NTA NET CSA Test Code NN1804 -

1. 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 ?

30 microseconds

34 microseconds

60 microseconds

68 microseconds

2. 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

310

324

320

321

3. 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

9 and 7

7 and 6

9 and 8

8 and 6

4. A file is downloaded in a home computer using a 56 kbps MODEM connected to an Internet Service Provider. If the download of file completes in 2 minutes, what is the maximum size of data downloaded?

112 Mbits

6.72 Mbits

67.2 Mbits

672 Mbits

5. A Trojan horse is

A program that performs a legitimate function that is known to an operating system or its user and also has a hidden component that can be used for nefarious purposes like attacks on message security or impersonation

A piece of code that can attach itself to other programs in the system and spread to other systems when programs are copied or transferred

A program that spreads to other computer systems by exploiting security holes like weaknesses in facilities for creation of remote processes

All of the above

6. The problem of indefinite blockage of low-priority jobs in general priority scheduling algorithm can be solved using

Parity Bit

Aging

Compaction

Timer

7. Which of the following is not typically a benefit of dynamic linking?

Reduction in overall program execution time.
Reduction in overall space consumption in memory.
Reduction in overall space consumption on disk
Reduction in the cost of software updates.

1 only

4 only

1 and 4

2 and 3

8. An ER Model includes

An ER diagram portraying entity types.
Attributes for each entity type
Relationships among entity types
Semantic integrity constraints that reflects the business rules about data not captured in the ER diagram.

1, 2, 3, 4

1 and 3

1, 2, 4

2 and 4

9. What is Granularity?

The size of database

Size of record

size of file

size of data item

10. Consider the following four schedules due to three transactions (indicated by the subscript) using read and write on a data item X, denoted by r(X) and w(X) respectively. Which one of them is conflict serializable?

S₁ : r₁(X); r₂(X); w₁(X); r₃(X); w₂(X)

S₂ : r₂(X); r₁(X); w₂(X); r₃(X); w₁(X)

S₃ : r₃(X); r₂(X); r₁(X); w₂(X); w₁(X)

S₄ : r₂(X); w₂(X); r₃(X); r₁(X); w₁(X)