Consider the following set of processes and the length of CPU burst time given in milliseconds:

Process

CPU Burst time (ms)

P1

5

P2

7

P3

6

P4

4

 

Assume that processes being scheduled with Round-Robin Scheduling Algorithm with Time Quantum 4ms. Then the waiting time for P4 is _________ ms.

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UGC NET Computer Science (Paper 2) Dec 2018 Paper
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  1. 0
  2. 4
  3. 12
  4. 6

Answer (Detailed Solution Below)

Option 3 : 12
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Scheduling Algorithm: Round-Robin

Time Quantum: 4 milliseconds

Gantt chart:

P1

P2

P3

P4

P1

P2

P3

 

0 4 8 12 16 17 20 22

Process Table:

Process

Arrival Time (AT)

Burst Time (BT)

Completion Time (CT)

Turnaround Time (TAT)

Waiting Time (WT)

P1

0

5

17

17

12

P2

0

7

20

20

13

P3

0

6

22

22

16

P4

0

4

16

16

12

 

Therefore, the waiting time for P4 is 12 milliseconds.

Formula used:

TAT = CT – AT

WT = TAT – BT

Important Points:

Since arrival time is not given of processes is not given consider all the process arrive at time = 0 and by convention, the process with lowest id associated with it executes first, that is, P1 followed by P2 and so on.

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