Operating System Group Presentation Presentation Slide Made by: Solaiman Hridoy

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CPU
Scheduling
Algorithm
(SJF, Round-Robin, Priority)
- Non Preemptive
P r e s e n t e d B y
M e h e n a z T a h e r i n
S o l a i m a n H r i d o y
M d . E h s a n u l I s l a m K h a n
S a m i a A k t e r
P u s h p i t a D u t t a
I D : 1 7 0 1 0 1 1 4
I D : 1 7 0 1 0 1 1 5
I D : 1 7 0 1 0 1 1 6
I D : 1 7 0 1 0 1 1 7
I D : 1 7 0 1 0 1 1 8

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Table of Contents
• Definitions …………………………………………………………………………….. 01
• Shortest Job First (SJF) – without arrival time …………………………..02
• Shortest Job First (SJF) – with arrival time ……………………………….03
• Priority – without arrival time …………………………………………………. 04
• Priority – with arrival time …………………………..…………………………..05
• Round-Robin – without arrival time …………….……………………………06

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Definitions
• SJF : Shortest Job First scheduling works on the process with
the shortest burst time or duration first.
• Priority: In this scheduling, processes are scheduled
according to their priorities, i.e., highest priority process is
scheduled first. If priorities of two processes match, then
schedule according to arrival time.
• Round –Robin: A fixed time is allotted to each process,
called quantum, for execution. Once a process is executed for given
time period that process is preempted and other process executes for
given time period.
01

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Shortest Job First(SJF)
without arrival time – Non Preemptive
Process Burst Time
P1 21
P2 3
P3 6
P4 2
P4 P2 P3 P1
TABLE
Gantt
Chart
0 2 5 11 32
Waiting Time, P1 = 11, P2 = 2, P3 = 5, P4 = 0
Average Waiting Time = (11+2+5+0) / 4 = 4.5 ms
02

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Shortest Job First(SJF)
with arrival time – Non Preemptive
Process AT BT CT TAT WT
P1 1 21 22 21 0
P2 3 3 27 24 21
P3 6 6 33 27 21
P4 7 2 24 17 15
P1 P4 P2 p3
TABLE
Gantt
Chart
22
TAT = CT – AT
WT = TAT - BT
Average Waiting Time = (0+21+21+15) / 4 = 14.25 ms
0 1 24 27 33
AT = Arrival Time
BT = Burst Time
CT = Completion Time
TAT = Turn Around Time
WT = Waiting Time
Average Turn Around Time = (21+24+27+17) / 4 = 22.25 ms
03

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Priority Scheduling
without arrival time – Non Preemptive
Process Burst
Time
Priority
P1 10 3
P2 1 1
P3 2 4
P4 1 5
p5 5 2
P2 P5 P1 P3 p4
TABLE
Gantt
Chart
Waiting Time, P1 = 6, P2 = 0, P3 = 16 , P4 = 18, P5 = 1
Average Waiting Time = (6+0+16+18+1) / 5 = 8.2 ms
0 1 6 16 1918
Process Burst
Time
Priority
P2 1 1
P5 5 2
P1 10 3
P3 2 4
P4 1 5
Sorted Table
04

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Priority Scheduling
with arrival time – Non Preemptive
Proces
s
AT BT Prio
rity
CT TAT WT
P1 0 6 2 6 6 0
P2 2 1 4 14 12 11
P3 4 4 1 10 6 2
P4 5 3 3 13 8 5
P1 P3 P4 P2
TABLE
Gantt
Chart
TAT = CT – AT
WT = TAT - BT
Average Waiting Time = (0+11+2+5) / 4 = 4.5 ms
60 10 13 14
AT = Arrival Time
BT = Burst Time
CT = Completion Time
TAT = Turn Around Time
WT = Waiting Time
Average Turn Around Time = (6+12+6+8) / 4 = 8 ms
05

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Round-Robin Scheduling
without arrival time – Non Preemptive
P1 P2 P3 P4 P5 P1 P2 P4 p5 P1 P2 P5
TABLE
Gantt
Chart
Average TAT= (19+20+6+15+23) / 5 = 16.6 ms
0 2 17 19 23201264
Time Quantum = 2 ms
Arrival Time = 0
06
Process BT RT WT CT TAT
P1 6 4, 2, 0 13 19 19
P2 5 3,1,0 15 20 20
P3 2 0 4 6 6
P4 3 1,0 12 15 15
p5 7 5,3,0 16 23 23
AT = Arrival Time
BT = Burst Time
CT = Completion Time
TAT = Turn Around Time
WT = Waiting Time
Average Waiting Time = (13+15+4+12+16) / 5 = 12 ms
TAT = CT – AT
WT = TAT – BT
Ready Queue: P1, P2, P3, P4, P5, P1, P2, P4, P5, P1,P2, P5
8 10 14 15

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Thank You