# OpenHarmony - [Introduction](#section1270210396435) - [Technical Architecture](#section2502124574318) - [Technical Features](#section12212842173518) - [OS Types](#section145241459142416) - [Subsystems](#section25831825174419) - [Getting Started](#section44681652104210) - [Code Repository Addresses](#section107651249181914) - [OpenHarmony Documentation](#section21031470109) - [Source Code Downloading](#section39011923144212) - [How to Participate](#section19611528174215) - [License Agreement](#section1245517472115) - [Contact Info](#section61728335424) ## Introduction OpenHarmony is an open-source project incubated and operated by the OpenAtom Foundation. It is an open-source operating system with a framework and platform applicable to smart devices in all scenarios of a fully-connected world. It aims to promote the development of the Internet of Everything (IoE). ## Technical Architecture OpenHarmony is designed with a layered architecture, which from bottom to top, consists of the kernel layer, system service layer, framework layer, and application layer. System functions are expanded by levels, from system to subsystem, and further to module. In a multi-device deployment scenario, unnecessary modules can be excluded from the system as required. The following figure shows the technical architecture of OpenHarmony. ![](https://gitee.com/openharmony/docs/raw/master/en/figures/1.png) **Kernel Layer** - Kernel subsystem: OpenHarmony uses a multi-kernel design \(Linux or LiteOS\) so that different kernels can be selected for devices with different resource limitations. The kernel abstraction layer \(KAL\) hides differences in kernel implementations and provides the upper layer with basic kernel capabilities, including process and thread management, memory management, file system, network management, and peripheral management. - Driver subsystem: Hardware Driver Foundation \(HDF\) lays the foundation for an open OpenHarmony hardware ecosystem. It allows for unified access from peripheral devices and provides foundation for driver development and management. **System Service Layer** The system service layer provides a complete set of capabilities essential for OpenHarmony to offer services for apps through the framework layer. This layer consists of the following parts: - Basic system capability subsystem set: Implements distributed app running, scheduling, and migration across OpenHarmony devices. This subsystem set provides the following basic capabilities: Intelligent Soft Bus, distributed data management, Distributed Scheduler, Utils, multimodal input, graphics, security, and AI. - Basic software service subsystem set: Provides OpenHarmony with common universal software services, including common event and notification, telephony, multimedia, and Design For X \(DFX\). - Enhanced software service subsystem set: Provides OpenHarmony with differentiated enhanced software services, including those dedicated to smart TVs, wearables, IoT devices, and more. - Hardware service subsystem set: Provides OpenHarmony with hardware services, including location, biometric recognition, as well as those dedicated to wearables and IoT devices. The basic software service, enhanced software service, and hardware service subsystem sets can be modified by the subsystems, and each subsystem can be modified by various functions, depending on the deployment scenario for a particular device form. **Framework layer** This layer provides with what you need to develop OpenHarmony apps: application framework and ability framework, specific to multiple languages \(like C, C++, and JS\), JS UI framework, as well as multi-language APIs for hardware and software services. The APIs designed for different OpenHarmony devices can be modified based on various system components. **Application layer** This layer consists of system apps and third-party apps. Each OpenHarmony app is powered by one or more Feature Abilities \(FAs\) or Particle Abilities \(PAs\). An FA provides a UI for user interaction. A PA has no UI and provides background task processing as well as data access. Apps developed based on FAs and PAs provide specific service characteristics and enable cross-device scheduling and distribution, delighting users with consistent and efficient experience. ## Technical Features 1. **Hardware collaboration and resource sharing** This feature is implemented through the following modules: - Intelligent Soft Bus Intelligent Soft Bus is a unified base for seamless interconnection among devices. It powers OpenHarmony with distributed communication capabilities to quickly discover and connect devices, and efficiently transmit data. - Distributed data management Intelligent Soft Bus manages apps and user data distributed across different devices. Under such management, user data is no longer bound to a single physical device, and service logic is decoupled from storage. As your apps are running across devices, their data is seamlessly transmitted from one device to another, creating a foundation for a user experience that is smooth and consistent. - Distributed Scheduler The Distributed Scheduler is designed based on technical features such as Intelligent Soft Bus, distributed data management, and distributed profile. It builds a unified distributed service management mechanism \(including service discovery, synchronization, registration, and invocation\), and supports remote startup, remote invocation, binding/unbinding, and migration of apps across devices. This way, your app can select the most suitable device to perform distributed tasks based on the capabilities, locations, running status, and resource usage of different devices, as well as user habits and intentions. - Device virtualization A distributed device virtualization platform enables cross-device resource convergence, device management, and data processing so that virtual peripherals can function as capability extensions of smartphones to form a super virtual terminal. 2. **One-time development for multi-device deployment** OpenHarmony provides you with the user application, ability, and UI frameworks. With these frameworks, you can develop your apps once, and then flexibly deploy them across a broad range of different devices. Consistent APIs ensure the operational compatibility of apps across devices. - Adaptation of device capabilities \(including CPU, memory, peripheral, and software resources\) can be previewed. - Resources can be scheduled based on the compatibility between user apps and the software platform. 3. **A unified OS for flexible deployment** OpenHarmony enables hardware resources to be scaled with its component-based and small-scale designs. It can be deployed on demand for a diverse range of devices, including ARM, RISC-V, and x86 architectures, and providing RAM volumes ranging from hundreds of KiB to GiB. ## OS Types OpenHarmony supports the following types: - Mini system A mini system runs on the devices whose memory is greater than or equal to 128 KiB and that are equipped with MCU processors such as Arm Cortex-M and 32-bit RISC-V. This system provides multiple lightweight network protocols and graphics frameworks, and a wide range of read/write components for the IoT bus. Typical products include connection modules, sensors, and wearables for smart home. - Small system A small system runs on the devices whose memory is greater than or equal to 1 MiB and that are equipped with application processors such as Arm Cortex-A. This system provides higher security capabilities, standard graphics frameworks, and video encoding and decoding capabilities. Typical products include smart home IP cameras, electronic cat eyes, and routers, and event data recorders \(EDRs\) for smart travel. - Standard system A standard system runs on the devices whose memory is greater than or equal to 128 MiB and that are equipped with application processors such as ARM Cortex-A. This system provides a complete application framework supporting the enhanced interaction, 3D GPU, hardware composer, diverse components, and rich animations. This system applies to high-end refrigerator displays. ## Subsystems You need to understand the following basic concepts related to OpenHarmony: - Subsystem OpenHarmony is designed with a layered architecture, which from bottom to top consists of the kernel layer, system service layer, framework layer, and application layer. System functions are expanded by levels, from system to subsystem, and further to module. In a multi-device deployment scenario, unnecessary modules can be excluded from the system as required. A subsystem is a logical concept and is a flexible combination of functions. - Module A module is a reusable software binary unit that contains source code, configuration files, resource files, and build scripts. A module can be built independently, integrated in binary mode, and then tested independently. The following table describes the subsystems of OpenHarmony. For details about the readme files of these subsystems, see [https://gitee.com/openharmony/docs/tree/master/en/readme](https://gitee.com/openharmony/docs/tree/master/en/readme).