<s>
In	O
optical	B-General_Concept
storage	I-General_Concept
,	O
three	O
types	O
of	O
storage	O
are	O
usually	O
recognized	O
,	O
and	O
given	O
customary	O
abbreviations	O
:	O
read-only	O
(	O
"	O
ROM	O
"	O
)	O
,	O
Write	O
once	O
(	O
"	O
R	O
"	O
)	O
and	O
read/writable	O
(	O
"	O
RW	O
"	O
,	O
or	O
for	O
Blu-ray	O
,	O
"	O
E	O
"	O
for	O
"	O
erasable	O
"	O
)	O
.	O
</s>
<s>
BD-RE	B-Operating_System
represents	O
a	O
Blu-ray	O
disc	O
which	O
can	O
be	O
read	O
or	O
written	O
many	O
times	O
.	O
</s>
<s>
In	O
addition	O
some	O
of	O
these	O
media	O
support	O
MultiLevel	B-Device
Recording	I-Device
formats	O
,	O
for	O
example	O
dual	O
layer	O
(	O
written	O
as	O
"	O
DL	O
"	O
)	O
,	O
and	O
DVD	O
also	O
supports	O
a	O
"	O
RAM	O
"	O
version	O
(	O
similar	O
to	O
RW	O
)	O
,	O
although	O
this	O
is	O
not	O
widely	O
used	O
in	O
the	O
popular	O
consumer	O
market	O
.	O
</s>
<s>
Likewise	O
other	O
niche	O
formats	O
are	O
excluded	O
,	O
such	O
as	O
GD-ROM	B-Device
(	O
used	O
by	O
some	O
Sega	O
game	O
consoles	O
)	O
and	O
Ultra	B-Application
Density	I-Application
Optical	I-Application
and	O
the	O
like	O
(	O
commercial	O
archiving	O
storage	O
rather	O
than	O
mass	O
market	O
)	O
.	O
</s>
<s>
Thus	O
the	O
article	O
covers	O
the	O
following	O
popular	O
recordable	O
formats	O
:	O
CD	O
(	O
CD-R	O
,	O
CD-RW	O
)	O
;	O
DVD	O
(	O
DVD±R	O
,	O
DVD±RW	O
)	O
;	O
HD	B-Operating_System
DVD	I-Operating_System
(	O
)	O
;	O
Blu-ray	O
(	O
BD-R	B-Operating_System
,	O
BD-E	O
)	O
,	O
and	O
for	O
all	O
except	O
CD	O
,	O
their	O
respective	O
dual	O
-	O
or	O
multi-layer	O
formats	O
.	O
</s>
<s>
Although	O
research	O
into	O
optical	B-General_Concept
data	I-General_Concept
storage	I-General_Concept
has	O
been	O
ongoing	O
for	O
many	O
decades	O
,	O
the	O
first	O
popular	O
system	O
was	O
CD	O
,	O
introduced	O
in	O
1982	O
,	O
adapted	O
from	O
audio	O
(	O
CD-DA	O
)	O
to	O
data	O
storage	O
(	O
the	O
CD-ROM	B-Device
format	O
)	O
with	O
the	O
1985	O
Yellow	B-Device
Book	I-Device
,	O
and	O
re-adapted	O
as	O
the	O
first	O
mass	O
market	O
optical	B-General_Concept
storage	I-General_Concept
medium	O
with	O
CD-R	O
and	O
CD-RW	O
in	O
1988	O
.	O
</s>
<s>
Compact	O
Disc	O
is	O
still	O
the	O
de	O
facto	O
standard	O
for	O
audio	O
recordings	O
,	O
although	O
its	O
place	O
for	O
other	O
multimedia	O
recordings	O
and	O
optical	B-General_Concept
data	I-General_Concept
storage	I-General_Concept
has	O
largely	O
been	O
superseded	O
by	O
DVD	O
.	O
</s>
<s>
It	O
was	O
resolved	O
with	O
both	O
surviving	O
however	O
:	O
DVD-R	O
predominating	O
for	O
stand-alone	O
DVD	O
recorders	O
and	O
players	O
,	O
and	O
(	O
for	O
computers	O
)	O
most	O
DVD	O
devices	O
being	O
engineered	O
as	O
dual	B-Device
format	I-Device
,	O
to	O
be	O
compatible	O
with	O
both	O
.	O
</s>
<s>
With	O
the	O
development	O
of	O
high-definition	B-Device
television	I-Device
,	O
and	O
the	O
popularization	O
of	O
broadband	B-General_Concept
and	O
digital	O
storage	O
of	O
movies	O
,	O
a	O
further	O
format	O
development	O
took	O
place	O
,	O
again	O
giving	O
rise	O
to	O
two	O
camps	O
:	O
HD	B-Operating_System
DVD	I-Operating_System
and	O
Blu-ray	O
,	O
based	O
upon	O
a	O
switch	O
from	O
red	O
to	O
blue-violet	O
laser	O
and	O
tighter	O
engineering	O
tolerances	O
.	O
</s>
<s>
The	O
following	O
are	O
examples	O
of	O
optical	B-General_Concept
storage	I-General_Concept
media	O
excluded	O
from	O
this	O
article	O
:	O
</s>
<s>
Holographic	B-Algorithm
data	I-Algorithm
storage	I-Algorithm
-	O
either	O
still	O
in	O
development	O
,	O
or	O
available	O
but	O
generally	O
only	O
encountered	O
in	O
niche	O
usage	O
as	O
of	O
2007	O
.	O
</s>
<s>
Optical	B-Device
jukebox	I-Device
-	O
hold	O
massive	O
amounts	O
of	O
data	O
on	O
multiple	O
discs	O
allowing	O
scalability	O
into	O
the	O
petabyte	O
range	O
.	O
</s>
