<s>
A	O
sense	B-Device
switch	I-Device
,	O
or	O
program	B-Device
switch	I-Device
,	O
is	O
a	O
switch	O
on	O
the	O
front	B-Device
panel	I-Device
of	O
a	O
computer	O
whose	O
state	O
can	O
be	O
tested	O
by	O
conditional	O
branch	O
instructions	O
in	O
software	O
.	O
</s>
<s>
Most	O
early	O
computers	O
had	O
several	O
sense	B-Device
switches	I-Device
.	O
</s>
<s>
On	O
the	O
IBM	B-Device
1620	I-Device
there	O
are	O
four	O
switches	O
,	O
and	O
their	O
state	O
can	O
be	O
tested	O
via	O
special	O
forms	O
of	O
the	O
IF-statement	O
offered	O
by	O
the	O
FORTRAN	B-Application
compiler	O
for	O
the	O
IBM	B-Device
1620	I-Device
.	O
</s>
<s>
For	O
the	O
IBM	B-Device
1130	I-Device
there	O
are	O
sixteen	O
switches	O
matching	O
the	O
sixteen-bit	O
word	O
size	O
of	O
the	O
computer	O
,	O
plus	O
a	O
toggle	O
switch	O
adjacent	O
to	O
the	O
power	O
on/off	O
switch	O
.	O
</s>
<s>
These	O
bit-switches	O
are	O
more	O
normally	O
used	O
with	O
the	O
computer	O
stopped	O
to	O
specify	O
some	O
memory	O
address	O
to	O
be	O
viewed	O
(	O
via	O
the	O
indicator	O
lights	O
on	O
the	O
front	B-Device
panel	I-Device
)	O
,	O
or	O
set	O
.	O
</s>
<s>
The	O
IBM	B-Device
1130	I-Device
also	O
has	O
an	O
"	O
Interrupt	O
Request	O
"	O
key	O
associated	O
with	O
the	O
console	B-Device
printer	O
,	O
whose	O
pressing	O
might	O
cause	O
a	O
suitably	O
programmed	O
long-running	O
program	O
to	O
type	O
a	O
progress	O
report	O
on	O
the	O
console	B-Device
printer	O
.	O
</s>
<s>
The	O
front	B-Device
panel	I-Device
of	O
the	O
Data	B-Device
General	I-Device
Eclipse	I-Device
computer	O
has	O
5	O
sense	B-Device
switches	I-Device
,	O
16	O
address	O
switches	O
,	O
and	O
5	O
control	O
switches	O
,	O
as	O
shown	O
(	O
left	O
to	O
right	O
)	O
in	O
the	O
figure	O
at	O
right	O
.	O
</s>
<s>
Personal	O
computers	O
replace	O
the	O
function	O
of	O
fixed	O
sense	B-Device
switches	I-Device
with	O
the	O
keyboard	O
and	O
screen	O
user	O
interface	O
.	O
</s>
<s>
If	O
a	O
program	O
does	O
not	O
regularly	O
test	O
the	O
state	O
of	O
sense	B-Device
switches	I-Device
during	O
a	O
long	O
calculation	O
,	O
they	O
are	O
ineffective	O
at	O
changing	O
the	O
program	O
's	O
operation	O
.	O
</s>
