<s>
HelenOS	B-Operating_System
is	O
an	O
operating	B-General_Concept
system	I-General_Concept
based	O
on	O
a	O
multiserver	O
microkernel	B-Operating_System
design	O
.	O
</s>
<s>
The	O
source	O
code	O
of	O
HelenOS	B-Operating_System
is	O
written	O
in	O
C	B-Language
and	O
published	O
under	O
the	O
BSD-3-Clause	B-Operating_System
license	O
.	O
</s>
<s>
The	O
system	O
is	O
described	O
as	O
a	O
“	O
research	O
development	O
open-source	B-Application
operating	B-General_Concept
system	I-General_Concept
”	O
.	O
</s>
<s>
The	O
microkernel	B-Operating_System
handles	O
multitasking	B-Operating_System
,	O
memory	O
management	O
and	O
inter-process	B-Operating_System
communication	I-Operating_System
.	O
</s>
<s>
It	O
also	O
provides	O
kernel-based	O
threads	B-Operating_System
and	O
supports	O
symmetric	B-Operating_System
multiprocessing	I-Operating_System
.	O
</s>
<s>
Typical	O
to	O
microkernel	B-Operating_System
design	O
,	O
file	O
systems	O
,	O
networking	O
,	O
device	O
drivers	O
and	O
graphical	O
user	O
interface	O
are	O
isolated	O
from	O
each	O
other	O
into	O
a	O
collection	O
of	O
user	O
space	O
components	O
that	O
communicate	O
via	O
a	O
message	O
bus	O
.	O
</s>
<s>
Each	O
process	O
(	O
called	O
task	O
)	O
can	O
contain	O
several	O
threads	B-Operating_System
(	O
preemptively	O
scheduled	O
by	O
the	O
kernel	O
)	O
which	O
,	O
in	O
turn	O
,	O
can	O
contain	O
several	O
fibers	B-Operating_System
scheduled	O
cooperatively	O
in	O
user	O
space	O
.	O
</s>
<s>
Device	O
and	O
file-system	O
drivers	O
,	O
as	O
well	O
as	O
other	O
system	O
services	O
,	O
are	O
implemented	O
by	O
a	O
collection	O
of	O
user-space	O
tasks	O
(	O
servers	O
)	O
,	O
creating	O
thus	O
the	O
multiserver	O
nature	O
of	O
HelenOS	B-Operating_System
.	O
</s>
<s>
Tasks	O
communicate	O
via	O
HelenOS	B-Operating_System
IPC	O
,	O
which	O
is	O
connection	B-Protocol
oriented	I-Protocol
and	O
asynchronous	O
.	O
</s>
<s>
HelenOS	B-Operating_System
development	O
is	O
community-driven	O
.	O
</s>
<s>
In	O
2011	O
,	O
2012	O
and	O
2014	O
,	O
HelenOS	B-Operating_System
participated	O
in	O
the	O
Google	B-Application
Summer	I-Application
of	I-Application
Code	I-Application
as	O
a	O
mentoring	O
organization	O
.	O
</s>
<s>
In	O
2013	O
,	O
the	O
project	O
was	O
a	O
mentoring	O
organization	O
in	O
the	O
ESA	O
Summer	B-Application
of	I-Application
Code	I-Application
in	O
Space	O
2013	O
program	O
.	O
</s>
<s>
The	O
source	O
code	O
of	O
HelenOS	B-Operating_System
is	O
published	O
under	O
the	O
BSD-3-Clause	B-Operating_System
license	O
,	O
while	O
some	O
third-party	O
components	O
are	O
available	O
under	O
the	O
GNU	B-License
General	I-License
Public	I-License
License	I-License
.	O
</s>
<s>
Both	O
of	O
these	O
licences	O
are	O
free	B-License
software	I-License
licenses	I-License
,	O
making	O
HelenOS	B-Operating_System
free	B-Application
software	I-Application
.	O
</s>
<s>
HelenOS	B-Operating_System
runs	O
on	O
several	O
different	O
CPU	B-General_Concept
architectures	I-General_Concept
including	O
ARM	B-Architecture
,	O
x86-64	B-Device
,	O
IA-32	B-Device
,	O
IA-64	B-General_Concept
(	O
Itanium	B-General_Concept
)	O
,	O
MIPS	B-Device
,	O
PowerPC	B-Architecture
(	O
32-bit	O
only	O
)	O
,	O
SPARC	B-Architecture
V9	I-Architecture
and	O
RISC-V	B-Device
.	O
At	O
some	O
point	O
in	O
time	O
,	O
various	O
versions	O
of	O
HelenOS	B-Operating_System
ran	O
on	O
real	O
hardware	O
from	O
each	O
architecture	O
(	O
as	O
opposed	O
to	O
running	O
only	O
in	O
a	O
simulator	O
of	O
that	O
architecture	O
)	O
.	O
</s>
<s>
HelenOS	B-Operating_System
supports	O
PATA	B-Protocol
,	O
SATA	O
,	O
USB	B-Architecture
mass	I-Architecture
storage	I-Architecture
,	O
USB	O
HID	O
,	O
an	O
Atheros	O
USB	O
WiFi	O
dongle	O
,	O
several	O
Ethernet	O
network	O
cards	O
,	O
SoundBlaster	B-Device
16	I-Device
and	O
Intel	O
HDA	O
audio	O
devices	O
,	O
serial	O
ports	O
,	O
keyboards	O
,	O
mice	O
and	O
framebuffers	O
.	O
</s>
<s>
HelenOS	B-Operating_System
is	O
being	O
used	O
for	O
research	O
in	O
the	O
area	O
of	O
software	O
components	O
and	O
verification	O
by	O
the	O
Department	O
of	O
Distributed	O
and	O
Dependable	O
Systems	O
,	O
Charles	O
University	O
,	O
Prague	O
.	O
</s>
<s>
Besides	O
that	O
,	O
HelenOS	B-Operating_System
has	O
been	O
used	O
by	O
students	O
as	O
a	O
platform	O
for	O
software	O
projects	O
and	O
master	O
theses	O
.	O
</s>
