C++ Interview Question Part#4

Job C++ Interview Question with Answer:

C++ Interview Question : What is a COPY CONSTRUCTOR and when is it called?
A copy constructor is a method that accepts an object of the same class and copies it’s data members to the object on the left part of assignement: class Point2D{int x; int y;public int color;protected bool pinned;public Point2D() : x(0) , y(0) {} //default (no argument) constructorpublic Point2D( const Point2D & ) ;};Point2D::Point2D( const Point2D & p ){this->x = p.x;this->y = p.y;this->color = p.color;this->pinned = p.pinned;}main(){Point2D MyPoint;MyPoint.color = 345;Point2D AnotherPoint = Point2D( MyPoint ); // now AnotherPoint has color = 345

C++ Interview Question : What is virtual class and friend class?
Friend classes are used when two or more classes are designed to work together and need access to each other's implementation in ways that the rest of the world shouldn't be allowed to have. In other words, they help keep private things private. For instance, it may be desirable for class DatabaseCursor to have more privilege to the internals of class Database than main() has.

C++ Interview Question : What is the difference between an object and a class?
Classes and objects are separate but related concepts. Every object belongs to a class and every class contains one or more related objects.- A Class is static. All of the attributes of a class are fixed before, during, and after the execution of a program. The attributes of a class don't change.- The class to which an object belongs is also (usually) static. If a particular object belongs to a certain class at the time that it is created then it almost certainly will still belong to that class right up until the time that it is destroyed.- An Object on the other hand has a limited lifespan. Objects are created and eventually destroyed. Also during that lifetime, the attributes of the object may undergo significant change.

C++ Interview Question : What is friend function?
As the name suggests, the function acts as a friend to a class. As a friend of a class, it can access its private and protected members. A friend function is not a member of the class. But it must be listed in the class definition.

C++ Interview Question : What are virtual functions?
A virtual function allows derived classes to replace the implementation provided by the base class. The compiler makes sure the replacement is always called whenever the object in question is actually of the derived class, even if the object is accessed by a base pointer rather than a derived pointer. This allows algorithms in the base class to be replaced in the derived class, even if users don't know about the derived class.

C++ Interview Question : What is the difference between an external iterator and an internal iterator? Describe an advantage of an external iterator.
An internal iterator is implemented with member functions of the class that has items to step through. .An external iterator is implemented as a separate class that can be "attach" to the object that has items to step through. .An external iterator has the advantage that many difference iterators can be active simultaneously on the same object.

C++ Interview Question : What do you mean by pure virtual functions?
A pure virtual member function is a member function that the base class forces derived classes to provide. Normally these member functions have no implementation. Pure virtual functions are equated to zero.class Shape { public: virtual void draw() = 0; };