Question

1. What is the average waiting time for Processes If the Operating System uses the Shortest-Job-First (SJF) Scheduling Algorithm?

(P1=5 ms, P2=10 ms, P3=15 ms)

2. How many page faults occur in the Optimum Page Replacement algorithm (OPR) with the following reference string for three-page frames?   

Reference String: 4,2,1,3,2,3,4,1

3. What is the average waiting time for Processes If the Operating System uses Shortest-Job-Remaining-First (SJRF) Scheduling Algorithm?

(P1=5 ms, P2=10 ms, P3=15 ms)

Arrival Time ( P1=0 ms, P2=5 ms, P3=10 ms)

4. What is the average waiting time for Processes If Operating System uses the First Come First Serve (FCFS) Scheduling Algorithm?

(P1=5 ms, P2=10 ms, P3=15 ms)

Process Order: P2, P1, P3

5. What is the average waiting time for Processes If the Operating System uses Round Robin (RR) Scheduling Algorithm?

(P1=5 ms, P2=10 ms, P3=15 ms)

Time slice/ quantum = 5 ms

6. What is the average waiting time for Processes If the Operating System uses the Priority Scheduling (PS) Scheduling Algorithm?

(P1=5 ms, P2=10 ms, P3=15 ms)

Priority Order: P3, P1, P2

7. How many page faults occur in the FIFO replacement algorithm with the following reference string for THREE-page frames?   

Reference String: 4,2,1,3,2,3,4,1

8. How many page faults occur in the Least Recently Used Algorithm (LRU) with the following reference string for three-page frames?   

Reference String: 4,2,1,3,2,3,4,1

Answer 1

SCHEDULING ALGORITHMS:

turn around time : it is interval between arrval time and completion time of the process

turn around time(TAT)=completion time(CT)- arrival time(AT)

waiting time:interval between TAT and burst time(BT) and the time it waits in the ready queue

waiting time:TAT-BT

burst time:time to run a process

arrival time:the time for process to more from new ready to new

Completion time:time to move from to terminate state(see in the gantt chart)

average waiting time(WT)=sum of all processes waiting time/number of process

FCFS(first come first serve):

Selection criteria:arrival time

mode of operation:non preemptive

conflict resolution:lower process id

SJF(shortest job first):

Selection criteria:burst time

mode of operation:non preemptive

conflict resolution:lower process id

SRJF(shortest remaining job first):

Selection criteria:burst time

mode of operation:preemptive

conflict resolution:lower process id

RR(round robin):

preemption of the running process is based on completing of time quantum allocated to a process.

Selection criteria:arrival time+time quantum

mode of operation:preemptive

Priority scheduling:

Selection criteria:priority

mode of operation:non preemptive

conflict resolution:lower process id

PAGE REPLACEMENT ALGORITHMS:

Optimal page replacement algo:

in the event of page fault,victimise that page which will not be used for the largest duration of time in future refrences.

FCFS(First come fisrt serve):

criteria:time of load

LRU(least recently used):

in the event of page fault,victimise that page which was not used recently.