Priority scheduling is a non-preemptive algorithm and one of the most common scheduling algorithms in batch systems. Each process is assigned first arrival time (less arrival time process first) if two processes have same arrival time, then compare to priorities (highest process first). Also, if two processes have same priority then compare to process number (less process number first). This process is repeated while all process get executed.

Characteristics of Non-reemptive Priority Scheduling :

Schedules tasks based on priority.
When the higher priority work arrives while a task with less priority is executed, the higher priority work takes the place of the less priority one.
The latter is suspended until the execution is complete.
Lower is the number assigned, higher is the priority level of a process.

Advantages of Non-preemptive Priority Scheduling :

The average waiting time is less than FCFS
Less complex

Disadvantages of Preemptive Priority Scheduling :

One of the most common demerits of the Preemptive priority CPU scheduling algorithm is the Starvation Problem.