#include <stdlib.h>
using namespace std;
void fun(int i = 30, int j = 20, int k = 10);
int main(){
        fun();
        fun(100);
        fun(200);
        fun(300);
}
void fun(int i, int j, int k)
{
        cout << i << "," << j << "," << k << endl;
}

error: 'cout' was not declared in this scope

error: 'endl' was not declared in this scope

这是什么情况