How is the data organized in your program? Ie, is it in an 2 dimensional array? In that case you should be able to do something like this:
To read it in again, you pretty much just do the reverse using ReadFile.
Note: I've never actually used these functions, I'm just reading a programming reference. It should work though.
You shouldn't have to do this, unless you want to store different data objects in the one file. If that's the case, a newline or return character is probably not the best separator, because a string may contain that character, therefore disrupting the way the data is read back in.
One of the main problems that I have run across is that I don't know how to output a 'return' or newline to the file.
But if you really want to, then the characters are ASCII codes 13 (CR) and 10 (newline).