What was new? Stuff for more sophisticated computations, including those using polar coordinates, and trig in radians and gradians (1/400 of a circle), not only degrees (1/360 of a circle). The HP-45 was introduced at the same price of $395 the HP-35 dropped to $295. A year later, HP offered an upgraded model, the HP-45, which approached the power of the HP-9100A desktop calculator. The market for basic slide-rule calculators was huge. (And yes, that was a suitable wedding present-at least for techies!) It was given to me as a wedding present by my father-in-law, who purchased it during his career as a naval and aviation architect. All this at an amazing eight digits of accuracy. The calculator performed exponents (uniquely in HP calculators, performed as x y instead of y x), roots, logarithms, roots, sine, cosine, tangent-plus the invest arcsine, arccosine, and arctangent. What did the HP-35 do? Well, basic slide-rule operations, plus addition and subtraction (something that slide rules didn’t do). Note that exponents are uniquely calculated as x y with the HP-35. This one was a wedding present from my father-in-law. The HP-35 was Hewlett-Packard’s first slide-rule pocket calculator. It was wild, especially for a device that had a few minor math bugs in its first shipping batch (HP gave everyone a free replacement). Companies like General Electric ordered tens of thousands of units. However, back in 1972, and at a price of only $395 ($2,350 in 2017 dollars), the HP-35 changed the world. The calculator app in your smartphone is much more powerful. If you look at the HP-35 today, it seems laughably simplistic. The earliest days: Basic slide-rule calculators And that became the pocket slide-rule calculator revolution, starting off with the amazing HP-35. However, something better was needed, something affordable, something that could become a mass-market item. However, it was big and it was expensive-about $35,900 in 2017 dollars, or the price of a nice car! HP had a market for the HP-9100A, since it already sold test equipment into many labs. The HP-9100A did everything a slide rule could do, and more-such as trig, polar/rectangular conversions, and exponents and roots. Hewlett-Packard unleashed a monster when it created the HP-9100A desktop calculator, released in 1968 at a price of about $5,000. And if you were chaining calculations (needed in all but the simplest problems), accuracy dropped with each successive operation. With slide rules, you had to keep track of the decimal point yourself: The slide rule might tell you the answer is 641, but you had to know if that was 64.1 or 0.641 or 641.0. Three digits was fine for real-world engineering, but not enough for finance. They were good to about three digits of accuracy, no more, in the hands of a skilled operator. Doing trig, like sines, cosines, and tangents? Easy. Slide rules are really good at few things. Mathematicians never carried slide rules, but astronauts did, as their backup computers.Įverything the slide rule could do, a so-called slide-rule calculator could do better-and more accurately. Rather, they are asked by working engineers, technicians, military ballistics officers, and financiers, all of whom need an actual number: Given this set of inputs, tell me the answer.īefore the modern era (say, the 1970s), these problems could be hard to solve, requiring a lot of pencils and paper, a book of tables, or a slide rule. Those sorts of questions aren’t asked by mathematicians, who are the people who derive equations to solve problems in a general way. At the current rate of rainfall, when will your local reservoir overflow its banks? If you shoot a rocket at an angle of 60 degrees into a headwind, how far will it fly with 40 pounds of propellant and a 5-pound payload? Assuming a 100-month loan for $75,000 at 5.11 percent, what will the payoff balance be after four years? If a lab culture is doubling every 14 hours, how many viruses will there be in a week?
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