<s>
A	O
light	B-Device
pen	I-Device
is	O
a	O
computer	B-Device
input	I-Device
device	I-Device
in	O
the	O
form	O
of	O
a	O
light-sensitive	O
wand	O
used	O
in	O
conjunction	O
with	O
a	O
computer	O
's	O
cathode-ray	B-Device
tube	I-Device
(	O
CRT	O
)	O
display	O
.	O
</s>
<s>
It	O
allows	O
the	O
user	O
to	O
point	O
to	O
displayed	O
objects	O
or	O
draw	O
on	O
the	O
screen	O
in	O
a	O
similar	O
way	O
to	O
a	O
touchscreen	B-Device
but	O
with	O
greater	O
positional	O
accuracy	O
.	O
</s>
<s>
A	O
light	B-Device
pen	I-Device
can	O
work	O
with	O
any	O
CRT-based	O
display	O
,	O
but	O
its	O
ability	O
to	O
be	O
used	O
with	O
LCDs	B-Device
was	O
unclear	O
(	O
though	O
Toshiba	O
and	O
Hitachi	O
displayed	O
a	O
similar	O
idea	O
at	O
the	O
"	O
Display	O
2006	O
"	O
show	O
in	O
Japan	O
)	O
.	O
</s>
<s>
A	O
light	B-Device
pen	I-Device
detects	O
changes	O
in	O
brightness	O
of	O
nearby	O
screen	O
pixels	O
when	O
scanned	O
by	O
cathode-ray	B-Device
tube	I-Device
electron	O
beam	O
and	O
communicates	O
the	O
timing	O
of	O
this	O
event	O
to	O
the	O
computer	O
.	O
</s>
<s>
The	O
first	O
light	B-Device
pen	I-Device
,	O
at	O
this	O
time	O
still	O
called	O
"	O
light	B-Device
gun	I-Device
"	O
,	O
was	O
created	O
around	O
1951	O
–	O
1955	O
as	O
part	O
of	O
the	O
Whirlwind	B-Device
I	I-Device
project	O
at	O
MIT	O
,	O
where	O
it	O
was	O
used	O
to	O
select	O
discrete	O
symbols	O
on	O
the	O
screen	O
,	O
and	O
later	O
at	O
the	O
SAGE	B-Device
project	I-Device
,	O
where	O
it	O
was	O
used	O
for	O
tactical	O
real-time-control	O
of	O
a	O
radar-networked	O
airspace	O
.	O
</s>
<s>
One	O
of	O
the	O
first	O
more	O
widely	O
deployed	O
uses	O
was	O
in	O
the	O
Situation	O
Display	O
consoles	O
of	O
the	O
AN/FSQ	B-Device
-7	I-Device
for	O
military	O
airspace	O
surveillance	O
.	O
</s>
<s>
This	O
is	O
not	O
very	O
surprising	O
,	O
given	O
its	O
relationship	O
with	O
the	O
Whirlwind	B-Device
projects	O
.	O
</s>
<s>
See	O
Semi-Automatic	B-Device
Ground	I-Device
Environment	I-Device
for	O
more	O
details	O
.	O
</s>
<s>
During	O
the	O
1960s	O
,	O
light	B-Device
pens	I-Device
were	O
common	O
on	O
graphics	O
terminals	O
such	O
as	O
the	O
IBM	B-Device
2250	I-Device
and	O
were	O
also	O
available	O
for	O
the	O
IBM	B-Operating_System
3270	I-Operating_System
text-only	O
terminal	O
.	O
</s>
<s>
Light	B-Device
pen	I-Device
usage	O
was	O
expanded	O
in	O
the	O
early	O
1980s	O
to	O
music	O
workstations	O
such	O
as	O
the	O
Fairlight	O
CMI	O
and	O
personal	O
computers	O
such	O
as	O
the	O
BBC	B-Device
Micro	I-Device
.	O
</s>
<s>
IBM	B-Device
PC	I-Device
compatible	O
CGA	B-Device
,	O
HGC	B-Device
and	O
some	O
EGA	B-Device
graphics	I-Device
cards	O
also	O
featured	O
a	O
connector	O
compatible	O
with	O
a	O
light	B-Device
pen	I-Device
,	O
as	O
did	O
early	O
Tandy	O
1000	O
computers	O
,	O
the	O
Thomson	B-Device
MO5	I-Device
computer	O
family	O
,	O
the	O
Amiga	B-Device
,	O
Atari	B-Device
8-bit	I-Device
,	O
Commodore	O
8-bit	O
,	O
some	O
MSX	B-Operating_System
computers	O
and	O
Amstrad	B-Device
PCW	I-Device
home	O
computers	O
.	O
</s>
<s>
For	O
the	O
MSX	B-Operating_System
computers	O
,	O
Sanyo	O
produced	O
a	O
light	B-Device
pen	I-Device
interface	O
cartridge	O
.	O
</s>
<s>
Because	O
the	O
user	O
was	O
required	O
to	O
hold	O
their	O
arm	O
in	O
front	O
of	O
the	O
screen	O
for	O
long	O
periods	O
of	O
time	O
(	O
potentially	O
causing	O
"	O
gorilla	O
arm	O
"	O
)	O
or	O
to	O
use	O
a	O
desk	O
that	O
tilts	O
the	O
monitor	O
,	O
the	O
light	B-Device
pen	I-Device
fell	O
out	O
of	O
use	O
as	O
a	O
general-purpose	O
input	B-Device
device	I-Device
.	O
</s>
