Differentiate Between Aperiodic, Periodic and Sporadic Tasks of an Real-Time System

 Aperiodic Task

Real time systems are required to respond to external events which occur at random instant of time. The system execute a set of job in response to these events. The release time of these jobs are not known until the event triggering.

Example includes Garbage Collection, Typical Branch Instruction

Periodic Task

Periodic tasks are time driven i.e the characteristics are known in advance and they execute at periodical instants of time. Every task T_i is characterized by (p_i, e_i) where p_i is task period and e_i is the worst case execution time, P_i is the minimum time period between job release.

Example includes cyclic code, processed schedule by internal clock.

Sporadic Task

Sporadic Task are the jobs with hard deadlines. These jobs are executed to accomplish the mode change. Every task is characterized by arrival time and deadline.