C++ Quiz 3

1) By default, all members of a class have ___________ access for all its members     

    a) Public
    b) Protected
    c) No access
    d) private

2) Which operator is used to define a member of a class from outside the class definition itself?    

    a) ::
    b) :
    c) >>
    d) <<

3) What is a constructor?   

    a) A class automatically called whenever a new object of this class is  

        created.

    b) A class automatically called whenever a new object of this class is 

        destroyed.

    c) A function automatically called whenever a new object of this class is 

        created.

    d) A function automatically called whenever a new object of this class is 

        destroyed.

4) Under what conditions a destructor destroys an object?    

    a) Scope of existence has finished
    b) Object dynamically assigned and it is released using the operator 

       delete.

    c) Program terminated.
    d) Both a and b.

5) If no constructor is declared, the compiler assumes the class to have a default constructor with no arguments    
   
    a)True
    b) False

6) How would you read the expression x.y as?

    a) member y of object pointed by x
    b) member y of object x
    c) member x of object y
    d) All of the above

7) Which type of class has only one unique value for all the objects of that same class?    

    a) this
    b) Friend
    c) Static
    d) both a and b

8) What is the output of the following code snippet?
    class test 

    {
           public:
                   static int n;
                   test () { n++; };
                   ~test () { n--; };
    };    int test::n=0;
    int main () 

    {
         test a;
         test b[5];
         test * c = new test;
         cout << a.n << endl;
         delete c;
         cout << test::n << endl;
       return 0;
    }

    a) 7 6
    b) 6 7
    c) 5 6
    d) 6 5

9) For which type of class private and protected members of the class can be accessed from outside the same class in which they are declared    

    a) No such class exist
    b) Friend
    c) Static
    d) Virtual

10) Which of the following cannot be inherited from the base class?

    a) Constructor
    b) Friend
    c) Both a and b cannot be inherited
    d) Both a and b can be inherited

11) If a class x needs to be derived from a class y, which of the following ways is correct to do so?

    a) class x : public y
    b) class y : public x
    c) class x derives public y
    d) class y derives public x

12) A class cannot inherit members from more than one class

    a) True
    b) False

13) What is a virtual member?

    a) A member of a friend class that can be redefined in its derived classes
    b) A member of a virtual class that cannot be redefined in its derived classes    

    c) A member of a static class that can be redefined in its derived classes
    d) A member of a class that can be redefined in its derived classes

14) What is the output of the following code snippet assuming user enters the side as 4?    

    class square
    {
        public:
                double side1;
                double area()
                {
                      return(side1*side1);
                }
    };
    int main(){
         double area1=0;
         square c1,c2;
         cout << "Enter the length of the square" << endl;
         cin >> c1.side;
         cout << "The area of the square is : " << c1.area1() << endl;
      return(0);
    }   

   a) 16
   b) Will result in an error
   c) 8
   d) 12

15) In C++ two different functions can have the same name if their parameter types are same.   

   a) True
   b) False

16) Can inline functions be used to improve performance?

   a) yes
   b) No
   c) yes, depends on the situation
   d) Both a and b

17) Which type of casting can be used only with pointers and references to objects?

   a) Dynamic_cast
   b) cast
   c) Static_cast
   d) Pointer_Cast

18) What is reinterpret_cast used for?  

   a) converts integer pointer type to any other integer pointer type
   b) Converts any pointer type to any other pointer type
   c) converts any pointer type to only integer pointer type
   d) Both a and b

19) Can #define accept parameters?   

   a) Yes
   b) No

20) #if or #elif can be used to evaluate   

   a) Constant expressions
   b) Macro expressions
   c) Both a and b
   d) All expressions

C++ Quiz Questions Set 2

1) What is the out put?

void main()
{
 int a, *pa, &ra;
 pa = &a;
 ra = a;
 cout << "a=" << a << "*pa=" << *pa << "ra=" << ra;
}

Answer:
Compiler Error: 'ra',reference must be initialized

Explanation:
Pointers are different from references. One of the main differences is that the pointers can be both initialized and assigned, whereas references can only be initialized. So this code issues an error.

C++ Quiz Questions Set 1

1) Predict the output or error(s) for the following:

#include
using namespace std;
class Sample
{
public:
        int *ptr;
        Sample(int i)
        {
              ptr = new int(i);
        }
        ~Sample()
        {
              delete ptr;
        }
        void PrintVal()
        {
              cout « "The value is " « *ptr;
        }
};
void SomeFunc(Sample x)
{
     cout « "Say i am in someFunc " « endl;
}
int main()
{
     Sample s1= 10;
     SomeFunc(s1);
     s1.PrintVal();
}

Answer:
 prompt> g++ Sample.cpp
 prompt> ./a.out
       Say i am in someFunc 
       Null pointer assignment(Run-time error) 

Explanation: As the object is passed by value to SomeFunc the destructor of the object is called when the control returns from the function. So when PrintVal is called it meets up with ptr that has been freed.

The solution is to pass the Sample object by reference to SomeFunc:

void SomeFunc(Sample &x) 

{ 

      cout « "Say i am in someFunc " « endl; 

}

prompt> g++ Sample.cpp
prompt> ./a.out

      Say i am in someFunc
      The value is 10


because when we pass objects by reference that object is not destroyed. while returning from the function.

2) Which is the parameter that is added to every non-static member function when it is called? 'this' pointer

3) What is the Out Put?

class base
{
        public:
               int bval;
               base()
               { 
                  bval=0;
               }
};
class deri:public base
{
        public:
               int dval;
               deri()
               { 
                  dval=1;
               }
};
void SomeFunc(base *arr,int size)
{
    for(int i=0; i‹size; i++,arr++)
         cout«arr-›bval;
    cout«endl;
}
int main()
{
    base BaseArr[5];
    SomeFunc(BaseArr,5);
    deri DeriArr[5];
    SomeFunc(DeriArr,5);
}

Answer:      
     00000
     01010

Explanation:
The function SomeFunc expects two arguments.The first one is a pointer to an array of base class objects and the second one is the sizeof the array.The first call of someFunc calls it with an array of bae objects, so it works correctly and prints the bval of all the objects. When Somefunc is called the second time the argument passed is the pointeer to an array of derived class objects and not the array of base class objects. But that is what the function expects to be sent. So the derived class pointer is promoted to base class pointer and the address is sent to the function. SomeFunc() knows nothing about this and just treats the pointer as an array of base class objects. So when arr++ is met, the size of base class object is taken into consideration and is incremented by sizeof(int) bytes for bval (the deri class objects have bval and dval as members and so is of size ›= sizeof(int)+sizeof(int) ).

4) What is the Out Put?

class base
{
        public:
              void baseFun()
              { 
                   cout«"from base"«endl;
              }
};
class deri:public base
{
        public:
              void baseFun()
              { 
                   cout« "from derived"«endl;
              }
};
void SomeFunc(base *baseObj)
{
    baseObj->baseFun();
}
int main()
{
    base baseObject;
    SomeFunc(&baseObject);
    deri deriObject;
    SomeFunc(&deriObject);
}

Answer:
       from base
       from base

Explanation:

As we have seen in the previous case, SomeFunc expects a pointer to a base class. Since a pointer to a derived class object is passed, it treats the argument only as a base class pointer and the corresponding base function is called.

5) What is the Out Put?

class base
        {
        public:
         virtual void baseFun(){ cout«"from base"«endl;}
        };
 class deri:public base
        {
        public:
         void baseFun(){ cout« "from derived"«endl;}
        };
void SomeFunc(base *baseObj)
{
        baseObj->baseFun();
}
int main()
{
base baseObject;
SomeFunc(&baseObject);
deri deriObject;
SomeFunc(&deriObject);
}

Answer:        
            from base        
            from derived
Explanation:
Remember that baseFunc is a virtual function. That means that it supports run-time polymorphism. So the function corresponding to the derived class object is called.