HelenOS is an operating system based on a multiserver microkernel design. The source code of HelenOS is written in C and published under the

BSD-3-Clause BSD licenses are a family of permissive free software licenses, imposing minimal restrictions on the use and distribution of covered software. This is in contrast to copyleft licenses, which have share-alike requirements. The original BSD lic ...

license. The system is described as a “research development open-source operating system”.

Technical overview

The microkernel handles multitasking, memory management and

inter-process communication In computer science, inter-process communication or interprocess communication (IPC) refers specifically to the mechanisms an operating system provides to allow the processes to manage shared data. Typically, applications can use IPC, categori ...

. It also provides kernel-based

thread Thread may refer to: Objects * Thread (yarn), a kind of thin yarn used for sewing ** Thread (unit of measurement), a cotton yarn measure * Screw thread, a helical ridge on a cylindrical fastener Arts and entertainment * ''Thread'' (film), 2016 ...

s and supports

symmetric multiprocessing Symmetric multiprocessing or shared-memory multiprocessing (SMP) involves a multiprocessor computer hardware and software architecture where two or more identical processors are connected to a single, shared main memory, have full access to all ...

. Typical to microkernel design, file systems, networking, device drivers and graphical user interface are isolated from each other into a collection of user space components that communicate via a message bus. Each process (called ''task'') can contain several

threads Thread may refer to: Objects * Thread (yarn), a kind of thin yarn used for sewing ** Thread (unit of measurement), a cotton yarn measure * Screw thread, a helical ridge on a cylindrical fastener Arts and entertainment * ''Thread'' (film), 2016 ...

(preemptively scheduled by the kernel) which, in turn, can contain several

fibers Fiber or fibre (from la, fibra, links=no) is a natural or artificial substance that is significantly longer than it is wide. Fibers are often used in the manufacture of other materials. The strongest engineering materials often incorporate ...

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 Asynchrony is the state of not being in synchronization. Asynchrony or asynchronous may refer to: Electronics and computing * Asynchrony (computer programming), the occurrence of events independent of the main program flow, and ways to deal with ...

. 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.

Development

HelenOS development is community-driven. The developer community consists of a small core team, mainly staff and former and contemporary students of the Faculty of Mathematics and Physics at Charles University in Prague, and a number of contributors around the world. In 2011, 2012 and 2014, HelenOS participated in the Google Summer of Code as a mentoring organization. In 2013, the project was a mentoring organization in the ESA Summer of Code in Space 2013 program. The source code of HelenOS is published under the

license, while some third-party components are available under the GNU General Public License. Both of these licences are free software licenses, making HelenOS free software.

Hardware support

HelenOS runs on several different CPU architectures including ARM, x86-64, IA-32, IA-64 ( Itanium), MIPS,

PowerPC PowerPC (with the backronym Performance Optimization With Enhanced RISC – Performance Computing, sometimes abbreviated as PPC) is a reduced instruction set computer (RISC) instruction set architecture (ISA) created by the 1991 Apple Inc., App ...

(32-bit only), SPARC V9 and RISC-V. 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). HelenOS supports PATA, SATA, USB mass storage, USB HID, an Atheros USB WiFi dongle, several Ethernet network cards, SoundBlaster 16 and

Intel HDA Intel High Definition Audio (IHDA) (also called HD Audio or development codename Azalia) is a specification for the audio sub-system of personal computers. It was released by Intel in 2004 as the successor to their AC'97 PC audio standard. Featur ...

audio devices, serial ports, keyboards, mice and framebuffers.

Research and academic use

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 that, HelenOS has been used by students as a platform for software projects and master theses.Defended HelenOS theses at Faculty of Mathematics and Physics, Charles University in Prague
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References

External links

HelenOS home page

HelenOS theses, papers and documentation.

HelenOS
on GitHub {{Hobbyist operating systems Free software operating systems Microkernel-based operating systems MIPS operating systems X86 operating systems Microkernels Software using the BSD license Hobbyist operating systems