The Curta—The First Multi Function Calculator

Anyone who is surprised at seeing my name on the Guest Bastard list is no less surprised than I was when Les asked me if I would consider being a contributor. In addition to being surprised, I had many of the same reservations as Brock. I have been visiting SEB since last summer, and I know that most all of the regulars have studied and thought long and hard about a wide variety of subjects and can quickly lay down lucid comments that continue to impress me. That is why I consider myself more a Guest Bastard Junior Grade (GBJG using some jargon from the past.)

I subscribe to the New York Times and Buzzflash headline services and regularly review The Progress Report.  So, most of my posts are going to be political and anti-administration, at least until November. After that I may have to consider Tahiti, the Balearic Islands, or Australia as places to live.

This one won’t be political. Les gets into Blog software, games, computer repair, and the occasional electronic gizmo. What little techno geekiness I have is snagged somewhere near the middle of the last century. That is why this one is about an amazing little mechanical device.

The Curious History of the First Pocket Calculator, an article, in the January 2004 issue of Scientific American, described the Curta, the first and last hand held mechanical calculator. The article opens like this.

Johannes Kepler, Issac Newton and Lord Kelvin all complained about the time they had to waste doing simple arithmetic. Foolscap covered with numbers obscured answers; elegant equations led to numerical drudgery.

Oh, for a pocket calculator that could add, subtract, multiply and divide! One with digital readouts and memory. A simple, finger-friendly interface.

In the 1960s an advertisement appeared in Scientific American saying

The Curta is a precision calculating machine for all arithmetical operations. Curtra adds, subtracts, multiplies, divides, square and cube roots…and every other computation arising in science and commerce…Available on a trial basis. Price $125

All of this in an 8 oz. Package. One operated the device by entering numbers, using slides on the side of the device, and then turning the crank the required number of times. The subtraction process used 9s complement addition, so there was a certain elegance in the processor’s design. Early Curtas had 8 setting knobs and 11 digits in the results register. Later versions had 11 input digits and gave 15 digit answers.

Since the Curta had more functionality than the desktop calculators of that day, it was a natural for scientists and engineers. Because of its portability it was a boon to accountants, and it also caught on with sports car rally enthusiasts.

How this machine came into being is an amazing story in itself. The inventor, Curt Herzstark, was born in Austria, the son of a Jewish father and a Catholic mother. Because of the family business he was familiar with calculators even as a child. During the war he was imprisoned in Buchenwald after he stood up for two Jewish employees. Because of his skills, he was put in charge of a machine shop that manufactured precision parts, and he was allowed to work on the design of a miniature calculator in his spare time.

By the time he was released he had completed a set of pencil drawings that included dimensions and tolerances. He located a machine shop in Weimar and within two months had three prototypes in hand. When the Russians moved into East Germany, Herzstark bummed his way to Austria where he filed patent applications.

He finally found a sponsors in Lichtenstein. (The ruling family wanted to develop some industrial capability in their largely agricultural country.) Contina, the company that Herzstark and his backers founded, put the machine on sale in 1948. After passing up an order for 10,000 units from an American Department Store, the company made reasonable progress in ramping up their production. At that point, the financiers reorganized the company annulling Herzstark’s stock shares. However, he still owned the patents, and, therefore, had the leverage to demand and receive royalties from the company.

These machines are still in existence and are collectors items. When I checked eBay yesterday the high bid, in an auction with five days to run, was $910. The asking prices ranged from $860 to $1,000.

Here are some URLs that provide general information and manuals, disassembly instructions, and algorithms. The first site also has a picture gallery showing various models of the Curta.

When I was in high school I pestered my folks for months for their permission to buy a $25 K&E Log-Log Duplex Vector slide rule with my own money. (They were children of the depression and didn’t see the need for me to have one before I went to college. I did eventually prevail and I still have the slide rule.) It’s a good thing that I didn’t know about this machine back then. I would have been insufferable.

About ten minutes into drafting this post, I decided that I really wanted a Curta. However, on second thought, I would probably be better off if I scouted up a battery pack for my HP45 (I was always more comfortable with RPN.)

7 thoughts on “The Curta—The First Multi Function Calculator

  1. When I submitted this post I got two ping errors


    Not sure what that means.

    The image is NOT to scale. I suspect I should have selcted thumbnail.

  2. You forgot to mention a recent revival of interest in the Curta since the publication of William Gibson’s book Pattern Recognition in which it plays a supporting role.

  3. What a pleasure to get home, click on SEB, and see your post about the curta! The Curtas are running $600 to $1,500 on eBay, so that will not be in my forseeable future, alas.

    There are people who just stretch my concept of how far human intelligence can go, like the guys who built a working model of the Japanese encoding machine in WWII… from analyzing intercepted transmissions… and they didn’t even know Japanese when they started!  Herzstark is in that class.  Imagine him working in a freaking prison camp visualizing that thing.

    I saw the article in SciAm and it completely blew my mind.  Here’s a page I wrote after reading it and my head was still spinning, but your post is way more detailed.

    I had a K&E Log-Log Decitrig in high school and it was stolen.  Replaced with a Post (which I still use) but it just wasn’t the same: the K&E had my dad’s initials carved in it.  Last year I acquired an eight-inch circular aluminum slide rule from the 1930’s just because it’s so damn cool.  Traded several nice plastic Post/Teledyne 9-inch straight rules from the ‘70’s for it.

    Keep writing!

  4. I went ahead and rescaled the image for you. You can click on it for a bigger version. Also, don’t worry if a ping fails here or there. That happens sometimes, it’s just notifying the various services that we updated and isn’t critical.

    Oh, and that’s a damned cool article. Even if I hate math and would never touch such a thing or a slide rule to save my life. grin

  5. Welcome, VernR, to your Guest Bastardship. Try not to make this look too easy – and may I say that I’m glad the Curta-ins have opened to reveal your first presentation. ba dump dum!

  6. i ahve a great condition CURTA II for sale, if anyone is interested you can e-mail me and i can send pictures !!!
    this unit is in very good condition if not considered excellent.

  7. Hah!  I, too, have a Curta, and I think I will put it up for sale on Ebay.  This one is in mint condition, and still has its original cardboard box, though the box has become worn over the years.

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