<s>
A	O
thumb	B-Device
keyboard	I-Device
,	O
or	O
a	O
thumb	O
board	O
,	O
is	O
a	O
type	O
of	O
keyboard	B-Device
commonly	O
found	O
on	O
PDAs	B-Application
,	O
mobile	O
phones	O
,	O
and	O
PDA	B-Application
phones	I-Application
which	O
has	O
a	O
familiar	O
layout	O
to	O
an	O
ordinary	O
keyboard	B-Device
,	O
such	O
as	O
QWERTY	O
.	O
</s>
<s>
The	O
inputting	O
surface	O
is	O
usually	O
relatively	O
small	O
,	O
and	O
is	O
intended	O
for	O
typing	B-Application
using	O
the	O
available	O
thumbs	O
,	O
while	O
holding	O
the	O
device	O
.	O
</s>
