Which way is up?

[Richard Billington <Buff@cis.upenn.edu>]

The "y-down" coordinate system may seem counter-intuitive to you when you're
trying to do traditional graphics, however remember that the majority of
windows on a Symbolics are scrolling dynamic windows. This means that the
extent of the y-dimension is constantly being increased. If you started out
with (0,0) in the bottom left corner, what would the next line be, (0,-1)?
Then all windows would run from (0,750) to (0,-SomeBigY). You could have
statically-sized windows have a "y-up" coordinate system and dynamically-
sized windows have a "y-down" coordinate system, but that would add another
element of confusion. Personally, I prefer consistancy.