Thread: Help with copy constructor

I am new to c++ programming.
I want to create a program which includes the following line of codes

Code:

class cars
{
.
.
.
};
class PatrolCars:public cars
{
.
.
.
};
class CNGCars:public cars
{
.
.
.
};

now what the problem is that i want to write a member function which can copy each of the drive class objects to each other I mean these lines should be valid

Code:

PatrolCars patcar;
CNGCars cngcar;
patcar=cngcar;

should i create a copy constructor or should i overload an operator for this?
plz help!