>>509
-- User Option: truncate-lines
This buffer-local variable controls how Emacs displays lines that
extend beyond the right edge of the window. The default is `nil',
which specifies continuation. If the value is non-`nil', then
these lines are truncated.

If the variable `truncate-partial-width-windows' is non-`nil',
then truncation is always used for side-by-side windows (within one
frame) regardless of the value of `truncate-lines'.