<s>
Environmental	B-General_Concept
subsystems	I-General_Concept
are	O
central	O
components	O
of	O
operating	B-General_Concept
systems	I-General_Concept
of	O
the	O
Windows	B-Device
NT	I-Device
type	O
.	O
</s>
<s>
They	O
allow	O
the	O
operating	B-General_Concept
system	I-General_Concept
to	O
run	O
software	O
developed	O
for	O
the	O
platform	O
in	O
question	O
.	O
</s>
<s>
For	O
example	O
,	O
Windows	B-Device
NT	I-Device
4.0	O
has	O
four	O
environmental	B-General_Concept
subsystems	I-General_Concept
,	O
viz	O
Win32	O
,	O
DOS	O
or	O
Win16	O
,	O
OS/2	B-Application
,	O
and	O
POSIX	O
,	O
the	O
latter	O
of	O
which	O
is	O
a	O
Unix	O
standard	O
.	O
</s>
<s>
The	O
environmental	B-General_Concept
subsystems	I-General_Concept
are	O
one	O
part	O
of	O
the	O
strategy	O
Microsoft	O
developed	O
for	O
making	O
the	O
Windows	B-Device
NT	I-Device
stream	O
of	O
operating	B-General_Concept
systems	I-General_Concept
a	O
hub	O
for	O
multi-platform	O
computing	O
Others	O
include	O
four	O
Hardware	B-Operating_System
Abstraction	I-Operating_System
layers	I-Operating_System
,	O
one	O
for	O
Intel	O
processors	O
,	O
three	O
for	O
RISC	B-Architecture
processors	I-Architecture
(	O
DEC	O
Alpha	O
,	O
PowerPC	O
,	O
Mips	O
)	O
,	O
and	O
a	O
driver	O
for	O
the	O
HPFS	B-Application
,	O
the	O
standard	O
for	O
OS/2	B-Application
.	O
</s>
<s>
Since	O
Windows	O
2000	O
,	O
the	O
FAT32	B-Application
file	O
system	O
first	O
introduced	O
with	O
Windows	O
95	O
has	O
also	O
been	O
present	O
,	O
with	O
HPFS	B-Application
deprecated	O
then	O
being	O
omitted	O
in	O
later	O
systems	O
.	O
</s>
<s>
A	O
third-party	O
driver	O
for	O
FAT32	B-Application
can	O
be	O
used	O
on	O
the	O
earlier	O
NT	O
operating	B-General_Concept
systems	I-General_Concept
.	O
</s>
<s>
Therefore	O
,	O
Windows	B-Device
NT	I-Device
as	O
of	O
version	O
4.0	O
had	O
a	O
default	O
of	O
four	O
file	O
systems	O
(	O
NTFS	B-Application
,	O
HPFS	B-Application
,	O
FAT12	B-Application
,	O
and	O
FAT16	B-Application
)	O
,	O
and	O
installations	O
of	O
the	O
system	O
with	O
a	O
driver	O
allowing	O
access	O
to	O
a	O
fifth	O
FAT32	B-Application
)	O
are	O
very	O
common	O
,	O
and	O
tools	O
allowing	O
access	O
to	O
Unix	O
file	O
systems	O
are	O
also	O
in	O
existence	O
.	O
</s>
