Octave 4.0 is a major new release with many new features,
including a graphical user interface, support for classdef
object-oriented programming, better compatibility with Matlab,
and many new and improved functions.
A list of important user-visible changes is availble at
http://octave.org/NEWS-4.0.html, by selecting the Release Notes
item in the News menu of the GUI, or by typing news at the Octave
command prompt.