<s>
The	O
Commodore	B-Device
1540	I-Device
(	O
also	O
known	O
as	O
the	O
VIC-1540	B-Device
)	O
introduced	O
in	O
1982	O
is	O
the	O
companion	O
floppy	B-Device
disk	I-Device
drive	I-Device
for	O
the	O
VIC-20	B-Device
home	O
computer	O
.	O
</s>
<s>
It	O
uses	O
single-sided	O
5¼	O
"	O
floppy	B-Device
disks	I-Device
,	O
on	O
which	O
it	O
stores	O
roughly	O
of	O
data	O
utilizing	O
Commodore	O
's	O
GCR	B-Device
data	O
encoding	O
scheme	O
.	O
</s>
<s>
Because	O
of	O
the	O
low	O
price	O
of	O
both	O
the	O
VIC-20	B-Device
and	O
the	O
1540	O
,	O
this	O
combination	O
was	O
the	O
first	O
computer	O
with	O
a	O
disk	O
drive	O
to	O
be	O
offered	O
on	O
the	O
US	O
market	O
for	O
less	O
than	O
although	O
the	O
combination	O
of	O
the	O
Commodore	O
64	O
and	O
1541	B-Device
would	O
prove	O
more	O
enduring	O
.	O
</s>
<s>
The	O
1540	O
is	O
an	O
"	O
intelligent	O
peripheral	O
"	O
in	O
that	O
it	O
has	O
its	O
own	O
MOS	B-General_Concept
Technology	I-General_Concept
6502	I-General_Concept
CPU	O
(	O
just	O
like	O
its	O
VIC-20	B-Device
host	O
)	O
and	O
the	O
resident	O
Commodore	B-Device
DOS	I-Device
on	O
board	O
in	O
ROM	B-Device
contrary	O
to	O
almost	O
all	O
other	O
home	O
computer	O
systems	O
of	O
the	O
time	O
,	O
where	O
the	O
DOS	B-Device
was	O
loaded	O
from	O
a	O
boot	O
floppy	B-Device
and	O
was	O
executed	O
on	O
the	O
computer	O
's	O
CPU	O
.	O
</s>
<s>
The	O
better-known	O
1541	B-Device
is	O
mechanically	O
and	O
nearly	O
electronically	O
identical	O
to	O
the	O
1540	O
but	O
has	O
a	O
revised	O
ROM	B-Device
that	O
permits	O
it	O
to	O
work	O
with	O
the	O
C64	O
by	O
slowing	O
the	O
drive	O
down	O
slightly	O
.	O
</s>
<s>
However	O
,	O
it	O
is	O
possible	O
to	O
revert	O
the	O
1541	B-Device
into	O
1540	O
mode	O
with	O
a	O
Commodore	B-Language
BASIC	I-Language
software	O
command	O
(	O
OPEN	O
15	O
,	O
8	O
,	O
15	O
,	O
"	O
UI-	O
"	O
:	O
CLOSE	O
15	O
)	O
to	O
permit	O
better	O
speed	O
when	O
used	O
with	O
a	O
VIC-20	B-Device
.	O
</s>
<s>
While	O
cheaper	O
than	O
most	O
other	O
drives	O
of	O
the	O
day	O
,	O
it	O
was	O
more	O
expensive	O
than	O
the	O
VIC-20	B-Device
computer	O
itself	O
,	O
and	O
the	O
disk	O
media	O
was	O
also	O
still	O
relatively	O
pricey	O
.	O
</s>
<s>
Also	O
,	O
the	O
relatively	O
small	O
memory	O
of	O
the	O
VIC	O
meant	O
that	O
the	O
faster	O
program	O
loading	O
times	O
of	O
the	O
drive	O
did	O
not	O
gain	O
more	O
than	O
a	O
few	O
seconds	O
compared	O
to	O
tape	B-Device
media	I-Device
.	O
</s>
<s>
Thirdly	O
,	O
almost	O
all	O
commercial	O
software	O
for	O
the	O
VIC-20	B-Device
was	O
sold	O
on	O
cartridge	O
or	O
cassette	O
tape	B-Device
media	I-Device
,	O
giving	O
low	O
incentive	O
to	O
buy	O
a	O
floppy	B-Device
drive	I-Device
.	O
</s>
<s>
The	O
C64	O
followed	O
close	O
on	O
the	O
heels	O
of	O
the	O
VIC-20	B-Device
,	O
quickly	O
discontinuing	O
the	O
1540	O
.	O
</s>
<s>
Most	O
1540s	O
still	O
in	O
existence	O
were	O
modified	O
with	O
a	O
1541	B-Device
ROM	B-Device
so	O
it	O
would	O
work	O
with	O
a	O
C64	O
.	O
</s>
