ISRO CS 2007


Question 1
The Boolean expression Y = (A + B' + A'B)C' is given by
A
AC'
B
BC'
C
C'
D
AB
Digital Logic & Number representation    ISRO CS 2007    Logic functions and Minimization    
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Question 1 Explanation: 
Y = (A + B' + A'B)C'
Y = AC' + B'C' + A'BC'
Y = (A + A'B)C' + B'C'
Y = (A + B)C' + B'C'
Y = AC' + BC' + B'C'
Y = AC' + C'(B + B') // B + B' = 1
Y = AC' + C'
Y = C'
So, option (C) is correct.
Question 2
The circuit shown in the following figure realizes the function
A
(( A + B )' +C ) ( D'E' )
B
(( A + B )' + C ) ( DE' )
C
( A + ( B + C )' ) ( D'E )
D
( A + B + C' ) ( D'E' )
Digital Logic & Number representation    ISRO CS 2007    Logic functions and Minimization    
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Question 2 Explanation: 
The given function is equivalent to the following expression:
Y = (((A + B)' + C)' + ((D + E)')')'
Y = ((A + B)' + C)')' . (D + E)'
Y = ((A + B)' + C) (D'E')
Option (A) is correct.
Question 3
The circuit shown in the given figure is a
A
full adder
B
full subtracter
C
shift register
D
decade counter
Digital Logic & Number representation    ISRO CS 2007    Combinational Circuits    
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Question 3 Explanation: 
The circuit shown in the given figure is a full subtractor. Refer: Digital Logic | Full Subtractor Option (B) is correct.
Question 4
When two numbers are added in excess-3 code and the sum is less than 9, then in order to get the correct answer it is necessary to
A
subtract 0011 from the sum
B
add 0011 to the sum
C
subtract 0110 from the sum
D
add 0110 to the sum
Digital Logic & Number representation    ISRO CS 2007    Combinational Circuits    
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Question 5
The characteristic equation of an SR flip-flop is given by
A
Qn+1 = S + RQn
B
Qn+1= RQ'n + SQn
C
Qn+1= S' + RQn
D
Qn+1 = S + R'Qn
Digital Logic & Number representation    ISRO CS 2007    Sequential circuits    
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Question 5 Explanation: 
The characteristic table of an SR flip-flop is: So, by simplifying using k-maps: characteristic equation of an SR flip-flop = Qn+1 = S + R'Qn Option(D) is correct.
Question 6
A graph with n vertices and n-1 edges that is not a tree, is
A
Connected
B
Disconnected
C
Euler
D
A circuit
Graph Theory    ISRO CS 2007    
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Question 6 Explanation: 
If a graph has n vertices and n-1 edges and it is not a tree than its a disconnected graph which contains at least a cycle. Option (B) is correct.
Question 7
If a graph requires k different colours for its proper colouring, then the chromatic number of the graph is
A
1
B
k
C
k-1
D
k/2
Graph Theory    ISRO CS 2007    
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Question 7 Explanation: 
The chromatic number of a graph is the smallest number of colors needed to color the vertices of so that no two adjacent vertices share the same color and if a graph requires k different colours for its proper colouring, then k is the chromatic number of the graph.
Question 8
A read bit can be read
A
and written by CPU
B
and written by peripheral
C
by peripheral and written by CPU
D
by CPU and written by the peripheral
OS Input Output Systems    ISRO CS 2007    
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Question 8 Explanation: 
The read and write functionality depends on the type of microcontroller peripheral. Generally, the status bits have a read only status and can be modified by peripherals only. So, read bit can be read by CPU and written by the peripheral. Option (D) is correct.
Question 9
A read bit can be read
A
and written by CPU
B
and written by peripheral
C
by peripheral and written by CPU
D
by CPU and written by the peripheral
ISRO CS 2007    
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Question 10
The term ‘aging’ refers to
A
booting up the priority of the process in multi-level of queue without feedback.
B
keeping track of the following a page has been in memory for the purpose of LRU replacement
C
letting job reside in memory for a certain amount of time so that the number of pages required can be estimated accurately.
D
gradually increasing the priority of jobs that wait in the system for a long time to remedy infinite blocking
OS Memory Management    ISRO CS 2007    
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Question 10 Explanation: 
In Operating systems, aging is a scheduling technique used to avoid starvation. In this, the priority of the jobs that have a longer waiting time is increased as compared to the newer processes, to avoid the starvation of older processes. Option (D) is correct.
There are 80 questions to complete.


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