\end command issue a
\vfill command? I notice that in plain TeX, you have a
\bye that issues it but after some experimentation I think
\end also issues a
\vfill, which is rather confusing.
Case 1: Hello World\vfil Hello World\end
Case 2: Hello World\vfill Hello World\end
Comparing the above two cases, we note that Case 1 place both lines of texts normally while in Case 2 TeX placed the second line of text in the middle. Now, if
\end did not come with a
\vfill, the first case would have also place the second line of text in the middle. This is where I am confused.