What is use of copy constructor

Well, somehow we must have a way to tell the compiler how it can copy an object of our class into another. Such copy operations happen when we pass an object as a parameter to a function and several other situations. In such cases the compiler uses the copy constructor. And if you don't declare one, it creates a default version of it to its best knowledge, which in simple words copies the object member by member.

For some classes this default copy constructor does not what we want to do. For example, imagine your class contains a pointer to another object and "owns" that object. In such cases you want to be able to specify what exactly should happen with the pointer value, i.e. do we want another object be created which is now owned by the copy? Or we might need to increment a reference count ...

Do you understand now, why it is necessary that we specify how objects should be copied?

The copy constructor is needed in many situations, even if you do not call it explicitely. Some examples are:

1. Pass an object as a function argument by value
2. Return an object from a function by value
3. Create a temporary copy, e. g. when overriding the postifx operators ++ or --

while you can choose to work around the third case, and may (in fact, should!) pass a const reference instead of a value in the first case, the second case cannot be easily avoided.

Note that often, but not always, the assignment operator can be used instead of the copy constructor. these two are closely related.

See http://www.cplusplus.com/articles/y8hv0pDG/[^] for more info.

Hi, refer following link :
http://www.cplusplus.com/articles/y8hv0pDG/[^]