Why would Vim add a new line at the end of a file?

Question

I work with wordpress a lot, and sometimes I changed wordpress core files temporarily in order to understand what is going on, especially when debugging. Today I got a littl

Answer 1

3.206 Line A sequence of zero or more non- characters plus a terminating character.

Interestingly, vim will allow you to open a new file, write the file, and the file will be zero bytes. If you open a new file and append a line using o then write the file it will be two characters long. If you open said file back up and delete the second line dd and write the file it will be one byte long. Open the file back up and delete the only line remaining and write the file it will be zero bytes. So vim will let you write a zero byte file only as long as it is completely empty. Seems to defy the posix definition above. I guess...