KVS PGT Computer Science Question Paper - January 2017 (Question No 21-25)

KVS PGT Computer Science Question Paper - January 2017 (Question No 21-25)

Q 21. Ten signals, each requiring 3000 Hz, are multiplexed onto a single channel using FDM. How much minimum bandwidth is required for the multiplexed channel? Assume that the guard bands are 300 Hz wide. 

   1)  30,000
   2)  33,000
   3)  32,700 
   4)  33,700

  Answer : 3)  32,700
  Solution : Ten signals need 10 x 3000 = 30000 Hz
                   Nine (10-1) Guard bands (or gaps) needs =300 x 9 = 2700 Hz
                   So Minimum Bandwidth need 30000 + 2700 = 32700Hz 

Q 22. In which addressing mode, the operand is given explicitly in the instruction (Example instruction: ADD R4, #3) ?

   1)  Absolute mode 

   2)  Register indirect mode. 

   3)  Immediate mode 

   4)  Based Indexed mode.

Answer : 3)  Immediate mode. 

Solution : An addressing mode is a way in which an operand is specified in an instruction. There are different ways in which an operand may be specified in an instruction. An operand may be specified using the immediate, direct, extended, indexed, and inherent modes.

Q 23. In relational database the natural join of two tables is :

   1)  Combination of Union and filtered Cartesian product.

   2)  Combination of Projection and filtered Cartesian product.

   3)  Combination of Selection and filtered Cartesian product.

   4)  Cartesian product always.

Answer : 2)  Combination of Projection and filtered Cartesian product.

Solution :   Projection to remove duplicate attributes in the resultant relation(common column will be present twice in Cartesian product) and Filtering with match on common column.

Q 24. Which of the following memory improves the speed of execution of a program ?

   1)  Primary Memory

   2)  Cache Memory

   3)  Secondary Memory

   4)  Virtual Memory

Answer : 2)  Cache Memory

Solution : Cache is a small amount of memory which is part of the CPU which is physically closer to the CPU than RAM is. The more cache there is, the more data can be stored closer to the CPU.

Cache memory is beneficial because:

• Cache memory holds frequently used instructions/data which the processor may require next and it is faster access memory than RAM, since it is on the same chip as the processor.
  
• This reduces the need for frequent slower memory retrievals from main memory, which may otherwise keep the CPU waiting.
  

The more cache the CPU has, the less time the computer spends accessing slower main memory and as a result programs may run faster.

Q 25. Which of the following devices understands the format and contents of the data and translate message from one format to another ?

   1)  Hub

   2)  Router

   3)  Switch

   4)  Gateway

Answer : 4)  Gateway

Solution : A gateway is a device, system, or application that translates data from one format to another.