Calculator or Slide Rule?

In February 1972, the first relatively affordable and hand-held electronic calculator was made available, for scientists only, priced at $395. Hewlett Packard's HP-35 was the first handheld calculator to perform advanced mathematical functions.

I was in my senior year at NYU Engineering and since my freshman year, I had a totally plastic, cheap, plastic slide rule since I could not afford any of the earlier 1970s calculators like the Canon Pocketronic, Sharp EL-8 or Busicom LE-120A devices that the “rich” kids had. That slide rule got me through my quizzes and tests at NYU to earn me my degree just as well as those fancy, expensive ones by the “Whiz kids”. It was better than an abacus which would have been my second choice or maybe Napier’s Bones from the 1600s, invented by John Napier which was based on a numerical scheme called the Arabian Lattice.

Some people called the slide rule a slipstick, but it was a mechanical “computer” to the EEs on campus at the NYU University Heights campus in the Bronx (Although our campus computer was a Sperry Univac that filled an air-conditioned room with tape drives, punch card programs and we studied Fortran IV programming language in those days). We were allowed to use it during tests because the calculations were the least of your worries in engineering school, it was analyzing and setting up the schematic diagrams using that 1845 German physicist, Kirchoff’s Voltage and Current Laws and later on setting up matrices.

Anyway, it is said that in 1620, William Gunter developed the forerunner to the slide rule—-a logarithmic rule for multiplication and division using dividers.

Here are some more interesting articles on this topic:

Slideshow: Slide rules and charts – a personal collection

5 Engineers: Do engineers still use hand slide rules?

Last slide rule manufactured, July 11, 1976

5 comments on “Calculator or Slide Rule?

  1. Jiri Polivka
    February 4, 2015

    After living with slide rules and tables for more exact calculations, HP-35 was a wonder! In 1972 I borrowed the HP-35 to do many calculations for my Ph.D. thesis work.  All seemed to be easy and nice.

    Only shortly before defening my thesis, one of the referees doubted about one of my graphs. This graph used HP-35 calculations of sinh and cosh functions, and an unexpected dip appeared on a smooth curve.

    The problem was too much confidence in HP-35 capabilities. Sinh and Cosh functions are performed by summing series, and this method quite badly converges to an exact result. I should have used the traditional “paper” tables.


    The new technology can and did bring an ugly surprise.  Today's scientific calculators are a bit better in Sinh and Cosh functions, but to be sure, I would recommend to carefully check using them for “special” functions. Old tables can be worth of use still now.

  2. Ocelot
    February 4, 2015

    There was a similar issue with the polar to rectangular conversion in an HP calculator years later.  I bought one and then took it back because of that.

  3. Steve Taranovich
    February 4, 2015

    @Jiri—thanks for that detailed information about the nuances of that HP calculator. We need to know and understand our tools well in order to do a proper design.

  4. Bob.Shepard
    February 4, 2015

    I saw an HP-35 advertisement the summer of '72 before I started on my Electronics Engineering degree.  Most of the money I earned that summer went to buy one for over $400.  While waiting weeks for it to arive, I carried a picture of it so I could practice using Reverse Polish Notation. 

    It's not surprising that the first scientific pocket-calculator had an error or two.  I've read from a few sources that many of the first math tables were riddled with errors.  Those errors were what led Babbage to work on mechanical computing.


  5. RGG instruments
    February 5, 2015

    Back in the 1980's I regularly used a complex number slide rule to check computer calculations on frequency responses from 10 to 24 order equations.

    Bob Green UK

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