<s>
Write	B-Device
precompensation	I-Device
(	O
abbreviated	O
WPcom	B-Device
in	O
the	O
literature	O
)	O
is	O
a	O
technical	O
aspect	O
of	O
the	O
design	O
of	O
hard	B-Device
disks	I-Device
,	O
floppy	B-Device
disks	I-Device
and	O
other	O
digital	O
magnetic	O
recording	O
devices	O
.	O
</s>
<s>
CAV	O
recording	O
is	O
used	O
by	O
most	O
floppy	B-Device
disk	I-Device
systems	O
and	O
by	O
older	O
hard	B-Device
disk	I-Device
systems	O
;	O
the	O
term	O
CAV	O
is	O
not	O
applicable	O
to	O
non-circular	O
media	O
,	O
such	O
as	O
magnetic	O
tapes	O
.	O
</s>
<s>
In	O
the	O
past	O
one	O
of	O
the	O
hard	B-Device
disk	I-Device
parameters	I-Device
stored	O
in	O
a	O
PC	O
's	O
CMOS	O
memory	O
was	O
the	O
WPcom	B-Device
number	O
,	O
a	O
marker	O
of	O
the	O
track	O
where	O
stronger	O
precompensation	O
begins	O
,	O
i.e.	O
</s>
<s>
This	O
was	O
needed	O
by	O
the	O
old	O
MFM	O
and	O
RLL	O
hard	B-Device
disk	I-Device
controllers	O
in	O
common	O
use	O
until	O
the	O
early	O
1990s	O
.	O
</s>
<s>
One	O
of	O
these	O
parameters	O
was	O
the	O
WPcom	B-Device
number	O
.	O
</s>
<s>
All	O
hard	B-Device
disk	I-Device
types	O
in	O
common	O
use	O
after	O
the	O
early	O
1990s	O
have	O
a	O
drive-specific	O
controller	O
built	O
into	O
the	O
actual	O
drive	O
enclosure	O
.	O
</s>
<s>
This	O
includes	O
all	O
IDE	O
,	O
SCSI	O
,	O
SATA	O
,	O
and	O
SAS	O
hard	B-Device
drive	I-Device
types	O
,	O
among	O
others	O
.	O
</s>
<s>
Therefore	O
,	O
they	O
ignore	O
any	O
WPcom	B-Device
numbers	O
stored	O
in	O
the	O
computer	O
's	O
CMOS	O
memory	O
.	O
</s>
<s>
Until	O
the	O
late	O
1990s	O
,	O
many	O
PC	O
BIOS	O
setup	O
programs	O
still	O
allowed	O
the	O
user	O
to	O
set	O
WPcom	B-Device
numbers	O
and	O
other	O
drive	O
parameters	O
for	O
use	O
with	O
older	O
hard	B-Device
disk	I-Device
types	O
should	O
the	O
need	O
arise	O
;	O
it	O
was	O
n't	O
always	O
made	O
very	O
clear	O
to	O
the	O
user	O
that	O
his	O
more	O
modern	O
drive	O
would	O
almost	O
certainly	O
ignore	O
the	O
setting	O
.	O
</s>
<s>
Since	O
then	O
,	O
the	O
WPcom	B-Device
number	O
is	O
no	O
longer	O
even	O
offered	O
as	O
a	O
BIOS	O
setting	O
any	O
more	O
,	O
as	O
it	O
has	O
become	O
a	O
fully	O
automated	O
and	O
internally	O
handled	O
feature	O
of	O
disk	O
drives	O
.	O
</s>
<s>
Floppy	B-Device
disk	I-Device
controllers	O
still	O
need	O
to	O
deal	O
with	O
precompensation	O
,	O
but	O
since	O
there	O
have	O
never	O
been	O
more	O
than	O
five	O
or	O
six	O
common	O
floppy	B-Device
drive	I-Device
types	O
in	O
use	O
on	O
PCs	O
,	O
all	O
of	O
which	O
need	O
the	O
same	O
kind	O
of	O
precompensation	O
,	O
there	O
was	O
never	O
a	O
need	O
for	O
a	O
BIOS	O
setting	O
concerning	O
precompensation	O
on	O
floppy	B-Device
disk	I-Device
drives	I-Device
.	O
</s>
