<s>
A	O
floppy	O
disk	B-Device
or	O
floppy	O
diskette	O
(	O
casually	O
referred	O
to	O
as	O
a	O
floppy	O
or	O
a	O
diskette	O
)	O
is	O
a	O
type	O
of	O
disk	B-Device
storage	I-Device
composed	O
of	O
a	O
thin	O
and	O
flexible	O
disk	B-Device
of	O
a	O
magnetic	B-Architecture
storage	I-Architecture
medium	O
in	O
a	O
square	O
or	O
nearly	O
square	O
plastic	O
enclosure	O
lined	O
with	O
a	O
fabric	O
that	O
removes	O
dust	O
particles	O
from	O
the	O
spinning	O
disk	B-Device
.	O
</s>
<s>
Floppy	O
disks	B-Device
store	O
digital	B-General_Concept
data	I-General_Concept
which	O
can	O
be	O
read	O
and	O
written	O
when	O
the	O
disk	B-Device
is	O
inserted	O
into	O
a	O
floppy	O
disk	B-Device
drive	I-Device
(	O
FDD	O
)	O
connected	O
to	O
or	O
inside	O
a	O
computer	O
or	O
other	O
device	O
.	O
</s>
<s>
The	O
first	O
floppy	O
disks	B-Device
,	O
invented	O
and	O
made	O
by	O
IBM	O
,	O
had	O
a	O
disk	B-Device
diameter	O
of	O
.	O
</s>
<s>
3½-inch	O
floppy	O
disks	B-Device
can	O
still	O
be	O
used	O
with	O
an	O
external	O
USB	B-Protocol
floppy	O
disk	B-Device
drive	I-Device
.	O
</s>
<s>
USB	B-Protocol
drives	O
for	O
5¼-inch	O
,	O
8-inch	O
,	O
and	O
other-size	B-Operating_System
floppy	O
disks	B-Device
are	O
rare	O
to	O
non-existent	O
.	O
</s>
<s>
Some	O
individuals	O
and	O
organizations	O
continue	O
to	O
use	O
older	O
equipment	O
to	O
read	O
or	O
transfer	O
data	O
from	O
floppy	O
disks	B-Device
.	O
</s>
<s>
Floppy	O
disks	B-Device
were	O
so	O
common	O
in	O
late	O
20th-century	O
culture	O
that	O
many	O
electronic	O
and	O
software	O
programs	O
continue	O
to	O
use	O
save	O
icons	O
that	O
look	O
like	O
floppy	O
disks	B-Device
well	O
into	O
the	O
21st	O
century	O
,	O
as	O
a	O
form	O
of	O
skeuomorphic	O
design	O
.	O
</s>
<s>
While	O
floppy	O
disk	B-Device
drives	I-Device
still	O
have	O
some	O
limited	O
uses	O
,	O
especially	O
with	O
legacy	B-Device
industrial	I-Device
computer	I-Device
equipment	I-Device
,	O
they	O
have	O
been	O
superseded	O
by	O
data	O
storage	O
methods	O
with	O
much	O
greater	O
data	O
storage	O
capacity	O
and	O
data	O
transfer	O
speed	O
,	O
such	O
as	O
USB	B-Protocol
flash	B-Device
drives	I-Device
,	O
memory	B-Device
cards	I-Device
,	O
optical	B-Device
discs	I-Device
,	O
and	O
storage	O
available	O
through	O
local	O
computer	B-Architecture
networks	I-Architecture
and	O
cloud	O
storage	O
.	O
</s>
<s>
The	O
first	O
commercial	O
floppy	O
disks	B-Device
,	O
developed	O
in	O
the	O
late	O
1960s	O
,	O
were	O
in	O
diameter	O
;	O
they	O
became	O
commercially	O
available	O
in	O
1971	O
as	O
a	O
component	O
of	O
IBM	O
products	O
and	O
both	O
drives	O
and	O
disks	B-Device
were	O
then	O
sold	O
separately	O
starting	O
in	O
1972	O
by	O
Memorex	O
and	O
others	O
.	O
</s>
<s>
These	O
disks	B-Device
and	O
associated	O
drives	O
were	O
produced	O
and	O
improved	O
upon	O
by	O
IBM	O
and	O
other	O
companies	O
such	O
as	O
Memorex	O
,	O
Shugart	O
Associates	O
,	O
and	O
Burroughs	O
Corporation	O
.	O
</s>
<s>
The	O
term	O
"	O
floppy	O
disk	B-Device
"	O
appeared	O
in	O
print	O
as	O
early	O
as	O
1970	O
,	O
IBM	O
's	O
370/145	O
Uncovered	O
;	O
Interesting	O
Curves	O
Revealed	O
,	O
Datamation	O
,	O
November	O
1	O
,	O
1970	O
and	O
although	O
IBM	O
announced	O
its	O
first	O
media	O
as	O
the	O
Type	O
1	O
Diskette	O
in	O
1973	O
,	O
the	O
industry	O
continued	O
to	O
use	O
the	O
terms	O
"	O
floppy	O
disk	B-Device
"	O
or	O
"	O
floppy	O
"	O
.	O
</s>
<s>
There	O
were	O
competing	O
floppy	B-Device
disk	I-Device
formats	I-Device
,	O
with	O
hard	O
-	O
and	O
soft-sector	O
versions	O
and	O
encoding	O
schemes	O
such	O
as	O
differential	B-Protocol
Manchester	I-Protocol
encoding	I-Protocol
(	O
DM	O
)	O
,	O
modified	B-Protocol
frequency	I-Protocol
modulation	I-Protocol
(	O
MFM	B-Protocol
)	O
,	O
M2FM	O
and	O
group	B-Device
coded	I-Device
recording	I-Device
(	O
GCR	B-Device
)	O
.	O
</s>
<s>
The	O
5¼-inch	O
format	O
displaced	O
the	O
8-inch	O
one	O
for	O
most	O
uses	O
,	O
and	O
the	O
hard-sectored	B-Architecture
disk	B-Application
format	I-Application
disappeared	O
.	O
</s>
<s>
The	O
most	O
common	O
capacity	O
of	O
the	O
5¼-inch	O
format	O
in	O
DOS-based	O
PCs	B-Device
was	O
360	O
KB	O
(	O
368,640	O
bytes	O
)	O
for	O
the	O
Double-Sided	O
Double-Density	O
(	O
DSDD	O
)	O
format	O
using	O
MFM	B-Protocol
encoding	I-Protocol
.	O
</s>
<s>
In	O
1984	O
,	O
IBM	O
introduced	O
with	O
its	O
PC/AT	B-Operating_System
the	O
1.2	O
MB	O
(	O
1,228,800	O
bytes	O
)	O
dual-sided	O
5¼-inch	O
floppy	O
disk	B-Device
,	O
but	O
it	O
never	O
became	O
very	O
popular	O
.	O
</s>
<s>
IBM	O
started	O
using	O
the	O
720	O
KB	O
double	B-Device
density	I-Device
3½-inch	O
microfloppy	O
disk	B-Device
on	O
its	O
Convertible	B-Device
laptop	O
computer	O
in	O
1986	O
and	O
the	O
1.44	O
MB	O
high-density	O
version	O
with	O
the	O
IBM	B-Device
Personal	I-Device
System/2	I-Device
(	O
PS/2	B-Device
)	O
line	O
in	O
1987	O
.	O
</s>
<s>
These	O
disk	B-Device
drives	I-Device
could	O
be	O
added	O
to	O
older	O
PC	O
models	O
.	O
</s>
<s>
In	O
1988	O
,	O
Y-E	O
Data	O
introduced	O
a	O
drive	O
for	O
2.88	O
MB	O
Double-Sided	O
Extended-Density	O
(	O
DSED	O
)	O
diskettes	O
which	O
was	O
used	O
by	O
IBM	O
in	O
its	O
top-of-the-line	O
PS/2	B-Device
and	O
some	O
RS/6000	B-Device
models	O
and	O
in	O
the	O
second-generation	O
NeXTcube	B-Device
and	O
NeXTstation	B-Device
;	O
however	O
,	O
this	O
format	O
had	O
limited	O
market	O
success	O
due	O
to	O
lack	O
of	O
standards	O
and	O
movement	O
to	O
1.44	O
MB	O
drives	O
.	O
</s>
<s>
245	O
–	O
7	O
Several	O
solutions	O
were	O
developed	O
,	O
with	O
drives	O
at	O
2-	O
,	O
2½-	O
,	O
3-	O
,	O
3¼-	O
,	O
Picture	O
of	O
disk	B-Device
3½	O
-	O
and	O
4-inches	O
(	O
and	O
Sony	O
's	O
disk	B-Device
)	O
offered	O
by	O
various	O
companies	O
.	O
</s>
<s>
They	O
all	O
had	O
several	O
advantages	O
over	O
the	O
old	O
format	O
,	O
including	O
a	O
rigid	O
case	O
with	O
a	O
sliding	O
metal	O
(	O
or	O
later	O
,	O
sometimes	O
plastic	O
)	O
shutter	O
over	O
the	O
head	O
slot	O
,	O
which	O
helped	O
protect	O
the	O
delicate	O
magnetic	B-Architecture
medium	I-Architecture
from	O
dust	O
and	O
damage	O
,	O
and	O
a	O
sliding	O
write	B-Device
protection	I-Device
tab	O
,	O
which	O
was	O
far	O
more	O
convenient	O
than	O
the	O
adhesive	O
tabs	O
used	O
with	O
earlier	O
disks	B-Device
.	O
</s>
<s>
Generally	O
,	O
the	O
term	O
floppy	O
disk	B-Device
persisted	O
,	O
even	O
though	O
later	O
style	O
floppy	O
disks	B-Device
have	O
a	O
rigid	O
case	O
around	O
an	O
internal	O
floppy	O
disk	B-Device
.	O
</s>
<s>
By	O
the	O
end	O
of	O
the	O
1980s	O
,	O
5¼-inch	O
disks	B-Device
had	O
been	O
superseded	O
by	O
3½-inch	O
disks	B-Device
.	O
</s>
<s>
During	O
this	O
time	O
,	O
PCs	B-Device
frequently	O
came	O
equipped	O
with	O
drives	O
of	O
both	O
sizes	O
.	O
</s>
<s>
By	O
the	O
mid-1990s	O
,	O
5¼-inch	O
drives	O
had	O
virtually	O
disappeared	O
,	O
as	O
the	O
3½-inch	O
disk	B-Device
became	O
the	O
predominant	O
floppy	O
disk	B-Device
.	O
</s>
<s>
The	O
advantages	O
of	O
the	O
3½-inch	O
disk	B-Device
were	O
its	O
higher	O
capacity	O
,	O
its	O
smaller	O
physical	O
size	O
,	O
and	O
its	O
rigid	O
case	O
which	O
provided	O
better	O
protection	O
from	O
dirt	O
and	O
other	O
environmental	O
risks	O
.	O
</s>
<s>
Floppy	O
disks	B-Device
became	O
commonplace	O
during	O
the	O
1980s	O
and	O
1990s	O
in	O
their	O
use	O
with	O
personal	B-Device
computers	I-Device
to	O
distribute	O
software	O
,	O
transfer	O
data	O
,	O
and	O
create	O
backups	B-Protocol
.	O
</s>
<s>
Before	O
hard	B-Device
disks	I-Device
became	O
affordable	O
to	O
the	O
general	O
population	O
,	O
floppy	O
disks	B-Device
were	O
often	O
used	O
to	O
store	O
a	O
computer	O
's	O
operating	B-General_Concept
system	I-General_Concept
(	O
OS	B-General_Concept
)	O
.	O
</s>
<s>
Most	O
home	O
computers	O
from	O
that	O
time	O
have	O
an	O
elementary	O
OS	B-General_Concept
and	O
BASIC	O
stored	O
in	O
read-only	B-Device
memory	I-Device
(	O
ROM	B-Device
)	O
,	O
with	O
the	O
option	O
of	O
loading	O
a	O
more	O
advanced	O
OS	B-General_Concept
from	O
a	O
floppy	O
disk	B-Device
.	O
</s>
<s>
By	O
the	O
early	O
1990s	O
,	O
the	O
increasing	O
software	O
size	O
meant	O
large	O
packages	O
like	O
Windows	B-Application
or	O
Adobe	B-Operating_System
Photoshop	I-Operating_System
required	O
a	O
dozen	O
disks	B-Device
or	O
more	O
.	O
</s>
<s>
In	O
1996	O
,	O
there	O
were	O
an	O
estimated	O
five	O
billion	O
standard	O
floppy	O
disks	B-Device
in	O
use	O
.	O
</s>
<s>
Then	O
,	O
distribution	O
of	O
larger	O
packages	O
was	O
gradually	O
replaced	O
by	O
CD-ROMs	B-Device
,	O
DVDs	O
,	O
and	O
online	O
distribution	O
.	O
</s>
<s>
An	O
attempt	O
to	O
enhance	O
the	O
existing	O
3½-inch	O
designs	O
was	O
the	O
SuperDisk	B-Device
in	O
the	O
late	O
1990s	O
,	O
using	O
very	O
narrow	O
data	O
tracks	O
and	O
a	O
high	O
precision	O
head	O
guidance	O
mechanism	O
with	O
a	O
capacity	O
of	O
120	O
MB	O
and	O
backward-compatibility	B-General_Concept
with	O
standard	O
3½-inch	O
floppies	O
;	O
a	O
format	O
war	O
briefly	O
occurred	O
between	O
SuperDisk	B-Device
and	O
other	O
high-density	O
floppy-disk	O
products	O
,	O
although	O
ultimately	O
recordable	O
CDs/DVDs	O
,	O
solid-state	O
flash	O
storage	O
,	O
and	O
eventually	O
cloud-based	O
online	O
storage	O
would	O
render	O
all	O
these	O
removable	O
disk	B-Application
formats	I-Application
obsolete	O
.	O
</s>
<s>
External	O
USB-based	O
floppy	O
disk	B-Device
drives	I-Device
are	O
still	O
available	O
,	O
and	O
many	O
modern	O
systems	O
provide	O
firmware	B-Application
support	O
for	O
booting	O
from	O
such	O
drives	O
.	O
</s>
<s>
In	O
the	O
mid-1990s	O
,	O
mechanically	O
incompatible	O
higher-density	O
floppy	O
disks	B-Device
were	O
introduced	O
,	O
like	O
the	O
Iomega	B-Operating_System
Zip	I-Operating_System
disk	I-Operating_System
.	O
</s>
<s>
Adoption	O
was	O
limited	O
by	O
the	O
competition	O
between	O
proprietary	O
formats	O
and	O
the	O
need	O
to	O
buy	O
expensive	O
drives	O
for	O
computers	O
where	O
the	O
disks	B-Device
would	O
be	O
used	O
.	O
</s>
<s>
In	O
some	O
cases	O
,	O
failure	O
in	O
market	O
penetration	O
was	O
exacerbated	O
by	O
the	O
release	O
of	O
higher-capacity	O
versions	O
of	O
the	O
drive	O
and	O
media	O
being	O
not	O
backward-compatible	B-General_Concept
with	O
the	O
original	O
drives	O
,	O
dividing	O
the	O
users	O
between	O
new	O
and	O
old	O
adopters	O
.	O
</s>
<s>
Apple	O
introduced	O
the	O
iMac	B-Device
G3	I-Device
in	O
1998	O
with	O
a	O
CD-ROM	B-Device
drive	O
but	O
no	O
floppy	O
drive	O
;	O
this	O
made	O
USB-connected	O
floppy	O
drives	O
popular	O
accessories	O
,	O
as	O
the	O
iMac	O
came	O
without	O
any	O
writable	O
removable	O
media	O
device	O
.	O
</s>
<s>
Recordable	O
CDs	O
were	O
touted	O
as	O
an	O
alternative	O
,	O
because	O
of	O
the	O
greater	O
capacity	O
,	O
compatibility	O
with	O
existing	O
CD-ROM	B-Device
drives	O
,	O
and	O
—	O
with	O
the	O
advent	O
of	O
re-writeable	O
CDs	O
and	O
packet	O
writing	O
—	O
a	O
similar	O
reusability	O
as	O
floppy	O
disks	B-Device
.	O
</s>
<s>
Other	O
formats	O
,	O
such	O
as	O
magneto-optical	B-Device
discs	I-Device
,	O
had	O
the	O
flexibility	O
of	O
floppy	O
disks	B-Device
combined	O
with	O
greater	O
capacity	O
,	O
but	O
remained	O
niche	O
due	O
to	O
costs	O
.	O
</s>
<s>
High-capacity	O
backward	B-General_Concept
compatible	I-General_Concept
floppy	O
technologies	O
became	O
popular	O
for	O
a	O
while	O
and	O
were	O
sold	O
as	O
an	O
option	O
or	O
even	O
included	O
in	O
standard	O
PCs	B-Device
,	O
but	O
in	O
the	O
long	O
run	O
,	O
their	O
use	O
was	O
limited	O
to	O
professionals	O
and	O
enthusiasts	O
.	O
</s>
<s>
Flash-based	O
USB-thumb	O
drives	O
finally	O
were	O
a	O
practical	O
and	O
popular	O
replacement	O
,	O
that	O
supported	O
traditional	O
file	O
systems	O
and	O
all	O
common	O
usage	O
scenarios	O
of	O
floppy	O
disks	B-Device
.	O
</s>
<s>
As	O
opposed	O
to	O
other	O
solutions	O
,	O
no	O
new	O
drive	O
type	O
or	O
special	O
software	O
was	O
required	O
that	O
impeded	O
adoption	O
,	O
since	O
all	O
that	O
was	O
necessary	O
was	O
an	O
already	O
common	O
USB	B-Protocol
port	O
.	O
</s>
<s>
thumb|left|A	O
floppy	B-Device
hardware	I-Device
emulator	I-Device
,	O
same	O
size	O
as	O
a	O
3½-inch	O
drive	O
,	O
provides	O
a	O
USB	B-Protocol
interface	O
to	O
the	O
user	O
.	O
</s>
<s>
By	O
2002	O
,	O
most	O
manufacturers	O
still	O
provided	O
floppy	O
disk	B-Device
drives	I-Device
as	O
standard	O
equipment	O
to	O
meet	O
user	O
demand	O
for	O
file-transfer	O
and	O
an	O
emergency	B-Operating_System
boot	I-Operating_System
device	O
,	O
as	O
well	O
as	O
for	O
the	O
general	O
secure	O
feeling	O
of	O
having	O
the	O
familiar	O
device	O
.	O
</s>
<s>
Subsequently	O
,	O
enabled	O
by	O
the	O
widespread	O
support	O
for	O
USB	B-Protocol
flash	B-Device
drives	I-Device
and	O
BIOS	B-Operating_System
boot	O
,	O
manufacturers	O
and	O
retailers	O
progressively	O
reduced	O
the	O
availability	O
of	O
floppy	O
disk	B-Device
drives	I-Device
as	O
standard	O
equipment	O
.	O
</s>
<s>
In	O
February	O
2003	O
,	O
Dell	O
,	O
one	O
of	O
the	O
leading	O
personal	B-Device
computer	I-Device
vendors	O
,	O
announced	O
that	O
floppy	O
drives	O
would	O
no	O
longer	O
be	O
pre-installed	O
on	O
Dell	O
Dimension	O
home	O
computers	O
,	O
although	O
they	O
were	O
still	O
available	O
as	O
a	O
selectable	O
option	O
and	O
purchasable	O
as	O
an	O
aftermarket	O
OEM	O
add-on	O
.	O
</s>
<s>
By	O
January	O
2007	O
,	O
only	O
2%	O
of	O
computers	O
sold	O
in	O
stores	O
contained	O
built-in	O
floppy	O
disk	B-Device
drives	I-Device
.	O
</s>
<s>
Floppy	O
disks	B-Device
are	O
used	O
for	O
emergency	B-Operating_System
boots	I-Operating_System
in	O
aging	O
systems	O
lacking	O
support	O
for	O
other	O
bootable	B-Operating_System
media	I-Operating_System
and	O
for	O
BIOS	B-Operating_System
updates	O
,	O
since	O
most	O
BIOS	B-Operating_System
and	O
firmware	B-Application
programs	O
can	O
still	O
be	O
executed	O
from	O
bootable	B-Operating_System
floppy	I-Operating_System
disks	B-Device
.	O
</s>
<s>
If	O
BIOS	B-Operating_System
updates	O
fail	O
or	O
become	O
corrupt	O
,	O
floppy	O
drives	O
can	O
sometimes	O
be	O
used	O
to	O
perform	O
a	O
recovery	O
.	O
</s>
<s>
The	O
music	O
and	O
theatre	O
industries	O
still	O
use	O
equipment	O
requiring	O
standard	O
floppy	O
disks	B-Device
(	O
e.g.	O
</s>
<s>
synthesizers	O
,	O
samplers	O
,	O
drum	O
machines	O
,	O
sequencers	O
,	O
and	O
lighting	B-Application
consoles	I-Application
)	O
.	O
</s>
<s>
Industrial	O
automation	O
equipment	O
such	O
as	O
programmable	O
machinery	O
and	O
industrial	O
robots	O
may	O
not	O
have	O
a	O
USB	B-Protocol
interface	O
;	O
data	O
and	O
programs	O
are	O
then	O
loaded	O
from	O
disks	B-Device
,	O
damageable	O
in	O
industrial	O
environments	O
.	O
</s>
<s>
This	O
equipment	O
may	O
not	O
be	O
replaced	O
due	O
to	O
cost	O
or	O
requirement	O
for	O
continuous	O
availability	O
;	O
existing	O
software	O
emulation	O
and	O
virtualization	B-General_Concept
do	O
not	O
solve	O
this	O
problem	O
because	O
a	O
customized	O
operating	B-General_Concept
system	I-General_Concept
is	O
used	O
that	O
has	O
no	O
drivers	B-Application
for	O
USB	B-Protocol
devices	O
.	O
</s>
<s>
Hardware	B-Device
floppy	I-Device
disk	I-Device
emulators	I-Device
can	O
be	O
made	O
to	O
interface	O
floppy-disk	B-Device
controllers	I-Device
to	O
a	O
USB	B-Protocol
port	O
that	O
can	O
be	O
used	O
for	O
flash	B-Device
drives	I-Device
.	O
</s>
<s>
In	O
May	O
2016	O
,	O
the	O
United	O
States	O
Government	O
Accountability	O
Office	O
released	O
a	O
report	O
that	O
covered	O
the	O
need	O
to	O
upgrade	O
or	O
replace	O
legacy	B-Device
computer	I-Device
systems	I-Device
within	O
federal	O
agencies	O
.	O
</s>
<s>
According	O
to	O
this	O
document	O
,	O
old	O
IBM	B-Device
Series/1	I-Device
minicomputers	O
running	O
on	O
8-inch	O
floppy	O
disks	B-Device
are	O
still	O
used	O
to	O
coordinate	O
"	O
the	O
operational	O
functions	O
of	O
the	O
United	O
States	O
 '	O
nuclear	O
forces	O
"	O
.	O
</s>
<s>
Windows	B-Operating_System
10	I-Operating_System
and	O
Windows	B-Application
11	I-Application
no	O
longer	O
comes	O
with	O
drivers	B-Application
for	O
floppy	O
disk	B-Device
drives	I-Device
(	O
both	O
internal	O
and	O
external	O
)	O
.	O
</s>
<s>
However	O
,	O
they	O
will	O
still	O
support	O
them	O
with	O
a	O
separate	O
device	B-Application
driver	I-Application
provided	O
by	O
Microsoft	O
.	O
</s>
<s>
The	O
British	O
Airways	O
Boeing	O
747-400	O
fleet	O
,	O
up	O
to	O
its	O
retirement	O
in	O
2020	O
,	O
used	O
3.5-inch	O
floppy	O
disks	B-Device
to	O
load	O
avionics	O
software	O
.	O
</s>
<s>
Some	O
workstations	O
in	O
corporate	O
computing	O
environments	O
still	O
retained	O
floppy	O
disks	B-Device
while	O
disabling	O
USB	B-Protocol
ports	O
,	O
both	O
moves	O
done	O
to	O
restrict	O
the	O
amount	O
of	O
data	O
that	O
could	O
be	O
copied	O
by	O
unscrupulous	O
employees	O
.	O
</s>
<s>
Sony	O
,	O
who	O
had	O
been	O
in	O
the	O
floppy	O
disk	B-Device
business	O
since	O
1983	O
,	O
ended	O
domestic	O
sales	O
of	O
all	O
six	O
3.5-inch	O
floppy	O
disk	B-Device
models	O
as	O
of	O
March	O
2011	O
.	O
</s>
<s>
This	O
has	O
been	O
viewed	O
by	O
some	O
as	O
the	O
end	O
of	O
the	O
floppy	O
disk	B-Device
.	O
</s>
<s>
While	O
production	O
of	O
new	O
floppy	O
disk	B-Device
media	O
has	O
ceased	O
,	O
sales	O
and	O
uses	O
of	O
this	O
media	O
from	O
inventories	O
is	O
expected	O
to	O
continue	O
until	O
at	O
least	O
2026	O
.	O
</s>
<s>
For	O
more	O
than	O
two	O
decades	O
,	O
the	O
floppy	O
disk	B-Device
was	O
the	O
primary	O
external	O
writable	O
storage	O
device	O
used	O
.	O
</s>
<s>
Most	O
computing	O
environments	O
before	O
the	O
1990s	O
were	O
non-networked	O
,	O
and	O
floppy	O
disks	B-Device
were	O
the	O
primary	O
means	O
to	O
transfer	O
data	O
between	O
computers	O
,	O
a	O
method	O
known	O
informally	O
as	O
sneakernet	O
.	O
</s>
<s>
Unlike	O
hard	B-Device
disks	I-Device
,	O
floppy	O
disks	B-Device
are	O
handled	O
and	O
seen	O
;	O
even	O
a	O
novice	O
user	O
can	O
identify	O
a	O
floppy	O
disk	B-Device
.	O
</s>
<s>
Because	O
of	O
these	O
factors	O
,	O
a	O
picture	O
of	O
a	O
3½-inch	O
floppy	O
disk	B-Device
became	O
an	O
interface	B-Architecture
metaphor	I-Architecture
for	O
saving	O
data	O
.	O
</s>
<s>
The	O
floppy	O
disk	B-Device
symbol	O
is	O
still	O
used	O
by	O
software	O
on	O
user-interface	O
elements	O
related	O
to	O
saving	O
files	O
(	O
such	O
as	O
Microsoft	B-Application
Office	I-Application
2021	I-Application
)	O
even	O
though	O
physical	O
floppy	O
disks	B-Device
are	O
largely	O
obsolete	O
.	O
</s>
<s>
thumb|upright|Disk	O
notcher	O
converts	O
single-sided	O
5¼-inch	O
diskettes	O
to	O
double-sided	O
.	O
</s>
<s>
The	O
8-inch	O
and	O
5¼-inch	O
floppy	O
disks	B-Device
contain	O
a	O
magnetically	O
coated	O
round	O
plastic	O
medium	O
with	O
a	O
large	O
circular	O
hole	O
in	O
the	O
center	O
for	O
a	O
drive	O
's	O
spindle	O
.	O
</s>
<s>
The	O
medium	O
is	O
contained	O
in	O
a	O
square	O
plastic	O
cover	O
that	O
has	O
a	O
small	O
oblong	O
opening	O
in	O
both	O
sides	O
to	O
allow	O
the	O
drive	O
's	O
heads	O
to	O
read	O
and	O
write	O
data	O
and	O
a	O
large	O
hole	O
in	O
the	O
center	O
to	O
allow	O
the	O
magnetic	B-Architecture
medium	I-Architecture
to	O
spin	O
by	O
rotating	O
it	O
from	O
its	O
middle	O
hole	O
.	O
</s>
<s>
Inside	O
the	O
cover	O
are	O
two	O
layers	O
of	O
fabric	O
with	O
the	O
magnetic	B-Architecture
medium	I-Architecture
sandwiched	O
in	O
the	O
middle	O
.	O
</s>
<s>
The	O
fabric	O
is	O
designed	O
to	O
reduce	O
friction	O
between	O
the	O
medium	O
and	O
the	O
outer	O
cover	O
,	O
and	O
catch	O
particles	O
of	O
debris	O
abraded	O
off	O
the	O
disk	B-Device
to	O
keep	O
them	O
from	O
accumulating	O
on	O
the	O
heads	O
.	O
</s>
<s>
A	O
small	O
notch	O
on	O
the	O
side	O
of	O
the	O
disk	B-Device
identifies	O
that	O
it	O
is	O
writable	O
,	O
detected	O
by	O
a	O
mechanical	O
switch	O
or	O
phototransistor	O
above	O
it	O
;	O
if	O
it	O
is	O
not	O
present	O
,	O
the	O
disk	B-Device
can	O
be	O
written	O
;	O
in	O
the	O
8-inch	O
disk	B-Device
the	O
notch	O
is	O
covered	O
to	O
enable	O
writing	O
while	O
in	O
the	O
5¼-inch	O
disk	B-Device
the	O
notch	O
is	O
open	O
to	O
enable	O
writing	O
.	O
</s>
<s>
Tape	O
may	O
be	O
used	O
over	O
the	O
notch	O
to	O
change	O
the	O
mode	O
of	O
the	O
disk	B-Device
.	O
</s>
<s>
Punch	O
devices	O
were	O
sold	O
to	O
convert	O
read-only	O
disks	B-Device
to	O
writable	O
ones	O
and	O
enable	O
writing	O
on	O
the	O
unused	O
side	O
of	O
single	O
sided	O
disks	B-Device
;	O
such	O
modified	O
disks	B-Device
became	O
known	O
as	O
flippy	O
disks	B-Device
.	O
</s>
<s>
Another	O
LED/photo	O
-transistor	O
pair	O
located	O
near	O
the	O
center	O
of	O
the	O
disk	B-Device
detects	O
the	O
index	B-Architecture
hole	I-Architecture
once	O
per	O
rotation	O
in	O
the	O
magnetic	B-Architecture
disk	I-Architecture
;	O
it	O
is	O
used	O
to	O
detect	O
the	O
angular	O
start	O
of	O
each	O
track	O
and	O
whether	O
or	O
not	O
the	O
disk	B-Device
is	O
rotating	O
at	O
the	O
correct	O
speed	O
.	O
</s>
<s>
Early	O
8‑inch	O
and	O
5¼‑inch	O
disks	B-Device
had	O
physical	O
holes	O
for	O
each	O
sector	O
and	O
were	O
termed	O
hard	B-Architecture
sectored	I-Architecture
disks	B-Device
.	O
</s>
<s>
Later	O
soft-sectored	O
disks	B-Device
have	O
only	O
one	O
index	B-Architecture
hole	I-Architecture
,	O
and	O
sector	O
position	O
is	O
determined	O
by	O
the	O
disk	B-Device
controller	O
or	O
low-level	O
software	O
from	O
patterns	O
marking	O
the	O
start	O
of	O
a	O
sector	O
.	O
</s>
<s>
Generally	O
,	O
the	O
same	O
drives	O
are	O
used	O
to	O
read	O
and	O
write	O
both	O
types	O
of	O
disks	B-Device
,	O
with	O
only	O
the	O
disks	B-Device
and	O
controllers	O
differing	O
.	O
</s>
<s>
Some	O
operating	B-General_Concept
systems	I-General_Concept
using	O
soft	O
sectors	B-Application
,	O
such	O
as	O
Apple	B-Operating_System
DOS	I-Operating_System
,	O
do	O
not	O
use	O
the	O
index	B-Architecture
hole	I-Architecture
,	O
and	O
the	O
drives	O
designed	O
for	O
such	O
systems	O
often	O
lack	O
the	O
corresponding	O
sensor	O
;	O
this	O
was	O
mainly	O
a	O
hardware	O
cost-saving	O
measure	O
.	O
</s>
<s>
The	O
core	O
of	O
the	O
3½-inch	O
disk	B-Device
is	O
the	O
same	O
as	O
the	O
other	O
two	O
disks	B-Device
,	O
but	O
the	O
front	O
has	O
only	O
a	O
label	O
and	O
a	O
small	O
opening	O
for	O
reading	O
and	O
writing	O
data	O
,	O
protected	O
by	O
the	O
shutter	O
—	O
a	O
spring-loaded	O
metal	O
or	O
plastic	O
cover	O
,	O
pushed	O
to	O
the	O
side	O
on	O
entry	O
into	O
the	O
drive	O
.	O
</s>
<s>
Typical	O
3½-inch	O
disk	B-Device
magnetic	O
coating	O
materials	O
are	O
:	O
</s>
<s>
Two	O
holes	O
at	O
the	O
bottom	O
left	O
and	O
right	O
indicate	O
whether	O
the	O
disk	B-Device
is	O
write-protected	B-Device
and	O
whether	O
it	O
is	O
high-density	O
;	O
these	O
holes	O
are	O
spaced	O
as	O
far	O
apart	O
as	O
the	O
holes	O
in	O
punched	O
A4	O
paper	O
,	O
allowing	O
write-protected	B-Device
high-density	O
floppies	O
to	O
be	O
clipped	O
into	O
standard	O
ring	O
binders	O
.	O
</s>
<s>
The	O
dimensions	O
of	O
the	O
disk	B-Device
shell	O
are	O
not	O
quite	O
square	O
:	O
its	O
width	O
is	O
slightly	O
less	O
than	O
its	O
depth	O
,	O
so	O
that	O
it	O
is	O
impossible	O
to	O
insert	O
the	O
disk	B-Device
into	O
a	O
drive	O
slot	O
sideways	O
(	O
i.e.	O
</s>
<s>
A	O
diagonal	O
notch	O
at	O
top	O
right	O
ensures	O
that	O
the	O
disk	B-Device
is	O
inserted	O
into	O
the	O
drive	O
in	O
the	O
correct	O
orientation	O
—	O
not	O
upside	O
down	O
or	O
label-end	O
first	O
—	O
and	O
an	O
arrow	O
at	O
top	O
left	O
indicates	O
direction	O
of	O
insertion	O
.	O
</s>
<s>
The	O
drive	O
usually	O
has	O
a	O
button	O
that	O
,	O
when	O
pressed	O
,	O
ejects	O
the	O
disk	B-Device
with	O
varying	O
degrees	O
of	O
force	O
,	O
the	O
discrepancy	O
due	O
to	O
the	O
ejection	O
force	O
provided	O
by	O
the	O
spring	O
of	O
the	O
shutter	O
.	O
</s>
<s>
In	O
IBM	B-Device
PC	I-Device
compatibles	O
,	O
Commodores	O
,	O
Apple	O
II/IIIs	O
,	O
and	O
other	O
non-Apple-Macintosh	O
machines	O
with	O
standard	O
floppy	O
disk	B-Device
drives	I-Device
,	O
a	O
disk	B-Device
may	O
be	O
ejected	O
manually	O
at	O
any	O
time	O
.	O
</s>
<s>
The	O
drive	O
has	O
a	O
disk-change	O
switch	O
that	O
detects	O
when	O
a	O
disk	B-Device
is	O
ejected	O
or	O
inserted	O
.	O
</s>
<s>
Failure	O
of	O
this	O
mechanical	O
switch	O
is	O
a	O
common	O
source	O
of	O
disk	B-Device
corruption	O
if	O
a	O
disk	B-Device
is	O
changed	O
and	O
the	O
drive	O
(	O
and	O
hence	O
the	O
operating	B-General_Concept
system	I-General_Concept
)	O
fails	O
to	O
notice	O
.	O
</s>
<s>
One	O
of	O
the	O
chief	O
usability	B-General_Concept
problems	O
of	O
the	O
floppy	O
disk	B-Device
is	O
its	O
vulnerability	O
;	O
even	O
inside	O
a	O
closed	O
plastic	O
housing	O
,	O
the	O
disk	B-Device
medium	O
is	O
highly	O
sensitive	O
to	O
dust	O
,	O
condensation	O
and	O
temperature	O
extremes	O
.	O
</s>
<s>
As	O
with	O
all	O
magnetic	B-Architecture
storage	I-Architecture
,	O
it	O
is	O
vulnerable	O
to	O
magnetic	O
fields	O
.	O
</s>
<s>
Blank	O
disks	B-Device
have	O
been	O
distributed	O
with	O
an	O
extensive	O
set	O
of	O
warnings	O
,	O
cautioning	O
the	O
user	O
not	O
to	O
expose	O
it	O
to	O
dangerous	O
conditions	O
.	O
</s>
<s>
Rough	O
treatment	O
or	O
removing	O
the	O
disk	B-Device
from	O
the	O
drive	O
while	O
the	O
magnetic	B-Architecture
media	I-Architecture
is	O
still	O
spinning	O
is	O
likely	O
to	O
cause	O
damage	O
to	O
the	O
disk	B-Device
,	O
drive	B-Device
head	I-Device
,	O
or	O
stored	O
data	O
.	O
</s>
<s>
On	O
the	O
other	O
hand	O
,	O
the	O
3½‑inch	O
floppy	O
has	O
been	O
lauded	O
for	O
its	O
mechanical	O
usability	B-General_Concept
by	O
human	O
–	O
computer	O
interaction	O
expert	O
Donald	O
Norman	O
:	O
</s>
<s>
thumb|left|Visualization	O
of	O
magnetic	O
information	O
on	O
floppy	O
disk	B-Device
(	O
image	O
recorded	O
with	O
CMOS-MagView	O
)	O
A	O
spindle	O
motor	O
in	O
the	O
drive	O
rotates	O
the	O
magnetic	B-Architecture
medium	I-Architecture
at	O
a	O
certain	O
speed	O
,	O
while	O
a	O
stepper	O
motor-operated	O
mechanism	O
moves	O
the	O
magnetic	O
read/write	B-Device
heads	I-Device
radially	O
along	O
the	O
surface	O
of	O
the	O
disk	B-Device
.	O
</s>
<s>
Both	O
read	O
and	O
write	O
operations	O
require	O
the	O
media	O
to	O
be	O
rotating	O
and	O
the	O
head	O
to	O
contact	O
the	O
disk	B-Device
media	O
,	O
an	O
action	O
originally	O
accomplished	O
by	O
a	O
disk-load	O
solenoid	O
.	O
</s>
<s>
Later	O
drives	O
held	O
the	O
heads	O
out	O
of	O
contact	O
until	O
a	O
front-panel	O
lever	O
was	O
rotated	O
(	O
5¼-inch	O
)	O
or	O
disk	B-Device
insertion	O
was	O
complete	O
(	O
3½-inch	O
)	O
.	O
</s>
<s>
This	O
small	O
signal	O
is	O
amplified	O
and	O
sent	O
to	O
the	O
floppy	B-Device
disk	I-Device
controller	I-Device
,	O
which	O
converts	O
the	O
streams	O
of	O
pulses	O
from	O
the	O
media	O
into	O
data	O
,	O
checks	O
it	O
for	O
errors	O
,	O
and	O
sends	O
it	O
to	O
the	O
host	O
computer	O
system	O
.	O
</s>
<s>
During	O
formatting	O
,	O
the	O
magnetizations	O
of	O
the	O
particles	O
are	O
aligned	O
forming	O
tracks	O
,	O
each	O
broken	O
up	O
into	O
sectors	B-Application
,	O
enabling	O
the	O
controller	O
to	O
properly	O
read	O
and	O
write	O
data	O
.	O
</s>
<s>
The	O
tracks	O
are	O
concentric	O
rings	O
around	O
the	O
center	O
,	O
with	O
spaces	O
between	O
tracks	O
where	O
no	O
data	O
is	O
written	O
;	O
gaps	O
with	O
padding	O
bytes	O
are	O
provided	O
between	O
the	O
sectors	B-Application
and	O
at	O
the	O
end	O
of	O
the	O
track	O
to	O
allow	O
for	O
slight	O
speed	O
variations	O
in	O
the	O
disk	B-Device
drive	I-Device
,	O
and	O
to	O
permit	O
better	O
interoperability	O
with	O
disk	B-Device
drives	I-Device
connected	O
to	O
other	O
similar	O
systems	O
.	O
</s>
<s>
Each	O
sector	O
of	O
data	O
has	O
a	O
header	O
that	O
identifies	O
the	O
sector	O
location	O
on	O
the	O
disk	B-Device
.	O
</s>
<s>
A	O
cyclic	O
redundancy	O
check	O
(	O
CRC	O
)	O
is	O
written	O
into	O
the	O
sector	O
headers	O
and	O
at	O
the	O
end	O
of	O
the	O
user	O
data	O
so	O
that	O
the	O
disk	B-Device
controller	O
can	O
detect	O
potential	O
errors	O
.	O
</s>
<s>
Some	O
errors	O
are	O
soft	O
and	O
can	O
be	O
resolved	O
by	O
automatically	O
re-trying	O
the	O
read	O
operation	O
;	O
other	O
errors	O
are	O
permanent	O
and	O
the	O
disk	B-Device
controller	O
will	O
signal	O
a	O
failure	O
to	O
the	O
operating	B-General_Concept
system	I-General_Concept
if	O
multiple	O
attempts	O
to	O
read	O
the	O
data	O
still	O
fail	O
.	O
</s>
<s>
After	O
a	O
disk	B-Device
is	O
inserted	O
,	O
a	O
catch	O
or	O
lever	O
at	O
the	O
front	O
of	O
the	O
drive	O
is	O
manually	O
lowered	O
to	O
prevent	O
the	O
disk	B-Device
from	O
accidentally	O
emerging	O
,	O
engage	O
the	O
spindle	O
clamping	O
hub	O
,	O
and	O
in	O
two-sided	O
drives	O
,	O
engage	O
the	O
second	O
read/write	B-Device
head	I-Device
with	O
the	O
media	O
.	O
</s>
<s>
In	O
some	O
5¼-inch	O
drives	O
,	O
insertion	O
of	O
the	O
disk	B-Device
compresses	O
and	O
locks	O
an	O
ejection	O
spring	O
which	O
partially	O
ejects	O
the	O
disk	B-Device
upon	O
opening	O
the	O
catch	O
or	O
lever	O
.	O
</s>
<s>
This	O
enables	O
a	O
smaller	O
concave	O
area	O
for	O
the	O
thumb	O
and	O
fingers	O
to	O
grasp	O
the	O
disk	B-Device
during	O
removal	O
.	O
</s>
<s>
Newer	O
5¼-inch	O
drives	O
and	O
all	O
3½-inch	O
drives	O
automatically	O
engage	O
the	O
spindle	O
and	O
heads	O
when	O
a	O
disk	B-Device
is	O
inserted	O
,	O
doing	O
the	O
opposite	O
with	O
the	O
press	O
of	O
the	O
eject	O
button	O
.	O
</s>
<s>
On	O
Apple	B-Device
Macintosh	I-Device
computers	I-Device
with	O
built-in	O
3½-inch	O
disk	B-Device
drives	I-Device
,	O
the	O
ejection	O
button	O
is	O
replaced	O
by	O
software	O
controlling	O
an	O
ejection	O
motor	O
which	O
only	O
does	O
so	O
when	O
the	O
operating	B-General_Concept
system	I-General_Concept
no	O
longer	O
needs	O
to	O
access	O
the	O
drive	O
.	O
</s>
<s>
The	O
user	O
could	O
drag	O
the	O
image	O
of	O
the	O
floppy	O
drive	O
to	O
the	O
trash	O
can	O
on	O
the	O
desktop	O
to	O
eject	O
the	O
disk	B-Device
.	O
</s>
<s>
In	O
the	O
case	O
of	O
a	O
power	O
failure	O
or	O
drive	O
malfunction	O
,	O
a	O
loaded	O
disk	B-Device
can	O
be	O
removed	O
manually	O
by	O
inserting	O
a	O
straightened	O
paper	O
clip	O
into	O
a	O
small	O
hole	O
at	O
the	O
drive	O
's	O
front	O
panel	O
,	O
just	O
as	O
one	O
would	O
do	O
with	O
a	O
CD-ROM	B-Device
drive	O
in	O
a	O
similar	O
situation	O
.	O
</s>
<s>
The	O
Sharp	B-Device
X68000	I-Device
featured	O
soft-eject	O
5¼-inch	O
drives	O
.	O
</s>
<s>
Some	O
late-generation	O
IBM	B-Device
PS/2	I-Device
machines	O
had	O
soft-eject	O
3½-inch	O
disk	B-Device
drives	I-Device
as	O
well	O
for	O
which	O
some	O
issues	O
of	O
DOS	B-Device
(	O
i.e.	O
</s>
<s>
PC	O
DOS	B-Device
5.02	O
and	O
higher	O
)	O
offered	O
an	O
EJECT	O
command	O
.	O
</s>
<s>
Before	O
a	O
disk	B-Device
can	O
be	O
accessed	O
,	O
the	O
drive	O
needs	O
to	O
synchronize	O
its	O
head	O
position	O
with	O
the	O
disk	B-Device
tracks	O
.	O
</s>
<s>
In	O
some	O
drives	O
,	O
this	O
is	O
accomplished	O
with	O
a	O
Track	O
Zero	O
Sensor	O
,	O
while	O
for	O
others	O
it	O
involves	O
the	O
drive	B-Device
head	I-Device
striking	O
an	O
immobile	O
reference	O
surface	O
.	O
</s>
<s>
In	O
either	O
case	O
,	O
the	O
head	O
is	O
moved	O
so	O
that	O
it	O
is	O
approaching	O
track	O
zero	O
position	O
of	O
the	O
disk	B-Device
.	O
</s>
<s>
This	O
physical	O
striking	O
is	O
responsible	O
for	O
the	O
5¼-inch	O
drive	O
clicking	O
during	O
the	O
boot	O
of	O
an	O
Apple	O
II	O
,	O
and	O
the	O
loud	O
rattles	O
of	O
its	O
DOS	B-Device
and	O
ProDOS	O
when	O
disk	B-Device
errors	O
occurred	O
and	O
track	O
zero	O
synchronization	O
was	O
attempted	O
.	O
</s>
<s>
All	O
8-inch	O
and	O
some	O
5¼-inch	O
drives	O
used	O
a	O
mechanical	O
method	O
to	O
locate	O
sectors	B-Application
,	O
known	O
as	O
either	O
hard	B-Architecture
sectors	I-Architecture
or	O
soft	O
sectors	B-Application
,	O
and	O
is	O
the	O
purpose	O
of	O
the	O
small	O
hole	O
in	O
the	O
jacket	O
,	O
off	O
to	O
the	O
side	O
of	O
the	O
spindle	O
hole	O
.	O
</s>
<s>
A	O
light	O
beam	O
sensor	O
detects	O
when	O
a	O
punched	O
hole	O
in	O
the	O
disk	B-Device
is	O
visible	O
through	O
the	O
hole	O
in	O
the	O
jacket	O
.	O
</s>
<s>
For	O
a	O
soft-sectored	O
disk	B-Device
,	O
there	O
is	O
only	O
a	O
single	O
hole	O
,	O
which	O
is	O
used	O
to	O
locate	O
the	O
first	O
sector	O
of	O
each	O
track	O
.	O
</s>
<s>
Clock	O
timing	O
is	O
then	O
used	O
to	O
find	O
the	O
other	O
sectors	B-Application
behind	O
it	O
,	O
which	O
requires	O
precise	O
speed	O
regulation	O
of	O
the	O
drive	O
motor	O
.	O
</s>
<s>
For	O
a	O
hard-sectored	B-Architecture
disk	B-Device
,	O
there	O
are	O
many	O
holes	O
,	O
one	O
for	O
each	O
sector	O
row	O
,	O
plus	O
an	O
additional	O
hole	O
in	O
a	O
half-sector	O
position	O
,	O
that	O
is	O
used	O
to	O
indicate	O
sector	O
zero	O
.	O
</s>
<s>
The	O
Apple	O
II	O
computer	O
system	O
is	O
notable	O
in	O
that	O
it	O
did	O
not	O
have	O
an	O
index	B-Architecture
hole	I-Architecture
sensor	O
and	O
ignored	O
the	O
presence	O
of	O
hard	O
or	O
soft	O
sectoring	O
.	O
</s>
<s>
Instead	O
,	O
it	O
used	O
special	O
repeating	O
data	O
synchronization	O
patterns	O
written	O
to	O
the	O
disk	B-Device
between	O
each	O
sector	O
,	O
to	O
assist	O
the	O
computer	O
in	O
finding	O
and	O
synchronizing	O
with	O
the	O
data	O
in	O
each	O
track	O
.	O
</s>
<s>
The	O
later	O
3½-inch	O
drives	O
of	O
the	O
mid-1980s	O
did	O
not	O
use	O
sector	O
index	B-Architecture
holes	I-Architecture
,	O
but	O
instead	O
also	O
used	O
synchronization	O
patterns	O
.	O
</s>
<s>
Most	O
3½-inch	O
drives	O
used	O
a	O
constant	O
speed	O
drive	O
motor	O
and	O
contain	O
the	O
same	O
number	O
of	O
sectors	B-Application
across	O
all	O
tracks	O
.	O
</s>
<s>
This	O
is	O
sometimes	O
referred	O
to	O
as	O
Constant	B-Device
Angular	I-Device
Velocity	I-Device
(	O
CAV	O
)	O
.	O
</s>
<s>
In	O
order	O
to	O
fit	O
more	O
data	O
onto	O
a	O
disk	B-Device
,	O
some	O
3½-inch	O
drives	O
(	O
notably	O
the	O
Macintosh	B-Device
External	I-Device
400K	I-Device
and	I-Device
800K	I-Device
drives	I-Device
)	O
instead	O
use	O
Constant	B-Device
Linear	I-Device
Velocity	I-Device
(	O
CLV	O
)	O
,	O
which	O
uses	O
a	O
variable	O
speed	O
drive	O
motor	O
that	O
spins	O
more	O
slowly	O
as	O
the	O
head	O
moves	O
away	O
from	O
the	O
center	O
of	O
the	O
disk	B-Device
,	O
maintaining	O
the	O
same	O
speed	O
of	O
the	O
head(s )	O
relative	O
to	O
the	O
surface(s )	O
of	O
the	O
disk	B-Device
.	O
</s>
<s>
This	O
allows	O
more	O
sectors	B-Application
to	O
be	O
written	O
to	O
the	O
longer	O
middle	O
and	O
outer	O
tracks	O
as	O
the	O
track	O
length	O
increases	O
.	O
</s>
<s>
While	O
the	O
original	O
IBM	O
8-inch	O
disk	B-Device
was	O
actually	O
so	O
defined	O
,	O
the	O
other	O
sizes	O
are	O
defined	O
in	O
the	O
metric	O
system	O
,	O
their	O
usual	O
names	O
being	O
but	O
rough	O
approximations	O
.	O
</s>
<s>
Different	O
sizes	O
of	O
floppy	O
disks	B-Device
are	O
mechanically	O
incompatible	O
,	O
and	O
disks	B-Device
can	O
fit	O
only	O
one	O
size	O
of	O
drive	O
.	O
</s>
<s>
-inch	O
disks	B-Device
formatted	O
for	O
use	O
with	O
Apple	O
II	O
computers	O
would	O
be	O
unreadable	O
and	O
treated	O
as	O
unformatted	O
on	O
a	O
Commodore	O
.	O
</s>
<s>
As	O
computer	B-Device
platforms	I-Device
began	O
to	O
form	O
,	O
attempts	O
were	O
made	O
at	O
interchangeability	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
"	O
SuperDrive	B-Device
"	O
included	O
from	O
the	O
Macintosh	B-Device
SE	I-Device
to	O
the	O
Power	B-Device
Macintosh	I-Device
G3	I-Device
could	O
read	O
,	O
write	O
and	O
format	O
IBM	B-Device
PC	I-Device
format	O
-inch	O
disks	B-Device
,	O
but	O
few	O
IBM-compatible	O
computers	O
had	O
drives	O
that	O
did	O
the	O
reverse	O
.	O
</s>
<s>
8-inch	O
,	O
-inch	O
and	O
-inch	O
drives	O
were	O
manufactured	O
in	O
a	O
variety	O
of	O
sizes	O
,	O
most	O
to	O
fit	O
standardized	O
drive	B-Device
bays	I-Device
.	O
</s>
<s>
Alongside	O
the	O
common	O
disk	B-Device
sizes	O
were	O
non-classical	B-Operating_System
sizes	I-Operating_System
for	O
specialized	O
systems	O
.	O
</s>
<s>
Floppy	O
disks	B-Device
of	O
the	O
first	O
standard	O
are	O
8	O
inches	O
in	O
diameter	O
,	O
protected	O
by	O
a	O
flexible	O
plastic	O
jacket	O
.	O
</s>
<s>
Read/write	O
floppy	O
disks	B-Device
and	O
their	O
drives	O
became	O
available	O
in	O
1972	O
,	O
but	O
it	O
was	O
IBM	O
's	O
1973	O
introduction	O
of	O
the	O
3740	B-Device
data	I-Device
entry	I-Device
system	I-Device
that	O
began	O
the	O
establishment	O
of	O
floppy	O
disks	B-Device
,	O
called	O
by	O
IBM	O
the	O
Diskette	O
1	O
,	O
as	O
an	O
industry	O
standard	O
for	O
information	O
interchange	O
.	O
</s>
<s>
Early	O
microcomputers	B-Architecture
used	O
for	O
engineering	O
,	O
business	O
,	O
or	O
word	O
processing	O
often	O
used	O
one	O
or	O
more	O
8-inch	O
disk	B-Device
drives	I-Device
for	O
removable	O
storage	O
;	O
the	O
CP/M	B-Application
operating	I-Application
system	I-Application
was	O
developed	O
for	O
microcomputers	B-Architecture
with	O
8-inch	O
drives	O
.	O
</s>
<s>
The	O
family	O
of	O
8-inch	O
disks	B-Device
and	O
drives	O
increased	O
over	O
time	O
and	O
later	O
versions	O
could	O
store	O
up	O
to	O
1.2	O
MB	O
;	O
many	O
microcomputer	B-Architecture
applications	O
did	O
not	O
need	O
that	O
much	O
capacity	O
on	O
one	O
disk	B-Device
,	O
so	O
a	O
smaller	O
size	O
disk	B-Device
with	O
lower-cost	O
media	O
and	O
drives	O
was	O
feasible	O
.	O
</s>
<s>
The	O
head	O
gap	O
of	O
an	O
80‑track	O
high-density	O
(	O
1.2	O
MB	O
in	O
the	O
MFM	B-Protocol
format	O
)	O
‑inch	O
drive	O
(	O
a.k.a.	O
</s>
<s>
Mini	O
diskette	O
,	O
Mini	O
disk	B-Device
,	O
or	O
Minifloppy	O
)	O
is	O
smaller	O
than	O
that	O
of	O
a	O
40‑track	O
double-density	O
(	O
360	O
KB	O
if	O
double-sided	O
)	O
drive	O
but	O
can	O
also	O
format	O
,	O
read	O
and	O
write	O
40‑track	O
disks	B-Device
provided	O
the	O
controller	O
supports	O
double	O
stepping	O
or	O
has	O
a	O
switch	O
to	O
do	O
so	O
.	O
</s>
<s>
A	O
blank	O
40‑track	O
disk	B-Device
formatted	O
and	O
written	O
on	O
an	O
80‑track	O
drive	O
can	O
be	O
taken	O
to	O
its	O
native	O
drive	O
without	O
problems	O
,	O
and	O
a	O
disk	B-Device
formatted	O
on	O
a	O
40‑track	O
drive	O
can	O
be	O
used	O
on	O
an	O
80‑track	O
drive	O
.	O
</s>
<s>
Disks	B-Device
written	O
on	O
a	O
40‑track	O
drive	O
and	O
then	O
updated	O
on	O
an	O
80	O
track	O
drive	O
become	O
unreadable	O
on	O
any	O
40‑track	O
drives	O
due	O
to	O
track	O
width	O
incompatibility	O
.	O
</s>
<s>
Single-sided	O
disks	B-Device
were	O
coated	O
on	O
both	O
sides	O
,	O
despite	O
the	O
availability	O
of	O
more	O
expensive	O
double	O
sided	O
disks	B-Device
.	O
</s>
<s>
The	O
reason	O
usually	O
given	O
for	O
the	O
higher	O
price	O
was	O
that	O
double	O
sided	O
disks	B-Device
were	O
certified	O
error-free	O
on	O
both	O
sides	O
of	O
the	O
media	O
.	O
</s>
<s>
Double-sided	O
disks	B-Device
could	O
be	O
used	O
in	O
some	O
drives	O
for	O
single-sided	O
disks	B-Device
,	O
as	O
long	O
as	O
an	O
index	O
signal	O
was	O
not	O
needed	O
.	O
</s>
<s>
This	O
was	O
done	O
one	O
side	O
at	O
a	O
time	O
,	O
by	O
turning	O
them	O
over	O
(	O
flippy	O
disks	B-Device
)	O
;	O
more	O
expensive	O
dual-head	O
drives	O
which	O
could	O
read	O
both	O
sides	O
without	O
turning	O
over	O
were	O
later	O
produced	O
,	O
and	O
eventually	O
became	O
used	O
universally	O
.	O
</s>
<s>
thumb|upright|Internal	O
parts	O
of	O
a	O
-inch	O
floppy	O
disk	B-Device
.	O
</s>
<s>
A	O
consortium	O
of	O
21	O
companies	O
eventually	O
settled	O
on	O
a	O
-inch	O
design	O
known	O
as	O
the	O
Micro	O
diskette	O
,	O
Micro	O
disk	B-Device
,	O
or	O
Micro	O
floppy	O
,	O
similar	O
to	O
a	O
Sony	O
design	O
but	O
improved	O
to	O
support	O
both	O
single-sided	O
and	O
double-sided	O
media	O
,	O
with	O
formatted	O
capacities	O
generally	O
of	O
360	O
KB	O
and	O
720	O
KB	O
respectively	O
.	O
</s>
<s>
The	O
double-sided	O
,	O
high-density	O
1.44	O
MB	O
(	O
actually	O
1440	O
KiB	O
=	O
1.41	O
MiB	O
)	O
disk	B-Device
drive	I-Device
,	O
which	O
would	O
become	O
the	O
most	O
popular	O
,	O
first	O
shipped	O
in	O
1986	O
.	O
</s>
<s>
Reports	O
Sony	O
shipped	O
in	O
1Q	O
1986	O
The	O
first	O
Macintosh	B-Device
computers	I-Device
used	O
single-sided	O
-inch	O
floppy	O
disks	B-Device
,	O
but	O
with	O
400	O
KB	O
formatted	O
capacity	O
.	O
</s>
<s>
The	O
higher	O
capacity	O
was	O
achieved	O
at	O
the	O
same	O
recording	O
density	O
by	O
varying	O
the	O
disk-rotation	O
speed	O
with	O
head	O
position	O
so	O
that	O
the	O
linear	O
speed	O
of	O
the	O
disk	B-Device
was	O
closer	O
to	O
constant	O
.	O
</s>
<s>
Later	O
Macs	B-Device
could	O
also	O
read	O
and	O
write	O
1.44	O
MB	O
HD	O
disks	B-Device
in	O
PC	O
format	O
with	O
fixed	O
rotation	O
speed	O
.	O
</s>
<s>
Higher	O
capacities	O
were	O
similarly	O
achieved	O
by	O
Acorn	O
's	O
RISC	B-Operating_System
OS	I-Operating_System
(	O
800	O
KB	O
for	O
DD	B-Application
,	O
1,600	O
KB	O
for	O
HD	O
)	O
and	O
AmigaOS	B-Application
(	O
880	O
KB	O
for	O
DD	B-Application
,	O
1,760	O
KB	O
for	O
HD	O
)	O
.	O
</s>
<s>
All	O
-inch	O
disks	B-Device
have	O
a	O
rectangular	O
hole	O
in	O
one	O
corner	O
which	O
,	O
if	O
obstructed	O
,	O
write-enables	O
the	O
disk	B-Device
.	O
</s>
<s>
The	O
HD	O
1.44	O
MB	O
disks	B-Device
have	O
a	O
second	O
,	O
unobstructed	O
hole	O
in	O
the	O
opposite	O
corner	O
that	O
identifies	O
them	O
as	O
being	O
of	O
that	O
capacity	O
.	O
</s>
<s>
In	O
IBM-compatible	O
PCs	B-Device
,	O
the	O
three	O
densities	O
of	O
-inch	O
floppy	O
disks	B-Device
are	O
backwards-compatible	B-General_Concept
;	O
higher-density	O
drives	O
can	O
read	O
,	O
write	O
and	O
format	O
lower-density	O
media	O
.	O
</s>
<s>
It	O
is	O
also	O
possible	O
to	O
format	O
a	O
disk	B-Device
at	O
a	O
lower	O
density	O
than	O
that	O
for	O
which	O
it	O
was	O
intended	O
,	O
but	O
only	O
if	O
the	O
disk	B-Device
is	O
first	O
thoroughly	O
demagnetized	O
with	O
a	O
bulk	O
eraser	O
,	O
as	O
the	O
high-density	O
format	O
is	O
magnetically	O
stronger	O
and	O
will	O
prevent	O
the	O
disk	B-Device
from	O
working	O
in	O
lower-density	O
modes	O
.	O
</s>
<s>
Writing	O
at	O
different	O
densities	O
than	O
those	O
at	O
which	O
disks	B-Device
were	O
intended	O
,	O
sometimes	O
by	O
altering	O
or	O
drilling	O
holes	O
,	O
was	O
possible	O
but	O
not	O
supported	O
by	O
manufacturers	O
.	O
</s>
<s>
A	O
hole	O
on	O
one	O
side	O
of	O
a	O
-inch	O
disk	B-Device
can	O
be	O
altered	O
as	O
to	O
make	O
some	O
disk	B-Device
drives	I-Device
and	O
operating	B-General_Concept
systems	I-General_Concept
treat	O
the	O
disk	B-Device
as	O
one	O
of	O
higher	O
or	O
lower	O
density	O
,	O
for	O
bidirectional	O
compatibility	O
or	O
economical	O
reasons	O
.	O
</s>
<s>
Some	O
computers	O
,	O
such	O
as	O
the	O
PS/2	B-Device
and	O
Acorn	B-Device
Archimedes	I-Device
,	O
ignored	O
these	O
holes	O
altogether	O
.	O
</s>
<s>
Three-inch	O
disks	B-Device
similar	O
in	O
construction	O
to	O
3½-inch	O
were	O
manufactured	O
and	O
used	O
for	O
a	O
time	O
,	O
particularly	O
by	O
Amstrad	O
computers	O
and	O
word	O
processors	O
.	O
</s>
<s>
An	O
incompatible	O
two-inch	O
floppy	O
produced	O
by	O
Fujifilm	O
called	O
the	O
LT-1	O
was	O
used	O
in	O
the	O
Zenith	B-Device
Minisport	I-Device
portable	O
computer	O
.	O
</s>
<s>
None	O
of	O
these	O
sizes	O
achieved	O
much	O
market	O
success.Disk/Trend	O
Report-Flexible	O
Disk	B-Device
Drives	I-Device
,	O
Disk/Trend	O
Inc.	O
,	O
November	O
1991	O
,	O
pp	O
.	O
</s>
<s>
Floppy	O
disk	B-Device
size	O
is	O
often	O
referred	O
to	O
in	O
inches	O
,	O
even	O
in	O
countries	O
using	O
metric	O
and	O
though	O
the	O
size	O
is	O
defined	O
in	O
metric	O
.	O
</s>
<s>
The	O
ANSI	O
specification	O
of	O
-inch	O
disks	B-Device
is	O
entitled	O
in	O
part	O
"	O
90	O
mm	O
(	O
3.5-inch	O
)	O
"	O
though	O
90	O
mm	O
is	O
closer	O
to	O
3.54	O
inches.ANSI	O
X3.137	O
,	O
One	O
-	O
and	O
Two-Sided	O
,	O
Unformatted	O
,	O
90-mm	O
(	O
3.5-inch	O
)	O
5	O
,	O
3-tpmm	O
(	O
135-tpi	O
)	O
,	O
Flexible	O
Disk	B-Device
Cartridge	O
for	O
7958	O
bpr	O
Use	O
.	O
</s>
<s>
IBM	O
53FD	O
/	O
Shugart	O
850	O
1977	O
962	O
–	O
1,184	O
KB	O
depending	O
upon	O
sector	O
size	O
1.2	O
MB	O
-inch	O
DD	B-Application
1978	O
360	O
or	O
800	O
KB	O
360	O
KB	O
-inch	O
Apple	O
Disk	B-Device
II	O
(	O
Pre-DOS	O
3.3	O
)	O
1978	O
113.75	O
KB	O
(	O
256	O
byte	O
sectors	B-Application
,	O
13	O
sectors/track	O
,	O
35	O
tracks	O
)	O
113	O
KB	O
-inch	O
Atari	O
DOS	B-Device
2.0S	O
1979	O
90	O
KB	O
(	O
128	O
byte	O
sectors	B-Application
,	O
18	O
sectors/track	O
,	O
40	O
tracks	O
)	O
90	O
KB	O
-inch	O
Commodore	B-Device
DOS	I-Device
1.0	O
(	O
SSDD	O
)	O
1979	O
172.5	O
KB	O
170	O
KB	O
-inch	O
Commodore	B-Device
DOS	I-Device
2.1	O
(	O
SSDD	O
)	O
1980	O
170.75	O
KB	O
170	O
KB	O
-inch	O
Apple	O
Disk	B-Device
II	O
(	O
DOS	B-Device
3.3	O
)	O
1980	O
140	O
KB	O
(	O
256	O
byte	O
sectors	B-Application
,	O
16	O
sectors/track	O
,	O
35	O
tracks	O
)	O
140	O
KB	O
-inch	O
Apple	O
Disk	B-Device
II	O
(	O
Roland	O
Gustafsson	O
's	O
RWTS18	O
)	O
1988	O
157.5	O
KB	O
(	O
768	O
byte	O
sectors	B-Application
,	O
6	O
sectors/track	O
,	O
35	O
tracks	O
)	O
Game	O
publishers	O
privately	O
contracted	O
3rd	O
party	O
custom	O
DOS.-inch	O
Victor	O
9000	O
/	O
ACT	O
Sirius	O
1	O
(	O
SSDD	O
)	O
1982	O
612	O
KB	O
(	O
512	O
byte	O
sectors	B-Application
,	O
11-19	O
variable	O
sectors	B-Application
/	O
track	O
,	O
80	O
tracks	O
)	O
600	O
KB-inch	O
Victor	O
9000	O
/	O
ACT	O
Sirius	O
1	O
(	O
DSDD	O
)	O
1982	O
1,196	O
KB	O
(	O
512	O
byte	O
sectors	B-Application
,	O
11-19	O
variable	O
sectors	B-Application
/	O
track	O
,	O
80	O
tracks	O
)	O
1,200	O
KB	O
-inch	O
HP	O
SS	O
1982	O
280	O
KB	O
(	O
256	O
byte	O
sectors	B-Application
,	O
16	O
sectors/track	O
,	O
70	O
tracks	O
)	O
264	O
KB	O
-inch	O
Atari	O
DOS	B-Device
3	O
1983	O
127	O
KB	O
(	O
128	O
byte	O
sectors	B-Application
,	O
26	O
sectors/track	O
,	O
40	O
tracks	O
)	O
130	O
KB	O
3-inch	O
1982	O
?	O
</s>
<s>
500	O
KB	O
(	O
DS/DD	O
)	O
-inch	O
SS	O
DD	B-Application
(	O
at	O
release	O
)	O
1983	O
360	O
KB	O
(	O
400	O
KB	O
on	O
Macintosh	B-Device
)	O
500	O
KB	O
-inch	O
DS	O
DD	B-Application
1983	O
720	O
KB	O
(	O
800	O
KB	O
on	O
Macintosh	B-Device
and	O
RISC	B-Operating_System
OS	I-Operating_System
,	O
880	O
KB	O
on	O
Amiga	O
)	O
1	O
MB	O
-inch	O
QD	O
1980	O
720	O
KB	O
720	O
KB	O
-inch	O
RX50	O
(	O
SSQD	O
)	O
circa	O
1982	O
style	O
=	O
"	O
text-align	O
:	O
right	O
"	O
400	O
KB	O
-inch	O
HD	O
19821986	O
Disk/Trend	O
Report	O
,	O
Flexible	O
Disk	B-Device
Drives	I-Device
1,200	O
KB	O
1.2	O
MB	O
3-inch	O
Mitsumi	O
Quick	O
Disk	B-Device
1985	O
128	O
to	O
256	O
KB	O
?	O
</s>
<s>
3-inch	O
Famicom	B-Device
Disk	I-Device
System	I-Device
(	O
derived	O
from	O
Quick	O
Disk	B-Device
)	O
1986	O
112	O
KB	O
128	O
KB	O
2-inch	O
1989	O
720	O
KB	O
?	O
</s>
<s>
-inch	O
Sharp	O
CE-1600F	O
,	O
CE-140F	O
(	O
chassis	O
:	O
FDU-250	O
,	O
medium	O
:	O
CE-1650F	O
)	O
1986	O
turnable	O
diskette	O
with	O
62,464	O
bytes	O
per	O
side	O
(	O
512	O
byte	O
sectors	B-Application
,	O
8	O
sectors/track	O
,	O
16	O
tracks	O
,	O
GCR	B-Device
(	O
4/5	O
)	O
recording	O
)	O
2×	O
64	O
KB	O
(	O
128	O
KB	O
)	O
-inch	O
Perpendicular	O
1986	O
100	O
KB	O
per	O
inch	O
?	O
</s>
<s>
-inch	O
HD	O
1986	O
1,440	O
KB	O
(	O
1,760	O
KB	O
on	O
Amiga	O
)	O
1.44	O
MB	O
(	O
2.0	O
MB	O
unformatted	O
)	O
-inch	O
HD	O
1987	O
1,600	O
KB	O
on	O
RISC	B-Operating_System
OS	I-Operating_System
1.6	O
MB	O
-inch	O
ED	O
1987	O
2,880	O
KB	O
(	O
3,200	O
KB	O
on	O
Sinclair	O
QL	O
)	O
2.88	O
MB	O
-inch	O
Floptical	B-Device
(	O
LS	O
)	O
1991	O
20,385	O
KB	O
21	O
MB	O
-inch	O
SuperDisk	B-Device
(	O
LS-120	B-Device
)	O
1996	O
120,375	O
KB	O
120	O
MB	O
-inch	O
SuperDisk	B-Device
(	O
LS-240	B-Device
)	O
1997	O
240,750	O
KB	O
240	O
MB	O
-inch	O
HiFD	O
1998/99	O
?	O
</s>
<s>
150/200	O
MB	O
Abbreviations	O
:	O
Formatted	O
storage	O
capacity	O
is	O
total	O
size	O
of	O
all	O
sectors	B-Application
on	O
the	O
disk	B-Device
:	O
</s>
<s>
For	O
8-inch	O
see	O
List	B-Device
of	I-Device
floppy	I-Device
disk	I-Device
formats	I-Device
#IBM	O
8-inch	O
formats	O
.	O
</s>
<s>
Spare	O
,	O
hidden	O
and	O
otherwise	O
reserved	O
sectors	B-Application
are	O
included	O
in	O
this	O
number	O
.	O
</s>
<s>
Other	O
formats	O
may	O
get	O
more	O
or	O
less	O
capacity	O
from	O
the	O
same	O
drives	O
and	O
disks	B-Device
.	O
</s>
<s>
thumb|right|Two	O
boxes	O
of	O
about	O
80	O
floppy	O
disks	B-Device
together	O
with	O
one	O
USB	B-Protocol
memory	O
stick	O
.	O
</s>
<s>
The	O
stick	O
is	O
capable	O
of	O
holding	O
over	O
130	O
times	O
as	O
much	O
data	O
as	O
the	O
two	O
boxes	O
of	O
disks	B-Device
put	O
together	O
.	O
</s>
<s>
Data	O
is	O
generally	O
written	O
to	O
floppy	O
disks	B-Device
in	O
sectors	B-Application
(	O
angular	O
blocks	O
)	O
and	O
tracks	O
(	O
concentric	O
rings	O
at	O
a	O
constant	O
radius	O
)	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
HD	O
format	O
of	O
3½-inch	O
floppy	O
disks	B-Device
uses	O
512	B-Application
bytes	I-Application
per	O
sector	O
,	O
18	O
sectors	B-Application
per	O
track	O
,	O
80	O
tracks	O
per	O
side	O
and	O
two	O
sides	O
,	O
for	O
a	O
total	O
of	O
1,474,560	O
bytes	O
per	O
disk	B-Device
.	O
</s>
<s>
Some	O
disk	B-Device
controllers	O
can	O
vary	O
these	O
parameters	O
at	O
the	O
user	O
's	O
request	O
,	O
increasing	O
storage	O
on	O
the	O
disk	B-Device
,	O
although	O
they	O
may	O
not	O
be	O
able	O
to	O
be	O
read	O
on	O
machines	O
with	O
other	O
controllers	O
.	O
</s>
<s>
For	O
example	O
,	O
Microsoft	O
applications	O
were	O
often	O
distributed	O
on	O
-inch	O
1.68	O
MB	O
DMF	B-Device
disks	B-Device
formatted	O
with	O
21	O
sectors	B-Application
instead	O
of	O
18	O
;	O
they	O
could	O
still	O
be	O
recognized	O
by	O
a	O
standard	O
controller	O
.	O
</s>
<s>
On	O
the	O
IBM	B-Device
PC	I-Device
,	O
MSX	B-Operating_System
and	O
most	O
other	O
microcomputer	B-Architecture
platforms	B-Device
,	O
disks	B-Device
were	O
written	O
using	O
a	O
constant	B-Device
angular	I-Device
velocity	I-Device
(	O
CAV	O
)	O
format	O
,	O
with	O
the	O
disk	B-Device
spinning	O
at	O
a	O
constant	O
speed	O
and	O
the	O
sectors	B-Application
holding	O
the	O
same	O
amount	O
of	O
information	O
on	O
each	O
track	O
regardless	O
of	O
radial	O
location	O
.	O
</s>
<s>
Because	O
the	O
sectors	B-Application
have	O
constant	O
angular	O
size	O
,	O
the	O
512	B-Application
bytes	I-Application
in	O
each	O
sector	O
are	O
compressed	O
more	O
near	O
the	O
disk	B-Device
's	O
center	O
.	O
</s>
<s>
A	O
more	O
space-efficient	O
technique	O
would	O
be	O
to	O
increase	O
the	O
number	O
of	O
sectors	B-Application
per	O
track	O
toward	O
the	O
outer	O
edge	O
of	O
the	O
disk	B-Device
,	O
from	O
18	O
to	O
30	O
for	O
instance	O
,	O
thereby	O
keeping	O
nearly	O
constant	O
the	O
amount	O
of	O
physical	O
disk	B-Device
space	O
used	O
for	O
storing	O
each	O
sector	O
;	O
an	O
example	O
is	O
zone	B-Architecture
bit	I-Architecture
recording	I-Architecture
.	O
</s>
<s>
Apple	O
implemented	O
this	O
in	O
early	O
Macintosh	B-Device
computers	I-Device
by	O
spinning	O
the	O
disk	B-Device
more	O
slowly	O
when	O
the	O
head	O
was	O
at	O
the	O
edge	O
,	O
while	O
maintaining	O
the	O
data	O
rate	O
,	O
allowing	O
400	O
KB	O
of	O
storage	O
per	O
side	O
and	O
an	O
extra	O
80	O
KB	O
on	O
a	O
double-sided	O
disk	B-Device
.	O
</s>
<s>
This	O
higher	O
capacity	O
came	O
with	O
a	O
disadvantage	O
:	O
the	O
format	O
used	O
a	O
unique	O
drive	O
mechanism	O
and	O
control	O
circuitry	O
,	O
meaning	O
that	O
Mac	B-Device
disks	B-Device
could	O
not	O
be	O
read	O
on	O
other	O
computers	O
.	O
</s>
<s>
Apple	O
eventually	O
reverted	O
to	O
constant	B-Device
angular	I-Device
velocity	I-Device
on	O
HD	O
floppy	O
disks	B-Device
with	O
their	O
later	O
machines	O
,	O
still	O
unique	O
to	O
Apple	O
as	O
they	O
supported	O
the	O
older	O
variable-speed	O
formats	O
.	O
</s>
<s>
Disk	B-Application
formatting	I-Application
is	O
usually	O
done	O
by	O
a	O
utility	O
program	O
supplied	O
by	O
the	O
computer	O
OS	B-General_Concept
manufacturer	O
;	O
generally	O
,	O
it	O
sets	O
up	O
a	O
file	O
storage	O
directory	O
system	O
on	O
the	O
disk	B-Device
,	O
and	O
initializes	O
its	O
sectors	B-Application
and	O
tracks	O
.	O
</s>
<s>
Areas	O
of	O
the	O
disk	B-Device
unusable	B-General_Concept
for	O
storage	O
due	O
to	O
flaws	O
can	O
be	O
locked	O
(	O
marked	O
as	O
"	O
bad	O
sectors	B-Application
"	O
)	O
so	O
that	O
the	O
operating	B-General_Concept
system	I-General_Concept
does	O
not	O
attempt	O
to	O
use	O
them	O
.	O
</s>
<s>
When	O
floppy	O
disks	B-Device
were	O
often	O
used	O
,	O
disks	B-Device
pre-formatted	O
for	O
popular	O
computers	O
were	O
sold	O
.	O
</s>
<s>
The	O
unformatted	O
capacity	O
of	O
a	O
floppy	O
disk	B-Device
does	O
not	O
include	O
the	O
sector	O
and	O
track	O
headings	O
of	O
a	O
formatted	O
disk	B-Device
;	O
the	O
difference	O
in	O
storage	O
between	O
them	O
depends	O
on	O
the	O
drive	O
's	O
application	O
.	O
</s>
<s>
Floppy	O
disk	B-Device
drive	I-Device
and	O
media	O
manufacturers	O
specify	O
the	O
unformatted	O
capacity	O
(	O
for	O
example	O
,	O
2	O
MB	O
for	O
a	O
standard	O
-inch	O
HD	O
floppy	O
)	O
.	O
</s>
<s>
DMF	B-Device
was	O
introduced	O
permitting	O
1.68	O
MB	O
to	O
fit	O
onto	O
an	O
otherwise	O
standard	O
-inch	O
disk	B-Device
;	O
utilities	O
then	O
appeared	O
allowing	O
disks	B-Device
to	O
be	O
formatted	O
as	O
such	O
.	O
</s>
<s>
Whereas	O
semiconductor	O
memory	O
naturally	O
favors	O
powers	O
of	O
two	O
(	O
size	O
doubles	O
each	O
time	O
an	O
address	O
pin	O
is	O
added	O
to	O
the	O
integrated	O
circuit	O
)	O
,	O
the	O
capacity	O
of	O
a	O
disk	B-Device
drive	I-Device
is	O
the	O
product	O
of	O
sector	O
size	O
,	O
sectors	B-Application
per	O
track	O
,	O
tracks	O
per	O
side	O
and	O
sides	O
(	O
which	O
in	O
hard	B-Device
disk	I-Device
drives	I-Device
with	O
multiple	O
platters	O
can	O
be	O
greater	O
than	O
2	O
)	O
.	O
</s>
<s>
Although	O
other	O
sector	O
sizes	O
have	O
been	O
known	O
in	O
the	O
past	O
,	O
formatted	O
sector	O
sizes	O
are	O
now	O
almost	O
always	O
set	O
to	O
powers	O
of	O
two	O
(	O
256	O
bytes	O
,	O
512	B-Application
bytes	I-Application
,	O
etc	O
.	O
</s>
<s>
)	O
,	O
and	O
,	O
in	O
some	O
cases	O
,	O
disk	B-Device
capacity	O
is	O
calculated	O
as	O
multiples	O
of	O
the	O
sector	O
size	O
rather	O
than	O
only	O
in	O
bytes	O
,	O
leading	O
to	O
a	O
combination	O
of	O
decimal	O
multiples	O
of	O
sectors	B-Application
and	O
binary	O
sector	O
sizes	O
.	O
</s>
<s>
For	O
example	O
,	O
1.44	O
MB	O
-inch	O
HD	O
disks	B-Device
have	O
the	O
"	O
M	O
"	O
prefix	O
peculiar	O
to	O
their	O
context	O
,	O
coming	O
from	O
their	O
capacity	O
of	O
2,880	O
512-byte	O
sectors	B-Application
(	O
1,440	O
KiB	O
)	O
,	O
consistent	O
with	O
neither	O
a	O
decimal	O
megabyte	O
nor	O
a	O
binary	O
mebibyte	O
(	O
MiB	O
)	O
.	O
</s>
<s>
Hence	O
,	O
these	O
disks	B-Device
hold	O
1.47	O
MB	O
or	O
1.41	O
MiB	O
.	O
</s>
<s>
Usable	B-General_Concept
data	O
capacity	O
is	O
a	O
function	O
of	O
the	O
disk	B-Application
format	I-Application
used	O
,	O
which	O
in	O
turn	O
is	O
determined	O
by	O
the	O
FDD	O
controller	O
and	O
its	O
settings	O
.	O
</s>
<s>
Differences	O
between	O
such	O
formats	O
can	O
result	O
in	O
capacities	O
ranging	O
from	O
approximately	O
1,300	O
to	O
1,760	O
KiB	O
(	O
1.80	O
MB	O
)	O
on	O
a	O
standard	O
-inch	O
high-density	O
floppy	O
(	O
and	O
up	O
to	O
nearly	O
2	O
MB	O
with	O
utilities	O
such	O
as	O
2M/2MGUI	B-Application
)	O
.	O
</s>
<s>
The	O
highest	O
capacity	O
techniques	O
require	O
much	O
tighter	O
matching	O
of	O
drive	B-Device
head	I-Device
geometry	O
between	O
drives	O
,	O
something	O
not	O
always	O
possible	O
and	O
unreliable	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
LS-240	B-Device
drive	O
supports	O
a	O
32	O
MB	O
capacity	O
on	O
standard	O
-inch	O
HD	O
disks	B-Device
,	O
but	O
this	O
is	O
a	O
write-once	O
technique	O
,	O
and	O
requires	O
its	O
own	O
drive	O
.	O
</s>
<s>
The	O
raw	O
maximum	O
transfer	O
rate	O
of	O
-inch	O
ED	O
floppy	O
drives	O
(	O
2.88	O
MB	O
)	O
is	O
nominally	O
1,000	O
kilobits/s	O
,	O
or	O
approximately	O
83%	O
that	O
of	O
single-speed	O
CD‑ROM	O
(	O
71%	O
of	O
audio	O
CD	O
)	O
.	O
</s>
<s>
"	O
The	O
Disk	B-Device
II	O
"	O
:	O
A	O
detailed	O
essay	O
describing	O
one	O
of	O
the	O
first	O
commercial	O
floppy	O
disk	B-Device
drives	I-Device
(	O
from	O
the	O
Apple	O
II	O
History	O
website	O
)	O
.	O
</s>
<s>
Inside	O
Commodore	B-Device
DOS	I-Device
:	O
The	O
Complete	O
Guide	O
to	O
the	O
1541	O
Disk	B-Device
Operating	B-General_Concept
System	I-General_Concept
.	O
</s>
