Why is the copy constructor called when we pass an object as an argument by value to a method?

Question

Why is the copy constructor called when I pass an object as an argument by value to a function? Please see my below code: I am passing an object of a class as an argument by

Answer 1

As juanchopanza said:, you pass by value, which causes a copy to be made. If you want to prevent this you can pass by reference:

void display(const ClassA &obj)

On a sidenote: You should declare your copy ctor to take the argument as const reference:

ClassA(const ClassA &obj)

Otherwise you won't be able to use the copy ctor on named objects marked as const or with temporaries. It also prevents you from accidentally changing the passed in object.