Event Class

1
Event Class

• Events class
• class Event
• public
• int time //time event should take place
• int type //type of event
• int procId //process to which event belongs

2
Main Simulation Pseudocode

• int main()
• ...
• quitTime 300 sec
• initialize event queue EQ
• currentTime 0
• while (EQ is not empty currentTime lt
  quitTime)
• e EQ.remove_next_event()
• currentTime e.time
• handle_the_event (e)
• ...

3
Handle_the_event Pseudocode

• handle_the_event (Event e)
• Switch (e.type)
• case process_arrival
• handle_proc_arrival(e)
• break
• case CPU completion
• handle_CPU_completion(e)
• break
• case I/O completion
• handle_IO_completion(e)
• break
• case Timer expiration
• handle_Timer_expiration(e)
• break
• schedular.run()

4
Handle Process arrival

• Handle_proc_arrival(e)
• proc e.procId
• add proc to ready queue

5
Handle CPU Completion

• Handle_CPU_completion (e)
• proc e.procId
• if (proc has completed its total time)
• remove proc
• else
• generate a random IO burst length
• create a IO completion event
• add the new event into EQ

6
Handle I/O completion

• Handle_IO_completion (e)
• proc e.procId
• generate the length of next CPU burst
• add the proc to the ready queue

7
Handle Timer Expiration

• Handle_timer_expiration
• proc e.procId
• move running proc to ready queue and update its
  CPU burst length

8
Scheduler Class

• Class Scheduler
• void run
• if(CPU is idle)
• select and dispatch a proc from ready queue
• create a CPU completion event
• add the new event into EQ
• else if (preemptive scheduling and condition
  is true)
• move the running proc to ready queue
• select and dispatch a proc from ready queue
• create a CPU completion event
• add the new event into EQ