<s>
Stratus	B-General_Concept
VOS	I-General_Concept
(	O
Virtual	O
Operating	B-General_Concept
System	I-General_Concept
)	O
is	O
a	O
proprietary	B-Application
operating	B-General_Concept
system	I-General_Concept
running	O
on	O
Stratus	B-General_Concept
Technologies	I-General_Concept
fault-tolerant	B-General_Concept
computer	I-General_Concept
systems	I-General_Concept
.	O
</s>
<s>
VOS	O
is	O
notable	O
for	O
being	O
one	O
of	O
the	O
few	O
operating	B-General_Concept
systems	I-General_Concept
which	O
run	O
on	O
fully	O
lockstepped	B-General_Concept
hardware	O
.	O
</s>
<s>
During	O
the	O
1980s	O
,	O
an	O
IBM	O
version	O
of	O
Stratus	B-General_Concept
VOS	I-General_Concept
existed	O
and	O
was	O
called	O
the	O
System/88	B-General_Concept
Operating	B-General_Concept
System	I-General_Concept
.	O
</s>
<s>
VOS	O
was	O
designed	O
from	O
its	O
inception	O
as	O
a	O
high-security	O
transaction-processing	O
environment	O
tailored	O
to	O
fault-tolerant	B-General_Concept
hardware	O
.	O
</s>
<s>
It	O
incorporates	O
much	O
of	O
the	O
design	O
experience	O
that	O
came	O
out	O
of	O
the	O
MIT/Bell-Laboratories/General	O
-Electric	O
(	O
later	O
Honeywell	O
)	O
Multics	B-Application
project	O
.	O
</s>
<s>
In	O
1984	O
,	O
Stratus	O
added	O
a	O
UNIX	B-Operating_System
System	I-Operating_System
V	I-Operating_System
implementation	O
called	O
Unix	B-Application
System	I-Application
Facilities	O
(	O
USF	O
)	O
to	O
VOS	O
,	O
integrating	O
Unix	B-Application
and	O
VOS	O
at	O
the	O
kernel	B-Operating_System
level	O
.	O
</s>
<s>
Like	O
competing	O
proprietary	B-Application
operating	B-General_Concept
systems	I-General_Concept
,	O
VOS	O
has	O
seen	O
its	O
market	O
share	O
shrink	O
steadily	O
in	O
the	O
1990s	O
and	O
early	O
2000s	O
.	O
</s>
<s>
VOS	O
provides	O
compilers	O
for	O
PL/I	B-Language
,	O
COBOL	B-Application
,	O
Pascal	B-Application
,	O
FORTRAN	B-Application
,	O
C	B-Language
(	O
with	O
the	O
VOS	O
C	B-Language
and	O
GCC	B-Application
compilers	I-Application
)	O
,	O
and	O
C++	B-Language
(	O
also	O
GCC	B-Application
)	O
.	O
</s>
<s>
s$seq_read	O
to	O
read	O
a	O
record	O
from	O
a	O
file	O
)	O
,	O
and	O
has	O
extensions	O
to	O
support	O
varying-length	O
strings	O
in	O
PL/I	B-Language
style	O
.	O
</s>
<s>
In	O
its	O
history	O
,	O
Stratus	O
has	O
offered	O
hardware	O
platforms	O
based	O
on	O
the	O
Motorola	B-Device
68000	I-Device
microprocessor	I-Device
family	O
(	O
"	O
FT	B-Application
"	O
and	O
"	O
XA	O
"	O
series	O
)	O
,	O
the	O
Intel	B-General_Concept
i860	I-General_Concept
microprocessor	O
family	O
(	O
"	O
XA/R	O
"	O
series	O
)	O
,	O
the	O
HP	B-Device
PA-RISC	I-Device
processor	O
family	O
(	O
"	O
Continuum	O
"	O
series	O
)	O
,	O
and	O
the	O
Intel	B-Device
Xeon	I-Device
x86	B-Operating_System
processor	O
family	O
(	O
"	O
V	O
Series	O
"	O
)	O
.	O
</s>
<s>
Stratus	O
added	O
support	O
for	O
the	O
POSIX	O
API	O
in	O
VOS	O
Release	O
14.3	O
(	O
on	O
Continuum	O
)	O
,	O
and	O
added	O
support	O
for	O
the	O
GNU	O
C/C	O
++	O
compiler	O
,	O
GNU	O
gdb	O
debugger	O
,	O
and	O
many	O
POSIX	O
commands	O
in	O
VOS	O
Release	O
14.4	O
.	O
</s>
<s>
For	O
this	O
reason	O
,	O
beginning	O
with	O
Release	O
17.0	O
,	O
Stratus	O
renamed	O
VOS	O
to	O
OpenVOS	B-General_Concept
.	O
</s>
<s>
Stratus	O
offers	O
supported	O
ports	O
of	O
Samba	O
,	O
OpenSSL	O
,	O
OpenSSH	O
,	O
GNU	B-Application
Privacy	I-Application
Guard	I-Application
,	O
OpenLDAP	B-Language
,	O
Berkeley	B-Language
DB	I-Language
,	O
MySQL	O
Community	O
Server	O
,	O
Apache	O
,	O
IBM	B-Application
WebSphere	I-Application
MQ	I-Application
,	O
and	O
the	O
community	O
edition	O
of	O
Java	O
.	O
</s>
<s>
On	O
little	O
endian	O
servers	O
with	O
x86	B-Operating_System
processors	O
,	O
the	O
compilers	O
do	O
a	O
byte	O
swap	O
before	O
reading	O
or	O
writing	O
values	O
to	O
memory	O
to	O
transform	O
the	O
data	O
to	O
or	O
from	O
the	O
native	O
little	O
endian	O
format	O
.	O
</s>
<s>
VOS	O
command	O
macros	O
accept	O
arguments	O
on	O
the	O
command-line	B-Application
or	O
via	O
a	O
user	O
interface	O
"	O
form	O
"	O
.	O
</s>
<s>
VOS	O
was	O
coded	O
mainly	O
in	O
PL/I	B-Language
with	O
a	O
small	O
amount	O
of	O
assembly	B-Language
language	I-Language
before	O
it	O
was	O
migrated	O
to	O
ftServer	O
series	O
.	O
</s>
<s>
As	O
of	O
1991	O
,	O
the	O
system	O
was	O
written	O
in	O
PL/I	B-Language
and	O
C	B-Language
,	O
with	O
only	O
3%	O
in	O
assembly	O
.	O
</s>
<s>
Its	O
overall	O
structure	O
has	O
much	O
in	O
common	O
with	O
Multics	B-Application
,	O
and	O
many	O
of	O
the	O
system	O
's	O
features	O
can	O
be	O
traced	O
back	O
to	O
Multics	B-Application
to	O
varying	O
degrees	O
.	O
</s>
<s>
VOS	O
is	O
distributed	O
only	O
by	O
Stratus	B-General_Concept
Technologies	I-General_Concept
.	O
</s>
<s>
The	O
distribution	O
media	O
is	O
a	O
3.5mm	O
DAT	O
tape	O
for	O
Continuum	O
,	O
and	O
an	O
SDLT	B-Device
tape	O
for	O
early	O
V	O
Series	O
platforms	O
.	O
</s>
<s>
As	O
of	O
OpenVOS	B-General_Concept
Release	O
17.0	O
,	O
Stratus	O
offers	O
support	O
for	O
distributing	O
OpenVOS	B-General_Concept
on	O
a	O
DVD	O
or	O
by	O
downloading	O
a	O
release	O
file	O
.	O
</s>
<s>
The	O
command-line	B-Application
interface	I-Application
is	O
the	O
main	O
,	O
and	O
most	O
powerful	O
,	O
user	O
interface	O
for	O
a	O
VOS	O
system	O
.	O
</s>
<s>
Users	O
may	O
be	O
locked	O
into	O
"	O
form	O
"	O
based	O
sub-system	O
by	O
command	O
macro	O
scripts	O
if	O
required	O
,	O
although	O
a	O
skilled	O
user	O
would	O
be	O
able	O
to	O
break	O
out	O
of	O
this	O
and	O
get	O
command-line	B-Application
access	O
.	O
</s>
<s>
(	O
It	O
is	O
,	O
in	O
fact	O
,	O
possible	O
for	O
a	O
Stratus	O
system	O
administrator	O
to	O
set	O
up	O
a	O
user	O
's	O
account	O
such	O
that	O
an	O
attempt	O
to	O
break	O
out	O
of	O
FMS	O
—	O
the	O
Stratus	O
Forms	O
Management	O
System	O
—	O
to	O
the	O
command	B-Application
line	I-Application
results	O
in	O
the	O
user	O
being	O
logged	O
out	O
.	O
)	O
</s>
<s>
For	O
example	O
,	O
changes	O
the	O
working	B-Application
directory	I-Application
.	O
</s>
<s>
The	O
VOS	O
help	B-Protocol
system	O
uses	O
this	O
convention	O
to	O
assist	O
users	O
who	O
are	O
looking	O
for	O
a	O
subset	O
of	O
possible	O
commands	O
;	O
for	O
instance	O
,	O
those	O
referring	O
to	O
"	O
change	O
"	O
are	O
found	O
by	O
.	O
</s>
<s>
VOS	O
is	O
used	O
on	O
Continuum	O
and	O
ftServer	O
systems	O
,	O
both	O
of	O
which	O
are	O
designed	O
to	O
be	O
highly	O
fault-tolerant	B-General_Concept
.	O
</s>
<s>
Older	O
versions	O
of	O
VOS	O
implemented	O
a	O
non-OSI	O
standard	O
TCP/IP	B-Protocol
known	O
as	O
OS	O
TCP/IP	B-Protocol
(	O
Operating	B-General_Concept
System	I-General_Concept
TCP/IP	B-Protocol
.	O
)	O
</s>
<s>
Older	O
applications	O
using	O
OS	O
TCP/IP	B-Protocol
have	O
to	O
be	O
ported	O
in	O
order	O
to	O
use	O
STCP	O
.	O
</s>
<s>
This	O
can	O
mean	O
a	O
loss	O
of	O
functionality	O
as	O
OS	O
TCP/IP	B-Protocol
supported	O
several	O
functions	O
that	O
are	O
not	O
OSI-compliant	O
and	O
have	O
therefore	O
been	O
abandoned	O
.	O
</s>
<s>
The	O
ftServer	O
hardware	O
that	O
V	O
Series	O
runs	O
on	O
only	O
supports	O
TCP/IP	B-Protocol
and	O
X.25	B-Protocol
(	O
X.25	B-Protocol
only	O
when	O
equipped	O
with	O
the	O
optional	O
NIO	O
.	O
)	O
</s>
<s>
Websphere	B-Application
MQ	I-Application
6.0	O
(	O
a.k.a.	O
</s>
<s>
MQ	B-Application
Series	I-Application
)	O
is	O
TCP/IP	B-Protocol
based	O
;	O
so	O
,	O
that	O
is	O
also	O
supported	O
by	O
ftServer	O
hardware	O
.	O
</s>
<s>
Fault	B-General_Concept
tolerance	I-General_Concept
is	O
built	O
into	O
VOS	O
from	O
the	O
bottom	O
up	O
.	O
</s>
<s>
On	O
a	O
hardware	O
level	O
,	O
major	O
devices	O
are	O
run	O
in	O
lockstepped	B-General_Concept
duplex	I-General_Concept
mode	I-General_Concept
,	O
meaning	O
that	O
there	O
are	O
two	O
identical	O
devices	O
performing	O
the	O
same	O
action	O
at	O
the	O
same	O
time	O
.	O
</s>
<s>
These	O
boards	O
are	O
actively	O
monitored	O
by	O
the	O
operating	B-General_Concept
system	I-General_Concept
which	O
can	O
correct	O
any	O
minor	O
inconsistencies	O
(	O
such	O
as	O
bad	O
disk-writes	O
or	O
reads	O
)	O
.	O
</s>
<s>
The	O
operating	B-General_Concept
system	I-General_Concept
is	O
designed	O
to	O
avoid	O
crashes	O
due	O
to	O
a	O
simplexed	O
hardware	O
failure	O
.	O
</s>
<s>
Stream	O
files	O
:	O
a	O
stream	O
of	O
binary	O
data	O
,	O
corresponding	O
directly	O
with	O
the	O
concept	O
of	O
a	O
file	O
on	O
other	O
operating	B-General_Concept
systems	I-General_Concept
.	O
</s>
<s>
A	O
VOS	O
file	O
with	O
one	O
or	O
more	O
indexes	O
can	O
be	O
used	O
as	O
a	O
C-ISAM	O
database	O
table	O
.	O
</s>
<s>
VOS	O
uses	O
a	O
proprietary	B-Application
file	O
naming	O
syntax	O
which	O
includes	O
the	O
system	O
name	O
,	O
module	O
name	O
,	O
disk	O
number	O
,	O
and	O
directory	O
,	O
with	O
components	O
separated	O
by	O
the	O
"	O
>	O
"	O
symbol	O
.	O
</s>
<s>
These	O
paging	O
files	O
can	O
in	O
theory	O
consist	O
of	O
more	O
than	O
one	O
extent	O
(	O
which	O
is	O
viewed	O
by	O
the	O
kernel	B-Operating_System
as	O
a	O
mini-paging	O
partition	O
)	O
which	O
may	O
or	O
may	O
not	O
be	O
contiguous	O
.	O
</s>
<s>
VOS	O
inherited	O
access	O
control	O
lists	O
from	O
Multics	B-Application
and	O
also	O
implements	O
directory	O
access	O
control	O
lists	O
.	O
</s>
<s>
(	O
This	O
may	O
be	O
true	O
in	O
OpenVOS	B-General_Concept
,	O
but	O
does	O
not	O
apply	O
to	O
the	O
original	O
operating	B-General_Concept
system	I-General_Concept
.	O
)	O
</s>
<s>
VOS	O
has	O
always	O
been	O
a	O
network-aware	O
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
If	O
the	O
operation	O
is	O
n't	O
local	O
,	O
it	O
is	O
redirected	O
to	O
the	O
target	O
computer	O
via	O
remote	B-Operating_System
subroutine	I-Operating_System
call	I-Operating_System
.	O
</s>
<s>
Historically	O
,	O
StrataLINK	O
was	O
a	O
proprietary	B-Application
10Mb	O
CSMA/CD	O
ring	O
network	O
which	O
allowed	O
high	O
performance	O
(	O
for	O
the	O
time	O
)	O
with	O
very	O
low	O
memory	O
overhead	O
and	O
CPU	O
utilization	O
.	O
</s>
<s>
This	O
was	O
never	O
developed	O
beyond	O
10Mb	O
and	O
was	O
dropped	O
in	O
favor	O
of	O
using	O
TCP/IP	B-Protocol
because	O
Ethernet	O
became	O
the	O
dominant	O
networking	O
standard	O
and	O
because	O
memory	O
and	O
CPU	O
processing	O
got	O
cheaper	O
.	O
</s>
<s>
Open	O
StrataLINK	O
can	O
also	O
use	O
X.25	B-Protocol
for	O
wide	O
area	O
communications	O
.	O
</s>
