构造函数参数为0时，是默认构造函数吗

求大佬解答

例如：

#include<iostream>
#include<string>
#include<cmath>
using namespace std;
class Circle
{
private:
double r;
double c;
double s;
public:


Circle(double r=0)
{
this->r = r;
c = 2 * (3.14*r);
s = 3.14*(r*r);


}
Circle(Circle &m)
{
this->r = m.r;
c = m.c;
s = m.s;
}
void print()
{
cout << c << s << endl;
}
};
int main()
{
Circle c1(10), c2(c1), c3;
c1.print();
c2.print();
c3.print();
return 0;

}

中Circle(double r=0)这算默认构造函数吗