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HP Forum Archive 02

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Re: New RPN user?
Message #1 Posted by John on 9 Apr 2000, 2:15 p.m.

I bought my first HP when the 41 was introduced. I learned the RPN principle in two minutes, and have been convinced about it ever since. I have been using a 48SX since that one came on the market, with much pleasure (great manuals). I was, however, surprised to find that a friend of mine, a now retired professor at a major American university was violently against RPN: "It is a stupid and illogical system. I discourage my students from using it!"

I don't know how much damage he alone has done...


PS. Shortly after I got the 48 I wrote a small program that ought to have been built in: STSM (Stacksum) which will add everything on the stack.


This one is very convenient, and I do use it a lot!

Re: New RPN user?
Message #2 Posted by William L. Drylie on 9 Apr 2000, 3:18 p.m.,
in response to message #1 by John

Fortunately, there were professors who did good. Professor Byron Gottfreid who wrote the Schaums outline series book "Introduction to Engineering Calculations" has several pages devoted to to both AOS and RPN calculations in this outline. He exposed his first year students to both operating systems allowing them to choose which calculator was best for them, as it should be. Page 14 has a picture of an hp21 calculator. I know when I graduated from the University of Pittsburgh, the hp67 was the best selling item at the University book store. I was very pleased to have him as a professor. Later on when I became interested in programming, I really liked the conciseness of rpn as it cut programming lines in half as compared to the AOS system. I am still using my hp25 and hp67 to this day to the utter amazement of my colleagues who can not believe how I turn out accurate calculations so fast with such antiques! Cheers, Bill

Re: New RPN user?
Message #3 Posted by Simmer on 11 Apr 2000, 6:41 p.m.,
in response to message #1 by John

That's unfortunate about your friend. I'm convinced that RPN is totally LOGICAL! The problem is not with RPN (Post-fix notation) but rather with the fact that we are all taught In-Fix (a + b = c)notation in school (not a b +). I can only assume that your professor friend may feel a bit daunted by changing a long-familiar paradigm.

Oh well, to those who've seen the light, happy, speedy, finger-saving RPN calculating!

As to your stacksum calculator --- I like this. Could come in handy and very useful! Thankyou.

Re: New RPN user?
Message #4 Posted by Steve on 11 Apr 2000, 7:43 p.m.,
in response to message #3 by Simmer

Of course the ammusing thing is that we regularly speak prefix and postfix notation (and also infix -- we even combine them.

think of a * ( b + c ) / 2

explain that to someone...

first get b and c and add them (postfix) then multiply this by a (prefix) then divide by 2 (infix).

So given that the average person can understand this, the only reason why AOS seems so easy to people is that happens to be the way the calculation is written. (as opposed to the way we think about it, or do it)

Re: New RPN user?
Message #5 Posted by Keith Dicks on 12 Apr 2000, 7:31 a.m.,
in response to message #4 by Steve

Sadly I think the AOS is popular in schools (in the UK and I suspect in the US) as it makes it easier for kids to pass exams. The teacher looks good, the school looks good and the government looks good because educational standards appear to improve. However all the kids have learnt to do is press buttons in the right order and write down the answer in the correct space. OK for some people who may end up working for the rest of thier lives as data entry clerks (no insult intended) but no good for those destined for work involving more complex mathematical tasks.

You may say; 'but it allows kids to progress to higher levels of math in a shorter time' but this is pointless if they don't understand what is going on at the lower levels.

Kids just simply press the buttons in the same order as they appear of the page/black board and 'hey presto!' they get the correct answer! The not so bright kids do just as well as the bright ones. Never mind that they don't know WHY they get the correct answer.

I have found that if you understand the basics then this acts as a very firm foundation for everything else. Thats the key to RPN, you DO have to know a little to start with but it gives you MUCH more in return.

Re: New RPN user?
Message #6 Posted by Richard Anderson on 13 Apr 2000, 3:54 a.m.,
in response to message #5 by Keith Dicks

The thing that's amazing is that RPN is so little to learn. As others have said, it only takes a few minutes and a some getting used to. (It's worse going the other way.)

Here's a point that no one seems to have made...I think it was easiest to "make the switch" on a 42s with its two-line display. For basic arithmetic...the starting point after could see only and exactly what was happening. It's true for the big display models too but with their "command line", lotsa 3-way buttons and probably irrelevant stack levels showing, it's just too scary for beginners. Would I use my 48 for my income tax? No way!

I know I'm a blatant 42s partisan...and I am soooo sad...but I think that this friendly little, incredibly powerful calculator could have found a big market share if it had been sold right. (It may have been one of those things that was discontinued because it was just too good!) Richard

I can't agree more !
Message #7 Posted by Menno on 18 Apr 2000, 6:04 a.m.,
in response to message #6 by Richard Anderson

Yes RPN is the best and should be the standard calculator for technical education. Get them hooked on RPN. I switched 13 years ago from a TI-64 programmable to a 42s. After 1 month I never used the TI-64 again. And yes understanding RPN is easier with a 2-line display.


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