constructor calling

Question

#include<iostream>
using namespace std;
class A
{
public:
A()
{
cout<<"zero parameterozed constructor";
}
A(int a=0)
{
cout<<"default parameterized constructor";
}
};
int main()
{
A a();

}

why its giving no output?? plz explain

Answer 1

A a(); is a function declaration, it's not constructing an object.
https://en.wikipedia.org/wiki/Most_vexing_parse

Use A a; to initialize an object without arguments.

But with the code you have this still wouldn't compile because the call is ambiguous.

A() requires 0 arguments
A(int a = 0) requires 0 or 1 argument(s)

C++ has 2 options to pick from, but because C++ can't read your mind it just refuses to compile it.