Deck 4: Logic Circuit and Arithmetic Unit

Question 1

What type of logic circuit is represented by the figure shown below?

A)xor
B)xnor
C)and
D)xand

Answer 1

xnor

Question 2

What is the indication of a short to ground in the output of a driving gate?

A)only the output of the defective gate is affected
B)there is a signal loss to all load gates
C)the node may be stuck in either the high or the low state
D)the affected node will be stuck in the high state

Answer 2

there is a signal loss to all load gates

Question 3

For the device shown here, assume the D input is LOW, both S inputs are LOW and the input is LOW. What is the status of the Y' outputs?

A)d
B)a
C)c
D)b

Answer 3

d

Question 4

Which of the following combinations of logic gates can decode binary 1101?

A)one 4-input and gate
B)one 4-input and gate, one inverter
C)one 4-input and gate, one or gate
D)one 4-input nand gate, one inverter

Question 5

The carry propagation can be expressed as

A)cp = ab
B)cp = a + b
C)all but y0 are low
D)all but y0 are high

Question 6

3 bits full adder contains______________

A)3 combinational inputs
B)4 combinational inputs
C)6 combinational inputs
D)8 combinational inputs

Question 7

The basic building blocks of the arithmetic unit in a digital computers are______________        

A)subtractors
B)adders
C)multiplexer
D)comparator

Question 8

A digital system consists of____________types of circuits.

A)2
B)3
C)4
D)5

Question 9

In a sequential circuit, the output at any time depends only on the input values at that time.

A)past output values
B)intermediate values
C)both past output and present input
D)present input values

Question 10

The design of an ALU is based on______________        

A)sequential logic
B)combinational logic
C)multiplexing
D)de-multiplexing

Question 11

If the two numbers are unsigned, the bit conditions of interest are the____________carry and a possible____________ result.

A)input, zero
B)output, one
C)input, one
D)output, zero

Question 12

If the two numbers include a sign bit in the highest order position, the bit conditions of interest are the sign of the result, a zero indication and______________      

A)an underflow condition
B)a neutral condition
C)an overflow condition
D)one indication

Question 13

In parts of the processor, adders are used to calculate

A)addresses
B)table indices
C)increment and decrement operators
D)all of the mentioned

Question 14

Total number of inputs in a half adder is

A)2
B)3
C)4
D)1

Question 15

In which operation carry is obtained?

A)subtraction
B)addition
C)multiplication
D)both addition and subtraction

Question 16

If A and B are the inputs of a half adder, the carry is given by______________    

A)a and b
B)a or b
C)a xor b
D)a ex-nor b

Question 17

Half-adders have a major limitation in that they cannot______________    

A)accept a carry bit from a present stage
B)accept a carry bit from a next stage
C)accept a carry bit from a previous stage
D)accept a carry bit from the following stages

Question 18

If A, B and C are the inputs of a full adder then the carry is given by______________    

A)a and b or (a or b) and c
B)a or b or (a and b) c
C)(a and b) or (a and b)c
D)a xor b xor (a xor b) and c

Question 19

How many AND, OR and EXOR gates are required for the configuration of full adder?

A)1, 2, 2
B)2, 1, 2
C)3, 1, 2
D)4, 0, 1

Question 20

How many outputs are required for the implementation of a subtractor?

A)1
B)2
C)3
D)4

Question 21

Let the input of a subtractor is A and B then what the output will be if A = B?

A)0
B)1
C)a
D)b

Question 22

Let A and B is the input of a subtractor then the output will be______________      

A)a xor b
B)a and b
C)a or b
D)a exnor b

Question 23

Let A and B is the input of a subtractor then the borrow will be______________      

A)a and b'
B)a' and b
C)a or b
D)a and b

Question 24

The full subtractor can be implemented using

A)two xor and an or gates
B)two half subtractors and an or gate
C)two multiplexers and an and gate
D)two comparators and an and gate

Question 25

The output of a subtractor is given by (if A, B and X are the inputs).

A)a and b xor x
B)a xor b xor x
C)a or b nor x
D)a nor b xor x