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Consider the given snap of the system
Process Allocation Max Available
--- A B C A B C A B C
P0 0 0 1 0 0 1 1 5 2
P1 1 7 5 1 0 0 ---
P2 2 3 5 1 3 5 ---
P3 0 6 5 0 6 3 ---

Answer the following questions using bankers algorithm

i)Determine the total amount of resources of each type(A,B,C)?

ii)what is the content of needed matrix n?

iii)Determine the system is at safe state? why?

Subject: Operating System

Topic: PROCESS COORDINATION

Difficulty: Hard

1 Answer
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[i] Total amount of resources of type (A, B, C)?

The Total Amount of Resources = Sum of Columns of Allocation + Available Resource

= [2 9 11] + [1 5 2] = [3 14 13]

[ii] What are the contents of the Need matrix?

Calculation of the Need Matrix

Need [i] = Max [i] - Allocation [I]

Need for P0: (0, 0, 1) – (0, 0 , 1) = (0, 0, 1)

Need for P1: (1, 7, 5) – (1, 0, 0) = (0, 7, 5)

Need for P2: (2, 3, 5) – (1, 3, 5) = (1, 0, 0)

Need for P3: (0, 6, 5) – (0, 6, 3) = (0, 0, 2)

Need Matrix looks like in the following manner:

Need Matrix

[iii] Is the system in a safe state? Why?

Available Resources are Available = (1, 5, 2)

Now check if each type of resource request is available for each process or not

Step 1: For Process P0:

Need <= Available

0, 0, 1 <= 1, 5, 2 condition is True.

New available = available + Allocation

(1, 5, 2) + (0, 0, 1) => 1, 5, 3

Step 2: For Process P1:

Need <= Available

0, 7, 5 <= 1, 5, 3 condition is False.

Step 3: For Process P2:

Need <= Available

1, 0, 0 <= 1, 5, 3 condition is True.

New available = available + Allocation

(1, 5, 3) + (1, 3, 5) => 2, 8, 8

Step 4: For Process P3:

Need <= Available

0, 0, 2 <= 2, 8, 8 condition is True.

New available = available + Allocation

(2, 8, 8) + (0, 6, 5) => 2, 14, 13

Step 5: Now again check for Process P1:

Need <= Available

0, 7, 5 <= 2, 14, 13 condition is True.

New available = available + Allocation

(2, 14, 13) + (1, 0, 0) => 3, 14, 13

Hence, execute the banker's algorithm to find the safe state and the safe sequence like P0, P2, P3 and P1 for available resources (1, 5, 2)

Order of Safe Sequence = P0, P2, P3, P1

The system allocates all the needed resources to each process. So, we can say that the system is in a safe state.

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