface
hardware/interfaces/vibrator/aidl/	Vibrator HAL interface
hardware/libhardware/include/hardware/hardware.h	Legacy HAL module interface (hw_module_t)
system/libhidl/transport/HidlTransportSupport.cpp	HIDL transport initialization
system/tools/hidl/	HIDL compiler (hidl-gen)
system/tools/aidl/	AIDL compiler for HAL interfaces

Bionic and the Dynamic Linker (Chapter 7)

File Path	Purpose
bionic/libc/bionic/malloc_common.cpp	malloc dispatch (jemalloc/scudo selection)
bionic/libc/bionic/pthread_create.cpp	POSIX thread creation
bionic/libc/bionic/libc_init_dynamic.cpp	Dynamic-linked process startup
bionic/libc/bionic/libc_init_static.cpp	Static-linked process startup
bionic/libc/bionic/system_property_api.cpp	System property client API
bionic/libc/arch-arm64/	ARM64 architecture-specific code
bionic/libc/include/	Public C library headers
bionic/linker/linker.cpp	Dynamic linker main logic
bionic/linker/linker_phdr.cpp	ELF program header parsing and loading
bionic/linker/linker_namespaces.cpp	Linker namespace implementation
bionic/linker/linker_soinfo.cpp	Shared object info management
bionic/linker/linker_config.cpp	Linker configuration file parsing
system/core/rootdir/etc/ld.config.txt	Default linker namespace configuration
bionic/libm/	Math library implementation
bionic/libdl/libdl.cpp	dlopen/dlsym implementation

Binder IPC (Chapter 9)

File Path	Purpose
frameworks/native/libs/binder/IPCThreadState.cpp	Per-thread Binder transaction processing
frameworks/native/libs/binder/ProcessState.cpp	Per-process Binder driver state
frameworks/native/libs/binder/Binder.cpp	BBinder (local) base class
frameworks/native/libs/binder/BpBinder.cpp	BpBinder (proxy) base class
frameworks/native/libs/binder/Parcel.cpp	Data serialization for Binder transactions
frameworks/native/libs/binder/IServiceManager.cpp	Service manager client interface
frameworks/native/cmds/servicemanager/ServiceManager.cpp	Service manager daemon
frameworks/native/cmds/servicemanager/main.cpp	Service manager entry point
frameworks/base/core/java/android/os/Binder.java	Java-side Binder base class
frameworks/base/core/java/android/os/BinderProxy.java	Java-side Binder proxy
frameworks/base/core/java/android/os/Parcel.java	Java-side Parcel
frameworks/base/core/java/android/os/ServiceManager.java	Java service manager client
frameworks/base/core/jni/android_util_Binder.cpp	Binder JNI bridge

NDK -- Native Development Kit (Chapter 11)

File Path	Purpose
frameworks/native/include/android/	Public NDK native headers
frameworks/native/libs/nativewindow/include/android/native_window.h	ANativeWindow API
frameworks/native/include/android/native_activity.h	NativeActivity API
frameworks/native/include/android/sensor.h	Sensor NDK API
frameworks/native/include/android/asset_manager.h	Asset manager NDK API
frameworks/av/media/ndk/	Media NDK implementation (AMediaCodec, etc.)
packages/modules/NeuralNetworks/runtime/	NNAPI runtime implementation
frameworks/native/libs/nativewindow/	ANativeWindow implementation

Graphics and Render Pipeline (Chapter 13)

File Path	Purpose
frameworks/native/services/surfaceflinger/SurfaceFlinger.cpp	Compositor main class
frameworks/native/services/surfaceflinger/SurfaceFlinger.h	SurfaceFlinger declarations
frameworks/native/services/surfaceflinger/Scheduler/Scheduler.cpp	VSYNC scheduling and frame pacing
frameworks/native/services/surfaceflinger/Scheduler/VsyncController.cpp	VSYNC signal generation
frameworks/native/services/surfaceflinger/CompositionEngine/	Composition strategy engine
frameworks/native/services/surfaceflinger/DisplayHardware/HWComposer.cpp	HWC abstraction layer
frameworks/native/services/surfaceflinger/DisplayHardware/PowerAdvisor.cpp	Power hint integration
frameworks/native/services/surfaceflinger/Layer.cpp	Individual surface/layer management
frameworks/native/services/surfaceflinger/BufferLayer.cpp	Buffer-backed layer implementation
frameworks/native/services/surfaceflinger/FrontEnd/LayerLifecycleManager.cpp	Layer lifecycle tracking
frameworks/native/services/surfaceflinger/Tracing/TransactionTracing.cpp	Transaction trace capture
frameworks/native/libs/gui/Surface.cpp	Client-side Surface implementation
frameworks/native/libs/gui/BufferQueue.cpp	Producer-consumer buffer queue
frameworks/native/libs/gui/BufferQueueProducer.cpp	Buffer queue producer side
frameworks/native/libs/gui/BufferQueueConsumer.cpp	Buffer queue consumer side
frameworks/native/libs/gui/SurfaceComposerClient.cpp	SurfaceFlinger client interface
frameworks/native/libs/gui/BLASTBufferQueue.cpp	BLAST buffer queue (modern path)
frameworks/native/libs/renderengine/skia/SkiaGLRenderEngine.cpp	Skia-based GPU composition
frameworks/native/libs/renderengine/skia/SkiaVkRenderEngine.cpp	Skia Vulkan render engine
frameworks/native/opengl/libs/EGL/eglApi.cpp	EGL API entry points
frameworks/native/opengl/libs/EGL/Loader.cpp	EGL driver loader
frameworks/native/vulkan/libvulkan/driver.cpp	Vulkan loader/driver interface
frameworks/native/vulkan/libvulkan/api.cpp	Vulkan API dispatch
external/skia/src/gpu/ganesh/GrDirectContext.cpp	Skia GPU context
external/skia/src/gpu/graphite/	Skia Graphite (next-gen GPU backend)
frameworks/base/libs/hwui/renderthread/RenderThread.cpp	HWUI render thread
frameworks/base/libs/hwui/renderthread/CanvasContext.cpp	Per-window render context
frameworks/base/libs/hwui/pipeline/skia/SkiaOpenGLPipeline.cpp	Skia GL rendering pipeline
frameworks/base/libs/hwui/pipeline/skia/SkiaVulkanPipeline.cpp	Skia Vulkan rendering pipeline
frameworks/base/libs/hwui/RenderNode.cpp	Display list render node
frameworks/base/libs/hwui/RecordingCanvas.cpp	Display list recording canvas
frameworks/base/libs/hwui/DamageAccumulator.cpp	Dirty region tracking
frameworks/base/libs/hwui/JankTracker.cpp	Frame jank detection and reporting
frameworks/base/graphics/java/android/graphics/Canvas.java	Java Canvas API
frameworks/base/graphics/java/android/graphics/RenderNode.java	Java RenderNode API
frameworks/base/core/java/android/view/Choreographer.java	VSYNC-based callback scheduler
frameworks/base/core/java/android/view/ViewRootImpl.java	View hierarchy root; drives measure/layout/draw
frameworks/base/core/java/android/view/ThreadedRenderer.java	Java bridge to HWUI RenderThread

Animation System (Chapter 14)

File Path	Purpose
frameworks/base/core/java/android/animation/ValueAnimator.java	Core property animation engine
frameworks/base/core/java/android/animation/ObjectAnimator.java	Property-targeted animation
frameworks/base/core/java/android/animation/AnimatorSet.java	Coordinated animation sequencing
frameworks/base/core/java/android/view/animation/Animation.java	Legacy view animation base class
frameworks/base/core/java/android/transition/TransitionManager.java	Scene transition framework
frameworks/base/core/java/android/window/TransitionInfo.java	Shell transition metadata
frameworks/libs/systemui/animationlib/src/	SystemUI shared animation library

Audio System (Chapter 15)

File Path	Purpose
frameworks/av/services/audioflinger/AudioFlinger.cpp	Audio mixing daemon main class
frameworks/av/services/audioflinger/Threads.cpp	Playback and record thread implementations
frameworks/av/services/audioflinger/Tracks.cpp	Audio track management
frameworks/av/services/audioflinger/Effects.cpp	Audio effects chain processing
frameworks/av/services/audiopolicy/managerdefault/AudioPolicyManager.cpp	Audio routing policy
frameworks/av/services/audiopolicy/common/managerdefinitions/src/AudioPort.cpp	Audio port abstraction
frameworks/av/media/libaudioclient/AudioTrack.cpp	Client-side audio playback
frameworks/av/media/libaudioclient/AudioRecord.cpp	Client-side audio recording
frameworks/av/media/libaudioclient/AudioSystem.cpp	Audio system client interface
frameworks/av/media/libaudiohal/impl/DeviceHalAidl.cpp	Audio device HAL AIDL adapter
frameworks/base/media/java/android/media/AudioTrack.java	Java audio playback API
frameworks/base/services/core/java/com/android/server/audio/AudioService.java	Audio service (volume, routing)

Media and Video Pipeline (Chapter 16)

File Path	Purpose
frameworks/av/media/libmediaplayerservice/MediaPlayerService.cpp	Media player daemon
frameworks/av/media/codec2/sfplugin/CCodec.cpp	Codec2 framework plugin
frameworks/av/media/codec2/sfplugin/CCodecBufferChannel.cpp	Codec2 buffer management
frameworks/av/media/codec2/components/	Software codec implementations
frameworks/av/media/libstagefright/MediaCodec.cpp	MediaCodec native implementation
frameworks/av/media/libstagefright/ACodec.cpp	Legacy OMX codec adapter
frameworks/av/media/libstagefright/NuPlayer/NuPlayer.cpp	Media playback engine
frameworks/av/media/module/extractors/	Media file format extractors (MP4, MKV, etc.)
frameworks/av/services/camera/libcameraservice/CameraService.cpp	Camera service daemon
frameworks/av/drm/mediadrm/plugins/clearkey/	ClearKey DRM reference implementation
frameworks/base/media/java/android/media/MediaCodec.java	Java MediaCodec API
frameworks/base/media/java/android/media/MediaPlayer.java	Java MediaPlayer API

Native Services (Chapter 12)

File Path	Purpose
frameworks/native/services/inputflinger/InputDispatcher.cpp	Input event dispatch to windows
frameworks/native/services/inputflinger/InputReader.cpp	Input device event reading
frameworks/native/services/inputflinger/InputManager.cpp	Input subsystem coordinator
frameworks/native/services/sensorservice/SensorService.cpp	Sensor event multiplexing
frameworks/native/services/surfaceflinger/main_surfaceflinger.cpp	SurfaceFlinger process entry point
system/logging/logd/SerializedLogBuffer.cpp	System log ring buffer
system/memory/lmkd/lmkd.cpp	Low memory killer daemon
system/memory/lmkd/	Modern LMKD implementation
system/core/healthd/	Battery/health daemon
system/netd/server/NetdNativeService.cpp	Network daemon native service

system_server (Chapter 20)

File Path	Purpose
frameworks/base/services/java/com/android/server/SystemServer.java	system_server boot sequence
frameworks/base/services/core/java/com/android/server/SystemServiceManager.java	Service lifecycle manager
frameworks/base/services/core/java/com/android/server/am/ActivityManagerService.java	Activity Manager Service
frameworks/base/services/core/java/com/android/server/wm/WindowManagerService.java	Window Manager Service
frameworks/base/services/core/java/com/android/server/wm/ActivityTaskManagerService.java	Activity Task Manager Service
frameworks/base/services/core/java/com/android/server/pm/PackageManagerService.java	Package Manager Service
frameworks/base/services/core/java/com/android/server/power/PowerManagerService.java	Power management
frameworks/base/services/core/java/com/android/server/display/DisplayManagerService.java	Display management
frameworks/base/services/core/java/com/android/server/input/InputManagerService.java	Input management bridge
frameworks/base/core/java/com/android/internal/os/ZygoteInit.java	Zygote process initialization
frameworks/base/core/java/com/android/internal/os/ZygoteConnection.java	Zygote fork request handling
frameworks/base/core/java/com/android/internal/os/Zygote.java	Zygote fork mechanics
frameworks/base/core/java/com/android/internal/os/RuntimeInit.java	App process runtime initialization

Activity and Window Management (Chapter 22)

File Path	Purpose
frameworks/base/services/core/java/com/android/server/wm/Task.java	Task (back stack) container
frameworks/base/services/core/java/com/android/server/wm/ActivityRecord.java	Per-activity state tracking
frameworks/base/services/core/java/com/android/server/wm/ActivityStarter.java	Intent resolution and activity start
frameworks/base/services/core/java/com/android/server/wm/ActivityClientController.java	Activity lifecycle IPC handler
frameworks/base/services/core/java/com/android/server/wm/RootWindowContainer.java	Root of the window hierarchy
frameworks/base/services/core/java/com/android/server/wm/TaskFragment.java	Activity embedding container
frameworks/base/core/java/android/app/Activity.java	Application-side activity base class
frameworks/base/core/java/android/app/ActivityThread.java	Main thread of every Android app
frameworks/base/core/java/android/app/Instrumentation.java	Activity lifecycle instrumentation hooks

Window System (Chapter 23)

File Path	Purpose
frameworks/base/services/core/java/com/android/server/wm/WindowState.java	Per-window server state
frameworks/base/services/core/java/com/android/server/wm/WindowToken.java	Window grouping token
frameworks/base/services/core/java/com/android/server/wm/Session.java	Per-app WMS session
frameworks/base/services/core/java/com/android/server/wm/WindowSurfaceController.java	Window-to-Surface bridge
frameworks/base/services/core/java/com/android/server/wm/WindowAnimator.java	Window animation coordinator
frameworks/base/services/core/java/com/android/server/wm/InsetsStateController.java	System insets management
frameworks/base/services/core/java/com/android/server/wm/InsetsPolicy.java	Insets visibility policy
frameworks/base/core/java/android/view/WindowManager.java	Client window manager interface
frameworks/base/core/java/android/view/WindowManagerImpl.java	Window manager implementation
frameworks/base/core/java/android/view/View.java	Base UI component (measure/layout/draw)
frameworks/base/core/java/android/view/ViewGroup.java	Container for child views
frameworks/base/core/java/android/view/SurfaceView.java	Separate-surface view component

Display System (Chapter 24)

File Path	Purpose
frameworks/base/services/core/java/com/android/server/wm/DisplayContent.java	Per-display window container
frameworks/base/services/core/java/com/android/server/wm/DisplayPolicy.java	Per-display window policy (bars, cutouts)
frameworks/base/services/core/java/com/android/server/wm/DisplayRotation.java	Display rotation handling
frameworks/base/services/core/java/com/android/server/display/LogicalDisplay.java	Logical display abstraction
frameworks/base/services/core/java/com/android/server/display/DisplayDeviceInfo.java	Physical display properties
frameworks/base/services/core/java/com/android/server/display/LocalDisplayAdapter.java	Built-in display adapter

PackageManagerService (Chapter 26)

File Path	Purpose
frameworks/base/services/core/java/com/android/server/pm/PackageManagerService.java	Package management core
frameworks/base/services/core/java/com/android/server/pm/Settings.java	Package settings persistence
frameworks/base/services/core/java/com/android/server/pm/InstallPackageHelper.java	Package installation logic
frameworks/base/services/core/java/com/android/server/pm/PackageInstallerService.java	Installer session management
frameworks/base/services/core/java/com/android/server/pm/permission/PermissionManagerService.java	Runtime permission management
frameworks/base/services/core/java/com/android/server/pm/pkg/parsing/ParsingPackageUtils.java	APK manifest parsing
frameworks/base/services/core/java/com/android/server/pm/resolution/ComponentResolver.java	Intent filter resolution
frameworks/base/services/core/java/com/android/server/pm/dex/DexManager.java	DEX file optimization tracking
frameworks/base/core/java/android/content/pm/PackageManager.java	Public PackageManager API

ART Runtime (Chapter 18)

File Path	Purpose
art/runtime/runtime.cc	ART runtime initialization
art/runtime/class_linker.cc	Class loading and linking
art/runtime/interpreter/interpreter.cc	Bytecode interpreter entry point
art/runtime/jit/jit.cc	JIT compiler coordinator
art/runtime/jit/jit_code_cache.cc	JIT compiled code cache
art/runtime/gc/heap.cc	Garbage collector heap management
art/runtime/gc/collector/concurrent_copying.cc	Concurrent copying GC
art/runtime/thread.cc	Thread management
art/runtime/oat/oat_file.cc	OAT file format handling
art/runtime/mirror/object.h	Root object type for managed heap
art/runtime/mirror/class.h	Class metadata representation
art/compiler/optimizing/optimizing_compiler.cc	AOT/JIT optimizing compiler
art/compiler/optimizing/code_generator_arm64.cc	ARM64 code generation backend
art/compiler/optimizing/register_allocator_linear_scan.cc	Register allocation
art/dex2oat/dex2oat.cc	Ahead-of-time compilation tool
art/dex2oat/dex2oat_options.cc	DEX-to-OAT compilation options
art/libdexfile/dex/dex_file.h	DEX file format definitions
art/runtime/native_bridge_art_interface.cc	ART-side native bridge integration

Native Bridge and Binary Translation (Chapter 19)

File Path	Purpose
frameworks/libs/binary_translation/native_bridge/native_bridge.h	NativeBridgeCallbacks interface (v3-v8)
frameworks/libs/binary_translation/native_bridge/native_bridge.cc	Native bridge framework implementation
frameworks/libs/binary_translation/guest_loader/	Guest library loading and linking
frameworks/libs/binary_translation/guest_abi/	ABI conversion between host and guest
frameworks/libs/binary_translation/guest_state/	Guest CPU state abstraction
frameworks/libs/binary_translation/jni/	JNI trampoline generation
frameworks/libs/binary_translation/interpreter/	Guest instruction interpreter
frameworks/libs/binary_translation/decoder/	Guest instruction decoder
frameworks/libs/binary_translation/backend/	Host code generation backend
frameworks/libs/binary_translation/assembler/	Host instruction assembler
frameworks/libs/binary_translation/android_api/	Android framework proxy stubs
frameworks/libs/native_bridge_support/native_bridge_support.mk	Build synchronization for bridge support
art/libnativebridge/native_bridge.cc	System-side native bridge loading

CompanionDeviceManager and Virtual Devices (Chapter 51)

File Path	Purpose
frameworks/base/services/companion/java/com/android/server/companion/CompanionDeviceManagerService.java	CDM service
frameworks/base/services/companion/java/com/android/server/companion/virtual/VirtualDeviceManagerService.java	VDM service

SystemUI (Chapter 47)

File Path	Purpose
frameworks/base/packages/SystemUI/src/com/android/systemui/SystemUIApplication.java	SystemUI application entry
frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/phone/CentralSurfacesImpl.java	Status bar + notification shade
frameworks/base/packages/SystemUI/src/com/android/systemui/qs/QSPanelController.java	Quick Settings panel controller
frameworks/base/packages/SystemUI/src/com/android/systemui/recents/OverviewProxyService.java	Recents/overview proxy to Launcher
frameworks/base/packages/SystemUI/src/com/android/systemui/keyguard/KeyguardViewMediator.java	Lock screen coordinator
frameworks/base/packages/SystemUI/src/com/android/systemui/navigationbar/NavigationBar.java	Navigation bar
frameworks/base/packages/SystemUI/src/com/android/systemui/volume/VolumeDialogControllerImpl.java	Volume dialog logic
frameworks/base/packages/SystemUI/src/com/android/systemui/shade/NotificationPanelViewController.java	Notification panel controller

Launcher3 (Chapter 48)

File Path	Purpose
packages/apps/Launcher3/src/com/android/launcher3/Launcher.java	Main Launcher activity
packages/apps/Launcher3/src/com/android/launcher3/Workspace.java	Home screen workspace
packages/apps/Launcher3/src/com/android/launcher3/allapps/AllAppsContainerView.java	All-apps drawer
packages/apps/Launcher3/src/com/android/launcher3/model/LoaderTask.java	App list loading
packages/apps/Launcher3/src/com/android/launcher3/dragndrop/DragController.java	Drag-and-drop coordinator
packages/apps/Launcher3/quickstep/src/com/android/quickstep/RecentsActivity.java	Recents (overview) activity
packages/apps/Launcher3/quickstep/src/com/android/quickstep/TouchInteractionService.java	Gesture navigation service

Settings App (Chapter 49)

File Path	Purpose
packages/apps/Settings/src/com/android/settings/Settings.java	Main Settings activity
packages/apps/Settings/src/com/android/settings/dashboard/DashboardFragment.java	Preference dashboard base
packages/apps/Settings/src/com/android/settings/search/SearchFeatureProvider.java	Settings search
packages/apps/Settings/src/com/android/settings/biometrics/	Biometrics enrollment

Emulator (Chapter 58)

File Path	Purpose
external/qemu/android/emulation/	Emulator core emulation logic
external/qemu/android/android-emu/android/emulation/	Emulator hardware emulation
device/generic/goldfish/	Goldfish virtual device definitions
device/google/cuttlefish/	Cuttlefish virtual device definitions
device/google/cuttlefish/host/commands/run_cvd/	Cuttlefish launcher
external/crosvm/	CrosVM virtual machine monitor
external/qemu/android/android-grpc/	Emulator gRPC control interface

Architecture Support (Chapter 57)

File Path	Purpose
build/soong/cc/config/arm64_device.go	ARM64 toolchain: arch variants, CPU tuning, PAC/BTI
build/soong/cc/config/arm_device.go	ARM 32-bit toolchain: Thumb/ARM, errata workarounds
build/soong/cc/config/x86_device.go	x86 32-bit toolchain: SSE, stack realignment
build/soong/cc/config/x86_64_device.go	x86_64 toolchain: microarchitecture variants
build/soong/cc/config/riscv64_device.go	RISC-V 64-bit toolchain: ISA extensions
build/soong/cc/config/toolchain.go	Toolchain interface and factory registry
build/soong/cc/config/global.go	Global compiler/linker flags for all architectures
build/soong/cc/config/bionic.go	Bionic CRT objects and default shared libraries
build/soong/cc/config/clang.go	Clang unknown-flags filter
build/soong/android/arch.go	Arch struct, ArchType, multilib decode logic
bionic/libc/arch-arm64/ifuncs.cpp	ARM64 ifunc dispatchers (MTE, SVE selection)
art/runtime/arch/riscv64/instruction_set_features_riscv64.h	ART RISC-V feature detection
art/runtime/arch/arm64/instruction_set_features_arm64.h	ART ARM64 feature bitmap and errata

Security (Chapter 40)

File Path	Purpose
system/sepolicy/public/	Public SELinux policy definitions
system/sepolicy/private/	Private (platform) SELinux policy
system/sepolicy/vendor/	Vendor SELinux policy
system/security/keystore2/	Keystore2 service (Rust)
system/security/identity/	Identity credential service
external/selinux/	SELinux userspace tools
system/extras/verity/	dm-verity tools
system/core/fs_mgr/libfs_avb/	AVB (Android Verified Boot) integration
frameworks/base/services/core/java/com/android/server/biometrics/	Biometric authentication
frameworks/base/keystore/java/android/security/keystore2/	Keystore Java API

Virtualization Framework (Chapter 54)

File Path	Purpose
packages/modules/Virtualization/	Android Virtualization Framework top-level
packages/modules/Virtualization/android/virtualizationservice/	VM lifecycle management
packages/modules/Virtualization/build/microdroid/	Minimal guest OS (Microdroid) build files
packages/modules/Virtualization/guest/pvmfw/	Protected VM firmware
packages/modules/Virtualization/libs/libvm_payload/	Guest payload interface

Testing (Chapter 55)

File Path	Purpose
test/vts/	Vendor Test Suite top-level
cts/tests/	Compatibility Test Suite tests
tools/tradefederation/core/	Trade Federation test harness core
tools/tradefederation/core/src/com/android/tradefed/	TradeFed framework classes
platform_testing/tests/	Platform integration tests
frameworks/base/core/tests/	Framework core unit tests
frameworks/base/test-runner/	Android test runner framework

Mainline Modules (Chapter 52)

File Path	Purpose
packages/modules/Wifi/	Wi-Fi Mainline module
packages/modules/Bluetooth/	Bluetooth Mainline module
packages/modules/NetworkStack/	Network stack Mainline module
packages/modules/Permission/	Permission controller module
packages/modules/MediaProvider/	Media storage provider module
packages/modules/adb/	ADB Mainline module
packages/modules/common/	Shared Mainline module infrastructure
system/apex/apexd/	APEX daemon (module installer)
system/apex/apexd/apexd.cpp	APEX installation and activation
system/apex/libs/libapexutil/	APEX utility library

Automotive, TV, and Wear (Chapter 60)

File Path	Purpose
packages/services/Car/	Android Automotive service layer
packages/services/Car/service/src/com/android/car/CarServiceImpl.java	Automotive car service
packages/apps/Car/Launcher/	Automotive launcher
device/google/atv/	Android TV device configuration
packages/apps/TvSettings/	TV settings application
prebuilts/sdk/opt/wear/	Wear OS SDK prebuilts

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Note: Paths may shift between AOSP branches. The paths above target AOSP main as of early 2026. Use find or cs.android.com to verify against your checked-out branch.