C++ to ASCII

I need to write a program that encodes a ASCII file but I have no idea how to do it. I have this so far but I don't know where to enter my ASCII file (barnie.rle) in my command prompt.

int N;
char character;
int line=0;


cin >> N;
if ( N > 0)
{

cin >> character;
cout << endl;
}
else if (N < 0)
cout << "Wrong number" << endl;

else if (N ==0)
{
cout << endl;
}