HP-35 scientific calculator gets IEEE milestone award


I try not to cut-and-paste press releases, but I hope you'll excuse me in this case. I can't resist HP-35 trivia:

PALO ALTO, Calif., April 14, 2009 - HP today announced that IEEE, the world's largest technical professional association, has awarded HP the prestigious IEEE Milestone in Electrical Engineering and Computing award for its HP-35 Scientific Calculator.

Introduced in 1972, the HP-35 was the world's first handheld-sized scientific calculator. An instant hit, the HP-35 ultimately made the slide rule, which had previously been used by generations of engineers and scientists, obsolete.


• The HP-35, named for its 35 keys, was the first handheld calculator to perform transcendental functions such as trigonometric, logarithmic and exponential functions.

• At the time, contemporary calculators could only perform four basic functions - addition, subtraction, multiplication and division.

• The now classic "Reverse Polish Notation" (RPN) first used in the HP-35 has become the most efficient way known to computer science for evaluating mathematical expressions.

• In the first three years after its introduction in 1972, sales of the HP-35 Scientific Calculator exceeded 300,000 units.

• Forbes ASAP named HP 35 as one of the 20 "all time products" that have changed the world.

• It was the world's first handheld scientific calculator with a LED display.

• HP-35 has traveled to the top of Mt. Everest for use in altitude and navigation calculations.

• HP-35 is regularly used to navigate ships.

• HP-35 has been used by astronauts aboard spacecraft to calculate the exact angle of re-entry into the Earth's atmosphere.

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  1. I bought an HP-25c when I started university. It was my first calculator. Before that it was pen and paper, or sliderule and/or logarithmic tables.

    I remember duplicating my first ten computer science assignments on the 25c for fun. Stuff like shell-metzner sorts and histograms

    The actual assignments were done in FACET, a simple machine code/assembly language that was bundled with an excellent textbook. It was not a “real” language. Strictly for teaching computer theory. It was actually written in Fortran, and run on a Xerox mainframe via the dreaded DEC 300 baud keyboard/printer style terminal.

    I lost the 25c during a move, and replaced it with a 16c. I think still have the manual though.

  2. Arggh!!

    My Dad used to bang on endlessly about this.

    Reverse polish notation? is that the right name?

    He had this exact one then every single iteration of this until he died.

    Loved his maths did my dad.

  3. Jan Łukasiewicz is credited with inventing Polish Notation back in 1920, Bauer and Dijkstra are known with implementing Reverse Polish Notation in early computers in the 1950’s. Many of these concepts like “the stack” live on in current CPU architecture.

    I only bring this up because Łukasiewicz is the first use of an L with a stroke through I have seen… neat!

    P.S. I have an HP16c emulator on my iPod… Not quite the same thing.

  4. Once you take the trouble to learn RPN, you never want to go back… especially using a recent-vintage calculator with a large screen that shows you the last several entries in the stack.

    I still have my HP-48sx, and I love it. The build quality of this thing is excellent, and it has the best keypad of any calculator ever built.

    In my job, I do not do much advanced math. However, I still have a fond place in my heart for HP calculators, and RPN. The new HP-50 looks pretty sweet. If I ever needed a new advanced graphing scientific, this would be it.

    Anybody who does a lot of advanced math: do yourselves a favor and try RPN. It means never having to touch a parenthesis key again. It also means that you can make backup copies of intermediate values easily, without having to assign them to variables. The benefits really are too numerous to mention.

  5. I still have an original HP 35, passed down from my older brother (he paid about $400 for it when it was new). I used it all through high school and college and fairly often thereafter, keeping it plugged in after its battery pack lost the ability to hold a charge.

    Last time I tried to use it, it wouldn’t come on at all. I mourn.

    You’d think in almost 40 years trying, they’d have come up with a better calculator than that one, but I’ve yet to encounter one.

  6. If it was $400 in 1972, that’s equivalent to $2,030.56 today.

    I remember its successors, when I was in grad school in the late 1970s.

  7. …Hell, why doesn’t anyone give the venerable, original LED TI-30 it’s due? This was the first seriously affordable scientific calculator, handled all the basic Trig functions with memory, and even came with a neat denimesque hip case that looped through your belt just like slide rules did in those days. Best bang for the buck circa 1977, even if TI never did make the corduroy and black leather cases available as they promised.

    …On a side note, my two Captcha words below, ironically, are “calculator” and “fondness”. Go figger 🙂

  8. I’ve both the 35 and the 45.

    The HP-45 is on my computer desk right now, by the keyboard.

    I use it almost every day. I suspect that, long after I’m dead, someone else will be using these two calculators.

    It would not surprise me if a significant number of 35s and 45s will still be working on their respective centenaries.

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