How to write to a file in C++?

#include <iostream> 
#include <fstream>  
using namespace std;
int main() 
{ 
    ofstream fout; 
    string r; 
   
    fout.open("test.txt"); 
 
    while (fout) {
        getline(cin, r); 
        if (r == "-1") 
            break; 
        fout << line << endl; 
    } 
    fout.close(); 
   
    ifstream fin; 
    fin.open("test.txt"); 
    while (fin) { 
         getline(fin, line); 
          cout << line << endl; 
    } 
    fin.close(); 
    return 0; 
} 
62. What is