<s>
Unix	B-Operating_System
System	I-Operating_System
V	I-Operating_System
(	O
pronounced	O
:	O
"	O
System	O
Five	O
"	O
)	O
is	O
one	O
of	O
the	O
first	O
commercial	O
versions	O
of	O
the	O
Unix	B-Application
operating	I-Application
system	I-Application
.	O
</s>
<s>
Four	O
major	O
versions	O
of	O
System	B-Operating_System
V	I-Operating_System
were	O
released	O
,	O
numbered	O
1	O
,	O
2	O
,	O
3	O
,	O
and	O
4	O
.	O
</s>
<s>
System	B-Operating_System
V	I-Operating_System
Release	O
4	O
(	O
SVR4	O
)	O
was	O
commercially	O
the	O
most	O
successful	O
version	O
,	O
being	O
the	O
result	O
of	O
an	O
effort	O
,	O
marketed	O
as	O
Unix	B-Application
System	I-Application
Unification	O
,	O
which	O
solicited	O
the	O
collaboration	O
of	O
the	O
major	O
Unix	B-Application
vendors	O
.	O
</s>
<s>
It	O
was	O
the	O
source	O
of	O
several	O
common	O
commercial	O
Unix	B-Application
features	O
.	O
</s>
<s>
System	B-Operating_System
V	I-Operating_System
is	O
sometimes	O
abbreviated	O
to	O
SysV	B-Operating_System
.	O
</s>
<s>
,	O
the	O
AT&	O
T-derived	O
Unix	B-Application
market	O
is	O
divided	O
between	O
four	O
System	B-Operating_System
V	I-Operating_System
variants	O
:	O
IBM	O
's	O
AIX	B-Application
,	O
Hewlett	O
Packard	O
Enterprise	O
's	O
HP-UX	B-Application
and	O
Oracle	B-Application
's	O
Solaris	B-Application
,	O
plus	O
the	O
free-software	O
illumos	B-Application
forked	O
from	O
OpenSolaris	B-Operating_System
.	O
</s>
<s>
System	B-Operating_System
V	I-Operating_System
was	O
the	O
successor	O
to	O
1982	O
's	O
UNIX	B-Operating_System
System	I-Operating_System
III	I-Operating_System
.	O
</s>
<s>
While	O
AT&T	O
developed	O
and	O
sold	O
hardware	O
that	O
ran	O
System	B-Operating_System
V	I-Operating_System
,	O
most	O
customers	O
ran	O
a	O
version	O
from	O
a	O
reseller	O
,	O
based	O
on	O
T	O
's	O
reference	O
implementation	O
.	O
</s>
<s>
A	O
standards	O
document	O
called	O
the	O
System	B-Operating_System
V	I-Operating_System
Interface	I-Operating_System
Definition	I-Operating_System
outlined	O
the	O
default	O
features	O
and	O
behavior	O
of	O
implementations	O
.	O
</s>
<s>
During	O
the	O
formative	O
years	O
of	O
T	O
's	O
computer	O
business	O
,	O
the	O
division	O
went	O
through	O
several	O
phases	O
of	O
System	B-Operating_System
V	I-Operating_System
software	O
groups	O
,	O
beginning	O
with	O
the	O
Unix	B-Application
Support	O
Group	O
(	O
USG	O
)	O
,	O
followed	O
by	O
Unix	B-Application
System	I-Application
Development	O
Laboratory	O
(	O
USDL	O
)	O
,	O
followed	O
by	O
AT&T	O
Information	O
Systems	O
(	O
ATTIS	O
)	O
,	O
and	O
finally	O
Unix	B-Application
System	I-Application
Laboratories	O
(	O
USL	O
)	O
.	O
</s>
<s>
In	O
the	O
1980s	O
and	O
early-1990s	O
,	O
UNIX	B-Operating_System
System	I-Operating_System
V	I-Operating_System
and	O
the	O
Berkeley	B-Operating_System
Software	I-Operating_System
Distribution	I-Operating_System
(	O
BSD	B-Operating_System
)	O
were	O
the	O
two	O
major	O
versions	O
of	O
UNIX	B-Application
.	O
</s>
<s>
Historically	O
,	O
BSD	B-Operating_System
was	O
also	O
commonly	O
called	O
"	O
BSD	B-Operating_System
Unix	I-Operating_System
"	O
or	O
"	O
Berkeley	B-Operating_System
Unix	I-Operating_System
"	O
.	O
</s>
<s>
Eric	O
S	O
.	O
Raymond	O
summarizes	O
the	O
longstanding	O
relationship	O
and	O
rivalry	O
between	O
System	B-Operating_System
V	I-Operating_System
and	O
BSD	B-Operating_System
during	O
the	O
early	O
period	O
:	O
</s>
<s>
While	O
HP	O
,	O
IBM	O
and	O
others	O
chose	O
System	B-Operating_System
V	I-Operating_System
as	O
the	O
basis	O
for	O
their	O
Unix	B-Application
offerings	O
,	O
other	O
vendors	O
such	O
as	O
Sun	O
Microsystems	O
and	O
DEC	O
extended	O
BSD	B-Operating_System
.	O
</s>
<s>
Throughout	O
its	O
development	O
,	O
though	O
,	O
System	B-Operating_System
V	I-Operating_System
was	O
infused	O
with	O
features	O
from	O
BSD	B-Operating_System
,	O
while	O
BSD	B-Operating_System
variants	O
such	O
as	O
DEC	O
's	O
Ultrix	B-Operating_System
received	O
System	B-Operating_System
V	I-Operating_System
features	O
.	O
</s>
<s>
AT&T	O
and	O
Sun	O
Microsystems	O
worked	O
together	O
to	O
merge	O
System	B-Operating_System
V	I-Operating_System
with	O
BSD-based	O
SunOS	B-Operating_System
to	O
produce	O
Solaris	B-Application
,	O
one	O
of	O
the	O
primary	O
System	B-Operating_System
V	I-Operating_System
descendants	O
still	O
in	O
use	O
today	O
.	O
</s>
<s>
Since	O
the	O
early	O
1990s	O
,	O
due	O
to	O
standardization	O
efforts	O
such	O
as	O
POSIX	O
and	O
the	O
success	O
of	O
Linux	B-Application
,	O
the	O
division	O
between	O
System	B-Operating_System
V	I-Operating_System
and	O
BSD	B-Operating_System
has	O
become	O
less	O
important	O
.	O
</s>
<s>
System	B-Operating_System
V	I-Operating_System
,	O
known	O
inside	O
Bell	O
Labs	O
as	O
Unix	B-Application
5.0	O
,	O
succeeded	O
T	O
's	O
previous	O
commercial	O
Unix	B-Application
called	O
System	B-Operating_System
III	I-Operating_System
in	O
January	O
,	O
1983	O
.	O
</s>
<s>
Unix	B-Application
4.0	O
was	O
never	O
released	O
externally	O
,	O
which	O
would	O
have	O
been	O
designated	O
as	O
System	O
IV	O
.	O
</s>
<s>
This	O
first	O
release	O
of	O
System	B-Operating_System
V	I-Operating_System
(	O
called	O
System	O
V.0	O
,	O
System	B-Operating_System
V	I-Operating_System
Release	O
1	O
,	O
or	O
SVR1	B-Operating_System
)	O
was	O
developed	O
by	O
T	O
's	O
UNIX	B-Application
Support	O
Group	O
(	O
USG	O
)	O
and	O
based	O
on	O
the	O
Bell	O
Labs	O
internal	O
USG	O
UNIX	B-Application
5.0	O
.	O
</s>
<s>
System	B-Operating_System
V	I-Operating_System
also	O
included	O
features	O
such	O
as	O
the	O
vi	B-Application
editor	I-Application
and	O
curses	B-Device
from	O
4.1	O
BSD	B-Operating_System
,	O
developed	O
at	O
the	O
University	O
of	O
California	O
,	O
Berkeley	O
;	O
it	O
also	O
improved	O
performance	O
by	O
adding	O
buffer	O
and	O
inode	B-Application
caches	O
.	O
</s>
<s>
It	O
also	O
added	O
support	O
for	O
inter-process	B-Operating_System
communication	I-Operating_System
using	O
messages	O
,	O
semaphores	B-Operating_System
,	O
and	O
shared	B-Operating_System
memory	I-Operating_System
,	O
developed	O
earlier	O
for	O
the	O
Bell-internal	O
CB	B-Operating_System
UNIX	I-Operating_System
.	O
</s>
<s>
SVR1	B-Operating_System
ran	O
on	O
DEC	B-Device
PDP-11	I-Device
and	O
VAX	B-Device
minicomputers	B-Architecture
.	O
</s>
<s>
T	O
's	O
UNIX	B-Application
Support	O
Group	O
(	O
USG	O
)	O
transformed	O
into	O
the	O
UNIX	B-Application
System	I-Application
Development	O
Laboratory	O
(	O
USDL	O
)	O
,	O
which	O
released	O
System	B-Operating_System
V	I-Operating_System
Release	O
2	O
in	O
1984	O
.	O
</s>
<s>
SVR2	O
added	O
shell	B-Application
functions	O
and	O
the	O
SVID	B-Operating_System
.	O
</s>
<s>
SVR2.4	O
added	O
demand	B-General_Concept
paging	I-General_Concept
,	O
copy-on-write	B-Language
,	O
shared	B-Operating_System
memory	I-Operating_System
,	O
and	O
record	O
and	O
file	B-Application
locking	I-Application
.	O
</s>
<s>
Apple	O
Computer	O
's	O
A/UX	B-Operating_System
operating	B-General_Concept
system	I-General_Concept
was	O
initially	O
based	O
on	O
this	O
release	O
.	O
</s>
<s>
SCO	B-Application
XENIX	I-Application
also	O
used	O
SVR2	O
as	O
its	O
basis	O
.	O
</s>
<s>
The	O
first	O
release	O
of	O
HP-UX	B-Application
was	O
also	O
an	O
SVR2	O
derivative	O
.	O
</s>
<s>
Maurice	O
J	O
.	O
Bach	O
's	O
book	O
,	O
The	O
Design	O
of	O
the	O
UNIX	B-Application
Operating	I-Application
System	I-Application
,	O
is	O
the	O
definitive	O
description	O
of	O
the	O
SVR2	O
kernel	O
.	O
</s>
<s>
T	O
's	O
UNIX	B-Application
System	I-Application
Development	O
Laboratory	O
(	O
USDL	O
)	O
was	O
succeeded	O
by	O
AT&T	O
Information	O
Systems	O
(	O
ATTIS	O
)	O
,	O
which	O
distributed	O
UNIX	B-Operating_System
System	I-Operating_System
V	I-Operating_System
,	O
Release	O
3	O
,	O
in	O
1987	O
.	O
</s>
<s>
SVR3	B-Operating_System
included	O
STREAMS	B-Operating_System
,	O
Remote	B-Operating_System
File	I-Operating_System
Sharing	I-Operating_System
(	O
RFS	O
)	O
,	O
the	O
File	O
System	O
Switch	O
(	O
FSS	O
)	O
virtual	B-Application
file	I-Application
system	I-Application
mechanism	O
,	O
a	O
restricted	O
form	O
of	O
shared	O
libraries	O
,	O
and	O
the	O
Transport	B-Application
Layer	I-Application
Interface	I-Application
(	O
TLI	O
)	O
network	O
API	B-Application
.	O
</s>
<s>
The	O
final	O
version	O
was	O
Release	O
3.2	O
in	O
1988	O
,	O
which	O
added	O
binary	O
compatibility	O
to	O
Xenix	B-Application
on	O
Intel	O
platforms	O
(	O
see	O
Intel	B-Operating_System
Binary	I-Operating_System
Compatibility	I-Operating_System
Standard	I-Operating_System
)	O
.	O
</s>
<s>
User	O
interface	O
improvements	O
included	O
the	O
"	O
layers	O
"	O
windowing	O
system	O
for	O
the	O
DMD	B-Protocol
5620	I-Protocol
graphics	O
terminal	O
,	O
and	O
the	O
SVR3.2	O
curses	B-Device
libraries	I-Device
that	O
offered	O
eight	O
or	O
more	O
color	O
pairs	O
and	O
other	O
at	O
this	O
time	O
important	O
features	O
(	O
forms	O
,	O
panels	O
,	O
menus	O
,	O
etc	O
.	O
)	O
.	O
</s>
<s>
SCO	B-Operating_System
UNIX	I-Operating_System
was	O
based	O
upon	O
SVR3.2	O
,	O
as	O
was	O
ISC	B-Operating_System
386/ix	B-Operating_System
.	O
</s>
<s>
Among	O
the	O
more	O
obscure	O
distributions	O
of	O
SVR3.2	O
for	O
the	O
386	O
were	O
ESIX	O
3.2	O
by	O
Everex	O
and	O
"	O
System	B-Operating_System
V	I-Operating_System
,	O
Release	O
3.2	O
"	O
sold	O
by	O
Intel	O
themselves	O
;	O
these	O
two	O
shipped	O
"	O
plain	O
vanilla	O
"	O
T	O
's	O
codebase	O
.	O
</s>
<s>
IBM	O
's	O
AIX	B-Application
operating	I-Application
system	I-Application
is	O
an	O
SVR3	B-Operating_System
derivative	O
.	O
</s>
<s>
System	B-Operating_System
V	I-Operating_System
Release	I-Operating_System
4.0	I-Operating_System
was	O
announced	O
on	O
October	O
18	O
,	O
1988	O
and	O
was	O
incorporated	O
into	O
a	O
variety	O
of	O
commercial	O
Unix	B-Application
products	O
from	O
early	O
1989	O
onwards	O
.	O
</s>
<s>
A	O
joint	O
project	O
of	O
AT&T	B-Operating_System
Unix	I-Operating_System
System	O
Laboratories	O
and	O
Sun	O
Microsystems	O
,	O
it	O
combined	O
technology	O
from	O
:	O
</s>
<s>
From	O
BSD	B-Operating_System
:	O
</s>
<s>
From	O
SunOS	B-Operating_System
:	O
</s>
<s>
From	O
Xenix	B-Application
:	O
</s>
<s>
Many	O
companies	O
licensed	O
SVR4	O
and	O
bundled	O
it	O
with	O
computer	O
systems	O
such	O
as	O
workstations	B-Device
and	O
network	B-Application
servers	I-Application
.	O
</s>
<s>
SVR4	O
systems	O
vendors	O
included	O
Atari	O
(	O
Atari	B-Device
System	I-Device
V	I-Device
)	O
,	O
Commodore	O
(	O
Amiga	B-Operating_System
Unix	I-Operating_System
)	O
,	O
Data	O
General	O
(	O
DG/UX	B-Operating_System
)	O
,	O
Fujitsu	O
(	O
UXP/DS	B-Operating_System
)	O
,	O
Hitachi	O
(	O
HI-UX	O
)	O
,	O
Hewlett-Packard	O
(	O
HP-UX	B-Application
)	O
,	O
NCR	O
(	O
Unix/NS	B-Operating_System
)	O
,	O
NEC	O
(	O
EWS-UX	B-Operating_System
,	O
UP-UX	O
,	O
UX/4800	O
,	O
SUPER-UX	B-Operating_System
)	O
,	O
OKI	O
(	O
OKI	O
System	B-Operating_System
V	I-Operating_System
)	O
,	O
Pyramid	O
Technology	O
(	O
DC/OSx	B-Operating_System
)	O
,	O
SGI	O
(	O
IRIX	B-Operating_System
)	O
,	O
Siemens	O
(	O
SINIX	B-Operating_System
)	O
,	O
Sony	O
(	O
NEWS-OS	B-Operating_System
)	O
,	O
Sumitomo	O
Electric	O
Industries	O
(	O
SEIUX	O
)	O
,	O
and	O
Sun	O
Microsystems	O
(	O
Solaris	B-Application
)	O
with	O
illumos	B-Application
in	O
the	O
2010s	O
as	O
the	O
only	O
open-source	B-Application
platform	I-Application
.	O
</s>
<s>
Software	O
porting	O
houses	O
also	O
sold	O
enhanced	O
and	O
supported	O
Intel	B-Operating_System
x86	I-Operating_System
versions	O
.	O
</s>
<s>
SVR4	O
software	O
vendors	O
included	O
Dell	O
(	O
Dell	O
UNIX	B-Application
)	O
,	O
Everex	O
(	O
ESIX	O
)	O
,	O
Micro	O
Station	O
Technology	O
(	O
SVR4	O
)	O
,	O
Microport	O
(	O
SVR4	O
)	O
,	O
and	O
UHC	O
(	O
SVR4	O
)	O
.	O
</s>
<s>
The	O
primary	O
platforms	O
for	O
SVR4	O
were	O
Intel	B-Operating_System
x86	I-Operating_System
and	O
SPARC	B-Architecture
;	O
the	O
SPARC	B-Architecture
version	O
,	O
called	O
Solaris	B-Application
2	O
(	O
or	O
,	O
internally	O
,	O
SunOS	B-Operating_System
5.x	O
)	O
,	O
was	O
developed	O
by	O
Sun	O
.	O
</s>
<s>
The	O
relationship	O
between	O
Sun	O
and	O
AT&T	O
was	O
terminated	O
after	O
the	O
release	O
of	O
SVR4	O
,	O
meaning	O
that	O
later	O
versions	O
of	O
Solaris	B-Application
did	O
not	O
inherit	O
features	O
of	O
later	O
SVR4.x	O
releases	O
.	O
</s>
<s>
Sun	O
would	O
in	O
2005	O
release	O
most	O
of	O
the	O
source	O
code	O
for	O
Solaris	B-Application
10	I-Application
(	O
SunOS	B-Operating_System
5.10	O
)	O
as	O
the	O
open-source	B-Application
OpenSolaris	B-Operating_System
project	O
,	O
creating	O
,	O
with	O
its	O
forks	B-Application
,	O
the	O
only	O
open-source	B-Application
(	O
albeit	O
heavily	O
modified	O
)	O
System	B-Operating_System
V	I-Operating_System
implementation	O
available	O
.	O
</s>
<s>
After	O
Oracle	B-Application
took	O
over	O
Sun	O
,	O
Solaris	B-Application
was	O
forked	O
into	O
proprietary	B-Application
release	O
,	O
but	O
illumos	B-Application
as	O
the	O
continuation	O
project	O
is	O
being	O
developed	O
in	O
open-source	B-Application
.	O
</s>
<s>
A	O
consortium	O
of	O
Intel-based	O
resellers	O
including	O
Unisys	O
,	O
ICL	O
,	O
NCR	O
Corporation	O
,	O
and	O
Olivetti	O
developed	O
SVR4.0MP	O
with	O
multiprocessing	B-Operating_System
capability	O
(	O
allowing	O
system	O
calls	O
to	O
be	O
processed	O
from	O
any	O
processor	O
,	O
but	O
interrupt	O
servicing	O
only	O
from	O
a	O
"	O
master	O
"	O
processor	O
)	O
.	O
</s>
<s>
That	O
year	O
saw	O
the	O
release	O
System	O
V.4.2	O
as	O
Univel	O
UnixWare	B-Operating_System
,	O
featuring	O
the	O
Veritas	B-Application
File	I-Application
System	I-Application
.	O
</s>
<s>
Release	O
4.2MP	O
,	O
completed	O
late	O
1993	O
,	O
added	O
support	O
for	O
multiprocessing	B-Operating_System
and	O
it	O
was	O
released	O
as	O
UnixWare	B-Operating_System
2	O
in	O
1995	O
.	O
</s>
<s>
Eric	O
S	O
.	O
Raymond	O
warned	O
prospective	O
buyers	O
about	O
SVR4.2	O
versions	O
,	O
as	O
they	O
often	O
did	O
not	O
include	O
on-line	O
man	B-Protocol
pages	I-Protocol
.	O
</s>
<s>
In	O
his	O
1994	O
buyers	O
guide	O
,	O
he	O
attributes	O
this	O
change	O
in	O
policy	O
to	O
Unix	B-Application
System	I-Application
Laboratories	O
.	O
</s>
<s>
The	O
Santa	O
Cruz	O
Operation	O
(	O
SCO	O
)	O
,	O
owners	O
of	O
Xenix	B-Application
,	O
eventually	O
acquired	O
the	O
UnixWare	B-Operating_System
trademark	O
and	O
the	O
distribution	O
rights	O
to	O
the	O
System	B-Operating_System
V	I-Operating_System
Release	O
4.2	O
codebase	O
from	O
Novell	O
,	O
while	O
other	O
vendors	O
(	O
Sun	O
,	O
IBM	O
,	O
HP	O
)	O
continued	O
to	O
use	O
and	O
extend	O
System	B-Operating_System
V	I-Operating_System
Release	O
4	O
.	O
</s>
<s>
Novell	O
transferred	O
ownership	O
of	O
the	O
Unix	B-Application
trademark	O
to	O
The	B-Application
Open	I-Application
Group	I-Application
.	O
</s>
<s>
System	B-Operating_System
V	I-Operating_System
Release	O
5	O
was	O
developed	O
in	O
1997	O
by	O
the	O
Santa	O
Cruz	O
Operation	O
(	O
SCO	O
)	O
as	O
a	O
merger	O
of	O
SCO	B-Operating_System
OpenServer	I-Operating_System
(	O
an	O
SVR3-derivative	O
)	O
and	O
UnixWare	B-Operating_System
,	O
with	O
a	O
focus	O
on	O
large-scale	O
servers	O
.	O
</s>
<s>
It	O
was	O
released	O
as	O
SCO	B-Operating_System
UnixWare	I-Operating_System
7	O
.	O
</s>
<s>
SCO	O
's	O
successor	O
,	O
The	O
SCO	O
Group	O
,	O
also	O
based	O
SCO	B-Operating_System
OpenServer	I-Operating_System
6	O
on	O
SVR5	O
,	O
but	O
the	O
codebase	O
is	O
not	O
used	O
by	O
any	O
other	O
major	O
developer	B-Application
or	O
reseller	O
.	O
</s>
<s>
System	B-Operating_System
V	I-Operating_System
Release	O
6	O
was	O
announced	O
by	O
SCO	O
to	O
be	O
released	O
by	O
the	O
end	O
of	O
2004	O
,	O
but	O
was	O
apparently	O
cancelled	O
.	O
</s>
<s>
SCO	O
also	O
discontinued	O
Smallfoot	B-Application
in	O
2004	O
.	O
</s>
<s>
The	O
industry	O
has	O
coalesced	O
around	O
The	B-Application
Open	I-Application
Group	I-Application
's	O
Single	O
UNIX	B-Application
Specification	O
version	O
3	O
(	O
UNIX	B-Application
03	O
)	O
.	O
</s>
<s>
In	O
the	O
1980s	O
and	O
1990s	O
,	O
a	O
variety	O
of	O
SVR4	O
versions	O
of	O
Unix	B-Application
were	O
available	O
commercially	O
for	O
the	O
x86	B-Operating_System
PC	O
platform	O
.	O
</s>
<s>
However	O
,	O
the	O
market	O
for	O
commercial	O
Unix	B-Application
on	O
PCs	O
declined	O
after	O
Linux	B-Application
and	O
BSD	B-Operating_System
became	O
widely	O
available	O
.	O
</s>
<s>
In	O
late	O
1994	O
,	O
Eric	O
S	O
.	O
Raymond	O
discontinued	O
his	O
PC-clone	O
UNIX	B-Application
Software	O
Buyer	O
's	O
Guide	O
on	O
USENET	B-Application
,	O
stating	O
,	O
"	O
The	O
reason	O
I	O
am	O
dropping	O
this	O
is	O
that	O
I	O
run	O
Linux	B-Application
now	O
,	O
and	O
I	O
no	O
longer	O
find	O
the	O
SVr4	O
market	O
interesting	O
or	O
significant.	O
"	O
</s>
<s>
In	O
1998	O
,	O
a	O
confidential	O
memo	O
at	O
Microsoft	O
stated	O
,	O
"	O
Linux	B-Application
is	O
on	O
track	O
to	O
eventually	O
own	O
the	O
x86	B-Operating_System
UNIX	B-Application
market	O
"	O
,	O
and	O
further	O
predicted	O
,	O
"	O
I	O
believe	O
that	O
Linux	B-Application
–	O
moreso	O
than	O
NT	B-Device
–	O
will	O
be	O
the	O
biggest	O
threat	O
to	O
SCO	O
in	O
the	O
near	O
future.	O
"	O
</s>
<s>
An	O
InfoWorld	O
article	O
from	O
2001	O
characterized	O
SCO	B-Operating_System
UnixWare	I-Operating_System
as	O
having	O
a	O
"	O
bleak	O
outlook	O
"	O
due	O
to	O
being	O
"	O
trounced	O
"	O
in	O
the	O
market	O
by	O
Linux	B-Application
and	O
Solaris	B-Application
,	O
and	O
IDC	O
predicted	O
that	O
SCO	O
would	O
"	O
continue	O
to	O
see	O
a	O
shrinking	O
share	O
of	O
the	O
market	O
"	O
.	O
</s>
<s>
Project	O
Monterey	O
was	O
started	O
in	O
1998	O
to	O
combine	O
major	O
features	O
of	O
existing	O
commercial	O
Unix	B-Application
platforms	O
,	O
as	O
a	O
joint	O
project	O
of	O
Compaq	O
,	O
IBM	O
,	O
Intel	O
,	O
SCO	O
,	O
and	O
Sequent	O
Computer	O
Systems	O
.	O
</s>
<s>
The	O
target	O
platform	O
was	O
meant	O
to	O
be	O
Intel	O
's	O
new	O
IA-64	B-General_Concept
architecture	O
and	O
Itanium	B-General_Concept
line	O
of	O
processors	O
.	O
</s>
<s>
By	O
2001	O
,	O
several	O
major	O
Unix	B-Application
variants	O
such	O
as	O
SCO	B-Operating_System
UnixWare	I-Operating_System
,	O
Compaq	O
Tru64	B-Operating_System
UNIX	I-Operating_System
,	O
and	O
SGI	B-Operating_System
IRIX	I-Operating_System
were	O
all	O
in	O
decline	O
.	O
</s>
<s>
The	O
three	O
major	O
Unix	B-Application
versions	O
doing	O
well	O
in	O
the	O
market	O
were	O
IBM	B-Application
AIX	I-Application
,	O
Hewlett-Packard	O
'	O
s	O
HP-UX	B-Application
,	O
and	O
Sun	O
's	O
Solaris	B-Application
.	O
</s>
<s>
In	O
2006	O
,	O
when	O
SGI	O
declared	O
bankruptcy	O
,	O
analysts	O
questioned	O
whether	O
Linux	B-Application
would	O
replace	O
proprietary	B-Application
Unix	B-Application
altogether	O
.	O
</s>
<s>
In	O
a	O
2006	O
article	O
written	O
for	O
Computerworld	O
by	O
Mark	O
Hall	O
,	O
the	O
economics	O
of	O
Linux	B-Application
were	O
cited	O
as	O
a	O
major	O
factor	O
driving	O
the	O
migration	O
from	O
Unix	B-Application
to	O
Linux	B-Application
:	O
</s>
<s>
The	O
article	O
also	O
cites	O
trends	O
in	O
high-performance	B-Architecture
computing	I-Architecture
applications	O
as	O
evidence	O
of	O
a	O
dramatic	O
shift	O
from	O
Unix	B-Application
to	O
Linux	B-Application
:	O
</s>
<s>
In	O
a	O
November	O
2015	O
survey	O
of	O
the	O
top	B-Operating_System
500	I-Operating_System
supercomputers	I-Operating_System
,	O
Unix	B-Application
was	O
used	O
by	O
only	O
1.2	O
%	O
(	O
all	O
running	O
IBM	B-Application
AIX	I-Application
)	O
,	O
while	O
Linux	B-Application
was	O
used	O
by	O
98.8	O
%	O
;	O
the	O
same	O
survey	O
in	O
November	O
2017	O
reports	O
100%	O
of	O
them	O
using	O
Linux	B-Application
.	O
</s>
<s>
System	B-Operating_System
V	I-Operating_System
derivatives	O
continued	O
to	O
be	O
deployed	O
on	O
some	O
proprietary	B-Application
server	O
platforms	O
.	O
</s>
<s>
The	O
principal	O
variants	O
of	O
System	B-Operating_System
V	I-Operating_System
that	O
remain	O
in	O
commercial	O
use	O
are	O
AIX	B-Application
(	O
IBM	O
)	O
,	O
Solaris	B-Application
(	O
Oracle	B-Application
)	O
,	O
and	O
HP-UX	B-Application
(	O
HP	O
)	O
.	O
</s>
<s>
According	O
to	O
a	O
study	O
done	O
by	O
IDC	O
,	O
in	O
2012	O
the	O
worldwide	O
Unix	B-Application
market	O
was	O
divided	O
between	O
IBM	O
(	O
56%	O
)	O
,	O
Oracle	B-Application
(	O
19.2	O
%	O
)	O
,	O
and	O
HP	O
(	O
18.6	O
%	O
)	O
.	O
</s>
<s>
No	O
other	O
commercial	O
Unix	B-Application
vendor	O
had	O
more	O
than	O
2%	O
of	O
the	O
market	O
.	O
</s>
<s>
Industry	O
analysts	O
generally	O
characterize	O
proprietary	B-Application
Unix	B-Application
as	O
having	O
entered	O
a	O
period	O
of	O
slow	O
but	O
permanent	O
decline	O
.	O
</s>
<s>
OpenSolaris	B-Operating_System
and	O
its	O
derivatives	O
are	O
the	O
only	O
SVR4	O
descendants	O
that	O
are	O
open-source	B-Application
software	I-Application
.	O
</s>
<s>
Core	O
system	O
software	O
continues	O
to	O
be	O
developed	O
as	O
illumos	B-Application
used	O
in	O
illumos	B-Application
distributions	O
such	O
as	O
SmartOS	O
,	O
Omniosce	O
,	O
OpenIndiana	B-Application
and	O
others	O
.	O
</s>
<s>
The	O
System	B-Operating_System
V	I-Operating_System
interprocess	B-Operating_System
communication	I-Operating_System
mechanisms	O
are	O
available	O
in	O
Unix-like	O
operating	B-General_Concept
systems	I-General_Concept
not	O
derived	O
from	O
System	B-Operating_System
V	I-Operating_System
;	O
in	O
particular	O
,	O
in	O
Linux	B-Application
(	O
a	O
reimplementation	O
of	O
Unix	B-Application
)	O
as	O
well	O
as	O
the	O
BSD	B-Operating_System
derivative	O
FreeBSD	B-Operating_System
.	O
</s>
<s>
FreeBSD	B-Operating_System
maintains	O
a	O
binary	O
compatibility	O
layer	O
for	O
the	O
COFF	O
format	O
,	O
which	O
allows	O
FreeBSD	B-Operating_System
to	O
execute	O
binaries	O
compiled	O
for	O
some	O
SVR3.2	O
derivatives	O
such	O
as	O
SCO	B-Operating_System
UNIX	I-Operating_System
and	O
Interactive	B-Operating_System
UNIX	I-Operating_System
.	O
</s>
<s>
Modern	O
System	B-Operating_System
V	I-Operating_System
,	O
Linux	B-Application
,	O
and	O
BSD	B-Operating_System
platforms	O
use	O
the	O
ELF	O
file	O
format	O
for	O
natively	O
compiled	O
binaries	O
.	O
</s>
