Acknowledgments

Dave Nichols shared his C expertise at several points and as a result IPE is now written in a much more flexible, extensible manner that my first version. I appreciate Dave's help very much. I would also like to thank Andrew Gunstensen of MIT, who shared a nice interactive plot program called Tplot that he had written. Tplot, which is a truly interactive program, gave me the idea to make our batch programs ``somewhat'' interactive, which led to IPE.