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What is the average turn-around time using FCFS, SJF and Round -RObin(with a quantum of 1 sec) scheduling?
written 6.9 years ago by gravatar for priyad84 priyad84 • 350 modified 2.9 years ago by gravatar for binitamayekar binitamayekar ★ 6.6k

Subject: Operating System

Topic: Process Concept and Scheduling

Difficulty: Low

There are five process A to E which are waiting to be scheduled. Their arrival times are 0,1,3,9 and 12 sec respectively and their processing times are 3,5,2,5 and 5 seconds respectively. What is the average turn-around time using FCFS, SJF and Round -RObin(with a quantum of 1 sec) scheduling?
operating systems
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written 2.9 years ago by gravatar for binitamayekar binitamayekar ★ 6.6k

Turn Around Time = Process Completion Time – Process Arrival Time

First Come First Serve (FCFS) Scheduling

FCFS 1

Process Arrival Time Processing Time Process Completion Time Process Turn Around Time
A 0 3 3 3 – 0 = 3
B 1 5 8 8 – 1 = 7
C 3 2 10 10 – 3 = 7
D 9 5 15 15 – 9 = 6
E 12 5 20 20 – 12 = 8

Average Turn Around Time = (3 + 7 + 7 + 6 +8)/5 = 6.2 sec

Shortest Job First (SJF) Scheduling

SJF 1

Process Arrival Time Processing Time Process Completion Time Process Turn Around Time
A 0 3 3 3 – 0 =3
B 1 5 10 10 – 1 = 9
C 3 2 5 5 – 3 = 2
D 9 5 15 15 – 9 = 6
E 12 5 20 20 – 12 = 8

Average Turn Around Time = (3 + 9 + 2 + 6 + 8)/5 = 5.6 sec

Round Robin Scheduling

Round Robin 1

Quantum Size = 1 sec

Process Arrival Time Processing Time Process Completion Time Process Turn Around Time
A 0 3 6 6 – 0 = 6
B 1 5 11 11 – 1 = 10
C 3 2 8 8 – 3 = 5
D 9 5 18 18 – 9 = 9
E 12 5 20 20 – 12 = 8

Average Turn Around Time = (6 + 10 + 5 + 9 + 8)/5 = 7.6 sec
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