<s>
The	O
Installable	B-Application
File	I-Application
System	I-Application
(	O
IFS	B-Device
)	O
is	O
a	O
filesystem	B-Application
API	I-Application
in	O
MS-DOS/PC	O
DOS	O
4.x	O
,	O
IBM	B-Application
OS/2	I-Application
and	O
Microsoft	B-Application
Windows	I-Application
that	O
enables	O
the	O
operating	B-General_Concept
system	I-General_Concept
to	O
recognize	O
and	O
load	O
drivers	O
for	O
file	B-Application
systems	I-Application
.	O
</s>
<s>
When	O
IBM	O
and	O
Microsoft	O
were	O
co-developing	O
OS/2	B-Application
,	O
they	O
realized	O
that	O
the	O
FAT	B-Application
file	I-Application
system	I-Application
did	O
not	O
offer	O
some	O
of	O
the	O
features	O
modern	O
OSes	O
would	O
require	O
,	O
and	O
Microsoft	O
began	O
developing	O
the	O
High	B-Application
Performance	I-Application
File	I-Application
System	I-Application
(	O
HPFS	B-Application
)	O
,	O
codenamed	O
Pinball	B-Application
.	O
</s>
<s>
Instead	O
of	O
coding	O
it	O
inside	O
the	O
kernel	O
,	O
as	O
FAT	O
was	O
,	O
Microsoft	O
developed	O
a	O
"	O
driver-based	O
"	O
filesystem	B-Application
API	I-Application
that	O
could	O
allow	O
them	O
and	O
other	O
developers	O
to	O
add	O
new	O
filesystems	B-Application
to	O
the	O
kernel	O
without	O
needing	O
to	O
modify	O
it	O
.	O
</s>
<s>
When	O
Microsoft	O
stopped	O
working	O
on	O
OS/2	B-Application
,	O
IBM	O
continued	O
using	O
the	O
IFS	B-Device
interface	O
and	O
Microsoft	O
implemented	O
a	O
similar	O
one	O
in	O
Windows	O
NT	O
.	O
</s>
<s>
The	O
IFS	B-Device
provided	O
a	O
basic	O
and	O
powerful	O
interface	O
for	O
programming	O
filesystems	B-Application
.	O
</s>
<s>
It	O
was	O
introduced	O
in	O
1989	O
in	O
OS/2	B-Application
1.20	O
,	O
along	O
with	O
the	O
HPFS	B-Application
filesystem	I-Application
.	O
</s>
<s>
Filesystem	B-Application
drivers	O
executed	O
in	O
kernel-space	O
(	O
ring	B-Operating_System
0	I-Operating_System
)	O
and	O
are	O
divided	O
in	O
four	O
principal	O
pieces	O
:	O
microIFS	O
,	O
miniIFS	O
,	O
IFS	B-Device
,	O
helpers	O
.	O
</s>
<s>
Only	O
the	O
IFS	B-Device
and	O
the	O
filesystem	B-Application
code	O
itself	O
is	O
required	O
and	O
it	O
is	O
loaded	O
via	O
an	O
"	O
IFS	B-Device
=	O
"	O
statement	O
in	O
the	O
CONFIG.SYS	B-Device
file	O
.	O
</s>
<s>
It	O
is	O
a	O
NE	O
16-bit	B-Device
dynamically	B-Operating_System
loaded	I-Operating_System
library	I-Operating_System
.	O
</s>
<s>
No	O
matter	O
if	O
it	O
is	O
a	O
32-bit	O
OS/2	B-Application
(	O
2.0	O
and	O
newer	O
)	O
,	O
the	O
IFS	B-Device
is	O
always	O
16-bit	B-Device
(	O
although	O
extraofficially	O
you	O
can	O
make	O
a	O
32-bit	O
IFS	B-Device
)	O
.	O
</s>
<s>
It	O
is	O
usually	O
in	O
the	O
boot	O
portion	O
of	O
the	O
filesystem	B-Application
.	O
</s>
<s>
The	O
miniIFS	O
is	O
a	O
piece	O
of	O
code	O
that	O
is	O
called	O
by	O
the	O
kernel	O
to	O
load	O
the	O
first	O
IFS	B-Device
statement	O
that	O
appears	O
in	O
the	O
CONFIG.SYS	B-Device
file	O
,	O
so	O
the	O
first	O
IFS	B-Device
statement	O
must	O
be	O
the	O
boot	O
's	O
filesystem	B-Application
for	O
the	O
system	O
to	O
be	O
able	O
to	O
boot	O
.	O
</s>
<s>
The	O
helpers	O
are	O
16-bit	B-Device
(	O
for	O
OS/2	B-Application
1.x	O
)	O
or	O
32-bit	O
(	O
for	O
OS/2	B-Application
2.x	O
and	O
up	O
)	O
,	O
are	O
executed	O
in	O
user-space	O
(	O
ring	B-Operating_System
3	I-Operating_System
)	O
and	O
contain	O
the	O
code	O
used	O
for	O
typical	O
filesystem	B-Application
maintenance	O
,	O
and	O
are	O
called	O
by	O
CHKDSK	B-Device
and	O
FORMAT	B-Application
utilities	O
.	O
</s>
<s>
This	O
four-piece	O
scheme	O
allowed	O
developers	O
to	O
dynamically	O
add	O
a	O
new	O
bootable	O
filesystem	B-Application
,	O
as	O
the	O
ext2	B-Application
driver	B-Application
for	O
OS/2	B-Application
demonstrated	O
.	O
</s>
<s>
CD-ROM	B-Device
filesystem	B-Application
driver	B-Application
(	O
ISO	B-Application
9660	I-Application
)	O
was	O
added	O
in	O
OS/2	B-Application
2.0	O
,	O
UDF	O
was	O
added	O
in	O
OS/2	B-Application
4.0	O
and	O
JFS	B-Application
was	O
added	O
in	O
OS/2	B-Application
4.5	O
.	O
</s>
<s>
ArcaOS	B-Device
,	O
the	O
latest	O
packaging	O
of	O
OS/2	B-Application
,	O
has	O
a	O
number	O
of	O
filesystem	B-Application
drivers	O
available	O
,	O
including	O
FAT32	B-Application
.	O
</s>
<s>
There	O
was	O
also	O
an	O
official	O
32-bit	O
HPFS	B-Application
IFS	B-Device
,	O
called	O
HPFS386	B-Application
that	O
improved	O
performance	O
and	O
added	O
some	O
features	O
,	O
like	O
variable	O
size	O
cache	O
and	O
Access	O
Control	O
Lists	O
,	O
and	O
was	O
available	O
only	O
in	O
certain	O
OS/2	B-Application
server	O
editions	O
.	O
</s>
<s>
The	O
FAT	B-Application
filesystem	I-Application
was	O
never	O
removed	O
from	O
the	O
kernel	O
and	O
officially	O
never	O
an	O
IFS	B-Device
,	O
although	O
there	O
are	O
FAT	O
IFS	B-Device
that	O
added	O
features	O
like	O
long	O
file	O
names	O
(	O
LFNs	O
)	O
,	O
FAT32	B-Application
support	O
,	O
etc	O
.	O
</s>
<s>
Network	O
file-sharing	O
protocols	O
like	O
NFS	B-Protocol
and	O
SMB	B-Operating_System
are	O
also	O
implemented	O
using	O
IFS	B-Device
,	O
and	O
the	O
IFS	B-Device
interface	O
never	O
changed	O
.	O
</s>
<s>
IFSHLP.SYS	B-Application
(	O
the	O
Installable	B-Application
File	I-Application
System	I-Application
Helper	I-Application
)	O
is	O
an	O
MS-DOS	B-Application
device	B-Application
driver	I-Application
that	O
was	O
first	O
released	O
as	O
part	O
of	O
Microsoft	B-Application
Windows	I-Application
3.11	O
.	O
</s>
<s>
It	O
enables	O
native	O
32-bit	B-Device
file	I-Device
access	I-Device
in	O
Windows	O
386	O
Enhanced	O
Mode	O
by	O
bypassing	O
the	O
16-bit	B-Device
DOS	B-Application
API	I-Application
and	O
ensuring	O
that	O
no	O
other	O
real	B-Application
mode	I-Application
driver	B-Application
intercepts	O
INT	B-Application
21h	I-Application
calls	O
.	O
</s>
<s>
The	O
protected	O
mode	O
counterpart	O
of	O
IFSHLP.SYS	B-Application
is	O
IFSMGR.386	O
in	O
Windows	O
3.11	O
and	O
IFSMGR.VXD	O
in	O
Windows	O
95	O
and	O
Windows	O
98	O
.	O
</s>
<s>
The	O
IFS	B-Device
API	O
is	O
part	O
of	O
the	O
Windows	B-Application
Driver	I-Application
Kit	I-Application
.	O
</s>
<s>
When	O
Microsoft	O
stopped	O
developing	O
OS/2	B-Application
and	O
concentrated	O
on	O
what	O
was	O
then	O
called	O
OS/2	B-Application
NT	O
,	O
they	O
took	O
the	O
IFS	B-Device
ideas	O
with	O
it	O
,	O
along	O
with	O
the	O
HPFS	B-Application
filesystem	I-Application
.	O
</s>
<s>
Instead	O
of	O
being	O
a	O
four-piece	O
scheme	O
,	O
NT	O
IFS	B-Device
was	O
redesigned	O
into	O
a	O
two-piece	O
scheme	O
.	O
</s>
<s>
IFS	B-Device
and	O
helpers	O
remain	O
as	O
the	O
same	O
,	O
but	O
later	O
,	O
in	O
Windows	O
NT	O
4.0	O
,	O
a	O
defragmentation	B-Application
helper	O
(	O
DEFRAG	B-Application
)	O
was	O
added	O
.	O
</s>
<s>
Microsoft	O
's	O
original	O
NTLDR	O
was	O
coded	O
for	O
loading	O
the	O
NT	O
kernel	O
from	O
FAT	O
,	O
HPFS	B-Application
or	O
NTFS	B-Application
,	O
but	O
subsequent	O
versions	O
dropped	O
HPFS	B-Application
support	O
.	O
</s>
<s>
The	O
FAT	B-Application
file	I-Application
system	I-Application
was	O
moved	O
out	O
of	O
the	O
Kernel	O
to	O
an	O
IFS	B-Device
and	O
was	O
heavily	O
optimized	O
for	O
performance	O
,	O
taking	O
advantage	O
of	O
the	O
32-bit	O
processing	O
capabilities	O
(	O
being	O
called	O
FASTFAT	O
)	O
.	O
</s>
<s>
Original	O
Windows	O
NT	O
3.1	O
incorporated	O
FAT	O
,	O
HPFS	B-Application
(	O
Pinball	B-Application
)	O
and	O
the	O
newly	O
created	O
NTFS	B-Application
drivers	O
,	O
along	O
with	O
a	O
new	O
and	O
improved	O
CD-ROM	B-Device
filesystem	B-Application
driver	B-Application
that	O
incorporated	O
long	O
file	O
names	O
using	O
the	O
Microsoft	O
Joliet	O
filesystem	B-Application
.	O
</s>
<s>
Windows	O
NT	O
3.51	O
added	O
per-file	O
compression	O
to	O
NTFS	B-Application
and	O
to	O
the	O
IFS	B-Device
interface	O
.	O
</s>
<s>
In	O
Windows	O
NT	O
4.0	O
HPFS	B-Application
was	O
removed	O
.	O
</s>
<s>
In	O
Windows	O
2000	O
FASTFAT	O
was	O
updated	O
to	O
support	O
FAT32	B-Application
and	O
UDF	O
was	O
added	O
.	O
</s>
<s>
Windows	O
2000	O
modified	O
the	O
IFS	B-Device
interface	O
to	O
add	O
per-file	O
encryption	O
.	O
</s>
<s>
Network	O
file-sharing	O
protocols	O
and	O
antivirus	O
are	O
also	O
implemented	O
using	O
IFS	B-Device
'	O
file	B-Application
system	I-Application
filter	O
 '	O
drivers	O
which	O
intercept	O
file	O
I/O	O
operations	O
.	O
</s>
<s>
Apple	O
started	O
including	O
read	O
only	O
HFS+	B-Application
drivers	O
in	O
Mac	B-Device
OS	I-Device
X	I-Device
10.6	I-Device
'	O
s	O
version	O
of	O
Boot	B-Application
Camp	I-Application
for	O
use	O
in	O
Windows	B-Application
XP	I-Application
,	O
Windows	B-Application
Vista	I-Application
,	O
and	O
Windows	B-Device
7	I-Device
.	O
</s>
