<s>
Rodos	B-Operating_System
(	O
Realtime	O
Onboard	O
Dependable	O
Operating	O
System	O
)	O
is	O
a	O
real-time	B-Operating_System
operating	I-Operating_System
system	I-Operating_System
for	O
embedded	B-Architecture
systems	I-Architecture
and	O
was	O
designed	O
for	O
application	O
domains	O
demanding	O
high	O
dependability	O
.	O
</s>
<s>
Rodos	B-Operating_System
was	O
developed	O
at	O
the	O
German	O
Aerospace	O
Center	O
and	O
has	O
its	O
roots	O
in	O
the	O
operating	O
system	O
BOSS	B-Application
.	O
</s>
<s>
Rodos	B-Operating_System
is	O
further	O
enhanced	O
and	O
extended	O
at	O
the	O
German	O
Aerospace	O
Center	O
as	O
well	O
as	O
the	O
department	O
for	O
aerospace	O
information	O
technology	O
at	O
the	O
University	O
of	O
Würzburg	O
.	O
</s>
<s>
An	O
important	O
aspect	O
of	O
Rodos	B-Operating_System
is	O
its	O
integrated	O
real	O
time	O
middleware	O
.	O
</s>
<s>
Rodos	B-Operating_System
was	O
implemented	O
as	O
a	O
software	O
framework	O
in	O
C++	B-Language
with	O
an	O
object	B-Language
oriented	I-Language
application	O
interface	O
(	O
API	O
)	O
.	O
</s>
<s>
it	O
is	O
organized	O
in	O
layers	O
:	O
The	O
lowest	O
layer	O
(	O
1	O
)	O
is	O
responsible	O
for	O
control	O
of	O
the	O
embedded	B-Architecture
system	I-Architecture
hardware	O
(	O
HAL	O
:	O
Hardware	O
abstraction	O
layer	O
)	O
.	O
</s>
<s>
The	O
next	O
layer	O
(	O
2	O
)	O
kernel	O
:	O
administrates	O
the	O
local	O
resources	O
,	O
threads	B-Operating_System
and	O
time	O
.	O
</s>
<s>
As	O
mentioned	O
before	O
,	O
the	O
original	O
purpose	O
of	O
Rodos	B-Operating_System
was	O
to	O
control	O
satellites	O
.	O
</s>
<s>
Rodos	B-Operating_System
enables	O
the	O
user	O
to	O
write	O
realtime	O
applications	O
for	O
different	O
architectures	B-General_Concept
in	O
an	O
easy	O
,	O
efficient	O
way	O
.	O
</s>
<s>
During	O
the	O
development	O
special	O
attention	O
was	O
paid	O
to	O
implement	O
the	O
various	O
features	O
of	O
Rodos	B-Operating_System
in	O
a	O
simple	O
,	O
nevertheless	O
robust	O
way	O
.	O
</s>
<s>
Rodos	B-Operating_System
supports	O
typical	O
features	O
of	O
realtime	O
operatingsystems	O
,	O
like	O
threads	B-Operating_System
and	O
semaphores	B-Operating_System
.	O
</s>
<s>
Among	O
other	O
features	O
Rodos	B-Operating_System
offers	O
:	O
</s>
<s>
object-oriented	B-Language
C++	B-Language
interfaces	O
,	O
</s>
<s>
real	O
time	O
priority	O
controlled	O
preemptive	B-Operating_System
multithreading	I-Operating_System
,	O
</s>
<s>
thread	B-Operating_System
safe	O
communication	O
and	O
synchronisation	O
,	O
</s>
<s>
The	O
common	O
Hello	O
world	O
example	O
program	O
looks	O
like	O
this	O
in	O
Rodos	B-Operating_System
.	O
</s>
<s>
The	O
class	O
Thread	B-Operating_System
is	O
extended	O
by	O
a	O
custom	O
run( )	O
procedure	O
,	O
which	O
writes	O
Hello	O
World	O
to	O
the	O
standard	O
output	O
with	O
PRINTF	O
.	O
</s>
<s>
All	O
Rodos	B-Operating_System
components	O
needed	O
for	O
application	O
development	O
are	O
accessible	O
via	O
the	O
rodos.h	O
header	O
file	O
.	O
</s>
<s>
Rodos	B-Operating_System
uses	O
fair	O
priority	O
controlled	O
preemptive	B-Operating_System
scheduling	I-Operating_System
.	O
</s>
<s>
The	O
thread	B-Operating_System
with	O
the	O
highest	O
priority	O
is	O
executed	O
while	O
running	O
threads	B-Operating_System
with	O
a	O
lower	O
priority	O
are	O
paused	O
(	O
preemptive	B-Operating_System
multitasking	O
)	O
.	O
</s>
<s>
If	O
there	O
are	O
more	O
than	O
one	O
threads	B-Operating_System
with	O
the	O
same	O
priority	O
,	O
each	O
of	O
them	O
gets	O
a	O
fixed	O
share	O
of	O
computing	O
time	O
and	O
they	O
are	O
executed	O
in	O
turns	O
.	O
</s>
<s>
The	O
thread	B-Operating_System
LowPriorityThread	O
constantly	O
writes	O
the	O
character	O
"	O
.	O
"	O
</s>
<s>
and	O
is	O
interrupted	O
every	O
second	O
by	O
the	O
thread	B-Operating_System
HighPriorityThread	O
,	O
which	O
writes	O
the	O
character	O
"	O
*	O
"	O
.	O
</s>
<s>
Rodos	B-Operating_System
uses	O
so-called	O
Topics	O
to	O
enable	O
communication	O
between	O
threads	B-Operating_System
and	O
over	O
gateways	O
between	O
different	O
systems	O
.	O
</s>
<s>
A	O
thread	B-Operating_System
can	O
publish	O
Topics	O
as	O
well	O
as	O
subscribe	O
to	O
a	O
Topic	O
to	O
receive	O
all	O
messages	O
that	O
belong	O
to	O
a	O
type	O
of	O
message	O
.	O
</s>
<s>
The	O
message	O
system	O
conforms	O
to	O
the	O
publish	B-Operating_System
–	I-Operating_System
subscribe	I-Operating_System
pattern	I-Operating_System
.	O
</s>
<s>
The	O
Publisher-Thread	O
post	O
every	O
three	O
seconds	O
an	O
ascending	O
counter	O
value	O
,	O
while	O
the	O
Subscriber-Thread	O
simply	O
displays	O
the	O
received	O
integer	O
value	O
.	O
</s>
<s>
Supported	O
instruction	B-General_Concept
set	I-General_Concept
architectures	I-General_Concept
:	O
</s>
<s>
Furthermore	O
,	O
Rodos	B-Operating_System
can	O
run	O
as	O
a	O
guest	O
on	O
a	O
different	O
host	O
operating	O
system	O
.	O
</s>
