A system has 12 instances of a resource R shared among four processes. The maximum need and current allocation of each process are:

Process	Max Need	Current Allocation
P1	8	3
P2	9	4
P3	5	2
P4	3	1

With reference to the current allocation, is the system in a safe state? If so, what is a safe sequence?

Explanation

Total allocated = 3+4+2+1 = 10, so Available = 12 − 10 = 2. Each process's remaining Need = Max − Allocation: P1 needs 5, P2 needs 5, P3 needs 3, P4 needs 2. Only P4's need (2) can be met with Available=2, so run P4 to completion first; it releases its 1 allocated unit, raising Available to 3, which now covers P3's need (3) — run P3, releasing 2 more, raising Available to 5, which covers P1's need (5) — run P1, releasing 3 more, raising Available to 8, which comfortably covers P2's need (5). Every process finishes, so the system is safe with sequence P4, P3, P1, P2, option (iii).