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UGC-NET | UGC NET CS 2016 July – II | Question 37
• Last Updated : 20 Apr, 2018

Suppose there are four processes in execution with 12 instances of a Resource R in a system.
The maximum need of each process and current allocation are given below: With reference to current allocation, is system safe ? If so, what is the safe sequence ?
(A) No
(B) Yes, P1P2P3P4
(C) Yes, P4P3P1P2
(D) Yes, P2P1P3P4

Answer: (C)

Explanation: Current allocation of P1P2P3P4 are 3, 4, 2, 1 which is 10 in total.
We have 12 total no of resources and out of them 10 are allocated so, we have only 2 resources.
There is 5, 5, 3, 2 resources are needed for P1P2P3P4 respectively.
So, P4 will run first and free 3 resources after execution. Which are sufficient for P3 So it will execute and do free 5 resources.
Now P1 and P2 both require 5 resources each So we can execute any of them first but we will give priority to P1. The execution order will be P4P3P1P2.
SO, option (C) is correct.

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