Homework 2 Sarah Diesburg Operating Systems COP 4610

Why does OS loader set kernel mode? n OS needs to run with full privileges q q Sets more restrictive user mode bit for user programs Protects OS from errant user programs

Three Processes Process A Process B Process C Time 0 100 200 300 400 500 600 700 800

First In, First Out Process A Process B Process C FIFO C A B Time 0 100 200 300 400 500 600 700 800

First In, First Out Process A Process B Process C FIFO C A B Time 0 100 200 300 400 500 600 700 800 Average response time = [(300 -50) + (500 -150) + 0]/3 = 200

First In, First Out Process A Process B Process C FIFO C A B Time 0 100 200 300 400 500 600 700 800 Average wait time = [(300 -50) + (500 -150) + 0]/3 = 200

First In, First Out Process A Process B Process C FIFO C AA BB Time 0 100 200 300 400 500 600 700 800 Average turnaround time = [(500 -50) + (900 -150) + (300 -0)]/3 = 500

Round Robin (Time slice = 100) Process A Process B Process C RR C Time 0 100 200 300 400 500 600 700 800

Round Robin (Time slice = 100) Process A Process B Process C RR C A Time 0 100 200 300 400 500 600 700 800

Round Robin (Time slice = 100) Process A Process B Process C RR C A C Time 0 100 200 300 400 500 600 700 800

Round Robin (Time slice = 100) Process A Process B Process C RR C A C B Time 0 100 200 300 400 500 600 700 800

Round Robin (Time slice = 100) Process A Process B Process C RR C A C B A Time 0 100 200 300 400 500 600 700 800

Round Robin (Time slice = 100) Process A Process B Process C RR C A C B A C Time 0 100 200 300 400 500 600 700 800

Round Robin (Time slice = 100) Process A Process B Process C RR C A C B Time 0 100 200 300 400 500 600 700 800

Round Robin (Time slice = 100) Process A Process B Process C RR C A C B Time 0 100 200 300 400 500 600 700 800 Average response time = [(100 -50) + (300 – 150) + 0]/3 = 66. 7

Round Robin (Time slice = 100) Process A Process B Process C RR C A C B Time 0 100 200 300 400 500 600 700 800 Average wait time = {[(100– 50) + (400– 200)] + [(300– 150) + (600– 400)] + [0 + (200– 100) + (500– 300)]}/3 = [250 + 300]/3 = 300

Round Robin (Time slice = 100) Process A Process B Process C RR C A C B Time 0 100 200 300 400 500 600 700 800 Average turnaround time = [(500 – 50) + (900 – 150) + (600 – 0)]/3 = 600

Shortest Job Next Process A Process B Process C SJN C Time 0 100 200 300 400 500 600 700 800

Shortest Job Next Process A Process B Process C SJN C A Time 0 100 200 300 400 500 600 700 800

Shortest Job Next Process A Process B Process C SJN C A B Time 0 100 200 300 400 500 600 700 800

Shortest Job Next Process A Process B Process C SJN C A B Time 0 100 200 300 400 500 600 700 800 Average response time = [(300 -50) + (500 -150) + 0]/3 = 200

Shortest Job Next Process A Process B Process C SJN C A B Time 0 100 200 300 400 500 600 700 800 Average wait time = [(300 -50) + (500 -150) + 0]/3 = 200

Shortest Job Next Process A Process B Process C SJN C A B Time 0 100 200 300 400 500 600 700 800 Average turnaround time = [(500 -50) + (900 -150) + (300 -0)]/3 = 500

Shortest Remaining Time First Process A Process B Process C SRTF C Time 0 100 200 300 400 500 600 700 800

Shortest Remaining Time First Process A Process B Process C SRTF C A Time 0 100 200 300 400 500 600 700 800

Shortest Remaining Time First Process A Process B Process C SRTF C A C Time 0 100 200 300 400 500 600 700 800

Shortest Remaining Time First Process A Process B Process C SRTF C A C B Time 0 100 200 300 400 500 600 700 800

Shortest Remaining Time First Process A Process B Process C SRTF C A C B Time 0 100 200 300 400 500 600 700 800 Average response time = [0 + (500 -150) + 0]/3 = 117

Shortest Remaining Time First Process A Process B Process C SRTF C A C B Time 0 100 200 300 400 500 600 700 800 Average wait time = [0 + (500 – 150) + (250 – 50)]/3 = 183

Shortest Remaining Time First Process A Process B Process C SRTF C A C B Time 0 100 200 300 400 500 600 700 800 Average turnaround time = [(250 – 50) + (900 – 150) + (500 – 0)]/3 = 483