<s>
Disk	B-Operating_System
packs	I-Operating_System
and	O
disk	O
cartridges	O
were	O
early	O
forms	O
of	O
removable	B-Device
media	I-Device
for	O
computer	B-General_Concept
data	I-General_Concept
storage	I-General_Concept
,	O
introduced	O
in	O
the	O
1960s	O
.	O
</s>
<s>
A	O
disk	B-Operating_System
pack	I-Operating_System
is	O
a	O
layered	O
grouping	O
of	O
hard	B-Device
disk	I-Device
platters	I-Device
(	O
circular	O
,	O
rigid	O
discs	O
coated	O
with	O
a	O
magnetic	O
data	B-General_Concept
storage	I-General_Concept
surface	O
)	O
.	O
</s>
<s>
A	O
disk	B-Operating_System
pack	I-Operating_System
is	O
the	O
core	O
component	O
of	O
a	O
hard	B-Device
disk	I-Device
drive	I-Device
.	O
</s>
<s>
In	O
modern	O
hard	B-Device
disks	I-Device
,	O
the	O
disk	B-Operating_System
pack	I-Operating_System
is	O
permanently	O
sealed	O
inside	O
the	O
drive	O
.	O
</s>
<s>
In	O
many	O
early	O
hard	B-Device
disks	I-Device
,	O
the	O
disk	B-Operating_System
pack	I-Operating_System
was	O
a	O
removable	O
unit	O
,	O
and	O
would	O
be	O
supplied	O
with	O
a	O
protective	O
canister	O
featuring	O
a	O
lifting	O
handle	O
.	O
</s>
<s>
To	O
remove	O
the	O
disk	B-Operating_System
pack	I-Operating_System
,	O
the	O
drive	O
would	O
be	O
taken	O
off	O
line	O
and	O
allowed	O
to	O
spin	O
down	O
.	O
</s>
<s>
Its	O
access	O
door	O
could	O
then	O
be	O
opened	O
and	O
an	O
empty	O
shell	O
inserted	O
and	O
twisted	O
to	O
unlock	O
the	O
disk	B-Device
platter	I-Device
from	O
the	O
drive	O
and	O
secure	O
it	O
to	O
the	O
shell	O
.	O
</s>
<s>
A	O
different	O
disk	B-Operating_System
pack	I-Operating_System
could	O
then	O
be	O
inserted	O
by	O
removing	O
the	O
bottom	O
and	O
placing	O
the	O
disk	B-Operating_System
pack	I-Operating_System
with	O
its	O
shell	O
into	O
the	O
drive	O
.	O
</s>
<s>
Turning	O
the	O
handle	O
would	O
lock	O
the	O
disk	B-Operating_System
pack	I-Operating_System
in	O
place	O
and	O
free	O
the	O
shell	O
for	O
removal	O
.	O
</s>
<s>
The	O
first	O
removable	B-Device
disk	I-Device
pack	O
was	O
invented	O
in	O
1961	O
by	O
IBM	O
engineers	O
R	O
.	O
E	O
.	O
Pattison	O
as	O
part	O
of	O
the	O
LCF	O
(	O
Low	O
Cost	O
File	O
)	O
project	O
headed	O
by	O
Jack	O
Harker	O
.	O
</s>
<s>
The	O
14-inch	O
(	O
356mm	O
)	O
diameter	O
disks	O
introduced	O
by	O
IBM	O
became	O
a	O
de	O
facto	O
standard	O
,	O
with	O
many	O
vendors	O
producing	O
disk	B-General_Concept
drives	I-General_Concept
using	O
14-inch	O
disks	O
in	O
disk	B-Operating_System
packs	I-Operating_System
and	O
cartridges	O
into	O
the	O
1980s	O
.	O
</s>
<s>
Examples	O
of	O
disk	B-General_Concept
drives	I-General_Concept
that	O
employed	O
removable	B-Device
disk	I-Device
packs	O
include	O
the	O
IBM	B-Device
1311	I-Device
,	O
IBM	B-Device
2311	I-Device
,	O
and	O
the	O
Digital	O
RP04	O
.	O
</s>
<s>
An	O
early	O
disk	O
cartridge	O
was	O
a	O
single	O
hard	B-Device
disk	I-Device
platter	I-Device
encased	O
in	O
a	O
protective	O
plastic	O
shell	O
.	O
</s>
<s>
When	O
the	O
removable	O
cartridge	O
was	O
inserted	O
into	O
the	O
cartridge	O
drive	O
peripheral	B-Device
device	I-Device
,	O
the	O
read/write	B-Device
heads	I-Device
of	O
the	O
drive	O
could	O
access	O
the	O
magnetic	O
data	B-General_Concept
storage	I-General_Concept
surface	O
of	O
the	O
platter	O
through	O
holes	O
in	O
the	O
shell	O
.	O
</s>
<s>
The	O
disk	O
cartridge	O
was	O
a	O
direct	O
evolution	O
from	O
the	O
disk	B-Operating_System
pack	I-Operating_System
drive	O
,	O
or	O
the	O
early	O
hard	B-Device
drive	I-Device
.	O
</s>
<s>
As	O
the	O
storage	B-Device
density	I-Device
improved	O
,	O
even	O
a	O
single	O
platter	O
would	O
provide	O
a	O
useful	O
amount	O
of	O
data	B-General_Concept
storage	I-General_Concept
space	O
,	O
with	O
the	O
benefit	O
being	O
easier	O
to	O
handle	O
than	O
a	O
removable	B-Device
disk	I-Device
pack	O
.	O
</s>
<s>
An	O
example	O
of	O
a	O
cartridge	O
drive	O
is	O
the	O
IBM	B-Device
2310	I-Device
,	O
used	O
on	O
the	O
IBM	B-Device
1130	I-Device
.	O
</s>
<s>
Disk	O
cartridges	O
were	O
made	O
obsolete	O
by	O
floppy	B-Device
disks	I-Device
.	O
</s>
<s>
Disk	B-General_Concept
drives	I-General_Concept
with	O
exchangeable	O
disk	B-Operating_System
packs	I-Operating_System
or	O
disk	O
cartridges	O
generally	O
required	O
the	O
data	O
heads	O
to	O
be	O
aligned	O
to	O
allow	O
packs	O
formatted	O
on	O
one	O
drive	O
to	O
be	O
read	O
and	O
written	O
on	O
another	O
compatible	O
drive	O
.	O
</s>
<s>
Alignment	O
required	O
a	O
special	O
alignment	O
pack	O
,	O
an	O
oscilloscope	O
,	O
an	O
alignment	O
tool	O
that	O
moved	O
the	O
read/write	B-Device
heads	I-Device
,	O
and	O
patience	O
.	O
</s>
<s>
Special	O
CE	O
media	O
was	O
also	O
available	O
for	O
tape	O
drives	O
and	O
diskette	B-Device
drives	O
,	O
known	O
as	O
"	O
the	O
CE	O
tape	O
"	O
and	O
"	O
the	O
CE	O
floppy.	O
"	O
</s>
<s>
Later	O
drives	O
with	O
exchangeable	O
packs	O
(	O
such	O
as	O
the	O
CDC	O
8	B-Device
"	I-Device
Lark	O
drives	O
)	O
embedded	O
the	O
servo	O
with	O
the	O
data	O
and	O
did	O
n't	O
require	O
regular	O
head	O
alignment	O
.	O
</s>
