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Working up to the HP71B

Posted by Nick R on 12 Dec 2010, 6:56 p.m.

When I started high school in New Zealand in 1966 slide rules were prohibited in the mathematics class. We had to do all our calculations using log tables, which involved writing down laborious columns of numbers. Someone gave me an old K&E Mannheim slide rule which I began using surreptitiously under the desk to check my results, until I eventually got caught. (The maths classroom caught fire shortly afterwards, which had nothing to do with me but seemed to be divine retribution). By the following year things improved greatly, as the rule about slide rules was relaxed and I'd upgraded to a Hughes Owens Versalog which I could now use openly. Eventually I ended up in Canada and worked as a chainman for a land surveying company, where I got to use a mechanical calculator for the first time. Field computations back then were done with a Facit hand-crank machine and six figure trigonometric tables. The Facit was too heavy to pack along the survey line, so it stayed in the truck and we'd catch up on the calculation of coordinates at lunch time or at the end of the day. This would sometimes be a three man job - the other chainman would look up sines and cosines in the tables, I'd turn the crank on the Facit and the surveyor would write the results in the field book. The Facit was slow by modern standards, but it was a solidly built machine. We were forced to make an emergency stop one day and I watched with interest as the calculator went flying forwards and hit the steel dashboard hard enough to strike a spark. The impact didn't affect the Facit, but the surveyor complained that it would have been better if it had hit a chainman instead, as that would have avoided the dashboard damage. The next survey company I worked for had a Curta for use in the field, but none of the chainmen were allowed to touch it with their grubby fingers. At about that time the HP35 had become available, which finally put an end to looking up tables, at least until the batteries ran down. When that happened we'd revert to figuring out coordinates in the field using traverse tables. Battery life was one drawback of the HP35; the other being the difficulty of seeing the LED display on bright sunny days. This company also possessed a Compucorp Model 354 Surveyor, which was rarely allowed out in the field, probably due to a concern that it might get damaged if the man carrying it should fall off a cliff. At that time I thought I had a future in the survey business and went to technical college to learn more about it, and there I was introduced to a computer for the first time - an HP2115 running BASIC. This was a rack-mounted machine that impressed all of us with its flashing lights until we found how frustrating it was to have to load programs using punched paper tapes. I couldn't afford an electronic calculator so I bought an old Odhner pin wheel calculator for doing homework. Eventually the price of TI calculators came down to my level, and I finally owned a machine that had all the necessary functions built in. I can't remember which model it was, but I soon realized it was inferior to the HP calculators, and was able to replace it with an HP25C discovered in a pawn shop. After a couple of years I gave up surveying and went into forest fire control, selling the HP25C in the process, as I didn't think I'd have a need for it. No doubt I drank the proceeds while sitting in the pub on standby waiting for a fire call. As it turned out however I worked my way up the ladder and ended up using calculators in fire management planning. The first one was an HP10C purchased in the US and brought back across the border. (That was a great feature of the Voyager series - they could be easily concealed). It quickly became obvious that I needed a machine with more program steps, so I moved up to an HP41CX. For some reason this soon developed an intermittent problem with the PRGM/ALPHA switch so I returned it to the dealer, who took it back and sold me an HP71B in its place. This proved to be ideal for my purpose, as I was able to do fire weather and behaviour calculations while sitting on a stump on the fire line surrounded by smoke and blackflies, or sitting in the pub surrounded by smoke and bar flies. The HP71B was a great machine, and easily programmed by someone like me who was comfortable with BASIC and has never figured out RPL. Unfortunately when I left fire management this calculator stayed behind, together with an HP15C that eventually met an untimely end down a drain. All I have is the box the HP71B came in, which I haven't yet thrown out as there's always the hope I might run across another one someday.

Edited: 13 Dec 2010, 12:19 a.m.


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