Does anyone have either of the other calcs mentioned in my original post? TI-89 or hp-50g? How would you rate them against the classpad?
This is predominately a casio calculator forum, which is why most people are probably more knowledgeable and supportive of casio calculators. As a hp-50g user, I'll try to give a comparison of the hp's and ti's that you mention.
Anyway, the things I want to be able to do on my new calc:
deal with very big numbers (i.e bigger than the 10^99 you can get on standard scientific calcs)
The hp-50g supports infinite precision integers (within the limits of its memory) while in exact mode and exponents up to 10^499 in numeric mode. The ti-89 has similar integer support in exact mode, although I'm not sure how large of a number it supports in numeric mode. Note that although both calculators consider these numbers to be "integers", the division of two integers is still represented exactly, so you effectively have infinite precision for rational numbers if needed (calculations become much slower though).
draw nice big clear graphs (i.e cp's big screen is an advantage) and plot statistical data like scatter diagram, box plot etc
The hp-50g has the smallest screen size of the calculators listed and is thus at a disadvantage. Also, stat. plots such as histograms/box plots are a two-step process on the hp, again putting it at a disadvantage.
do fairly basic statistics stuff like normal distribution, confidence intervals, binomial distribution
Both the ti-89 and hp-50g do so with ease.
handle quantities with units (I work only in SI not imperial, I don't think I absolutely need something as full as the HP's unit support. I would want some kind of built in convertor and constants table)
Both the ti and hp support units and unit conversions, although on the hp they are easier to work with. Also both have constant tables which automatically return the unit with the constant asked for.
enter lots of data in lists or tables and then transfer to my computer in a usable format - I work only on <{GNULINUX}> with one windows install which I use only for music making.
Both the ti and the hp support linking with linux, although with the hp, linking with a computer running linux is more complicated (SD cards work well instead). I'm not sure about the ti-89, but all the hp-50g data is stored as a plain-text ascii file. Some text processing might be needed to remove the header though, and some characters used by the calculator that are not available in ascii are represented with a combination of characters.
do simple programming in a language which even a physicist can understand and learn
I think the programming language built in on all three calculators are fairly easy to understand and use for the short quick programs that they are meant to write. Among these though hp's userRPL is probably the furthest from traditional BASIC, but still fairly easy to learn. Lua support on the Classpad was mentioned, and the hp-50g also has Lua ported to it. Since gcc has also been targeted to ti's 6800k series of calculators--like the ti89--a port of Lua to the ti-89 would probably be fairly trivial. Nonetheless, I think that the built in language on each calculator would probably be the best way to go, because they are easier to input on-calc and allow full access to the calculators built in math and symbolic algebra routines (which are much more complete than Lua's).
enter things in a friendly style display (I got addicted to the textbook entry on the 991, don't want any of this sqrt(2) nonsense
Both the hp and ti support "textbook" style display, and using the Equation Writer on the hp is optional: results will be displayed in the textbook style just the same.
The stability thing is something I hadn't thought about too much, thanks for highlighting that. I hate software crashing on me all the time.
The hp-50g is extremely stable and I have never had it crash using any of the built in functions. Nonetheless, unofficial programs programmed in assembly or sysRPL (not easily accessible by the casual user), especially if they are programmed by an inexperienced programmer, may result in the calculator crashing or even loss of memory in RAM. I'm pretty sure this is the same with casio's or ti's.
(As HP's, and their non stop problems). Resetting the calc with the P button doesnt derive on a memory lost, is only a reboot (as a pc when you press reset).
I'm not entirely sure what you're trying to say, but again, the hp-50g should never crash under normal operation.
Some things you might not have considered yet: Although it wasn't mentioned, in general ti's and casio's are considered to be much easier to use, especially as a student. Also, the majority of teachers and users will probably be using ti's, making finding help for casio's and hp's more difficult. Furthermore, as an hp user, I can testify to the fact that the current generation of calculators' manuals suck. It is really more of a "quick start" guide and you will have to go online to get the full manual and Advanced User's Reference.
Also, it is important to note that ti has the largest userbase and not suprisingly the largest amount of programs developed for it (see
ti calc), with hp having the second largest amount of programs (see
hp calc), and with the casio being the newest and having the smallest application base.
Finally, good luck with whatever calculator you do end up choosing (all three of them should serve you well), but make sure you get the latest version of each. (In addition to more ram, the ti-89 Titanium will receive official rom updates for stuff like indefinite integrals that the ti-89 will never support officially. The keyboard of the hp-50g is much better than any calculator in the hp-49 series or the hp-48gii although they may look similar, and its 4 batteries will outlast the others' 3 [sounds stupid, but it is really significant in real life to have batteries last longer]. You seem to already know the advantages of the newest Classpad.)
For more information on the ti-89 and hp-50g, visit
this comparison between the two calculators by Al Borowski, but understand that he is fairly biased in favor of the hp (this is clearly stated on his site). Both the calculators compared are older models, but they are functionally equivalent to the new ones (aside from some stuff like implicit differentiation on the ti-89 titanium for which there will never be a rom update for the regular ti-89---the hp49g+ and the hp50g use the exact same roms).