i) Real time priority scheduling:

It has two types-

• Real time static priority: Priorities are predetermined and fixed at design time. Priorities are not changed while on the run. There is no processor overhead.
• Real time dynamic priority: Some examples of these algorithms are Earliest Deadline First (EDF), Least Slack Time First (LSF) and Rate Monotonic algorithm/ Shortest Job First (RMS/ SJF). The tasks are given priority in runtime. There is no fixed priority. There is a slight processor overhead.

ii) Non-preemptive scheduling:

In this case even if a higher priority task enters into the ready state, the current task (running task) is not pre-empted or suspended until it completes execution.

• FIFO/ FCFS (First In First Out/ First Come First Serve)
• LIFO/ LCFS (Last In First Out/ Last Come First Serve)

iii) Preemptive scheduling:

In this case, the higher priority task (T2) when enters the ready state is immediately shifted to running state where T1 with some priority is already running.

If priority T2 > priority T1

then task T2 will preempt the task T1 and enter into running state.

• Round robin
• Priority