<s>
Disk	O
density	O
is	O
a	O
capacity	O
designation	O
on	O
magnetic	B-Architecture
storage	I-Architecture
,	O
usually	O
floppy	B-Device
disks	I-Device
.	O
</s>
<s>
Each	O
designation	O
describes	O
a	O
set	O
of	O
characteristics	O
that	O
can	O
affect	O
the	O
areal	B-Device
density	I-Device
of	O
a	O
disk	O
or	O
the	O
efficiency	O
of	O
the	O
encoded	O
data	O
.	O
</s>
<s>
Such	O
characteristics	O
include	O
modulation	B-Application
method	O
,	O
track	O
width	O
,	O
coercivity	O
,	O
and	O
magnetic	O
field	O
direction	O
.	O
</s>
<s>
Single	O
density	O
(	O
SD	O
or	O
1D	O
)	O
describes	O
the	O
first	O
generation	O
of	O
floppy	B-Device
disks	I-Device
that	O
use	O
an	O
iron	O
oxide	O
coating	O
.	O
</s>
<s>
Floppy	B-Device
drives	I-Device
utilize	O
300-oersted	O
write	O
heads	O
,	O
FM	B-Protocol
encoding	I-Protocol
,	O
and	O
a	O
track	O
width	O
of	O
for	O
a	O
density	O
of	O
48	O
tracks-per-inch	O
(	O
tpi	O
)	O
and	O
5,876	O
bits-per-inch	O
(	O
bpi	O
)	O
.	O
</s>
<s>
Double	B-Device
density	I-Device
(	O
DD	O
or	O
2D	O
)	O
doubles	O
capacity	O
over	O
SD	O
by	O
replacing	O
FM	B-Protocol
encoding	I-Protocol
with	O
an	O
improved	O
line	B-Protocol
code	I-Protocol
,	O
such	O
as	O
modified	B-Protocol
frequency	I-Protocol
modulation	I-Protocol
(	O
MFM	B-Protocol
)	O
,	O
modified	O
modified	B-Protocol
frequency	I-Protocol
modulation	I-Protocol
(	O
M²FM	O
)	O
,	O
FM/MFM	O
or	O
group	B-Device
coded	I-Device
recording	I-Device
(	O
GCR	B-Device
)	O
.	O
</s>
<s>
The	O
Commodore	B-Device
8050	I-Device
and	O
8250	B-Device
are	O
rare	O
instances	O
of	O
drives	O
that	O
used	O
375kbit/s	O
GCR	B-Device
code	O
instead	O
of	O
the	O
usual	O
250kbit/s	O
double-density	O
format	O
and	O
they	O
could	O
store	O
roughly	O
500	O
kilobytes	O
on	O
one	O
side	O
of	O
a	O
disk	O
.	O
</s>
<s>
Double	B-Device
density	I-Device
(	O
DD	O
)	O
3½-inch	O
disks	O
use	O
an	O
iron	O
oxide	O
coating	O
,	O
just	O
as	O
with	O
5¼-inch	O
DD/QD	O
disks	O
.	O
</s>
<s>
Extra-high	B-Device
density	I-Device
(	O
ED	O
)	O
doubles	O
the	O
capacity	O
over	O
HD	O
by	O
using	O
a	O
barium	O
ferrite	O
coating	O
and	O
a	O
special	O
write	O
head	O
that	O
allows	O
the	O
use	O
of	O
perpendicular	B-Device
recording	I-Device
.	O
</s>
<s>
Line	B-Protocol
code	I-Protocol
FM	B-Protocol
MFM	B-Protocol
,	O
M²FM	O
,	O
FM/MFM	O
or	O
GCR	B-Device
FM	B-Protocol
MFM	B-Protocol
or	O
GCR	B-Device
MFM	B-Protocol
MFM	B-Protocol
MFM	B-Protocol
or	O
GCR	B-Device
MFM	B-Protocol
Track	O
width	O
 [ mm ] 	O
0.330	O
0.160	O
?	O
</s>
