Thanks for the nice welcome, and the quick response from both you and CVSoft. I look forward to learning more about the ribbon behind the mysterious black tape, and hearing about your experiences in fixing problems with it. The tape is really stuck on tight, so I approach removing it with some trepidation. I am really out of my element here, never was much for attempting hardware repairs. I once programmed very unskillfully in a language called FORTRAN, long, long ago, in a galaxy far, far away. You may remember it . I am a semi-retired theoretical physicist, currently teaching/tutoring math and physics at a small college. Perusing your website has whet my appetite for possibly learning how to program my TI calculators (I use an 84-Plus SE as well as the malfunctioning 83-Plus). Your book looks wonderful, and I may be buying it soon. I'll also be checking out CVSoft's website soon. Thank you both again.

You're most welcome, and thanks for that introduction. I'm glad that we have inspired you to look into calculator programming, and if you do end up getting my book (or even if you don't ), we'd be happy to help you with any programming questions you might have. You might not have to remove the black tape (or only partially remove it) to fix the calculator; I'll share my experiences after I attempt a repair this evening.

I'll wait to hear of your experience with repairing the ribbon before trying anything else. You are obviously a busy man, and I appreciate your looking into this problem. Whatever you find I suspect will be of interest to others as well.

Don't know what 1337 refers to, but I downloaded your TI-Basic guide to get an idea of what programming is like. I expect to be in for a .

1337 means "elite", and is slightly self-referential, in that "1337 speak" ("elite/leet speak") is the practice or replacing letters with numbers. For example, "elite", mutated into "leet", uses l=1, 3=e, and 7=t, assuming that you see the visual similarities between l and 1, etc. So "1337 Guide" is a tongue-in-cheek title meaning "Elite Guide". The tips in there are more optimizations and tricks; I usually recommend that beginner coders (or, in your case, coders brushing up their skills) start with unoptimized but easy-to-understand code, then work their way gradually into optimizing their code.

Ah so! Well, I am far from being a (an?) 1337 programmer, and that was clear as soon as I began skimming through the Guide. I'll be on the lookout for easy-to-understand code, then. Optimization will have to wait. Thanks for the recommendation and explanation.

No problem. I'll try not to be too self-serving, but I feel I do a good job with that progression in my book, if that helps. There are certainly a nice variety of tutorials out there in the community, too, though all are more brief than my book. Also, just to avoid going too off-topic here, I am going to split off our discussion of your BASIC explorations into a separate topic called "Quaternion's TI-BASIC Exploration", so that you can use it for any questions or comments about TI-BASIC as you learn.

Excellent. I'll move to the new topic when TI-BASIC questions arise.

I now have a copy of your book in my hot little hands, and am in an absolute programming frenzy, trying out your first examples and some simple math problems for practice. The book is excellent(!) and moves at just the right pace for someone like me who has always known he will never have the "right stuff" to become a really good programmer and will remain always in awe of those who are. I'll continue to dabble and hopefully improve, thanks to your careful and expertly written guidance. Sorry to see in the SAX that you are under the weather today ... hope you are feeling better soon. PS - I never have gotten up the courage to look beneath the black tape to see what the failing ribbon looks like on my TI-83+... maybe when you are back on top of your game we can talk about it again

Quaternion, I'm glad to hear that you're enjoying the book so much. If you happened to have grabbed it from Amazon, I would never say no to an (honest) review. Thanks for the kind wishes about my health; I'll do my best to get better soon. I also trust that you'll get yourself into the programmer mindset soon, and I look forward to hearing any questions and/or comments you may have.

KermM, I did get your book thru Amazon, and I will seriously consider writing a review after I have digested a bit more of it. It would, of course, be written from my perspective as a novice programmer. I have been wondering about the apps that ship with a calculator like my TI-84+SE...who creates them, are there programs for each existing somewhere, can one get to the source code, or is each proprietary to its developer (or perhaps TI itself)? It's nothing urgent, take whatever time is needed to feel better first.

The ones that ship with your calculator were written by a combination of TI and interns that worked with them many summers ago. They're almost all closed-source. However, there are many, many apps written by members of the community, published here or on ticalc.org, and open-sourced.

I like your handle quaternion, very fitting for a physicist!

Thank you, KermM, I've been curious about the origin of apps ever since I bought the calculators, and I will certainly be checking out the open source programs here and at ticalc.org. And thank you for the compliment, tr1p1ea. Quaternions and their history since Hamilton invented/discovered them in 1843 have always fascinated me, although they apparently never had quite the impact on physics that he had hoped. There is a very nice intro to their properties, and some great references, at http://mathworld.wolfram.com/Quaternion.html

I was forced to delve into quaternions in order to build the 3D engine behind my Graph3DP grapher, but I've never explored them in their physics context. Quaternion, to elaborate a bit more on apps on the TI-83 Plus/TI-84 Plus calculators, they're all written in z80 assembly language. You can also write non-app programs (similar to your TI-BASIC programs) in z80 assembly, although the contents are of course much much different. My book has a chapter introducing the rudimentary basics of z80 assembly, although you'll need further resources if you decide to continue working with it after you become a TI-BASIC expert.

KermM, you are one of the first persons I've talked with who has actually applied quaternions to a real problem, and I am mightily impressed! Many years ago, when I was involved with guided missile simulations, there was much discussion of changing from the Euler angle description of rotating reference frames to one using quaternions (as I recall, to avoid singularities at angles of 90 degrees, which could cause "gimbal lock" of tracking instruments on board the missile), but it was never acted upon, at least by me. I did read of others in the community doing it. I would love to know the details of your application in Graph3DP grapher, but I gather that programming the Casio Prizm takes things to a new, higher level. By the way, is there a 3D graphing program for TI calculators? Back to TI apps, I see there is all the more reason to try to learn z80 assembly, but that will probably not happen anytime soon.