The main problem is here: a_file<< num << endl;
when you're saying num you're actually saying it's adress, something like 0x09...
as I figured, num is an array... so...: a<<num[0]<<num[1]<<endl;
Furthermore, you were saying something about letters, so you should call a function to convers those ASCII into characters: a<<char(num[0])<<char(num[1])<<endl;
That's about it... oh... and this is not the place to ask such questions...