CSC 227 Operating Systems
			  Project Specification

Problem Definition:
You are asked to simulate the behavior of the Time-sharing Operating System. The OS should respond only to raised interrupts.  For each interrupt level, you should provide the adequate routine that deals with this specific interrupt. The list of all interrupts will be listed below. The computer system can be modeled with the following queuing diagram.


We assume that, there are 12 processes initially in the ready queue, numbered from 0 to 11. They should be in some random order and not necessarily ordered in ascending order of their PID. Processes 0 to 5 are monitor processes and processes 6 to 11 are user processes. Process 0 is the idle process that does nothing except looping while waiting for other processes to join the ready queue. Whereas the IO queue is initially empty. Assume that the CPU and IO times are not known a priori. The OS system has the following interrupt levels:

Timer int. that is triggered every quantum units.
End Program SVC called when the program terminates its execution
IO request SVC called when requesting an IO operation
IO complete SVC that is triggered when the IO operation completes
Trap 1 is triggered when execution an illegal instruction like a division by 0
Trap 2 is triggered when making an illegal memory access known as memory violation 
Trap 3 is triggered when a user’s program executes an illegal instruction. 
Simulation Model:
The simulation is event-driven; meaning that the simulator responds to events only. In our case, the user can set some events, as we will see in the output section. The quantum is fixed to 20 time units; where a time unit is equivalent 100 milliseconds.

Input:
The first input to the simulator is a warm up time. The simulation should run for this warm up time with no interaction with the user. This period will take the system to some stable state where simulation statistics are considered to be acceptable. During the simulation, it required to keep track of all processes and to be able to deliver some performance figures such as CPU utilization and turnaround time. At the end of the warm up phase, the simulator should output an interactive menu, which is explained in the next section.

Output:
An example of a possible menu is given below. The program should check first for the validity of the user choice and then respond to it by changing some simulation states or printing some results. An example of invalid request is triggering Trap 3 while a monitor process is using the CPU:

Display the CPU utilization percentage
Display CPU and IO times used by a specific process
Display the PID of the process that is currently running
Display the contents of the Ready Queue
Insert a new process or kill a process.
Display the PID of the process that is currently performing an IO operation
Trigger an interrupt and see how the OS react to this interrupt.
Terminate the simulation.

Deadline:
Projects, which are submitted after the deadline time, are not accepted. Consequently the group should be severely penalized.