| OS family | Multiserver operating systems |
|---|---|
| Source model | Open source |
| Latest stable release | 0.4.3 / March 26, 2011 |
| Supported platforms | IA-32, AMD64, IA-64, ARM, MIPS, PowerPC, SPARC V9 |
| Kernel type | Microkernel |
| License | BSD |
| Official website | www.helenos.org |
HelenOS is an operating system based on a multiserver microkernel design. The source code of HelenOS is published under a BSD License.
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HelenOS is based on a preemptible microkernel called SPARTAN. The microkernel handles multitasking, memory management and inter-process communication. It also provides kernel-based threads and supports symmetric multiprocessing.
Each process (called task) can contain several threads (preemptively scheduled by the kernel) which, in turn, can contain several fibers scheduled cooperatively in user space. Device and file-system drivers, as well as other system services, are implemented by a collection of user-space tasks (servers), creating thus the multiserver nature of HelenOS.
Tasks communicate via HelenOS IPC, which is connection-oriented and asynchronous. It can be used to send small fixed-size messages, blocks of bytes or to negotiate sharing of memory. Messages can be forwarded without copying bulk data or mapping memory to the address space of middle-men tasks.
HelenOS is partly hobbyist, partly academic, being developed mainly by staff and former and contemporary students of the Faculty of Mathematics and Physics at Charles University in Prague, with help from other contributors around the world.
The source code of HelenOS is published under the BSD licence, while some third-party components are available under the GNU General Public License. Both of these licences are free software licences, making HelenOS free software.
HelenOS runs on several different CPU architectures including ARM, x86-64, IA-32, IA-64 (Itanium), MIPS, PowerPC (32-bit only), and SPARC V9. At some point in time, various versions of HelenOS ran on real hardware from each architecture (as opposed to running only in a simulator of that architecture).
Support for peripheral devices is mostly limited to keyboards, display devices and simulated disks.
HelenOS is being used for research in the area of software components and verification by the Department of Distributed and Dependable Systems, Charles University, Prague. Besides of that, HelenOS has been used by students as a platform for software projects and master theses.