Consider the $$3$$ processes, $$P1,$$ $$P2$$ and $$P3$$ shown in the table.

Process	Arrival Time	Time Units Required
P1	0	5
P2	1	7
P3	3	4

The completion order of the $$3$$ processes under the policies $$FCFS$$ and $$RR2$$ (round robin scheduling with $$CPU$$ quantum of $$2$$ time units) are

Fetch_And_Add (X, i) is an atomic Read-Modify-Write instruction that reads the value of memory location X, increments it by the value i, and returns the old value of X. It is used in the pseudocode shown below to implement a busy-wait lock. L is an unsigned integer shared variable initialized to 0. The value of 0 corresponds to lock being available, while any non-zero value corresponds to the lock being not available.

AcquireLock(L){ 
  While (Fetch_And_Add(L,1)) 
  L = 1; 
} 
Release Lock(L){ 
  L = 0; 
}

This implementation

Consider the virtual page reference string $$$1,2,3,2,4,1,3,2,4,1$$$
On a demand paged virtual memory system running on a computer system that has main memory size of $$3$$ page frames which are initially empty. Let $$LRU,$$ $$FIFO$$ and $$OPTIMAL$$ denote the number of page faults under the corresponding page replacement policy. Then

A file system with 300 G Byte disk uses a file descriptor with 8 direct block addresses, 1 indirect block address and 1 doubly indirect block address. The size of each disk block is 128 Bytes and the size of each disk block address is 8 Bytes. The maximum possible file size in this file system is