[texhax] plain tex vbox question

[Hartmut Henkel]

On Mon, 12 Jan 2009, jw wrote:

> Thanks for the links, I hadn't seen them before. In general, I
> understand the idea of boxes. It seems to me that the only difference
> between my two examples is that one starts out in 'vertical' mode and
> the other is in 'internal vertical'. But why the text would be
> positioned lower in vertical mode still eludes me...

It's the \topskip, see:

% ---- begin file 1 ----
\topskip 100pt
The quick brown fox...
\bye
% ---- end file 1 ----

% ---- begin file 2 ----
\topskip 100pt
\vbox to \vsize{The quick brown fox...}
\bye
% ---- end file 2 ----

\topskip is not active within \vboxes, only at the top of the page. And
it's not zero by default.

Regards, Hartmut