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C++ Interview Questions

Q   |   QA

a) Using const protects you against programming errors that inadvertently alter data.
b) Using const allows function to process both const and non-const actual arguments, while a function without const in the prototype can only accept non constant arguments.
c) Using a const reference allows the function to generate and use a temporary variable appropriately.

Provided that function parameter is a "const reference", compiler generates temporary variable in following 2 ways.

a) The actual argument is the correct type, but it isn't Lvalue

double Cube(const double & num)
{
  num = num * num * num;
  return num;

}

double temp = 2.0;
double value = cube(3.0 + temp); // argument is a expression and not a Lvalue;

b) The actual argument is of the wrong type, but of a type that can be converted to the correct type

long temp = 3L;
double value = cuberoot ( temp); // long to double conversion 

When derived class overrides the base class method by redefining the same function, then if client wants to access redefined the method from derived class through a pointer from base class object, then you must define this function in base class as virtual function.

class parent
{
   void Show() 
{ 
cout << "i'm parent" << endl;
}
};

class child: public parent
{
   void Show() 
{ 
cout << "i'm child" << endl;
}

};

parent * parent_object_ptr = new child;

parent_object_ptr->show() // calls parent->show() i 

now we goto virtual world...

class parent
{
   virtual void Show() 
{ 
cout << "i'm parent" << endl;
}
};

class child: public parent
{
   void Show() 
{ 
cout << "i'm child" << endl;
}

};

parent * parent_object_ptr = new child;

parent_object_ptr->show() // calls child->show() 

When you define only function prototype in a base class without implementation and do the complete implementation in derived class. This base class is called abstract class and client won't able to instantiate an object using this base class.

You can make a pure virtual function or abstract class this way..

class Boo
{
void foo() = 0;
}

Boo MyBoo; // compilation error

The term alignment primarily means the tendency of an address pointer value to be a multiple of some power of two. So a pointer with two byte alignment has a zero in the least significant bit. And a pointer with four byte alignment has a zero in both the two least significant bits. And so on. More alignment means a longer sequence of zero bits in the lowest bits of a pointer.

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