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HP-35: an Epiphany

Posted by Doug Winkeljohn on 26 Jan 2010, 2:58 p.m.

In 1972 or 1973, an HP rep came through our plant demonstrating the brand new HP-35 RPN calculator. At that time I was a young engineer just a few years out of school in a staff of around 1200.

I spent a lot of my time in those days doing parametric trade studies involving repeated lengthy series of calculations with many variables. My calculating choices were: My K&E slide rule, a company Friden desktop mechanical calculator (with square root extraction if I was lucky), scheduling time on one of the 2 or 3 Wang desktop calculators available, or writing, debugging and turning in a computer program for overnight running on the company IBM 7094 mainframe. This was boring and fairly mindless activity that still required care.

Seeing the demonstration of the HP-35 was a life changing experience. None of us had seen anything remotely like it. It was as if the rep had just shown us the meaning of the universe. It was fast! It was quiet! It kept track of the decimal point! It handled trig and log functions! And best of all, it could be mine!

$395 was far beyond anything I could afford or pay for. In fact, that was more than 10% of the price of my first new car. This was when you could buy a TI 4 function calculator for less than $50. But at lunch I went right to the credit union and set up a $5 per week deduction from my paycheck, realizing it would take over 1-1/2 years to get the money to buy one. I ended up cheating on that and ordering the HP-35 before a year was out. When it came with its beautiful construction and its genuine leather case I was as proud as a new father and I never looked back.

Almost all of the other engineers thought I was crazy for spending the money and most just did not get RPN. That sentiment persisted for many years, and a lot of the old timers never gave up on their slide rules.

I have owned and used several HP calculators since then, and I still do, but I have many fond memories of my HP-35 and its flashing red display.

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