<s>
A	O
keyboard	B-Device
buffer	I-Device
is	O
a	O
section	O
of	O
computer	O
memory	B-General_Concept
used	O
to	O
hold	O
keystrokes	O
before	O
they	O
are	O
processed	O
.	O
</s>
<s>
Keyboard	B-Device
buffers	I-Device
have	O
long	O
been	O
used	O
in	O
command-line	B-Application
processing	O
.	O
</s>
<s>
As	O
a	O
user	O
enters	O
a	O
command	O
,	O
they	O
see	O
it	O
echoed	B-Error_Name
on	O
their	O
terminal	B-Device
and	O
can	O
edit	O
it	O
before	O
it	O
is	O
processed	O
by	O
the	O
computer	O
.	O
</s>
<s>
In	O
time-sharing	B-General_Concept
systems	I-General_Concept
,	O
the	O
location	O
of	O
the	O
buffer	O
depends	O
on	O
whether	O
communications	O
is	O
full-duplex	O
or	O
half-duplex	O
.	O
</s>
<s>
As	O
the	O
main	O
computer	O
receives	O
each	O
keystroke	O
,	O
it	O
ordinarily	O
appends	O
the	O
character	O
which	O
it	O
represents	O
to	O
the	O
end	O
of	O
the	O
keyboard	B-Device
buffer	I-Device
.	O
</s>
<s>
In	O
half-duplex	O
systems	O
,	O
keystrokes	O
are	O
echoed	B-Error_Name
locally	O
on	O
a	O
computer	B-General_Concept
terminal	I-General_Concept
.	O
</s>
<s>
The	O
user	O
can	O
see	O
the	O
command	B-Application
line	I-Application
on	O
his	O
terminal	B-Device
and	O
edit	O
it	O
before	O
it	O
is	O
transmitted	O
to	O
the	O
main	O
computer	O
.	O
</s>
<s>
On	O
some	O
early	O
home	O
computers	O
,	O
to	O
minimize	O
the	O
necessary	O
hardware	O
,	O
a	O
CPU	B-Device
interrupt	O
checked	O
the	O
keyboard	B-Device
's	O
switches	O
for	O
key	O
presses	O
multiple	O
times	O
each	O
second	O
,	O
and	O
recorded	O
the	O
key	O
presses	O
in	O
a	O
keyboard	B-Device
buffer	I-Device
for	O
the	O
operating	O
system	O
or	O
application	O
software	O
to	O
read	O
.	O
</s>
<s>
On	O
some	O
systems	O
,	O
if	O
the	O
user	O
presses	O
too	O
many	O
keys	O
at	O
once	O
,	O
the	O
keyboard	B-Device
buffer	I-Device
overflows	O
and	O
will	O
emit	O
a	O
beep	O
from	O
the	O
computer	O
's	O
internal	O
speaker	O
.	O
</s>
<s>
The	O
use	O
of	O
keyboard	B-Device
buffers	I-Device
is	O
sometimes	O
known	O
from	O
the	O
user	O
experience	O
side	O
as	O
typeahead	B-Device
.	O
</s>
