Q. An operating system supports a paged virtual memory, using a central processor with a cycle time of one microsecond. It costs an additional one microsecond to access a page other than the current one. Pages have 1000 words, and the paging device is a drum that rotates at 3000 revolutions per minute and transfers one million words per second. Further, one percent of all instructions executed accessed a page other than the current page. The instruction that accessed another page, 80% accessed a page already in memory and when a new page was required, the replaced page was modified 50% of the time. What is the effective access time on this system, assuming that the system is running only one process and the processor is idle during drum transfers ?

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Q. Consider the following page reference string :

1, 2, 3, 4, 2, 1, 5, 6, 2, 1, 2, 3, 7, 6, 3, 2, 1, 2, 3, 6

Which of the following options, gives the correct number of page faults related to LRU, FIFO, and optimal page replacement algorithms respectively, assuming 05 page frames and all frames are initially empty ?

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Q. Consider a file currently consisting of 50 blocks. Assume that the file control block and the index block is already in memory. If a block is added at the end (and the block information to be added is stored in memory), then how many disk I/O operations are required for indexed (single-level) allocation strategy ?

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Q. Suppose that the number of instructions executed between page faults is directly proportional to the number of page frames allocated to a program. If the available memory is doubled, the mean interval between page faults is also doubled. Further, consider that a normal instruction takes one micro second, but if a page fault occurs, it takes 2001 micro seconds. If a program takes 60 sec to run, during which time it gets 15000 page faults, how long would it take to run if twice as much memory were available?

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Q. Consider a disk with 16384 bytes per track having a rotation time of 16 msec and average seek time of 40 msec. What is the time in msec to read a block of 1024 bytes from this disk?

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Q. Match the following with respect to various memory management algorithms :

List - I                                     List - II
(a) Demand paging                 (i) degree of multiprogramming
(b) Segmentation                     (ii) working set
(c) Dynamic partitions             (iii) supports user view of memory
(d) Fixed partitions                  (iv) compaction

Codes :
      (a)  (b)   (c)  (d)

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Q. Function of memory management unit is :

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Q. Consider a system with twelve magnetic tape drives and three processes P1, P2 and P3. Process P1 requires maximum ten tape drives, process P2 may need as many as four tape drives and P3 may need upto nine tape drives. Suppose that at time t1, process P1 is holding five tape drives, process P2 is holding two tape drives and process P3 is holding three tape drives. At time t1, system is in:

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Q. In an operating system, indivisibility of operation means :

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Q. The character set used in Windows 2000 operating system is ...............

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Q. The distributed system is a collection of (P) and communication is achieved in distributed system by (Q) , where (P) and (Q) are :

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Q. In a paged memory management algorithm, the hit ratio is 70%. If it takes 30 nanoseconds to search Translation Look-aside Buffer (TLB) and 100 nanoseconds (ns) to access memory, the effective memory access time is

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Q. Match the following:

List-I                                                               List-II
a. Multilevel feedback queue           i. Time-slicing
b. FCFS                                                 ii. Criteria to move processes between queues
c. Shortest process next                   iii. Batch processing
d. Round Robin Scheduling             iv. Exponential Smoothening

Codes:
      a    b    c    d

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Q. Consider a system with five processes P0 through P4 and three resource types R1, R2 and R3. Resource type R1 has 10 instances, R2 has 5 instances and R3 has 7 instances. Suppose that at time T0, the following snapshot of the system has been taken :

Allocation R1 R2 R3 P0 0 1 0 P1 2 0 0 P2 3 0 2 P3 2 1 1 P4 0 2 2
Max R1 R2 R3 7 5 3 3 2 2 9 0 2 2 2 2 4 3 3
Available R1 R2 R3 3 3 2

Assume that now the process P1 requests one additional instance of type R1 and two instances of resource type R3. The state resulting after this allocation will be

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Q. Match the following:

List-I                                                      List-II
a. Contiguous Allocation       i. This scheme supports very large file sizes.
b. Linked allocation                 ii. This allocation technique supports only sequential files.
c. Indexed allocation               iii. Number of disks required to access file is minimal.
d. Multi-level indexed                         iv. This technique suffers from maximum wastage of space in storing pointers

Codes:
      a    b    c    d

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Q. Which of the following is the correct value returned to the operating system upon the successful completion of a program?

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Q. Match the following:

List – I                                                   List - II
Process state transition                   Reason for transition
a. Ready→Running                           i. Request made by the process
is satisfied or an event for which
it was waiting occurs.
b. Blocked→Ready                             ii. Process wishes to wait for
some action by another process.
c. Running→Blocked                         iii. The process is dispatched.
d Running→Ready                            iv. The process is preempted.

Codes :
      a   b   c    d

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Q. The hit ratio of a Translation Look Aside Buffer (TLAB) is 80%. It takes 20 nanoseconds (ns) to search TLAB and 100 ns to access main memory. The effective memory access time is ................

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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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