A2 (operating system)

A2 (formerly Active Object System (AOS) and later Bluebottle) is an object-oriented operating system developed at ETH Zurich. It includes features such as garbage-collected memory management and a zooming user interface.^[2]

A2

Developer	ETH Zurich
OS family	Oberon
Working state	Current
Source model	Open source
Initial release	2002; 23 years ago (2002)
Repository	gitlab.inf.ethz.ch/felixf/oberon
Platforms	IA-32, x86-64, ARM, Cell
Kernel type	Object-oriented
License	BSD-like ETH A2 License[1]
Official website	gitlab.inf.ethz.ch/felixf/oberon

History

A2 is a successor to Native Oberon, the x86 PC version of Niklaus Wirth's operating system Oberon.^[3][2][4] It supports multiprocessing computers, and provides soft real-time computing operation. It is entirely written in Active Oberon.

According to ETH Zurich’s documentation, A2's architecture supports the development of systems using active objects that operate directly on hardware, without relying on an interpreter or virtual machine.In the Active Oberon model used by A2, active objects combine conventional object-oriented structures with independently executing threads, allowing for parallelism within the operating system. In the Active Oberon implementation, an active object may include activity of its own, and of its ancestor objects.

The Oberon A2 desktop screen with the installer application open, along with a calendar and clock. (Using the default style)

The A2 system is written in a type-safe language with automatic memory management, and its design emphasizes modularity and simplicity, according to project documentation, combined with a set of primitives (at the level of programming language and runtime system) for synchronizing access to the internal properties of objects in competing execution contexts.

Above the kernel layer, A2 provides a set of modules providing unified abstractions for devices and services, such as file systems, user interfaces, computer network connections, media codecs, etc.

User interface

Bluebottle introduced a zooming user interface (ZUI), replacing the text-based interface of the original Oberon OS. The ZUI combines graphical elements with command-driven interaction. Like Oberon, though, its user interface supports a point and click interface metaphor to execute commands directly from text, similar to clicking hyperlinks in a web browser.

Reception and Adoption

There is limited independent coverage of A2 in mainstream computing literature. While primarily used in academic and experimental contexts, A2 and its predecessors have been cited in publications exploring lightweight operating system design, type safety, and concurrency models.

As of 2025, A2 remains under development, primarily by ETH Zurich and affiliated contributors.

See also

• Active Oberon
• Oberon (operating system)
• Oberon (programming language)
• Oberon-2 programming language
• Minimalism (computing)