C++ Programming - Constructors and Destructors - Discussion

By default only the constructors are called, but not the destructors because when we create the object of the class it calls the constructor only not the zero argument destructor.

As per my knowledge; it should be.

#include<iostream.h>
#include<conio.h>
class Anil
{
private:
int a;
public:
Anil(int A)
{
a=A;
cout<<"values is"<<A<<endl;
}
};
int main()
{
Anil A();
getch();
return 0;
}

First, what is the difference between run time and compile time? Please explain me.

Why constructor error generates at compile time?

Why constructor error generates at compile time?

When a class create object by default called implicit default constructor which may be parameterlessor with all parameter with default value, and if parameterized constructor is provided but no call made to that parameterized constructor explicit then compiler cannot create object and give compile time error.

Constructors initializes the object and the initialization of the object is done at compile time as we have created the parametrized constructors the class will not use its default constructors and the object we created is with zero arguments.

So during the compile time when constructor tries to initialize the object it will show and error and as this error took place during compilation the option A is correct.

The answer would be different if the class has unparameterized constructor because default constructor are generate only when there are no parameterized constructors.

When object is created constructor initialize the object. When we create parameterized constructor it requires argument and when compiler finds no arguments passing through the obj it leads compilation error.

Compile time error:- (Why), As we know constructor fired when object is created, at the same time compiler check for default constructor if you are not declare any constructor in your code, otherwise, on same time compiler ignore call for default constructor it make a call for user defined constructor.

Object is created at compile time, that's why error occur at compile time. (Some time object may be create at run time for to achieve run time polymorphism).