UGC NET CS 2015 Dec – III

Question 1

The three outputs x₁x₂x₃ from the 8 X 3 priority encoder are used to provide a vector address of the form 101x₁x₂x₃00. What is the second highest priority vector address in hexadecimal if the vector addresses are starting from the one with the highest priority ?

• A. BC
• B. A4
• C. BD
• D. AC

Answer: (B)

The priority preference for 8 X 3 priority encoder will be:

000 First 
001 Second 
010 Third
011 Fourth
100 Fifth
101 Sixth
110 Seventh 
111 Eighth 

According to question second highest priority vector address will be 10100100. i.e. 1010 0100. When we convert it to hexadecimal then it will be A4. So, option (B) is correct.

Question 2

What will be the output at PORT1 if the following program is executed ? MVI B, 82H MOV A, B MOV C, A MVI D, 37H OUT PORT1 HLT

• A. 37H
• B. 82H
• C. B9H
• D. 00H

Answer: (B)

Question 3

Which of the following 8085 microprocessor hardware interrupt has the lowest priority?

• A. RST 6.5
• B. RST 7.5
• C. TRAP
• D. INTR

Answer: (D)

8085 microprocessor has 5 hardware interrupts. Named TRAP, RST 7.5, RST 6.5, RST 5.5 and INTR. The above order is decreasing in priority. So, option (D) is correct.

Question 4

A dynamic RAM has refresh cycle of 32 times per msec. Each refresh operation requires 100 nsec and a memory cycle requires 250 nsec. What percentage of memory’s total operating time is required for refreshes?

• A. 0.64
• B. 0.96
• C. 2.00
• D. 0.32

Answer: (D)

Memory cycle time = 250 nsec memory is refreshed 32 times per msec i.e. Number of refreshes in 1 memory cycle (i.e in 250 nsec) = (32 * 250 * 10^-9) / 10^-3 = 8 * 10^-3. Time taken for each refresh = 100 nsec Time taken for 8 * 10^-3 refreshes = 8 * 10^-3 * 100 * 10^-9. = 8 * 10^-10 Percentage of the memory cycle time used for refreshing : = (Time taken to refresh in 1 memory cycle / Total time) * 100 = (8 * 10^-10 / 250 * 10^-9) * 100 = 0.032 * 10 = 0.32 So, option (D) is correct.

Question 5

A DMA controller transfers 32-bit words to memory using cycle stealing. The words are assembled from a device that transmits characters at a rate of 4800 characters per second. The CPU is fetching and executing instructions at an average rate of one million instructions per second. By how much will the CPU be slowed down because of the DMA transfer?

• A. 0.6%
• B. 0.12%
• C. 1.2%
• D. 2.5%

Answer: (B)

DMA controller transfers 32 bit(4 byte) words to memory(cycle stealing mode). Device transmits 4800 character per second (1 character = i byte) So, for 1 byte it will take 1 / 4800 sec. Since the controller transfers 4 byte in cycle stealing mode, it will take 4 * (1 / 4800) = 1 / 1200 sec. i.e. 1200 character will be transfered in cycle stealing mode and it is given that CPU is fetching and executing instructions at an average rate of one million instructions per second. slow down or cycle wasted % in DMA transfer = ( 1200 / 1000000) * 100 = 0.12 % So, option (B) is correct.

Question 6

A CPU handles interrupt by executing interrupt service subroutine __________.

• A. by checking interrupt register after execution of each instruction
• B. by checking interrupt register at the end of the fetch cycle
• C. whenever an interrupt is registered
• D. by checking interrupt register at regular time interval

Answer: (A)

A CPU handles interrupt by executing interrupt service subroutine by checking interrupt register after execution of each instruction. So, option (A) is correct.

Question 7

Given the following set of prolog clauses : father(X, Y) : parent(X, Y), male(X), parent(Sally, Bob), parent(Jim, Bob), parent(Alice, Jane), parent(Thomas, Jane), male(Bob), male(Jim), female(Salley), female(Alice). How many atoms are matched to the variable ‘X’ before the query father(X, Jane) reports a Result ?

• A. 1
• B. 2
• C. 3
• D. No option is correct.

Answer: (D)

Question 8

Forward chaining systems are __________ where as backward chaining systems are __________.

• A. Data driven, Data driven
• B. Goal driven, Data driven
• C. Data driven, Goal driven
• D. Goal driven, Goal driven

Answer: (C)

Forward chaining systems are data driven where as backward chaining systems are goal driven. So, option (C) is correct.

Question 9

Match the following w.r.t. programming language:

• A. (1)
• B. (2)
• C. (3)
• D. (4)
• E. No option is correct.

Answer: (E)

• JAVA is statically object oriented language.
• Python is dynamic object oriented language.
• Prolog is non object oriented language.
• ADA is statically object oriented language.

So, no option is correct.

Question 10

The combination of an IP address and a port number is known as ___________.

• A. network number
• B. socket address
• C. subnet mask number
• D. MAC address

Answer: (B)

The combination of an IP address and a port number is known as socket address.

Subnet mask number is a 32 bit number that mask the IP address.

MAC(Media Access Control) address is your computer's unique hardware number.

Network Number is the number which is logical AND between 32 bit IP address and a Network mask.

So, option (B) is correct.