<s>
A	O
hybrid	B-Application
disc	I-Application
is	O
a	O
disc	O
,	O
such	O
as	O
CD-ROM	B-Device
or	O
Blu-ray	O
,	O
which	O
contains	O
multiple	O
types	O
of	O
data	O
which	O
can	O
be	O
used	O
differently	O
on	O
different	O
devices	O
.	O
</s>
<s>
These	O
include	O
CD-ROM	B-Device
music	O
albums	O
containing	O
video	O
files	O
viewable	O
on	O
a	O
personal	B-Device
computer	I-Device
,	O
or	O
feature	O
film	O
Blu-rays	O
containing	O
interactive	O
content	O
when	O
used	O
with	O
a	O
PlayStation	B-Operating_System
3	I-Operating_System
game	O
console	O
.	O
</s>
<s>
A	O
hybrid	B-Application
disc	I-Application
is	O
an	O
optical	O
disc	O
that	O
has	O
multiple	O
file	B-Application
systems	I-Application
installed	O
on	O
it	O
,	O
typically	O
ISO	B-Application
9660	I-Application
and	O
HFS+	B-Application
(	O
or	O
HFS	B-Application
on	O
older	O
discs	O
)	O
.	O
</s>
<s>
One	O
reason	O
for	O
the	O
hybrid	O
format	O
is	O
the	O
restrictions	O
of	O
ISO	B-Application
9660	I-Application
(	O
filenames	O
of	O
only	O
eight	O
characters	O
,	O
and	O
a	O
maximum	O
depths	O
of	O
eight	O
directories	O
,	O
similar	O
to	O
the	O
Microsoft	O
FAT	B-Application
file	I-Application
system	I-Application
)	O
.	O
</s>
<s>
Another	O
key	O
factor	O
is	O
that	O
ISO	B-Application
9660	I-Application
does	O
not	O
support	O
resource	B-Operating_System
forks	I-Operating_System
,	O
which	O
is	O
critical	O
to	O
the	O
classic	B-Application
Mac	I-Application
OS	I-Application
 '	O
software	O
design	O
(	O
OS	O
X	O
or	O
macOS	B-Application
removed	O
much	O
of	O
the	O
need	O
for	O
resource	B-Operating_System
forks	I-Operating_System
in	O
application	O
design	O
)	O
.	O
</s>
<s>
Companies	O
that	O
released	O
products	O
for	O
both	O
DOS	B-Device
(	O
later	O
Windows	B-Application
)	O
and	O
the	O
classic	B-Application
Mac	I-Application
OS	I-Application
(	O
later	O
macOS	B-Application
)	O
could	O
release	O
a	O
CD	O
containing	O
software	O
for	O
both	O
,	O
natively	O
readable	O
on	O
either	O
system	O
.	O
</s>
<s>
In	O
a	O
"	O
true	O
"	O
(	O
or	O
"	O
shared	O
"	O
)	O
hybrid	O
HFS	B-Application
filesystem	B-Application
,	O
files	O
common	O
to	O
both	O
the	O
ISO	B-Application
9660	I-Application
and	O
HFS	B-Application
partitions	O
are	O
stored	O
only	O
once	O
,	O
with	O
the	O
ISO	B-Application
9660	I-Application
partition	O
pointing	O
to	O
file	O
content	O
in	O
the	O
HFS	B-Application
area	O
(	O
or	O
vice	O
versa	O
)	O
.	O
</s>
<s>
Blizzard	O
Entertainment	O
has	O
released	O
most	O
of	O
their	O
computer	O
games	O
on	O
hybrid	B-Application
CDs	I-Application
.	O
</s>
<s>
By	O
default	O
,	O
Mac	B-Operating_System
OS	I-Operating_System
9	I-Operating_System
and	O
macOS	B-Application
burn	O
hybrid	B-Application
discs	I-Application
.	O
</s>
<s>
An	O
ISO	O
9660/HFS	O
hybrid	B-Application
disc	I-Application
has	O
an	O
ISO	B-Application
9660	I-Application
primary	O
volume	O
descriptor	O
,	O
which	O
makes	O
it	O
a	O
valid	O
ISO	B-Application
9660	I-Application
disc	O
,	O
and	O
an	O
Apple	O
partition	O
.	O
</s>
<s>
It	O
may	O
also	O
have	O
an	O
Apple	B-Application
partition	I-Application
map	I-Application
,	O
although	O
this	O
is	O
not	O
necessary	O
.	O
</s>
<s>
The	O
ISO	B-Application
9660	I-Application
portion	O
of	O
the	O
disc	O
can	O
co-exist	O
with	O
an	O
Apple	O
partition	O
because	O
the	O
header	O
areas	O
which	O
define	O
the	O
contents	O
of	O
the	O
disc	O
are	O
located	O
in	O
different	O
places	O
.	O
</s>
<s>
The	O
ISO	B-Application
9660	I-Application
primary	O
volume	O
descriptor	O
begins	O
32,768	O
bytes	O
(	O
32KB	O
)	O
into	O
the	O
disc	O
.	O
</s>
<s>
If	O
present	O
,	O
an	O
Apple	B-Application
partition	I-Application
map	I-Application
begins	O
512	O
bytes	O
into	O
the	O
disc	O
;	O
if	O
there	O
is	O
no	O
partition	O
map	O
,	O
the	O
header	O
for	O
an	O
Apple	B-Application
HFS	I-Application
partition	O
(	O
known	O
as	O
a	O
Master	O
Directory	O
Block	O
,	O
or	O
MDB	O
)	O
begins	O
1,024	O
bytes	O
into	O
the	O
disc	O
.	O
</s>
<s>
Hybrid-CD	O
also	O
refers	O
to	O
an	O
audio	O
CD	O
which	O
also	O
includes	O
a	O
data	B-Application
track	I-Application
storing	O
MP3	B-Application
(	O
or	O
other	O
digital	O
audio	O
compression	O
format	O
)	O
copy	O
of	O
those	O
CD-DA	O
tracks	O
.	O
</s>
<s>
Before	O
the	O
introduction	O
and	O
subsequent	O
popularization	O
of	O
iTunes	B-Operating_System
and	O
the	B-Device
iPod	I-Device
,	O
such	O
discs	O
were	O
popular	O
for	O
sharing	O
music	O
on	O
compact	O
disc	O
without	O
requiring	O
the	O
recipient	O
to	O
extract	O
and	O
encode	O
the	O
CD-DA	O
themselves	O
—	O
a	O
technical	O
and	O
perhaps	O
time-consuming	O
process	O
on	O
older	O
computing	O
hardware	O
.	O
</s>
<s>
iTunes	B-Operating_System
,	O
Rhythmbox	B-Language
,	O
etc	O
.	O
)	O
</s>
<s>
and	O
the	O
lack	O
of	O
an	O
automated	O
hybrid	O
feature	O
in	O
that	O
very	O
same	O
software	O
,	O
popularity	O
of	O
such	O
hybrid	B-Application
CD	I-Application
has	O
subsequently	O
declined	O
.	O
</s>
<s>
However	O
,	O
such	O
hybrid	B-Application
discs	I-Application
do	O
remain	O
in	O
a	O
commercial	O
setting	O
as	O
a	O
digital	O
rights	O
management	O
enforcement	O
technique	O
,	O
where	O
encrypted	O
compressed	O
copies	O
of	O
the	O
digital	O
audio	O
are	O
provided	O
with	O
proprietary	B-Application
software	I-Application
for	O
listening	O
in	O
a	O
computer	O
disc	O
drive	O
,	O
while	O
the	O
CD-DA	O
is	O
included	O
for	O
playback	O
in	O
stand-alone	O
CD	O
players	O
.	O
</s>
<s>
In	O
recent	O
years	O
,	O
some	O
Blu-rays	O
have	O
been	O
released	O
as	O
Hybrid	B-Application
discs	I-Application
,	O
demonstrating	O
its	O
compatibility	O
with	O
the	O
PlayStation	B-Operating_System
3	I-Operating_System
console	O
,	O
which	O
uses	O
BD	O
as	O
its	O
primary	O
disc	O
format	O
.	O
</s>
<s>
These	O
discs	O
generally	O
include	O
a	O
movie	O
or	O
feature	O
that	O
can	O
be	O
played	O
on	O
any	O
Blu-ray	O
Disc	O
player	O
and	O
playable	O
content	O
which	O
is	O
accessible	O
when	O
run	O
on	O
a	O
PlayStation	B-Operating_System
3	I-Operating_System
console	O
.	O
</s>
