Character I/O for C++?

So, I have a project that is baffling me. The code I've written works right for the most part. Input is taken from a designated file, lines are numbered, all of that run correctly. However, I cannot seem to understand how to have what is displayed on screen for the user sent to a designated file to be saved. Any input or any help to understand this would be greatly appreciated, as I have about 8 other projects to work on.

#include <iostream>

#include <fstream>

#include <iomanip>

using namespace std;

ifstream in_stream;

ofstream out_stream;

int main ()

{

char next;

int line = 1;

char in_file_name[16], out_file_name[16];

cout << "Please enter filename to read from: ";

cin >> in_file_name;

in_stream.open (in_file_name);

if (in_stream.fail ())

{

cout << "Input file opening failed.\n";

system ("pause");

exit (1);

}

cout << "Please enter file name to save to: ";

cin >> out_file_name;

if (out_stream.fail())

{

cout << "Output file opening failed.\n";

system ("pause");

exit(1);

}

cout << "It worked!\n";

output not saving to blank file

cout << line << setw(3);

in_stream.get(next);

out_stream.put(next);

while (! in_stream.eof())

{

cout << next;

if (next == '\n')

{

line++;

cout << line << ":" << setw(3);

}

in_stream.get(next);

out_stream.put(next);

}

cout << endl;

in_stream.close ();

out_stream.close ();

return 0;

}