要用
#includ <iostream>
using namespace std;
void main()
{



}


的形式的

#include <iostream>
using namespace std;
void main()
{
    double a, b;
    cout<<"please enter two numbers:";
     cin >>a;
     cin>>b;
     cout<<a*b<<endl;
 
}

#include <iostream>  
using namespace std;  
void main()
{
  int a;
  int b;
  int c;
  cout<<"enter 2 NO.";
  cin>>a>>b;
  cout<<a*b<<endl;
}