Q. Consider the input/output (I/O) requests made at different instants of time directed at a hypothetical disk having 200 tracks as given in the following table.

Assume that:
Current head position is at track no. 65
Direction of last movement is towards higher numbered tracks
Current clock time is 160 milliseconds
Head movement time per track is 1 millisecond.

“look” is a variant of “SCAN” disk-arm scheduling algorithm. In this algorithm, if no more I/O requests are left in current direction, the disk head reverses its direction. The seek times in Shortest Seek First (SSF) and “look” disk-arm scheduling algorithms respectively are:

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Q. Consider a main memory with 3 page frames for the following page reference string :

5, 4, 3, 2, 1, 4, 3, 5, 4, 3, 4, 1, 4

Assuming that the execution of process is initiated after loading page 5 in memory, the number of page faults in FIFO and second chance replacement respectively are

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Q. A virtual memory based memory management algorithm partially swaps out a process. This is an example of

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Q. Assuming that the disk head is located initially at 32, find the number of disk moves required with FCFS if the disk queue of I/O block requests are 98, 37, 14, 124, 65, 67:

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Q. Let the page fault service time be 10 millisecond(ms) in a computer with average memory access time being 20 nanosecond(ns). If one page fault is generated for every 106 memory accesses, what is the effective access time for memory?

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Q. Match the following:

a. RAID 0          i. Bit interleaved parity
b. RAID 1          ii. Non redundant stripping
c. RAID 2           iii. Mirrored disks
d. RAID 3          iv. Error correcting codes

Codes:
      a   b   c    d

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Q. Consider the following processes with time slice of 4 milliseconds (I/O requests are ignored):

Process               A         B         C         D
Arrival time        0          1          2          3
CPU cycle         8          4          9          5

The average turn around time of these processes will be

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Q. A job has four pages A, B, C, D and the main memory has two page frames only. The job needs to process its pages in following order:

ABACABDBACD

Assuming that a page interrupt occurs when a new page is brought in the main memory, irrespective of whether the page is swapped out or not. The number of page interrupts in FIFO and LRU page replacement algorithms are

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Q. Suppose S and Q are two semaphores initialized to 1. P1 and P2 are two processes which are sharing resources.

P1 has statements                 P2 has statements
wait(S) ;                                     wait(Q) ;
wait(Q) ;                                     wait(S) ;
critical section1;                       critical section 2;
signal(S) ;                                 signal(Q) ;
signal(Q) ;                                 signal(S) ;

Their execution may sometimes lead to an undesirable situation called

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Q. An operating system using banker’s algorithm for deadlock avoidance has ten dedicated devices (of same type) and has three processes P1, P2 and P3 with maximum resource requirements of 4, 5 and 8 respectively. There are two states of allocation of devices as follows:

State 1   Processes                 P1       P2       P3
Devices allocated    2          3          4

State 2   Processes                 P1       P2       P3
Devices allocated    0          2          4

Which of the following is correct?

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Q. Let the time taken to switch between user mode and kernel mode of execution be T1 while time taken to switch between two user processes be T2. Which of the following is correct?

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Q. Working set model is used in memory management to implement the concept of

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Q. A thread is usually defined as a light weight process because an Operating System (OS) maintains smaller data structure for a thread than for a process. In relation to this, which of the following statement is correct?

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Q. The versions of windows operating system like windows XP and window Vista uses following file system:

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Q. Pre-emptive scheduling is the strategy of temporarily suspending a gunning process

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Q. In round robin CPU scheduling as time quantum is increased the average turn around time

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Q. Consider the following page trace : 4,3, 2, 1, 4, 3, 5, 4, 3, 2, 1, 5. Percentage of page fault that would occur if FIFO page replacement algorithm is used with number of frames for the JOB m=4 will be

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Q. Which of the following is scheme to deal with deadlock ?

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Q. A computer system supports 32 bit virtual address as well as 32 bit physical addresses. Since the virtual address space is of same size as that of physical address space, if we want to get rid of virtual memory, which one of the following is true ?

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Q. If an instruction takes ‘i’ microseconds and a page fault takes an additional ‘j’ microseconds. The effective instruction time, if on the average a page fault occurs every k instructions, is

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