<s>
Microsoft	B-Device
POSIX	I-Device
subsystem	I-Device
is	O
one	O
of	O
four	O
subsystems	O
shipped	O
with	O
the	O
first	O
versions	O
of	O
Windows	B-Device
NT	I-Device
,	O
the	O
other	O
three	O
being	O
the	O
Win32	B-Library
subsystem	O
which	O
provided	O
the	O
primary	O
API	B-Application
for	O
Windows	B-Device
NT	I-Device
,	O
plus	O
the	O
OS/2	B-Application
and	O
security	O
subsystems	O
.	O
</s>
<s>
This	O
subsystem	O
implements	O
only	O
the	O
POSIX.1	O
standard	O
also	O
known	O
as	O
IEEE	O
Std	O
1003.1-1990	O
or	O
ISO/IEC	O
9945-1:1990	O
primarily	O
covering	O
the	O
kernel	O
and	O
C	O
library	O
programming	B-Application
interfaces	I-Application
which	O
allowed	O
a	O
program	O
written	O
for	O
other	O
POSIX.1-compliant	O
operating	O
systems	O
to	O
be	O
compiled	O
and	O
run	O
under	O
Windows	B-Device
NT	I-Device
.	O
</s>
<s>
The	O
Windows	B-Device
NT	I-Device
POSIX	O
subsystem	O
did	O
not	O
provide	O
the	O
interactive	O
user	O
environment	O
parts	O
of	O
POSIX	O
,	O
originally	O
standardized	O
as	O
POSIX.2	O
.	O
</s>
<s>
That	O
is	O
,	O
Windows	B-Device
NT	I-Device
did	O
not	O
provide	O
a	O
POSIX	O
shell	O
nor	O
any	O
Unix	B-Application
commands	I-Application
out	O
of	O
the	O
box	O
,	O
except	O
for	O
pax	B-Device
.	O
</s>
<s>
The	O
NT	O
POSIX	O
subsystem	O
also	O
did	O
not	O
provide	O
any	O
of	O
the	O
POSIX	O
extensions	O
that	O
postdated	O
the	O
creation	O
of	O
Windows	B-Device
NT	I-Device
3.1	O
,	O
such	O
as	O
those	O
for	O
POSIX	B-Operating_System
Threads	I-Operating_System
or	O
POSIX	O
IPC	B-Operating_System
.	O
</s>
<s>
The	O
NT	O
POSIX	O
subsystem	O
was	O
included	O
with	O
the	O
first	O
versions	O
of	O
Windows	B-Device
NT	I-Device
because	O
of	O
1980s	O
US	O
federal	O
government	O
requirements	O
listed	O
in	O
Federal	O
Information	O
Processing	O
Standard	O
(	O
FIPS	O
)	O
151-2	O
.	O
</s>
<s>
Briefly	O
,	O
these	O
documents	O
required	O
that	O
certain	O
types	O
of	O
government	O
purchases	O
be	O
POSIX-compliant	O
,	O
so	O
that	O
if	O
Windows	B-Device
NT	I-Device
had	O
not	O
included	O
this	O
subsystem	O
,	O
computing	O
systems	O
based	O
on	O
it	O
would	O
not	O
have	O
been	O
eligible	O
for	O
some	O
government	O
contracts	O
.	O
</s>
<s>
Windows	B-Device
NT	I-Device
versions	O
3.5	B-Device
,	O
3.51	B-Device
and	O
4.0	B-Device
were	O
certified	O
as	O
compliant	O
with	O
FIPS	O
151-2	O
.	O
</s>
<s>
The	O
runtime	B-Device
environment	I-Device
of	O
the	O
subsystem	O
is	O
provided	O
by	O
two	O
files	O
:	O
and	O
.	O
</s>
<s>
The	O
POSIX	O
subsystem	O
was	O
replaced	O
in	O
Windows	B-Application
XP	I-Application
and	O
Windows	B-Application
Server	I-Application
2003	I-Application
by	O
"	O
Windows	O
Services	O
for	O
UNIX	O
"	O
,	O
(	O
SFU	O
)	O
which	O
is	O
based	O
in	O
part	O
on	O
OpenBSD	B-Operating_System
code	O
and	O
other	O
technology	O
developed	O
by	O
Interix	B-Operating_System
,	O
a	O
company	O
later	O
purchased	O
by	O
Microsoft	O
.	O
</s>
