<s>
Plurix	B-Operating_System
is	O
a	O
Unix-like	B-Operating_System
operating	I-Operating_System
system	I-Operating_System
developed	O
in	O
Brazil	O
in	O
the	O
early	O
1980s	O
.	O
</s>
<s>
Plurix	B-Operating_System
was	O
developed	O
in	O
the	O
Federal	O
University	O
of	O
Rio	O
de	O
Janeiro	O
(	O
UFRJ	O
)	O
,	O
at	O
the	O
Electronic	O
Computing	O
Center	O
(	O
NCE	O
)	O
.	O
</s>
<s>
The	O
NCE	O
researchers	O
,	O
after	O
returning	O
from	O
postgraduate	O
courses	O
in	O
the	O
USA	O
,	O
attempted	O
to	O
license	O
the	O
UNIX	B-Application
source	O
code	O
from	O
AT&T	O
in	O
the	O
late	O
1970s	O
without	O
success	O
.	O
</s>
<s>
In	O
1982	O
,	O
due	O
to	O
AT&T	O
refusing	O
to	O
license	O
the	O
code	O
,	O
a	O
development	O
team	O
led	O
by	O
Newton	O
Faller	O
decided	O
to	O
initiate	O
the	O
development	O
of	O
an	O
alternative	O
system	O
,	O
called	O
Plurix	B-Operating_System
( **	O
)	O
,	O
using	O
as	O
reference	O
UNIX	B-Application
Version	O
7	O
,	O
the	O
most	O
recent	O
at	O
the	O
time	O
,	O
that	O
they	O
had	O
running	O
on	O
an	O
old	O
Motorola	O
computer	O
system	O
.	O
</s>
<s>
In	O
1985	O
,	O
the	O
Plurix	B-Operating_System
system	O
was	O
up	O
and	O
running	O
on	O
the	O
Pegasus	O
32-X	O
,	O
a	O
shared-memory	O
,	O
multi-processor	O
computer	O
also	O
designed	O
at	O
NCE	O
.	O
</s>
<s>
Plurix	B-Operating_System
was	O
licensed	O
to	O
some	O
Brazilian	O
companies	O
in	O
1988	O
.	O
</s>
<s>
Two	O
other	O
Brazilian	O
universities	O
also	O
developed	O
their	O
own	O
UNIX	B-Application
systems	I-Application
:	O
Universidade	O
Federal	O
de	O
Minas	O
Gerais	O
(	O
UFMG	O
)	O
developed	O
the	O
DCC-IX	O
operating	B-General_Concept
system	I-General_Concept
,	O
and	O
University	O
of	O
São	O
Paulo	O
(	O
USP	O
)	O
developed	O
the	O
REAL	O
operating	B-General_Concept
system	I-General_Concept
in	O
1987	O
.	O
</s>
<s>
The	O
NCE/UFRJ	O
also	O
offered	O
technical	O
courses	O
on	O
OS	O
design	O
and	O
implementation	O
to	O
local	O
computer	O
companies	O
,	O
some	O
of	O
which	O
later	O
produced	O
their	O
own	O
proprietary	O
UNIX	B-Application
systems	I-Application
.	O
</s>
<s>
In	O
fact	O
,	O
these	O
Brazilian	O
companies	O
first	O
created	O
an	O
organization	O
of	O
companies	O
interested	O
in	O
UNIX	B-Application
(	O
called	O
API	O
)	O
and	O
tried	O
to	O
license	O
UNIX	B-Application
from	O
AT&T	O
.	O
</s>
<s>
COBRA	O
and	O
NCE/UFRJ	O
kept	O
developing	O
,	O
and	O
tried	O
to	O
convince	O
the	O
Brazilian	O
government	O
to	O
prohibit	O
the	O
further	O
entrance	O
of	O
AT&T	O
UNIX	B-Application
into	O
Brazil	O
,	O
since	O
the	O
operating	B-General_Concept
systems	I-General_Concept
they	O
developed	O
,	O
(	O
COBRA	O
and	O
Plurix	B-Operating_System
)	O
,	O
were	O
similar	O
to	O
T	O
's	O
and	O
could	O
do	O
the	O
same	O
things	O
.	O
</s>
<s>
Certainly	O
none	O
of	O
the	O
national	O
systems	O
had	O
the	O
comprehensiveness	O
of	O
the	O
original	O
UNIX	B-Application
System	I-Application
V	O
,	O
which	O
incorporated	O
software	O
from	O
different	O
origins	O
and	O
was	O
more	O
than	O
fifteen	O
years	O
ahead	O
.	O
</s>
<s>
However	O
,	O
the	O
evolution	O
of	O
the	O
national	O
systems	O
could	O
have	O
followed	O
a	O
viable	O
and	O
proper	O
way	O
and	O
still	O
preserved	O
the	O
basic	O
characteristics	O
(	O
"	O
Unix	B-Operating_System
philosophy	I-Operating_System
"	O
)	O
to	O
assure	O
compatibility	O
with	O
other	O
UNIX	B-Application
systems	I-Application
around	O
the	O
world	O
.	O
</s>
<s>
At	O
the	O
NCE	O
,	O
the	O
Plurix	B-Operating_System
Project	O
has	O
evolved	O
into	O
2	O
other	O
projects	O
:	O
</s>
<s>
Mulplix	O
is	O
a	O
Unix-like	B-Operating_System
operating	I-Operating_System
system	I-Operating_System
designed	O
to	O
support	O
medium-grain	O
parallelism	O
and	O
to	O
provide	O
an	O
efficient	O
environment	O
for	O
running	O
parallel	O
applications	O
within	O
MULTIPLUS	O
.	O
</s>
<s>
Developed	O
by	O
a	O
group	O
of	O
volunteers	O
,	O
(	O
like	O
Linux	B-Application
)	O
,	O
Tropix	B-Operating_System
is	O
a	O
fully	O
preemptive	O
real-time	O
Unix-like	B-Operating_System
operating	I-Operating_System
system	I-Operating_System
for	O
PCs	O
.	O
</s>
<s>
At	O
the	O
user	O
level	O
,	O
TROPIX	B-Operating_System
bears	O
a	O
reasonable	O
similarity	O
to	O
the	O
UNIX	B-Application
operating	I-Application
system	I-Application
.	O
</s>
<s>
Processes	O
are	O
created	O
through	O
fork-execs	O
,	O
I/O	B-General_Concept
is	O
always	O
treated	O
as	O
a	O
sequence	O
of	O
bytes	O
and	O
is	O
performed	O
through	O
open-read-write-close	O
primitives	O
,	O
signals	O
can	O
be	O
sent	O
to	O
processes	O
,	O
there	O
is	O
a	O
kernel	B-Operating_System
process	O
zero	O
(	O
swapper/pager	O
)	O
,	O
the	O
init	O
process	O
is	O
the	O
common	O
ancestor	O
of	O
all	O
other	O
user	O
processes	O
,	O
etc	O
.	O
</s>
<s>
Internally	O
,	O
the	O
TROPIX	B-Operating_System
kernel	B-Operating_System
structure	O
is	O
quite	O
different	O
from	O
UNIX	B-Application
.	O
</s>
<s>
TROPIX	B-Operating_System
has	O
a	O
fully	O
preemptible	O
kernel	B-Operating_System
and	O
many	O
specialized	O
system	O
calls	O
to	O
manipulate	O
and	O
coordinate	O
the	O
execution	O
of	O
real-time	O
processes	O
.	O
</s>
<s>
Besides	O
its	O
swapper/pager	O
,	O
TROPIX	B-Operating_System
kernel	B-Operating_System
standard	O
processes	O
include	O
a	O
unique	O
dispatcher	O
process	O
per	O
processor	O
.	O
</s>
<s>
Fine-grain	O
parallel	O
processing	O
within	O
executing	O
processes	O
is	O
also	O
possible	O
,	O
since	O
TROPIX	B-Operating_System
implements	O
threads	O
at	O
the	O
supervisor	O
level	O
.	O
</s>
