<s>
Domain/OS	B-Application
is	O
the	O
discontinued	O
operating	B-General_Concept
system	I-General_Concept
used	O
by	O
the	O
Apollo/Domain	B-Device
line	O
of	O
workstations	B-Device
manufactured	O
by	O
Apollo	O
Computer	O
.	O
</s>
<s>
It	O
was	O
originally	O
launched	O
in	O
1981	O
as	O
AEGIS	O
,	O
and	O
was	O
rebranded	O
to	O
Domain/OS	B-Application
in	O
1988	O
when	O
Unix	B-Application
environments	B-Operating_System
were	O
added	O
to	O
the	O
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
It	O
is	O
one	O
of	O
the	O
early	O
distributed	B-Operating_System
operating	I-Operating_System
systems	I-Operating_System
.	O
</s>
<s>
Hewlett-Packard	O
supported	O
the	O
operating	B-General_Concept
system	I-General_Concept
for	O
a	O
short	O
time	O
after	O
they	O
purchased	O
Apollo	O
,	O
but	O
they	O
later	O
ended	O
the	O
product	O
line	O
in	O
favor	O
of	O
HP-UX	B-Application
.	O
</s>
<s>
HP	O
ended	O
final	O
support	O
for	O
Domain/OS	B-Application
on	O
January	O
1	O
,	O
2001	O
.	O
</s>
<s>
The	O
prime	O
examples	O
of	O
this	O
are	O
the	O
file	B-Application
system	I-Application
,	O
which	O
is	O
fully	O
integrated	O
across	O
machines	O
,	O
as	O
opposed	O
to	O
Unix	B-Application
which	O
draws	O
a	O
distinction	O
between	O
file	B-Application
systems	I-Application
on	O
the	O
host	O
system	O
and	O
on	O
others	O
,	O
and	O
the	O
user	O
administration	O
system	O
,	O
which	O
is	O
fundamentally	O
network-based	O
.	O
</s>
<s>
So	O
basic	O
is	O
this	O
orientation	O
that	O
even	O
a	O
standalone	O
Apollo	O
machine	O
cannot	O
be	O
configured	O
without	O
a	O
network	B-Protocol
card	I-Protocol
.	O
</s>
<s>
Domain/OS	B-Application
implements	O
functionality	O
derived	O
from	O
both	O
System	B-Operating_System
V	I-Operating_System
and	O
early	O
BSD	B-Operating_System
Unix	I-Operating_System
systems	O
.	O
</s>
<s>
It	O
improves	O
on	O
AEGIS	O
by	O
providing	O
a	O
core	O
OS	O
upon	O
which	O
the	O
user	O
can	O
install	O
any	O
or	O
all	O
of	O
three	O
environments	B-Operating_System
:	O
AEGIS	O
,	O
System	B-Operating_System
V	I-Operating_System
Unix	I-Operating_System
,	O
and	O
BSD	B-Operating_System
Unix	I-Operating_System
.	O
</s>
<s>
This	O
was	O
done	O
in	O
order	O
to	O
provide	O
greater	O
compatibility	O
with	O
Unix	B-Application
;	O
AEGIS	O
version	O
SR9	O
,	O
which	O
immediately	O
preceded	O
Domain/OS	B-Application
(	O
itself	O
numbered	O
SR10	O
)	O
has	O
an	O
optional	O
product	O
called	O
Domain/IX	O
available	O
,	O
which	O
provides	O
a	O
similar	O
capability	O
,	O
but	O
with	O
some	O
drawbacks	O
,	O
principally	O
the	O
fact	O
that	O
core	O
administrative	O
tasks	O
still	O
require	O
AEGIS	O
commands	O
.	O
</s>
<s>
Also	O
,	O
the	O
SR9	O
permissions	O
system	O
is	O
not	O
fully	O
compatible	O
with	O
Unix	B-Application
behaviour	O
.	O
</s>
<s>
Domain/OS	B-Application
provides	O
new	O
administrative	O
commands	O
and	O
a	O
more	O
complex	O
permissions	O
system	O
which	O
can	O
be	O
configured	O
to	O
behave	O
properly	O
under	O
any	O
of	O
the	O
three	O
environments	B-Operating_System
.	O
</s>
<s>
Domain/OS	B-Application
also	O
provides	O
an	O
improved	O
version	O
of	O
the	O
X	B-Operating_System
Window	I-Operating_System
System	I-Operating_System
,	O
complete	O
with	O
VUE	B-Device
(	O
HP	O
's	O
predecessor	O
to	O
CDE	B-Application
)	O
,	O
but	O
performance	O
tends	O
to	O
be	O
poor	O
.	O
</s>
<s>
User	O
upgrading	O
from	O
AEGIS	O
SR9	O
to	O
Domain/OS	B-Application
SR10	O
was	O
slowed	O
by	O
the	O
fact	O
that	O
many	O
users	O
saw	O
no	O
requirement	O
,	O
by	O
increased	O
disk	O
space	O
requirements	O
,	O
by	O
new	O
and	O
more	O
complex	O
administration	O
tools	O
,	O
by	O
SR10	O
's	O
poorer	O
performance	O
,	O
and	O
by	O
the	O
buggy	O
nature	O
of	O
SR10.0	O
,	O
although	O
later	O
versions	O
are	O
more	O
reliable	O
.	O
</s>
<s>
However	O
,	O
later	O
HP/Apollo	O
machines	O
(	O
the	O
DN10000	O
,	O
DN2500	O
and	O
4xx	O
series	O
workstations	B-Device
)	O
can	O
only	O
run	O
SR10	O
.	O
</s>
<s>
Unlike	O
many	O
operating	B-General_Concept
systems	I-General_Concept
of	O
the	O
day	O
,	O
which	O
were	O
written	O
in	O
C	B-Language
or	O
assembly	B-Language
language	I-Language
,	O
many	O
Domain/OS	B-Application
components	O
are	O
written	O
in	O
Pascal	B-Application
.	O
</s>
<s>
Compilers	O
for	O
users	O
are	O
available	O
for	O
C	B-Language
,	O
C++	B-Language
,	O
Pascal	B-Application
,	O
and	O
Fortran	B-Application
.	O
</s>
<s>
All	O
of	O
the	O
distributed	O
administration	O
features	O
of	O
Domain/OS	B-Application
are	O
built	O
around	O
a	O
remote	B-Operating_System
procedure	I-Operating_System
call	I-Operating_System
system	O
called	O
NCS	O
RPC	O
.	O
</s>
<s>
Though	O
RPC	O
was	O
later	O
end-of-lifed	O
with	O
the	O
operating	B-General_Concept
system	I-General_Concept
,	O
HP	O
contributed	O
RPC	O
to	O
the	O
Open	B-Application
Software	I-Application
Foundation	I-Application
,	O
which	O
incorporated	O
its	O
Interface	B-General_Concept
Definition	I-General_Concept
Language	I-General_Concept
(	O
IDL	O
)	O
into	O
their	O
DCE	B-Operating_System
product	O
,	O
from	O
which	O
the	O
same	O
technology	O
was	O
later	O
used	O
for	O
CORBA	B-Architecture
.	O
</s>
<s>
One	O
of	O
the	O
original	O
developers	O
went	O
to	O
work	O
for	O
Microsoft	O
,	O
where	O
he	O
developed	O
MSRPC	B-General_Concept
as	O
a	O
fairly	O
compatible	O
clone	O
which	O
today	O
forms	O
a	O
central	O
component	O
of	O
Windows	O
systems	O
.	O
</s>
<s>
AEGIS	O
is	O
similar	O
to	O
other	O
workstations	B-Device
of	O
the	O
time	O
,	O
in	O
that	O
it	O
uses	O
a	O
high-resolution	O
graphics	O
screen	O
and	O
mouse	O
to	O
provide	O
a	O
GUI	B-Application
named	O
DM	O
(	O
Display	O
Manager	O
)	O
.	O
</s>
<s>
DM	O
is	O
integrated	O
with	O
the	O
operating	B-General_Concept
system	I-General_Concept
's	I-General_Concept
own	O
window	B-Application
manager	I-Application
known	O
as	O
wmgr	O
(	O
Window	B-Application
Manager	I-Application
)	O
.	O
</s>
<s>
The	O
DM	O
contains	O
two	O
built-in	O
functions	O
,	O
a	O
text	B-Application
editor	I-Application
and	O
a	O
transcript	O
,	O
which	O
is	O
a	O
kind	O
of	O
virtual	B-Application
terminal	I-Application
.	O
</s>
<s>
The	O
AEGIS	O
command	O
interface	O
is	O
similar	O
to	O
Unix	B-Application
,	O
in	O
that	O
it	O
has	O
a	O
command	B-Application
line	I-Application
interpreter	O
which	O
understands	O
pipes	B-Operating_System
,	O
redirection	B-Device
,	O
scripting	B-Language
,	O
etc.	O
,	O
and	O
invokes	O
other	O
commands	O
as	O
separate	O
programs	O
,	O
but	O
the	O
actual	O
commands	O
themselves	O
are	O
designed	O
to	O
be	O
easier	O
to	O
remember	O
and	O
use	O
than	O
their	O
Unix	B-Application
equivalents	O
,	O
and	O
wildcards	B-Algorithm
are	O
expected	O
to	O
be	O
expanded	O
by	O
individual	O
commands	O
rather	O
than	O
by	O
the	O
command	B-Application
line	I-Application
interpreter	O
itself	O
.	O
</s>
<s>
The	O
user	O
may	O
embed	O
environment	O
variables	O
in	O
symbolic	B-Application
links	I-Application
,	O
which	O
,	O
for	O
example	O
,	O
allows	O
switching	O
between	O
different	O
versions	O
of	O
Unix	B-Application
by	O
setting	O
the	O
SYSTYPE	O
environment	O
variable	O
accordingly	O
;	O
symbolic	B-Application
links	I-Application
then	O
point	O
to	O
the	O
appropriate	O
versions	O
of	O
the	O
files	O
.	O
</s>
<s>
Domain/OS	B-Application
incorporates	O
several	O
ideas	O
from	O
Multics	B-Application
,	O
including	O
single-level	B-Device
store	I-Device
and	O
dynamic	O
linking	O
.	O
</s>
