1. Periodic task:

The task that repeats itself after a fixed interval of time. The precise time intervals at which periodic tasks repeat are usually governed by clock interrupts. Therefore a clock driven task.

2. Aperiodic task:

It can occur at random intervals. Minimum separation between 2 tasks instances can be zero. It is identical to sporadic task.

3. Sporadic task:

It occurs at random instances. Consider following parameters