We need an interval timer to support a preemptive scheduler. The pseudo$-$code for an IntervalTimer$()$ is illustrated as follows:

IntervalTimer$()\{$

InterruptCount$--$;

if $($InterruptCount $<=0)\{$

InterruptRequest$=$True;

InterruptCount$=$K;

$\}$

$\}$

Q$->$How is the above routine IntervalTimer$()$ invoked? That is$,$ what triggers the IntervalTimer$()?$