<s>
A	O
computer	O
processor	O
is	O
described	O
as	O
idle	B-Algorithm
when	O
it	O
is	O
not	O
being	O
used	O
by	O
any	O
program	B-Application
.	O
</s>
<s>
Every	O
program	B-Application
or	O
task	O
that	O
runs	O
on	O
a	O
computer	O
system	O
occupies	O
a	O
certain	O
amount	O
of	O
processing	O
time	O
on	O
the	O
CPU	O
.	O
</s>
<s>
If	O
the	O
CPU	O
has	O
completed	O
all	O
tasks	O
it	O
is	O
idle	B-Algorithm
.	O
</s>
<s>
Modern	O
processors	O
use	O
idle	B-Algorithm
time	O
to	O
save	O
power	O
.	O
</s>
<s>
On	O
processors	O
that	O
have	O
a	O
halt	O
instruction	O
that	O
stops	O
the	O
CPU	O
until	O
an	O
interrupt	O
occurs	O
,	O
such	O
as	O
x86	B-Operating_System
's	O
HLT	B-Language
instruction	I-Language
,	O
it	O
may	O
save	O
significant	O
amounts	O
of	O
power	O
and	O
heat	O
if	O
the	O
idle	B-Algorithm
task	I-Algorithm
consists	O
of	O
a	O
loop	O
which	O
repeatedly	O
executes	O
HLT	B-Language
instructions	I-Language
.	O
</s>
<s>
Many	O
operating	B-General_Concept
systems	I-General_Concept
,	O
for	O
example	O
Windows	O
,	O
Linux	B-Application
,	O
and	O
macOS	B-Application
will	O
run	O
an	O
idle	B-Algorithm
task	I-Algorithm
,	O
which	O
is	O
a	O
special	O
task	O
loaded	O
by	O
the	O
OS	O
scheduler	O
on	O
a	O
CPU	O
when	O
there	O
is	O
nothing	O
for	O
the	O
CPU	O
to	O
do	O
.	O
</s>
<s>
The	O
idle	B-Algorithm
task	I-Algorithm
can	O
be	O
hard-coded	O
into	O
the	O
scheduler	O
,	O
or	O
it	O
can	O
be	O
implemented	O
as	O
a	O
separate	O
task	O
with	O
the	O
lowest	O
possible	O
priority	O
.	O
</s>
<s>
An	O
advantage	O
of	O
the	O
latter	O
approach	O
is	O
that	O
programs	O
monitoring	O
the	O
system	O
status	O
can	O
see	O
the	O
idle	B-Algorithm
task	I-Algorithm
along	O
with	O
all	O
other	O
tasks	O
;	O
an	O
example	O
is	O
Windows	B-Device
NT	I-Device
's	O
System	O
Idle	B-Algorithm
Process	I-Algorithm
.	O
</s>
<s>
Some	O
programs	O
are	O
designed	O
to	O
appear	O
to	O
make	O
use	O
of	O
CPU	O
idle	B-Algorithm
time	O
,	O
meaning	O
that	O
they	O
run	O
at	O
a	O
low	O
priority	O
(	O
but	O
slightly	O
higher	O
than	O
idle	B-Algorithm
priority	O
)	O
so	O
as	O
not	O
to	O
impact	O
programs	O
that	O
run	O
at	O
normal	O
priority	O
.	O
</s>
