<s>
TUNIS	B-Operating_System
(	O
Toronto	O
University	O
System	O
)	O
was	O
a	O
Unix-like	B-Operating_System
operating	I-Operating_System
system	I-Operating_System
,	O
developed	O
at	O
the	O
University	O
of	O
Toronto	O
in	O
the	O
early	O
1980s	O
.	O
</s>
<s>
TUNIS	B-Operating_System
was	O
a	O
portable	O
operating	B-General_Concept
system	I-General_Concept
compatible	O
with	O
Unix	B-Operating_System
V7	I-Operating_System
,	O
but	O
with	O
a	O
completely	O
redesigned	O
kernel	B-Operating_System
,	O
written	O
in	O
Concurrent	B-Language
Euclid	I-Language
.	O
</s>
<s>
Programs	O
that	O
ran	O
under	O
Unix	B-Operating_System
V7	I-Operating_System
could	O
be	O
run	O
under	O
TUNIS	B-Operating_System
with	O
no	O
modification	O
.	O
</s>
<s>
TUNIS	B-Operating_System
was	O
designed	O
for	O
teaching	O
,	O
and	O
was	O
intended	O
to	O
provide	O
a	O
model	O
for	O
the	O
design	O
of	O
well-structured	O
,	O
highly	O
portable	O
,	O
easily	O
understood	O
Unix-like	B-Operating_System
operating	I-Operating_System
systems	I-Operating_System
.	O
</s>
<s>
It	O
made	O
extensive	O
use	O
of	O
Concurrent	B-Language
Euclid	I-Language
modules	O
to	O
isolate	O
machine	O
dependencies	O
and	O
provide	O
a	O
clean	O
internal	O
structure	O
through	O
information	B-Application
hiding	I-Application
.	O
</s>
<s>
TUNIS	B-Operating_System
also	O
made	O
use	O
of	O
Concurrent	B-Language
Euclid	I-Language
's	O
built-in	O
processes	O
and	O
synchronization	O
features	O
to	O
make	O
it	O
easy	O
to	O
understand	O
and	O
maintain	O
.	O
</s>
<s>
TUNIS	B-Operating_System
targeted	O
the	O
PDP-11	B-Device
,	O
Motorola	B-Device
6809	I-Device
and	O
68000	B-Device
,	O
and	O
National	O
Semiconductor	O
32016	O
architectures	O
,	O
and	O
supported	O
distribution	O
across	O
multiple	O
CPUs	O
using	O
Concurrent	B-Language
Euclid	I-Language
's	O
synchronization	O
features	O
.	O
</s>
