# Andrew S. Tanenbaum (OS) Edition 4 Exercise 6 Question 21 (Page No. 467)

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Take a careful look at Fig. 6-11(b). If $D$ asks for one more unit, does this lead to a safe state or an unsafe one? What if the request came from $C$ instead of $D?$

Given :               a= Safe                b= Safe                c= Unsafe

But If  Fig. 6-11(b) , D asks for one more unit then  Need Table is

 A 5 B 4 C 2 D 2

we have only one unit left which can not satisfied any one of the Above process.. ………………

therefore If D asks for one more unit, does this lead to an unsafe State .

if the request came from C instead of D then it lead to a Safe state  check below Need table is

 A 5 B 4 C 1 D 3

Which can be easly Satisfied and lead to a Safe state.

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