hàm, truyền tham số cho hàm

#include <stdio.h>
#include <conio.h>
#include <iostream>
using namespace std;
void ham1(int a=0, int b=1)
{
cout<<" tham so 1= "<<a<<endl;
cout<<" tham so 2= "<<a<<endl;
}
int main()
{
int x=10, y=20;
cout<<" goi ham1 4 lan, ta duoc: "<<endl;
ham1(x,y);
ham1(x);
ham1(y);
ham1();
getch();
return 0;
}