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HPcalc memories

Posted by Wouter Peters on 21 Oct 2003, 2:56 p.m.

I met my first HP calculator in the latter half of my secondary school years, when my father bought – if I remember well – an HP35, and I was deeply impressed. The lack of an =key made it special. I quickly got he hang of RPN and learned to appreciate the elegancy of this logic of calculation. I borrowed this machine on countless occasions as a homework aid. From then on I’ve always found the algebraic logic to be a bit lame.

In 1972 I became a Chemistry student at Groningen University in the Netherlands. Accurate pocket Calculators were still far from common. A practical work course Analytical Chemistry was a tedious affair of repeated titration and browsing through logarithm tables to calculate the results. Yes, we had to do the up to 5-decimal accurate titre calculations the ancient way by manual addition and subtraction of logarithms. The lab assistants used a desktop calculator though to mark our work... After one or two titre calculations with the tables I decided I knew this approach thoroughly enough to look for a way to get to results more quickly. So I decided it could be sped up tremendously with a little electronic help (a lot of the calculations we had to do out of the lab in the evening hours, out of reach of the lab assistants).

Unfortunately the HP35 (or its successor) was too far out of reach of my budget to get one for myself - the few so called scientific pocket calculators I could afford didn’t use RPN and weren’t accurate enough to operate within the required accuracy interval. My father’s machine was also out of reach – geographically – but the phone was not. So each evening of that course I called my father, asked him get his HP, dictated the numbers and operators, got back the results and scribbled them down saving me quite a lot of tedious table work.

Then one day my father handed his HP35 over to me saying “It’s yours now, son”. “You’re kidding, dad” “No I am not. I’ve bought a new model.”

He had bought an HP25C and when he’d demonstrated this machine, I was deeply impressed again. A couple of years later I became the second owner of this nifty piece of equipment when my father moved on to an HP41C. Immediately I became addicted to the beauty of this “complete computer” as James Blodgett characterises this machine correctly (see his contribution to the “Articles forum”. Nr1: Hewlett Packard HP-25 Calculator: The Minimum Computer - 2 Apr 2000, 9:14 p.m.). Here he mentions “the educational advantage of a limited system” like the 25C and I totally agree with him. (In fact my reading his contribution stirred some memories of my own efforts with this machine and gave me the inspiration for this contribution to the forum.)

I those days I was discovering the ins and outs of statistics, studying the topic of Analysis of Variance and I decided to try writing a program to calculate one-way AoV for the HP25. Programming on a limited space surely forces one to optimise! It forces you to keep an open mind, to use and stimulate your creativity. I still remember finishing yet another pen-’n-paper version of the program and still ending up with a couple of lines too much to actually fit the program into the machines 49 program lines. Finally I succeeded, had even one or two spare lines! I still can feel the satisfaction of solving this problem. Running the program was a tedious affair though, especially data entry (there was hardly any room for a procedure to correct entry errors). One had to be VERY accurate entering all the necessary data, but the program worked correctly. Unfortunately I can’t find the actual program anymore.

After this whole exercise I had acquired a good knowledge of the actual topic of AoV as well as a good understanding of efficient and elegant programming and had greatly improved my skills programming the HP25. So much for “the educational advantage of a limited system”.

Much later in my career I moved to IT and became an application developer. Clearly my second hand HP25C was at the very beginning of this career change and those first efforts surely taught me that the ability to approach a problem from different angles often leads to more efficient and elegant solutions.

After a while, in the late eighties, I got my father’s HP41C system - including printer, wand, a couple of RAM and ROM-modules and a lot of manuals, solution books and bar codes on my wedding day as “yet another second hand from your father”. The same year I bought my first own HP: a half nut HP41CX with a card reader, to “get even more out of this great system”.

Up to today I am still using this machine.


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