Operating Systems — DU B.Sc. (Hons) Computer Science Previous Year Question Papers

(ii) What is the turnaround time of processes Pl and P4 for each of the scheduling algorithms given in par.t (i)? (iii) Which of the scheduling algorithms given in part (i) will result in the minimal average waiting time? (8) Parts of a question must be answered together. 1. (a) Give a one-word answer for the following : (i) Loading the pages of a process into memory only when they are needed is termed as (ii) The time needed for the disk to rotate the desired sector to the disk head is called (iii) CPU scheduler selects the processes from the secondary storage device. (iv) _ is a necessary condition for a deadlock according to which at least one resource is held in a non-sharable mode. (V). - fragmentation occurs when there is enough space in main memory, but it is not contiguous. (vi) The path name that begins at the root and follows a path down to the specified file is (b) The concurrent processes P1 and P2 execute the following code segments in a uniprocessor environment: where x is a shared variable. Discuss the problem that can occur due to such concurrent execution.. int maint) pthread_t tid; pthread_create (atid, NULL, func, NULL) ; void *func () (c) Consider the following set of processes, with the length of CPU burst time given in milliseconds: Process Arrival Time Burst Time Priority (i Draw Gantt charts illustrating the execution of these processes using Preemptive Priority Scheduling and Shortest Job First scheduling algorithm. (i) Draw the resource allocation graph. (ii) Is the system in a deadlock? If the answer is yes, then mention the processes in the deadlock; else, identify the sequence in which the processes can execute. (7) (c) Consider the following code segment : int a = 10, p = fork () ; if (p -- 0) (b) Consider a system with only two processes, Pl and P2. Write the structure of process PI to solve the critical section problem using Peterson's solution. Also, justify how this solution satisfies the necessary conditions required for correctly handling the critical-section problem. (8) wait (NULL); a--; cout << a << endl; (i) What will be the output of the above code s`egment? 7. (a) Consider a demand paging system with the page table stored in memory. What should be the maximum page fault rate to achieve an effective access time of 200 ns if the time taken for a memory reference is 100 ns? Assume that a page fault is serviced in 10 ns. (3) (ii) `What are the possible outputs if the wait() statement is removed? Justify. (d) Out of all disk-scheduling algorithms, FCFS scheduling is truly fair. Elaborate, giving a sui.table example. (3) (b) What will be the output of the following code fragment? Justify your answer. (4) (e)Discuss any three challenges faced in programming for multicore systelns. (3) (D Consider a 40-bit logical address. Find the number of bits required to represent the page number and page offset fields. It is given that the page size is