But it absolutely does matter.

No, it doesn't. To be clear (because we could confuse others with what we are saying matters and doesn't if we continue along this line):

I am saying it doesn't matter what writes the characters, only that they are there.

While you are saying it doesn't matter that they are there because of what writes them.

And, you know, this is what I hate about Windows... the pervasive attitude that the OS is doing something for you that you can just ignore.

Here's an assignment that would illustrate the difference... You are to write a textual file with X lines. Each line will have Y number of characters not including the newline. X and Y will be determined at runtime. Before writing the file, tell the user how big it will be on disk.

Update: Make it portable, of course.