<s>
DSOS	B-Operating_System
(	O
Deep	O
Six	O
Operating	B-General_Concept
System	I-General_Concept
)	O
was	O
a	O
real-time	B-Operating_System
operating	I-Operating_System
system	I-Operating_System
(	O
sometimes	O
termed	O
an	O
operating	B-Operating_System
system	I-Operating_System
kernel	I-Operating_System
)	O
developed	O
by	O
Texas	O
Instruments	O
 '	O
division	O
Geophysical	O
Services	O
Incorporated	O
(	O
GSI	O
)	O
in	O
the	O
mid-1970s	O
.	O
</s>
<s>
They	O
would	O
collect	O
data	O
in	O
likely	O
spots	O
around	O
the	O
world	O
,	O
process	O
that	O
data	O
using	O
high	B-Architecture
performance	I-Architecture
computers	I-Architecture
,	O
and	O
produce	O
analyses	O
that	O
guided	O
oil	O
companies	O
toward	O
promising	O
sites	O
for	O
drilling	O
.	O
</s>
<s>
The	O
GEONAV	O
systems	O
,	O
which	O
used	O
DSOS	B-Operating_System
(	O
Frailey	O
,	O
1975	O
)	O
as	O
their	O
operating	B-General_Concept
system	I-General_Concept
,	O
performed	O
the	O
required	O
navigation	O
,	O
and	O
collected	O
,	O
processed	O
,	O
and	O
stored	O
the	O
seismic	O
data	O
being	O
received	O
in	O
real-time	B-Operating_System
.	O
</s>
<s>
The	O
name	O
Deep	O
Six	O
Operating	B-General_Concept
System	I-General_Concept
was	O
the	O
brainchild	O
of	O
Phil	O
Ward	O
(	O
subsequently	O
a	O
world-renowned	O
GPS	O
expert	O
)	O
who	O
,	O
at	O
the	O
time	O
,	O
was	O
manager	O
of	O
the	O
project	O
and	O
slightly	O
skeptical	O
of	O
the	O
computer	B-General_Concept
science	I-General_Concept
professor	O
,	O
Dennis	O
Frailey	O
,	O
who	O
insisted	O
that	O
an	O
operating	B-General_Concept
system	I-General_Concept
was	O
the	O
solution	O
to	O
the	O
problem	O
at	O
hand	O
.	O
</s>
<s>
Supposedly	O
one	O
of	O
the	O
ships	O
hit	O
an	O
old	O
World	O
War	O
II	O
naval	O
mine	O
off	O
the	O
coast	O
of	O
Egypt	O
and	O
sank	O
while	O
being	O
navigated	O
by	O
GEONAV	O
and	O
DSOS	B-Operating_System
.	O
</s>
<s>
In	O
the	O
1970s	O
,	O
most	O
real-time	B-General_Concept
applications	I-General_Concept
did	O
not	O
use	O
operating	B-General_Concept
systems	I-General_Concept
because	O
the	O
latter	O
were	O
perceived	O
as	O
adding	O
too	O
much	O
overhead	O
.	O
</s>
<s>
Moreover	O
,	O
most	O
software	O
of	O
this	O
type	O
was	O
written	O
in	O
assembly	B-Language
language	I-Language
.	O
</s>
<s>
As	O
a	O
consequence	O
,	O
real-time	B-General_Concept
systems	I-General_Concept
were	O
classic	O
examples	O
of	O
spaghetti	O
code	O
:	O
complex	O
masses	O
of	O
assembly	B-Language
language	I-Language
software	O
using	O
all	O
sorts	O
of	O
machine-dependent	B-Architecture
tricks	O
to	O
achieve	O
maximum	O
performance	O
.	O
</s>
<s>
DSOS	B-Operating_System
ran	O
on	O
a	O
Texas	O
Instruments	O
980	O
minicomputer	B-Architecture
being	O
used	O
for	O
marine	O
navigation	O
on	O
GSI	O
's	O
fleet	O
.	O
</s>
<s>
DSOS	B-Operating_System
was	O
created	O
to	O
bring	O
some	O
order	O
to	O
the	O
chaos	O
that	O
was	O
typical	O
of	O
real-time	B-General_Concept
system	I-General_Concept
design	O
at	O
that	O
time	O
.	O
</s>
<s>
The	O
980	O
was	O
,	O
for	O
its	O
time	O
,	O
a	O
relatively	O
powerful	O
small	O
computer	O
that	O
offered	O
memory	B-General_Concept
protection	I-General_Concept
and	O
multiple-priority	O
interrupt	O
abilities	O
.	O
</s>
<s>
DSOS	B-Operating_System
was	O
designed	O
to	O
exploit	O
these	O
features	O
.	O
</s>
<s>
DSOS	B-Operating_System
(	O
Frailey	O
,	O
1975	O
)	O
was	O
one	O
of	O
the	O
pioneering	O
efforts	O
in	O
real-time	B-Operating_System
operating	I-Operating_System
systems	I-Operating_System
.	O
</s>
<s>
Incorporating	O
many	O
of	O
the	O
principles	O
being	O
introduced	O
at	O
the	O
time	O
in	O
mainframe	B-Architecture
computer	I-Architecture
systems	O
,	O
such	O
as	O
semaphores	B-Operating_System
,	O
memory	B-General_Concept
management	I-General_Concept
,	O
task	O
management	O
,	O
and	O
software	O
interrupts	O
,	O
it	O
used	O
a	O
clever	O
scheme	O
to	O
assure	O
appropriate	O
real-time	B-Operating_System
performance	O
while	O
providing	O
many	O
services	O
formerly	O
uncommon	O
in	O
the	O
real-time	B-Operating_System
domain	O
(	O
such	O
as	O
an	O
orderly	O
way	O
to	O
communicate	O
with	O
external	O
devices	O
and	O
computer	O
operators	O
,	O
multitasking	O
,	O
maintaining	O
records	O
,	O
a	O
disciplined	O
form	O
of	O
inter-task	O
communication	O
,	O
a	O
reliable	O
real-time	B-Operating_System
clock	O
,	O
memory	B-General_Concept
protection	I-General_Concept
,	O
and	O
debugging	O
support	O
)	O
.	O
</s>
<s>
It	O
remained	O
in	O
use	O
for	O
at	O
least	O
three	O
decades	O
and	O
it	O
demonstrated	O
that	O
,	O
if	O
well	O
designed	O
,	O
an	O
operating	B-General_Concept
system	I-General_Concept
can	O
make	O
a	O
real-time	B-General_Concept
system	I-General_Concept
faster	O
(	O
and	O
vastly	O
more	O
maintainable	O
)	O
than	O
what	O
had	O
been	O
typical	O
before	O
.	O
</s>
<s>
Today	O
,	O
almost	O
all	O
real-time	B-General_Concept
applications	I-General_Concept
use	O
operating	B-General_Concept
systems	I-General_Concept
of	O
this	O
type	O
.	O
</s>
