I found this interesting paper on calculator limitations while surfing around:
http://www.uclic.ucl.ac.uk/harold/srf/allcalcs.pdf
It mentions the HP20S many times.
Dave :)
Interesting paper on calculator limitations...

11302006, 06:25 AM
I found this interesting paper on calculator limitations while surfing around: It mentions the HP20S many times. Dave :)
11302006, 06:29 AM
and another version by the same author: Dave :)
11302006, 11:10 AM
I discovered Thimbleby works long ago, and I totally agree with him. Here's a complete list of his works about calculators: Hope this will be delighful.
 Antonio Edited: 30 Nov 2006, 11:12 a.m.
11302006, 01:50 PM
Those are interesting articles, made more so by their containing no discussion or consideration at all to RPN logic machines. That would seem to adversely affect the value of the conclusions drawn by the author. Most of the problem areas and his suggestions for improved design are not required RPN machines. Could it be that Prof. Thimbleby is completely unfamiliar with RPN? Mike / Alabama
11302006, 02:13 PM
Those papers help to explain why I find many Japanese (Casio, Sharp) calculators to be very difficult to use. Sometimes I wonder if there is anyone at home in the engineering departments of the major calculator manufacturers. I recently looked at a TI30X IIS, a common scientific calculator. The secondary key functions were printed in dark blue on a black background. Why not just use invisible ink?
11302006, 02:17 PM
He does mention them briefly, criticizing the fixed stack of the HP32SII. While RPN has its advantages, it doesn't solve many of the problems that he addresses.
11302006, 03:55 PM
See the top of page (3) of reference (1) above. He briefly mentions RPN and criticizes the 4level stack.
11302006, 04:09 PM
If you've started your calculating life on an HP, the consternation and disgust factor is just too much to bear, switching to a Casio or a Sharp or a kinPo. Having to switch to a "STAT mode" is distasteful and arbitrarily limiting. All that inconsistent crap that Thimbleby so rightfully attacks is just so plain obviously wrong. It isn't the RPN per se that makes HP better, it is that the others are just so stupid! I have a 30S and except for the nice screen and the basic idea of a formulabased entry, I hate it. Sometimes I can suffer it happily, as long as I don't push it to do the "advanced" stuff that it is supposed to do. I hate the fraction method, I hate the modes business, I hate the way the variables and registers are divided into "this one can save a formula, but this one can't" etc. I hate the totally bizarre handling of repeated function calls on cheap "4 function" calculators. Not features, bugs in my opinion. The funny thing about the thimbleby paper is that you've probably reacted viscerally to every one of the flaws he points out. I certainly have, for a long time. But Thibmeby takes those visceral reactions and makes a formal academic presentation. Brilliant stuff (that nobody will read, because it is academic!).
11302006, 05:25 PM
Harold Thimbleby has continued his work. Visit his homepage Enjoy, Juergen
11302006, 05:51 PM
I know, I know, I also downloaded his (his son's, to tell the truth) software calculator for Mac OS X which is a wonder!  Antonio P.S. I put his site among my favorites, and I check from time to time if there's something new. I also asked him if they ever will make a true (handheld) calculator. Here's their answer:
Quote: Let's hope for the future!
12012006, 03:18 AM
Hello!
Quote: I think I am a bit stupid, but I coudn't find this MacOS X version anywhere (I only found the Java version which won't run on my Mac (10.4.6)). Where did you get it from?
Quote: Have they contacted (Sir) Clive Sinclair about it yet  he is the only one who comes to mind who might be able to make this come true (or who might have been 30 years ago...). Greetings, Max
12012006, 03:20 AM
Hello, Antonio 
Quote: More than a year ago, I also had read at least three of the four documents you linked, and even emailed Prof. Thimbleby asking if he'd like some comments. Unfortunately, I haven't yet followed through. I agree with most of the criticisms he levied at modern massmarket calculators, which are often counterintuitive. However, I don't endorse his concept of a new calculator user interface. Fundamentally, the idea presented in the articles is a calculator that unravels and solves problems by combining algebra along with the function of calculation. The user specifies the variable to be solved by simply omitting it from the expression, then the calculator does the rest. The syntax is rather informal and unstructured  prone to ambiguity and misinterpretation, I believe. I disagree with that approach, primarily on those grounds. I would prefer instead the structure and userfriendliness of the HP17B/HP27S equation editor/solver: The user enters an expression with named variables if desired, then the calculator interprets and validates the expression, and subsequently provides an easy means of entering values for unknown variables and solving for the remaining one. That solver can even perform algebra to obtain a "direct" solution if the form of the expression suggests only one primary solution. That capability was incorporated into the HP33S' solver with a lesscapable equation editor, and the solvers on all three models have the unwelcome characteristic that they must be "tricked" in order to find solutions other than the primary one. That suggests my other objection to Thimbleby's concept: An expression might have multiple solutions for the unknown variable that lack a regular pattern, as is found with the roots of a polynomial. Which solution would his calculator find? As mentioned by others, Thimbleby's objection to the RPNbased HP32SII was its 4level stack. Of course, that is not a characteristic of RPN per se, but a constraint that could easily be changed. I have not reviewed his latest work.  KS
Edited: 2 Dec 2006, 4:15 p.m.
12012006, 03:46 AM
Porting the software to a PDA (Palm or Windows Mobile) might be a short/middleterm option. But I guess the source code is not available, and developing the calculator from scratch seems to be a big task...
12012006, 04:21 AM
Thank you for the hint. Looks like the beginning of a CAS with GUI. Ciao.....Mike
12022006, 09:07 AM
I cannot not find this Thimbleby OSX calculator either. After all the nice comments, naturally I want it! I found this webpage and link for an OSX calculator, but the link does not work. http://www.uclic.ucl.ac.uk/harold/calculators/ http://www.heathmoor.plus.com/downloads/TrueCalculatorBetaX.app.sit Further searching for "TrueCalculatorBeta", "truecalculator", etc., on Google does not lead to better results. So... how about a link?
Edited: 4 Dec 2006, 12:31 a.m. after one or more responses were posted
12022006, 11:28 AM
12022006, 12:02 PM
Very interesting applet!!!!!!!!!!!! I love the freehand numeric reconition! :) Namir
12042006, 12:32 AM
Thank you for the link, Patrick.
12072006, 02:47 AM
This is the link Will Thimbleby gave to me. Hope you will enjoy the program (for Mac OS X only!).
 Antonio Edited: 7 Dec 2006, 5:14 a.m.
12072006, 04:45 PM
Thanks, Patrick, for showing us this nice application! I played with it a bit and found it recognizes most handwritten digits and arithmetic symbols, and additionally "e" (the exponential), "pi" and square roots. Kind of undocumented features  at least there is no reference on the help screen. But I do not see a way to get trigonometric functions so far. Anyone has an idea? 
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