<s>
A	O
touchpad	B-Device
or	O
trackpad	B-Device
is	O
a	O
pointing	B-Device
device	I-Device
featuring	O
a	O
tactile	O
sensor	O
,	O
a	O
specialized	O
surface	O
that	O
can	O
translate	O
the	O
motion	O
and	O
position	O
of	O
a	O
user	O
's	O
fingers	O
to	O
a	O
relative	O
position	O
on	O
the	O
operating	O
system	O
that	O
is	O
made	O
output	O
to	O
the	O
screen	O
.	O
</s>
<s>
Touchpads	B-Device
are	O
a	O
common	O
feature	O
of	O
laptop	B-Device
computers	I-Device
as	O
opposed	O
to	O
using	O
a	O
mouse	B-Device
on	O
a	O
desktop	B-Device
,	O
and	O
are	O
also	O
used	O
as	O
a	O
substitute	O
for	O
a	O
mouse	B-Device
where	O
desk	O
space	O
is	O
scarce	O
.	O
</s>
<s>
Because	O
they	O
vary	O
in	O
size	O
,	O
they	O
can	O
also	O
be	O
found	O
on	O
personal	B-Application
digital	I-Application
assistants	I-Application
(	O
PDAs	B-Application
)	O
and	O
some	O
portable	O
media	O
players	O
.	O
</s>
<s>
Wireless	O
touchpads	B-Device
are	O
also	O
available	O
as	O
detached	O
accessories	O
.	O
</s>
<s>
Touchpads	B-Device
operate	O
in	O
one	O
of	O
several	O
ways	O
,	O
including	O
capacitive	B-Device
sensing	I-Device
or	O
resistive	B-Device
touchscreen	I-Device
.	O
</s>
<s>
Capacitance-based	O
touchpads	B-Device
will	O
not	O
sense	O
the	O
tip	O
of	O
a	O
pencil	O
or	O
other	O
similar	O
ungrounded	O
or	O
non-conducting	O
implements	O
.	O
</s>
<s>
Fingers	O
insulated	O
by	O
a	O
glove	O
may	O
also	O
be	O
problematic	O
,	O
and	O
capacitive	B-Device
touchpads	I-Device
are	O
rarely	O
used	O
as	O
pointing	B-Device
devices	I-Device
for	O
medical	O
hardware	O
.	O
</s>
<s>
While	O
touchpads	B-Device
,	O
like	O
touchscreens	O
,	O
are	O
able	O
to	O
sense	O
absolute	O
position	O
,	O
resolution	O
is	O
limited	O
by	O
their	O
size	O
.	O
</s>
<s>
For	O
common	O
use	O
as	O
a	O
pointer	O
device	O
,	O
the	O
dragging	O
motion	O
of	O
a	O
finger	O
is	O
translated	O
into	O
a	O
finer	O
,	O
relative	O
motion	O
of	O
the	O
cursor	O
on	O
the	O
output	O
to	O
the	O
display	O
on	O
the	O
operating	O
system	O
,	O
analogous	O
to	O
the	O
handling	O
of	O
a	O
mouse	B-Device
that	O
is	O
lifted	O
and	O
put	O
back	O
on	O
a	O
surface	O
.	O
</s>
<s>
Hardware	O
buttons	O
equivalent	O
to	O
a	O
standard	O
mouse	B-Device
's	O
left	O
and	O
right	O
buttons	O
are	O
sometimes	O
positioned	O
adjacent	O
to	O
the	O
touchpad	B-Device
.	O
</s>
<s>
Some	O
touchpads	B-Device
and	O
associated	O
device	B-Application
driver	I-Application
software	O
may	O
interpret	O
tapping	O
the	O
pad	O
as	O
a	O
mouse	B-Device
click	O
,	O
and	O
a	O
tap	O
followed	O
by	O
a	O
continuous	O
pointing	O
motion	O
(	O
a	O
"	O
click-and-a-half	O
"	O
)	O
can	O
indicate	O
dragging	O
.	O
</s>
<s>
Tactile	O
touchpads	B-Device
allow	O
for	O
clicking	O
and	O
dragging	O
by	O
incorporating	O
button	O
functionality	O
into	O
the	O
surface	O
of	O
the	O
touchpad	B-Device
itself	O
.	O
</s>
<s>
To	O
select	O
,	O
one	O
presses	O
down	O
on	O
the	O
touchpad	B-Device
instead	O
of	O
a	O
physical	O
button	O
.	O
</s>
<s>
Touchpad	B-Device
drivers	O
can	O
also	O
allow	O
the	O
use	O
of	O
multiple	O
fingers	O
to	O
emulate	O
the	O
other	O
mouse	B-Device
buttons	O
(	O
commonly	O
two-finger	O
tapping	O
for	O
the	O
center	O
button	O
)	O
.	O
</s>
<s>
Touchpads	B-Device
are	O
called	O
clickpads	O
if	O
it	O
does	O
not	O
have	O
physical	O
buttons	O
,	O
but	O
instead	O
relies	O
on	O
"	O
software	O
buttons	O
"	O
.	O
</s>
<s>
Some	O
touchpads	B-Device
have	O
"	O
hotspots	O
"	O
,	O
locations	O
on	O
the	O
touchpad	B-Device
used	O
for	O
functionality	O
beyond	O
a	O
mouse	B-Device
.	O
</s>
<s>
For	O
example	O
,	O
on	O
certain	O
touchpads	B-Device
,	O
moving	O
the	O
finger	O
along	O
an	O
edge	O
of	O
the	O
touch	B-Device
pad	I-Device
will	O
act	O
as	O
a	O
scroll	O
wheel	O
,	O
controlling	O
the	O
scrollbar	O
and	O
scrolling	O
the	O
window	O
that	O
has	O
the	O
focus	B-Application
,	O
vertically	O
or	O
horizontally	O
.	O
</s>
<s>
Many	O
touchpads	B-Device
use	O
two-finger	O
dragging	O
for	O
scrolling	O
.	O
</s>
<s>
Also	O
,	O
some	O
touchpad	B-Device
drivers	O
support	O
tap	O
zones	O
,	O
regions	O
where	O
a	O
tap	O
will	O
execute	O
a	O
function	O
,	O
for	O
example	O
,	O
pausing	O
a	O
media	O
player	O
or	O
launching	O
an	O
application	B-Application
.	O
</s>
<s>
All	O
of	O
these	O
functions	O
are	O
implemented	O
in	O
the	O
touchpad	B-Device
device	B-Application
driver	I-Application
software	O
,	O
and	O
can	O
be	O
disabled	O
.	O
</s>
<s>
By	O
1982	O
,	O
Apollo	O
desktop	B-Device
computers	I-Device
were	O
equipped	O
with	O
a	O
touchpad	B-Device
on	O
the	O
right	O
side	O
of	O
the	O
keyboard	O
.	O
</s>
<s>
Introduced	O
a	O
year	O
later	O
,	O
in	O
1983	O
,	O
the	O
first	O
battery	O
powered	O
clamshell	B-Device
laptop	I-Device
,	O
the	O
Gavilan	O
SC	O
included	O
a	O
touchpad	B-Device
,	O
which	O
was	O
mounted	O
above	O
its	O
keyboard	O
,	O
rather	O
than	O
below	O
,	O
which	O
became	O
the	O
norm	O
.	O
</s>
<s>
Psion	B-Application
's	O
MC	B-Operating_System
200/400/600/WORD	I-Operating_System
Series	I-Operating_System
,	O
introduced	O
in	O
1989	O
,	O
came	O
with	O
a	O
new	O
mouse-replacing	O
input	O
device	O
similar	O
to	O
a	O
touchpad	B-Device
,	O
although	O
more	O
closely	O
resembling	O
a	O
graphics	B-Device
tablet	I-Device
,	O
as	O
the	O
cursor	O
was	O
positioned	O
by	O
clicking	O
on	O
a	O
specific	O
point	O
on	O
the	O
pad	O
,	O
instead	O
of	O
moving	O
it	O
in	O
the	O
direction	O
of	O
a	O
stroke	O
.	O
</s>
<s>
Laptops	B-Device
with	O
touchpads	B-Device
were	O
then	O
launched	O
by	O
Olivetti	O
and	O
Triumph-Adler	O
in	O
1992	O
.	O
</s>
<s>
Cirque	O
introduced	O
the	O
first	O
widely	O
available	O
touchpad	B-Device
,	O
branded	O
as	O
GlidePoint	O
,	O
in	O
1994	O
.	O
</s>
<s>
Apple	O
introduced	O
touchpads	B-Device
with	O
modern	O
placing	O
in	O
the	O
PowerBook	B-Device
500	I-Device
series	I-Device
in	O
1994	O
,	O
using	O
Cirque	O
's	O
GlidePoint	O
technology	O
,	O
which	O
Apple	O
refers	O
to	O
as	O
a	O
"	O
trackpad	B-Device
"	O
;	O
it	O
replaced	O
the	O
trackball	B-Device
of	O
previous	O
PowerBook	B-Device
models	O
.	O
</s>
<s>
Since	O
2008	O
,	O
Apple	O
's	O
revisions	O
of	O
the	O
MacBook	B-Device
and	O
MacBook	B-Device
Pro	I-Device
incorporated	O
a	O
"	O
Tactile	O
Touchpad	B-Device
"	O
design	O
with	O
a	O
button	O
integrated	O
into	O
the	O
tracking	O
surface	O
(	O
the	O
lower	O
part	O
of	O
the	O
touchpad	B-Device
surface	O
acts	O
as	O
a	O
clickable	O
button	O
)	O
.	O
</s>
<s>
Another	O
early	O
adopter	O
of	O
the	O
GlidePoint	O
pointing	B-Device
device	I-Device
was	O
Sharp	O
.	O
</s>
<s>
Later	O
,	O
Synaptics	B-Language
introduced	O
their	O
touchpad	B-Device
into	O
the	O
marketplace	O
,	O
branded	O
the	O
TouchPad	B-Device
,	O
and	O
Epson	O
was	O
an	O
early	O
adopter	O
of	O
this	O
product	O
with	O
their	O
ActionNote	B-Device
.	O
</s>
<s>
As	O
touchpads	B-Device
began	O
to	O
be	O
introduced	O
in	O
laptops	B-Device
in	O
the	O
1990s	O
,	O
there	O
was	O
often	O
confusion	O
as	O
to	O
what	O
the	O
product	O
should	O
be	O
called	O
.	O
</s>
<s>
No	O
consistent	O
term	O
was	O
used	O
,	O
and	O
references	O
varied	O
,	O
such	O
as	O
:	O
glidepoint	O
,	O
touch	O
sensitive	O
input	O
device	O
,	O
touchpad	B-Device
,	O
trackpad	B-Device
,	O
and	O
pointing	B-Device
device	I-Device
.	O
</s>
<s>
Users	O
were	O
often	O
presented	O
with	O
the	O
option	O
to	O
purchase	O
a	O
pointing	B-Device
stick	I-Device
,	O
touchpad	B-Device
,	O
or	O
trackball	B-Device
.	O
</s>
<s>
Combinations	O
of	O
the	O
devices	O
were	O
common	O
,	O
though	O
touchpads	B-Device
and	O
trackballs	B-Device
were	O
rarely	O
included	O
together	O
.	O
</s>
<s>
Since	O
the	O
early	O
2000s	O
,	O
touchpads	B-Device
have	O
become	O
the	O
dominant	O
laptop	B-Device
pointing	B-Device
device	I-Device
as	O
most	O
consumer	O
laptops	B-Device
produced	O
during	O
this	O
period	O
and	O
beyond	O
includes	O
only	O
touchpads	B-Device
,	O
displacing	O
the	O
pointing	B-Device
stick	I-Device
.	O
</s>
<s>
Touchpads	B-Device
are	O
primarily	O
used	O
in	O
self-contained	O
portable	O
laptop	B-Device
computers	I-Device
and	O
do	O
not	O
require	O
a	O
flat	O
surface	O
near	O
the	O
machine	O
.	O
</s>
<s>
The	O
touchpad	B-Device
is	O
close	O
to	O
the	O
keyboard	O
,	O
and	O
relatively	O
short	O
finger	O
movements	O
are	O
required	O
to	O
move	O
the	O
cursor	O
across	O
the	O
display	O
screen	O
;	O
while	O
advantageous	O
,	O
this	O
also	O
makes	O
it	O
possible	O
for	O
a	O
user	O
's	O
palm	O
or	O
wrist	O
to	O
move	O
the	O
mouse	B-Device
cursor	O
accidentally	O
while	O
typing	O
.	O
</s>
<s>
Laptops	B-Device
today	O
feature	O
multitouch	B-Application
touchpads	B-Device
that	O
can	O
sense	O
in	O
some	O
cases	O
up	O
to	O
five	O
fingers	O
simultaneously	O
,	O
providing	O
more	O
options	O
for	O
input	O
,	O
such	O
as	O
the	O
ability	O
to	O
bring	O
up	O
the	O
context	O
menu	O
by	O
tapping	O
two	O
fingers	O
,	O
dragging	O
two	O
fingers	O
for	O
scrolling	O
,	O
or	O
gestures	O
for	O
zoom	O
in/out	O
or	O
rotate	O
.	O
</s>
<s>
The	O
touchpads	B-Device
with	O
physical	O
buttons	O
now	O
are	O
only	O
hi-end	O
business	O
\professional	O
laptops	B-Device
option	O
.	O
</s>
<s>
One-dimensional	O
touchpads	B-Device
are	O
the	O
primary	O
control	O
interface	O
for	O
menu	O
navigation	O
on	O
iPod	B-Operating_System
Classic	I-Operating_System
portable	O
music	O
players	O
and	O
additional	O
input	O
method	O
on	O
some	O
Wacom	O
digitizer	B-Device
tablets	I-Device
,	O
where	O
they	O
are	O
referred	O
to	O
as	O
"	O
click	O
wheels	O
"	O
,	O
since	O
they	O
only	O
sense	O
motion	O
along	O
one	O
axis	O
,	O
which	O
is	O
wrapped	O
around	O
like	O
a	O
wheel	O
.	O
</s>
<s>
Creative	O
Labs	O
also	O
uses	O
a	O
touchpad	B-Device
for	O
their	O
Zen	O
line	O
of	O
MP3	O
players	O
,	O
beginning	O
with	O
the	O
Zen	O
Touch	O
.	O
</s>
<s>
The	O
second-generation	O
Microsoft	O
Zune	B-Library
product	O
line	O
(	O
the	O
Zune	B-Library
80/120	O
and	O
Zune	B-Library
4/8	O
)	O
uses	O
touch	O
for	O
the	O
Zune	B-Device
Pad	I-Device
.	O
</s>
<s>
Touchpads	B-Device
also	O
exist	O
for	O
desktop	B-Device
computers	I-Device
as	O
an	O
external	O
peripheral	O
,	O
albeit	O
rarely	O
seen	O
.	O
</s>
<s>
But	O
touchpad	B-Device
layer	O
can	O
be	O
integrated	O
with	O
graphics	B-Device
tablet	I-Device
as	O
additional	O
input	O
option	O
.	O
</s>
<s>
External	O
computer	O
keyboards	O
can	O
be	O
equipped	O
with	O
integrated	O
touchpads	B-Device
(	O
particularly	O
keyboards	O
oriented	O
for	O
HTPC	O
use	O
)	O
,	O
and	O
some	O
keyboards	O
can	O
have	O
only	O
touch	O
input	O
surface	O
instead	O
of	O
hardware	O
buttons	O
(	O
a	O
typical	O
solution	O
for	O
clean	O
rooms	O
)	O
.	O
</s>
<s>
Optical	B-Device
trackpads	I-Device
primary	O
can	O
be	O
used	O
as	O
part	O
of	O
ultraportable	O
electronics	O
;	O
some	O
handheld	O
laptops	B-Device
and	O
early	O
smartphones	O
can	O
be	O
equipped	O
with	O
optical	B-Device
trackpads	I-Device
.	O
</s>
<s>
There	O
are	O
two	O
principal	O
means	O
by	O
which	O
touchpads	B-Device
work	O
.	O
</s>
<s>
The	O
capacitive	O
shunt	O
method	O
,	O
described	O
in	O
an	O
application	B-Application
note	O
by	O
manufacturer	O
Analog	O
Devices	O
,	O
senses	O
the	O
change	O
in	O
capacitance	O
between	O
a	O
transmitter	O
and	O
receiver	O
that	O
are	O
on	O
opposite	O
sides	O
of	O
the	O
sensor	O
.	O
</s>
<s>
Trackpads	B-Device
such	O
as	O
those	O
found	O
in	O
some	O
Blackberry	O
smartphones	O
work	O
optically	O
,	O
like	O
an	O
optical	O
computer	B-Device
mouse	I-Device
.	O
</s>
