ISRO CS 2007
Question 1 
The Boolean expression Y = (A + B' + A'B)C' is given by
AC'  
BC'  
C'  
AB 
Discuss it
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 + B )' +C ) ( D'E' )  
(( A + B )' + C ) ( DE' )  
( A + ( B + C )' ) ( D'E )  
( A + B + C' ) ( D'E' ) 
Discuss it
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
full adder  
full subtracter
 
shift register  
decade counter 
Discuss it
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 excess3 code and the sum is less than 9, then in order to get the correct answer it is necessary to
subtract 0011 from the sum  
add 0011 to the sum  
subtract 0110 from the sum  
add 0110 to the sum 
Discuss it
Question 5 
The characteristic equation of an SR flipflop is given by
Q_{n+1} = S + RQ_{n}  
Q_{n+1}= RQ'_{n} + SQ_{n}  
Q_{n+1}= S' + RQ_{n}  
Q_{n+1} = S + R'Q_{n} 
Discuss it
Question 5 Explanation:
The characteristic table of an SR flipflop is:
So, by simplifying using kmaps:
characteristic equation of an SR flipflop = Q_{n+1} = S + R'Q_{n}
Option(D) is correct.
Question 6 
A graph with n vertices and n1 edges that is not a tree, is
Connected  
Disconnected  
Euler  
A circuit 
Discuss it
Question 6 Explanation:
If a graph has n vertices and n1 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
1  
k  
k1  
k/2 
Discuss it
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
and written by CPU  
and written by peripheral  
by peripheral and written by CPU  
by CPU and written by the peripheral 
Discuss it
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
and written by CPU  
and written by peripheral  
by peripheral and written by CPU  
by CPU and written by the peripheral

Discuss it
Question 10 
The term ‘aging’ refers to
booting up the priority of the process in multilevel of queue without feedback.  
keeping track of the following a page has been in memory for the purpose of LRU replacement  
letting job reside in memory for a certain amount of time so that the number of pages required can be estimated accurately.  
gradually increasing the priority of jobs that wait in the system for a long time to remedy infinite blocking 
Discuss it
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.