Call to constructor function

Call to the constructor function

#define _crt_secure_no_warnings
#include <iostream>
#include <string>
using namespace std;
Class A
{public
:
	A () {a=1;}
	A (int a) {
		this->a=a;
	}
	void ShowA () {
		cout<<a<<endl;
	}
Protected:
private:
	int A;
};

int main (int args,const char * argv[])
{
	
	A a0 ();  function declaration, not creating object
	//a0.showa ();   Error

	A A1;//parameterless constructor calls without parentheses
	A1.showa ();

	A A2 (2); A parametric constructor
	A2.showa ();

	A a3=3;//has a parametric constructor and calls the transformation constructor
	A3.showa ();

	A a4= (1,2,3,4); A parameter constructor, which invokes the transformation constructor, uses the comma expression
	a4.showa ();

	A A5=a (5);  An anonymous object was created
	A5.showa ();

	cout<< "\n###################" <<endl;
	return 0;
}