Many users mistakenly believe that Android is a monolithic app created in a single programming language. However, the actual architecture of this operating system is a complex multi-layered pie, with each layer performing its own unique tasks and written in the tool most suitable for this purpose. The answer to the question of what Android is written in cannot be unambiguous, since the system combines the power of low-level code and the flexibility of high-level languages.
If you look under the hood of the most popular mobile OS in the world, you can find an amazing combination of time-tested technologies and modern solutions. From the kernel that controls the hardware to the interface with which the user interacts, different approaches are used everywhere. Understanding this structure is necessary for developers to create effective applications, and for enthusiasts to gain a deep understanding of how their gadgets work.
In this article, we will analyze in detail each layer of the software architecture so that you can get a complete picture of how exactly the app code “communicates” with the physical components of your smartphone. We will find out why Google developers chose this hybrid approach and what advantages it provides.
System foundation: Linux kernel and low-level code
The basis of the entire Android operating system is the kernel Linux. This is not just a metaphor, but a technical fact: it is Linux that provides basic interaction with the device hardware. The kernel is written primarily in language C using assembler for critical sections of the code that require direct work with the processor. It is this layer that is responsible for memory management, task scheduling, security and network protocols.
The use of the C language in the kernel is driven by the need for maximum performance and minimal resource overhead. When you run a heavy game or camera, it is the low-level code that allocates CPU and RAM resources so that the device does not freeze. In addition, Linux provides the necessary security mechanisms, isolating processes from each other at the kernel level.
⚠️ Attention: Modifying the Linux kernel (creating custom kernels) without in-depth knowledge can lead to unstable operation of the device or complete loss of warranty, as this affects fundamental security settings.
Android developers make specific changes to the standard Linux kernel, adding drivers for unique hardware mobile devices such as communication modules, touch screens and accelerometers. These drivers are also written in C, since they need to work as closely as possible to the hardware.
Knowledge of the C language is useful for understanding how Android manages memory, but it is not required to create regular applications.
Native libraries and the ART runtime
Above the Linux kernel there is a layer of native libraries, which are also written primarily on C i C++. These libraries provide functionality to the upper levels of the system. This includes graphics rendering engines (such as Skia), multimedia codecs for video and audio playback, and a browser engine. The speed of operation of these components is critical, so the use of compiled languages is the only solution here.
The runtime environment deserves special attention. Android Runtime (ART). Unlike the old Dalvik system, ART uses Ahead-of-Time (AOT) compilation. This means that the application code is compiled into machine code at installation time, rather than at startup time. Although the virtual machine itself is written in C++, it is designed to execute bytecode that the system can understand.
The HAL (Hardware Abstraction Layer) serves as a bridge between software and hardware. It is also written in C/C++ and provides standard interfaces for the upper levels of the system, hiding the specifics of driver implementation from device manufacturers.
What is the difference between C and C++ in Android?
The C language is used where maximum simplicity and speed of working with memory (kernel) is needed, and C++ is used to create complex object-oriented libraries that require higher abstraction, but maintaining high performance.
Java and Kotlin: Framework-level languages
When we talk about what Android applications are written in, we primarily mean the languages Java and Kotlin. The entire Android framework that application developers interact with is written in Java. This includes window managers, notification systems, file management and networking. It is this layer that provides the APIs that programmers use.
Kotlin, which has become the official language of choice for Android development, is fully compatible with Java. It runs on top of the same virtual machine and uses the same libraries. The only difference is the syntactic brevity and modern language features that make life easier for developers. Both languages are compiled into bytecode (DEX files), which is then executed by the ART environment.
It is important to note that Java code in Android does not work directly with hardware. All requests to hardware (camera, GPS, Bluetooth) go through JNI (Java Native Interface) - an interface that allows Java code to call native functions written in C/C++. This provides the necessary balance between the security of high-level code and the performance of low-level code.
Comparison of languages in the Android architecture
To better understand the distribution of roles, consider a table demonstrating what tasks are solved using different programming languages in the Android ecosystem. This will help organize information about where exactly each of the tools is used.
| System level | Main language | Tasks | Component example |
|---|---|---|---|
| Kernel | C, Assembler | Memory management, drivers, security | Linux Kernel, DRM |
| Native libraries | C, C++ | Graphics, multimedia, WebGL | Skia, WebKit, OpenGL |
| Runtime | C, C++ | Compilation, management streams | ART, Bionic Libc |
| Framework | Java, Kotlin | API of applications, UI, services | Activity Manager, View System |
| Applications | Java, Kotlin | User interface, logic | Telegram, WhatsApp, Camera |
As can be seen from the table, The lower levels of the system, responsible for the hardware, are written in C/C++, while the upper levels, with which the user and application developer interact, use Java and Kotlin.. This architecture allows the system to be both fast and secure.
Separation of responsibilities allows you to update the upper levels (for example, release a new version of Android with a new interface) without having to rewrite device drivers for each new one smartphone. This speeds up the adaptation of the system to new devices.
Build tools and Gradle
The process of turning source code in Java and Kotlin into a working application occurs using the build system Gradle. This tool, written in Groovy and Kotlin, manages dependencies, asset compilation, and packaging of the resulting APK or AAB file. Although Gradle itself is not part of the Android runtime, it is critical to the development ecosystem.
It is Gradle that provides communication between code in different languages. It collects Java classes, native libraries (.so files) and resources into a single package. Without this tool, creating complex applications using native code via JNI would be extremely difficult.
☑️ What you need to know about Android languages
The future of languages in the Android ecosystem
The evolution of programming languages in Android continues. Google is actively introducing support Kotlin Multiplatform, which allows you to share code between Android, iOS and web versions. The language is also gaining popularity Rust, which is gradually beginning to replace C/C++ in some system components due to its memory safety guarantees, which avoids an entire class of vulnerabilities.
The introduction of Rust in Android is a strategic step to improve system security. Since memory management errors in C/C++ are a common cause of security bugs, switching to Rust in new native components (for example, Bluetooth reverse engineer) is already showing results.
⚠️ Attention: Information about the introduction of new languages (Rust) and architecture changes may be updated with the release of new versions of Android. It's always worth checking the official documentation for developers for current data.
Despite the emergence of new tools, Java and Kotlin will remain the main languages for creating custom applications for many years due to the huge base of existing code and ecosystem.
Android is a hybrid: a core in C, libraries in C++, a framework in Java/Kotlin, which provides a balance of speed and ease of development.
Frequently asked questions (FAQ)
Is it possible to write the entire Android in Java?
Theoretically You can create an operating system entirely in Java, but it will run much slower and consume more resources, since Java does not have direct access to the hardware and requires a virtual machine. A C kernel is necessary for efficient hardware management.
Why did Google choose Kotlin over Java?
Kotlin was chosen as the language of choice due to its more concise syntax, better Null-safety (protection against null values) and full compatibility with existing Java libraries, which made it possible to switch to a new language without rewriting the entire systems.
Do you need to know C++ to develop for Android?
To create most standard applications, knowledge of C++ is not required. However, it is necessary for developing high-performance games, rendering engines, or when working with existing native libraries through JNI.
What is JNI in the context of Android?
The Java Native Interface (JNI) is a mechanism that allows code running in the Java Virtual Machine (Dalvik/ART) to interact with native applications and libraries written in other languages. languages such as C, C++ and assembly.