<s>
Phase-change	B-Device
Dual	I-Device
(	O
or	O
Phase-change	O
Disc	O
)	O
is	O
a	O
rewritable	O
optical	B-Device
disc	I-Device
and	O
a	O
standard	O
for	O
it	O
,	O
developed	O
by	O
Matsushita	O
Electric	O
Industrial	O
Co	O
.	O
,	O
Ltd	O
.	O
in	O
April	O
1995	O
.	O
</s>
<s>
The	O
built-in	O
PD	B-Device
drive	I-Device
and	O
the	O
external	O
type	O
are	O
sold	O
,	O
respectively	O
,	O
and	O
both	O
of	O
them	O
can	O
read	O
the	O
CD-ROM	B-Device
.	O
</s>
<s>
Both	O
drive	O
and	O
media	O
,	O
most	O
of	O
which	O
are	O
manufactured	O
by	O
Matsushita	O
Electric	O
Appliances	O
only	O
,	O
the	O
company	O
also	O
released	O
a	O
notebook	B-Device
PC	I-Device
with	O
a	O
650	O
MB	O
auxiliary	O
storage	O
device	O
and	O
a	O
4×	O
CD-ROM	B-Device
drive	O
,	O
a	O
PRONOTE	O
PD	O
(	O
August	O
1996	O
)	O
.	O
</s>
<s>
CD-RW	O
can	O
be	O
cited	O
as	O
a	O
re-writable	O
medium	O
at	O
the	O
same	O
time	O
,	O
but	O
it	O
is	O
characterized	O
by	O
being	O
able	O
to	O
write	O
and	O
delete	O
on	O
a	O
file	O
basis	O
,	O
which	O
is	O
close	O
to	O
the	O
feeling	O
of	O
handling	O
CD-RW	O
and	O
floppy	B-Device
disk	I-Device
using	O
packet	B-Device
write	I-Device
system	I-Device
.	O
</s>
<s>
Although	O
the	O
writing	O
speed	O
of	O
PD	O
is	O
not	O
fast	O
,	O
it	O
is	O
about	O
to	O
be	O
faster	O
than	O
writing	O
to	O
floppy	B-Device
,	O
but	O
at	O
the	O
time	O
of	O
sale	O
,	O
it	O
was	O
not	O
a	O
speed	O
that	O
made	O
it	O
so	O
difficult	O
.	O
</s>
<s>
Meanwhile	O
,	O
MO	B-Device
,	O
ZIP	B-Operating_System
drive	I-Operating_System
,	O
SyQuest	O
,	O
etc	O
.	O
</s>
<s>
existed	O
as	O
re-writable	O
media	O
close	O
to	O
the	O
feeling	O
of	O
handling	O
floppy	B-Device
disks	I-Device
,	O
but	O
the	O
advantage	O
that	O
the	O
PD	B-Device
drive	I-Device
can	O
be	O
read	O
by	O
the	O
CD-ROM	B-Device
was	O
merit	O
compared	O
with	O
those	O
.	O
</s>
<s>
At	O
that	O
time	O
the	O
CD-ROM	B-Device
drive	O
was	O
becoming	O
an	O
essential	O
peripheral	O
device	O
,	O
but	O
it	O
was	O
not	O
necessarily	O
built	O
in	O
every	O
PC	O
yet	O
,	O
desktop	O
machines	O
that	O
were	O
mainstream	O
at	O
that	O
time	O
had	O
many	O
models	O
with	O
only	O
one	O
drive	O
bay	O
.	O
</s>
<s>
In	O
such	O
an	O
environment	O
,	O
a	O
PD	O
capable	O
of	O
serving	O
as	O
both	O
a	O
CD-ROM	B-Device
drive	O
and	O
a	O
large	O
capacity	O
(	O
then	O
)	O
auxiliary	O
storage	O
device	O
was	O
advantageous	O
both	O
in	O
terms	O
of	O
cost	O
and	O
installation	O
.	O
</s>
<s>
At	O
this	O
point	O
PD	B-Device
drives	I-Device
and	O
media	O
effectively	O
disappeared	O
from	O
the	O
market	O
.	O
</s>
