Page 274 - Computer science 868 Class 12
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Previous Years' Questions


                  1. With reference to the code given below, answer the questions that follow along with dry run/working.    [ISC 2023]

                    boolean num(int x)
                    {
                    int a=1;
                    for(int c=x; c>0;c/=10)
                    a*=10;
                    return(x*x%a)==x;}
                    (a)   What will the function num() return when the value of x = 25?
                Ans.   x = 25
                    a = 1
                    c = 25  so, a = a * 10 = 10
                    c = 25/10 = 2 so, a = a * 10 = 100
                    c = 2/10 = 0
                    x * x = 25 * 25 = 625
                    625%100 = 25 so, it will return True
                    (b)   What is the method num() performing?
                Ans. The method num() is checking whether the number x is an automorphic number or not i.e. checking whether the number x is
                    present in its square or not
                  2. With reference to the following program code, answer the questions that follow:
                      int solve(int p, int q)
                          {    for(int r=0; p>0;r=q%p,q=p,p=r);
                               return(p=0)?q:-1;
                          }
                    (i)  What will be the output of the method solve() when the values of p=12 and q=8?        [ISC 2022]
                       (a)  8                                   (b)  16
                       (c)  96                                  (d)  4
                Ans. (d)
                    (ii)  What is the method solve() performing?                                               [ISC 2022]
                       (a)  LCM of two numbers                  (b)  Checking the divisibility of two numbers
                       (c)  HCF of two numbers                  (d)  Counting the common Prime factors of two numbers
                Ans. (d)
                  3. (i)  A class CalSeries has been defined to calculate the sum of the series:               [ISC 2022]
                                          n
                       sum = 1 +x+x +x .. ... +x
                                  2
                                    3
                     Some of the members of the class are given below:
                     Class name                   :   CalSeries
                     Data Members/Instance variables
                     x                            :    integer to store the value of x
                     n                            :   integer to store the value of n
                     sum                          :   integer to store the sum of the series
                     Member Functions/Methods
                     CalSeries()                  :   default constructor
                     void input()                 :     to accept the values of x and n
                     int power(int p,int q)       :   return the power of p raised to q (pq) using recursive technique.
                     void cal()                   :     calculates the sum of the series by invoking the method power() and displays the
                                                      result with an appropriate message
                      Specify the class CalSeries, giving details of the constructor, void input( ), int power(int,int) and void cal(). Define the main)
                    function to create an object and call the member function accordingly to enable the task.
                Ans.  import java.util.*;
                    class CalSeries
                    {  int x, n,sum;


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