CPU Schedulers Simulator

A java program to simulate the following schedulers:

1. preemptive Shortest-Job First (SJF) Scheduling with context switching

2. Round Robin (RR) with context switching

3. preemptive Priority Scheduling (Provide a solution to avoid starvation problem)

4. Multi level Scheduling:

   a. The Schedule consists of 2 queues;

   b. The first queue is Round Robin (Quantum will be input);

   c. The second queue is FCFS (preemptive);

   d. The first queue always has a higher priority. So the second queue starts/resume execution only if the first queue is empty;

   e. The process input is name, arrival, burst and the queue number(1 or 2);

   f. The process doesn't change the queue that it enters.

Example:

Quantum time for the first queue (RR): 2

Answer:

Example Description:

At starting both queues have process so process in queue 1(P1, P2) runs first (because of higher priority) in the round robin fashion and completes after 7 units then process in queue 2(P3) starts running (as there is no process in queue 1) but while it is running P4 comes in queue 1 and interrupts P3 and start running for 5 second and after its completion P3 takes the CPU and completes its execution.

Program Input

• Number of processes 
• Name of each process
• Burst Time
• Arrival time
• Context switching (for question 1 and 2 only)
• Round robin Time Quantum (for question 2 and 4 only)
• Priority (for question 3 only)
• Queue number that the process will enter (for question 4 only)

Program Output

For each scheduler output the following:

• Processes execution order 
• Waiting Time for each process
• Turnaround  Time  for each process
• Average Waiting Time 
• Average Turnaround Time