<s>
An	O
optical	B-General_Concept
disc	I-General_Concept
image	I-General_Concept
(	O
or	O
ISO	B-General_Concept
image	I-General_Concept
,	O
from	O
the	O
ISO	B-Application
9660	I-Application
file	B-Application
system	I-Application
used	O
with	O
CD-ROM	B-Device
media	O
)	O
is	O
a	O
disk	B-Application
image	I-Application
that	O
contains	O
everything	O
that	O
would	O
be	O
written	O
to	O
an	O
optical	B-Device
disc	I-Device
,	O
disk	B-Application
sector	I-Application
by	O
disc	B-Application
sector	I-Application
,	O
including	O
the	O
optical	B-Device
disc	I-Device
file	B-Application
system	I-Application
.	O
</s>
<s>
ISO	B-General_Concept
images	I-General_Concept
are	O
expected	O
to	O
contain	O
the	O
binary	O
image	O
of	O
an	O
optical	B-Device
media	I-Device
file	B-Application
system	I-Application
(	O
usually	O
ISO	B-Application
9660	I-Application
and	O
its	O
extensions	O
or	O
UDF	O
)	O
,	O
including	O
the	O
data	O
in	O
its	O
files	B-Operating_System
in	O
binary	O
format	O
,	O
copied	O
exactly	O
as	O
they	O
were	O
stored	O
on	O
the	O
disc	O
.	O
</s>
<s>
The	O
data	O
inside	O
the	O
ISO	B-General_Concept
image	I-General_Concept
will	O
be	O
structured	O
according	O
to	O
the	O
file	B-Application
system	I-Application
that	O
was	O
used	O
on	O
the	O
optical	B-Device
disc	I-Device
from	O
which	O
it	O
was	O
created	O
.	O
</s>
<s>
ISO	B-General_Concept
images	I-General_Concept
can	O
be	O
created	O
from	O
optical	B-Device
discs	I-Device
by	O
disk	B-Application
imaging	I-Application
software	I-Application
,	O
or	O
from	O
a	O
collection	O
of	O
files	B-Operating_System
by	O
optical	B-Device
disc	I-Device
authoring	O
software	O
,	O
or	O
from	O
a	O
different	O
disk	B-Application
image	I-Application
file	O
by	O
means	O
of	O
conversion	B-General_Concept
.	O
</s>
<s>
Software	O
distributed	O
on	O
bootable	O
discs	O
is	O
often	O
available	O
for	O
download	O
in	O
ISO	B-General_Concept
image	I-General_Concept
format	O
.	O
</s>
<s>
And	O
like	O
any	O
other	O
ISO	B-General_Concept
image	I-General_Concept
,	O
it	O
may	O
be	O
written	O
to	O
an	O
optical	B-Device
disc	I-Device
such	O
as	O
CD	B-Device
,	O
DVD	O
and	O
Blu-Ray	O
.	O
</s>
<s>
Optical	B-General_Concept
disc	I-General_Concept
images	I-General_Concept
are	O
uncompressed	O
and	O
do	O
not	O
use	O
a	O
particular	O
container	O
format	O
;	O
they	O
are	O
a	O
sector-by-sector	O
copy	O
of	O
the	O
data	O
on	O
an	O
optical	B-Device
disc	I-Device
,	O
stored	O
inside	O
a	O
binary	O
file	O
.	O
</s>
<s>
Other	O
than	O
ISO	B-Application
9660	I-Application
media	O
,	O
an	O
ISO	B-General_Concept
image	I-General_Concept
might	O
also	O
contain	O
a	O
UDF	O
(	O
ISO/IEC	O
13346	O
)	O
file	B-Application
system	I-Application
(	O
commonly	O
used	O
by	O
DVDs	O
and	O
Blu-ray	O
Discs	O
)	O
,	O
including	O
the	O
data	O
in	O
its	O
files	B-Operating_System
in	O
binary	O
format	O
,	O
copied	O
exactly	O
as	O
they	O
were	O
stored	O
on	O
the	O
disc	O
.	O
</s>
<s>
The	O
data	O
inside	O
the	O
ISO	B-General_Concept
image	I-General_Concept
will	O
be	O
structured	O
according	O
to	O
the	O
file	B-Application
system	I-Application
that	O
was	O
used	O
on	O
the	O
optical	B-Device
disc	I-Device
from	O
which	O
it	O
was	O
created	O
.	O
</s>
<s>
The	O
.iso	B-General_Concept
file	I-General_Concept
extension	O
is	O
the	O
one	O
most	O
commonly	O
used	O
for	O
this	O
type	O
of	O
disc	B-Application
images	I-Application
.	O
</s>
<s>
The	O
.img	B-General_Concept
extension	O
can	O
also	O
be	O
found	O
on	O
some	O
ISO	B-General_Concept
image	I-General_Concept
files	B-Operating_System
,	O
such	O
as	O
in	O
some	O
images	O
from	O
Microsoft	O
DreamSpark	O
;	O
however	O
,	O
IMG	B-General_Concept
files	I-General_Concept
,	O
which	O
also	O
use	O
the	O
.img	B-General_Concept
extension	O
,	O
tend	O
to	O
have	O
slightly	O
different	O
contents	O
.	O
</s>
<s>
The	O
.udf	O
file	O
extension	O
is	O
sometimes	O
used	O
to	O
indicate	O
that	O
the	O
file	B-Application
system	I-Application
inside	O
the	O
ISO	B-General_Concept
image	I-General_Concept
is	O
actually	O
UDF	O
and	O
not	O
ISO	B-Application
9660	I-Application
.	O
</s>
<s>
ISO	B-General_Concept
files	I-General_Concept
store	O
only	O
the	O
user	O
data	O
from	O
each	O
sector	B-Application
on	O
an	O
optical	B-Device
disc	I-Device
ignoring	O
the	O
control	O
headers	O
and	O
error	O
correction	O
data	O
,	O
and	O
are	O
therefore	O
slightly	O
smaller	O
than	O
a	O
raw	O
disc	B-Application
image	I-Application
of	O
optical	B-Device
media	I-Device
.	O
</s>
<s>
Since	O
the	O
size	O
of	O
the	O
user	O
data	O
portion	O
of	O
a	O
sector	B-Application
(	O
logical	O
sector	B-Application
)	O
in	O
data	O
optical	B-Device
discs	I-Device
is	O
2,048	O
bytes	O
,	O
the	O
size	O
of	O
an	O
ISO	B-General_Concept
image	I-General_Concept
will	O
be	O
a	O
multiple	O
of	O
2,048	O
.	O
</s>
<s>
Any	O
single-track	O
CD-ROM	B-Device
,	O
DVD	O
or	O
Blu-ray	O
disc	O
can	O
be	O
archived	O
in	O
ISO	B-General_Concept
format	O
as	O
a	O
true	O
digital	O
copy	O
of	O
the	O
original	O
.	O
</s>
<s>
Unlike	O
a	O
physical	O
optical	B-Device
disc	I-Device
,	O
an	O
image	O
can	O
be	O
transferred	O
over	O
any	O
data	O
link	O
or	O
removable	O
storage	O
medium	O
.	O
</s>
<s>
An	O
ISO	B-General_Concept
image	I-General_Concept
can	O
be	O
opened	O
with	O
almost	O
every	O
multi-format	O
file	B-Application
archiver	I-Application
.	O
</s>
<s>
Native	O
support	O
for	O
handling	O
ISO	B-General_Concept
images	I-General_Concept
varies	O
from	O
operating	O
system	O
to	O
operating	O
system	O
.	O
</s>
<s>
An	O
ISO	B-General_Concept
can	O
be	O
"	O
mounted	O
"	O
with	O
suitable	O
driver	B-Application
software	I-Application
,	O
i.e.	O
</s>
<s>
treated	O
by	O
the	O
operating	O
system	O
as	O
if	O
it	O
were	O
a	O
physical	O
optical	B-Device
disc	I-Device
.	O
</s>
<s>
Most	O
Unix-based	O
operating	O
systems	O
,	O
including	O
Linux	B-Application
and	O
macOS	B-Application
,	O
have	O
built-in	O
capability	O
to	O
mount	O
an	O
ISO	B-General_Concept
.	O
</s>
<s>
Versions	O
of	O
Windows	O
beginning	O
with	O
Windows	B-Application
8	I-Application
also	O
have	O
such	O
capability	O
.	O
</s>
<s>
For	O
other	O
operating	O
systems	O
software	B-Application
drivers	I-Application
can	O
be	O
installed	O
to	O
achieve	O
the	O
same	O
objective	O
.	O
</s>
<s>
A	O
CD	B-Device
can	O
have	O
multiple	O
tracks	O
,	O
which	O
can	O
contain	O
computer	O
data	O
,	O
audio	O
,	O
or	O
video	O
.	O
</s>
<s>
File	B-Application
systems	I-Application
such	O
as	O
ISO	B-Application
9660	I-Application
are	O
stored	O
inside	O
one	O
of	O
these	O
tracks	O
.	O
</s>
<s>
Since	O
ISO	B-General_Concept
images	I-General_Concept
are	O
expected	O
to	O
contain	O
a	O
binary	O
copy	O
of	O
the	O
file	B-Application
system	I-Application
and	O
its	O
contents	O
,	O
there	O
is	O
no	O
concept	O
of	O
a	O
"	O
track	O
"	O
inside	O
an	O
ISO	B-General_Concept
image	I-General_Concept
,	O
since	O
a	O
track	O
is	O
a	O
container	O
for	O
the	O
contents	O
of	O
an	O
ISO	B-General_Concept
image	I-General_Concept
.	O
</s>
<s>
This	O
means	O
that	O
CDs	B-Device
with	O
multiple	O
tracks	O
ca	O
n't	O
be	O
stored	O
inside	O
a	O
single	O
ISO	B-General_Concept
image	I-General_Concept
;	O
at	O
most	O
,	O
an	O
ISO	B-General_Concept
image	I-General_Concept
will	O
contain	O
the	O
data	O
inside	O
one	O
of	O
those	O
multiple	O
tracks	O
,	O
and	O
only	O
if	O
it	O
is	O
stored	O
inside	O
a	O
standard	O
file	B-Application
system	I-Application
.	O
</s>
<s>
This	O
also	O
means	O
that	O
audio	O
CDs	B-Device
,	O
which	O
are	O
usually	O
composed	O
of	O
multiple	O
tracks	O
,	O
ca	O
n't	O
be	O
stored	O
inside	O
an	O
ISO	B-General_Concept
image	I-General_Concept
.	O
</s>
<s>
Furthermore	O
,	O
not	O
even	O
a	O
single	O
track	O
of	O
an	O
audio	O
CD	B-Device
can	O
be	O
stored	O
as	O
an	O
ISO	B-General_Concept
image	I-General_Concept
,	O
since	O
audio	O
tracks	O
do	O
not	O
contain	O
a	O
file	B-Application
system	I-Application
inside	O
them	O
,	O
but	O
only	O
a	O
continuous	O
stream	O
of	O
encoded	O
audio	O
data	O
.	O
</s>
<s>
This	O
audio	O
is	O
stored	O
on	O
sectors	O
of	O
2352	O
bytes	O
different	O
from	O
those	O
that	O
store	O
a	O
file	B-Application
system	I-Application
and	O
it	O
is	O
not	O
stored	O
inside	O
files	B-Operating_System
;	O
it	O
is	O
addressed	O
with	O
track	O
numbers	O
,	O
index	O
points	O
and	O
a	O
CD	B-Device
time	O
code	O
that	O
are	O
encoded	O
into	O
the	O
lead-in	O
of	O
each	O
session	O
of	O
the	O
CD-Audio	O
disc	O
.	O
</s>
<s>
Video	O
CDs	B-Device
and	O
Super	O
Video	O
CDs	B-Device
require	O
at	O
least	O
two	O
tracks	O
on	O
a	O
CD	B-Device
,	O
so	O
it	O
is	O
also	O
not	O
possible	O
to	O
store	O
an	O
image	O
of	O
one	O
of	O
these	O
discs	O
inside	O
an	O
ISO	B-General_Concept
image	I-General_Concept
file	O
,	O
however	O
an	O
.IMG	B-General_Concept
file	I-General_Concept
can	O
achieve	O
this	O
.	O
</s>
<s>
Formats	O
such	O
as	O
CUE/BIN	O
,	O
CCD/IMG	O
and	O
MDS/MDF	B-General_Concept
formats	O
can	O
be	O
used	O
to	O
store	O
multi-track	O
disc	B-Application
images	I-Application
,	O
including	O
audio	O
CDs	B-Device
.	O
</s>
<s>
These	O
formats	O
store	O
a	O
raw	O
disc	B-Application
image	I-Application
of	O
the	O
complete	O
disc	O
,	O
including	O
information	O
from	O
all	O
tracks	O
,	O
along	O
with	O
a	O
companion	O
file	O
describing	O
the	O
multiple	O
tracks	O
and	O
the	O
characteristics	O
of	O
each	O
of	O
those	O
tracks	O
.	O
</s>
<s>
This	O
would	O
allow	O
an	O
optical	B-Device
media	I-Device
burning	O
tool	O
to	O
have	O
all	O
the	O
information	O
required	O
to	O
correctly	O
burn	O
the	O
image	O
on	O
a	O
new	O
disc	O
.	O
</s>
<s>
For	O
audio	O
CDs	B-Device
,	O
one	O
can	O
also	O
transfer	O
the	O
audio	O
data	O
into	O
uncompressed	O
audio	O
files	B-Operating_System
like	O
WAV	O
or	O
AIFF	O
,	O
optionally	O
reserving	O
the	O
metadata	O
(	O
see	O
CD	B-Device
ripping	O
)	O
.	O
</s>
<s>
Most	O
software	O
that	O
is	O
capable	O
of	O
writing	O
from	O
ISO	B-General_Concept
images	I-General_Concept
to	O
hard	O
disks	O
or	O
recordable	O
media	O
(	O
CD	B-Device
/	O
DVD	O
/	O
BD	O
)	O
is	O
generally	O
not	O
able	O
to	O
write	O
from	O
ISO	B-General_Concept
disk	I-General_Concept
images	I-General_Concept
to	O
flash	O
drives	O
.	O
</s>
<s>
However	O
,	O
since	O
2011	O
,	O
various	O
software	O
has	O
existed	O
to	O
write	O
raw	O
image	O
files	B-Operating_System
to	O
USB	O
flash	O
drives	O
.	O
</s>
<s>
.ISO	B-General_Concept
files	I-General_Concept
are	O
commonly	O
used	O
in	O
emulators	B-Application
to	O
replicate	O
a	O
CD	B-Application
image	I-Application
.	O
</s>
<s>
Emulators	B-Application
such	O
as	O
Dolphin	B-Application
and	O
PCSX2	B-Application
use	O
.iso	B-General_Concept
files	I-General_Concept
to	O
emulate	O
Wii	B-Operating_System
and	O
GameCube	B-Application
games	O
,	O
and	O
PlayStation	B-Device
2	I-Device
games	O
,	O
respectively	O
.	O
</s>
<s>
They	O
can	O
also	O
be	O
used	O
as	O
virtual	O
CD-ROMs	B-Device
for	O
hypervisors	O
such	O
as	O
VMware	B-Operating_System
Workstation	I-Operating_System
or	O
VirtualBox	B-Operating_System
.	O
</s>
<s>
Other	O
uses	O
are	O
burning	O
disk	B-Application
images	I-Application
of	O
operating	O
systems	O
to	O
physical	O
install	O
media	O
.	O
</s>
