The Once and Future Slide Rule, Great and Terrible

Because the most productive thing I’ve done today is receive a slide rule in the mail and learn how to multiply by pi in a novel way, let’s start with that as the basis for a blog post with which to rectify my sloth.

The slide rule I got is a Pickett N600-ES (“eye-saver”, meaning bright yellow) circa 1970 that I won on eBay for about $50. This model is relatively small, made of aluminum and therefore lightweight and durable, displaying a large number of “scales” or number lines with which to calculate. Those are some of the reasons this model was taken to the moon on no less than five Apollo missions, including Apollo 11 (Neil Armstrong and Buzz Aldrin both carried this very model) and Apollo 13, where, I trust, it served them well. And yes, those are some of the reasons I, in turn, bought this compact beauty.


Figure 1. Ceci n’est pas Buzz Aldrin’s actual fucking slide rule, man!



Figure 2. What the box for Buzz Aldrin’s slide rule would have looked like if he had lost the first one and bought a replacement a few years later out of his own pocket.

My slide-rule bender goes back only a month or so, but once I get interested in something, it’s hard to deflect me. First, I posted my top five personal retrocomputing desiderata, and then was intrigued when my friend Zenoli did the same and one of his was a decent slide rule of some kind.

Next, there was a long, unrelated thread about slide rules on the TRS-80 Model 100 list, a list which occasionally veers into other retrocomputing topics. It amused me that people were talking about whipping out their big ten-inch to impress younger engineers (I paraphrase, but only slightly), completely unironically. (Alas, I can only whip out six inches. Before today, I couldn’t even do that.)

Finally, one evening during some documentation builds at work, I started googling about, looking for slide rule manufacturers, and was astonished to discover that there are in some important senses literally none at present. I mean, not even for homeschoolers? I’m not being sarcastic; using a slide rule will improve your numeracy in ways that using a calculator or calculator app never will. It’s a mentat skill.

This is all we have: A few years ago ThinkGeek did manufacture one as a novelty, but the quality was poor and the experiment was not repeated. There is also a Japanese company called Concise that still manufactures special-purpose circular slide rules. And that’s it.

But they can hardly replace the little plastic slipstick my uncle gave me and taught me how to use when I was 10 (he worked at Boeing and had probably just gotten a calculator). For nostalgia is what this quixotic retropursuit is all about, no? (Not quite; see below.) Then, too, my wife Marty’s late father had one, and she thinks it’s here in the garage somewhere… Well, wish us luck with that.

While googling, I learned about the talismanic lunar magic of the N600-ES, and what a solid little performer it is generally, so I sniped one on eBay that was firing in a couple days. And now it’s mine. For me, that’s part of the “great” part of “great and terrible”.

What’s the “terrible” part? We built the Hoover Dam, the Empire State Building, and to a large extent, the Apollo program and its precursors with slide rules. That’s pretty badass, don’t you agree?

“Once and Future,” the “future” part

I assume I don’t need to explain the “once” part…

If you don’t want to buy an N600-ES yourself — or any other kind of slide rule — there are all kinds of “modern-day fun” (as the Retrobits Podcast says) to be had without one. For example, you can play with an N600-ES “virtual slide rule” emulator online or on your Android. There are virtual slide rules for iOS. too. In fact, there are a huge number of slide rule emulators available online and off, not just of my model.

Another bit of modern-day slide rule fun is the UltraLog, a slide rule that was scrupulously designed a couple of years ago by Zvi Doron (who is now deceased) but which was never built. The UltraLog was meant to be the slide-rule fan’s slide rule, about a foot and a half long with 40 well-chosen and ergonomically-presented scales (mine has about 20, and that’s considered a lot; the model Einstein and von Braun used had only nine). There were incipient plans for an independently-funded production run of 500; this is the kind of thing destined for success on Kickstarter, but perhaps Zvi wasn’t familiar with that business model. It might even succeed today. In any case, there seem to be high-quality digital graphics of the UltraLog available; why can’t there be an online UltraLog emulator, at least? (I’ll get right on it.)

There is, by the way, a really good course for learning how to use slide rules at the online International Slide Rule Museum, but it won’t give you much theory. If you want to learn why a slide rule works as well as how, I highly recommend Isaac Asimov‘s lucid 1965 book An Easy Introduction to the Slide Rule, available as a PDF, also at the Museum, or as a used pbook for extortionate prices from your friendly online bookseller.

The gaming/retrocomputing connection

So why am I obsessed with slide rules, and retrocomputing generally?

I’m writing a dictionary of imaginary games notionally published on the equally imaginary planet Glob. A few days ago, I was musing about the games with slide rules there, where they can calculate with things other than numbers, such as days of the week, months of the year, and planets of the solar system. (Yes, I figured out how to do this; my book is “design fiction”, so every game in it is possible to implement in theory. I hope people do, in fact, after the book is published.)

It was then I understood the reason why all this time that I’ve been sketching imaginary games, I’ve also been busy sketching imaginary retrocomputers: machines that still boot into Lisp or Forth, “writer’s notebook” computers with the “cinematic form factor” similar to the Model 100 but with higher resolution, and so on. The people of Glob are my people, as the Elves are Tolkien’s, and they share my aesthetics, as the Elves share Tolkien’s. And I like elegant things.

I am no fan of the board games Advanced Squad Leader or Star Fleet Battles; I can barely comprehend (com-prehend, “togethergrasp”) in my mind the 30-page rulebook to Elder Sign, let alone its big sib Arkham Horror — or, I flatter myself, I don’t care to. The most fun I had at game night recently was playing Nonesuch, a simple trick-taking game for the Decktet that nevertheless offers plenty of emergent complexity. I enjoy the complex, rather than the complicated. I enjoy things I can “grasp together” in my mind and turn from side to side to see, yet which still surprise me — whether they be card games, computer games, or computers.

Returning to computers, I had to install one of the smaller versions of Microsoft Visual Studio at work the other day. Do you know how big the install was? Over seven gigabytes. Do you know how big all of the firmware native to my 1987 Tandy 102 laptop is, including all the applications, and the operating system, such as it is? 32 kilobytes. Does Visual Studio do more than my Tandy 102? Sure, a lot more. Does it do five orders of magnitude more? Does it have 221,000 times more functionality? I’ve been using the previous version for most of a year, and I assure you it does not. (Don’t accuse me of Microsoft-bashing; Microsoft also wrote the Model 100 / Tandy 102 firmware I appreciate back in 1982. Famously, it’s the last code Bill Gates ever touched.) I like elegant computers too, and often that means retrocomputers.

So for games, give me chess variants, games with slide rules, and ten-dimensional card game systems that are nevertheless less complicated than Dominion. For computers, give me the Model 100 and its kin, not Visual Studio.

This is largely the origin of my retrofascination.

Model Mmm

If you have noticed that this post is longer than usual, it may be because I have been writing it on an item from my retrocomputing wishlist: a Model M keyboard, specifically a brand-new Unicomp Ultra Classic USB keyboard. After years of using a netbook as my main computer, I had forgotten until my Tandy 102 how sweet it can be to write on a real computer keyboard, and they don’t come much realer or sweeter than the Model M.


So that’s one item (plus a slide rule bonus) off my wishlist, and four to go. I may give up on the Jupiter Ace, though, because the FIGnition kit, modeled in some ways on the Ace, is so much more available, and I stand to learn much by building one.

Finally, for more information about slide rules than you probably care to know — but it’s curated! — let me direct you to my slide rule bookmarks on Pinboard.

Image credits


21 thoughts on “The Once and Future Slide Rule, Great and Terrible

  1. Very interesting. I haven’t gotten into slide rules much (mostly due to the fact that they are hard for me to see) but I can talk your ear off about mechanical calculator design. 🙂

    The large slide rules I know about were designed to be more detailed and have more decimal places. Pretty much the opposite of large-print design. Yes, there are classroom-size slide rules, which are also (AFAIK) simplistic and too large to handle easily.


    • Derek, thanks for your reply.

      So you’re interested in mechanical calculator design? Very interesting! Did you see that I have a Curta Calculator on my wishlist? Do you have any Curtas that you can bring to the next Seattle Retro-Computing Society meeting? I have never played with a real one, only emulators.

      On your view, which is more useful (or would have been useful back in the day), a decent slide rule or a Curta?

      What other kinds of mechanical calculator interest you?


      • Ron–when do these meetings happen? I have a Curta Type II I’d be happy to show you. Or, if the meeting doesn’t work, there are some lovely pubs in South Seattle I hang out in… 🙂


      • Unfortunately, I don’t have a Curta and I’ve only seen one “in the flesh” a few times. I’ve brought some of my other calculators to SRCS meetings and I’m happy to do it again. Age and disrepair, plus fancy engineering—or both—can make them difficult to maintain (plus I have basically no experience in that kind of thing).

        Usefulness depends on the problems you are trying to solve. Slide rules are very robust, analog, low-precision, good at physics and some engineering problems. Mechanical calculators can be robust or finicky. They are digital and can be high-precision. For example, they can do double-precision multiplication or handle more than 8-digit numbers. But they really work with integers (not decimals) and they are best for discrete math. I have a numerical-analysis book that describes using them for interpolation and other numerical approximations to engineering problems. It would be hard to do that on a slide rule.

        They tend to be less automated than a modern calculator, which means you can create strange variations on ordinary arithmetic operations. That allows you to do square roots in clever ways, decimal-to-octal conversion, quicker multiplication and division, multiplying A and B by C at the same time, etc. The Comptometer is one example of this. It only does addition, carry suppression, and clearing. You have to build everything else up (including subtraction and division) from that. The large family of “pin wheel” machines is another example. I have one with a 10-key keyboard and it’s quite a pleasant design. However, mine does not have the extremely useful “back transfer” feature.

        As you might guess, I like the “sweet spot” machines with what you might call a “solid building blocks” design. The very fancy automated machines are technically amazing but vastly more complex. (Fancy in their own world, a weak approximation to a simple pocket calculator in our world. Cheap electronic calculators absolutely obliterated the practicality of mechanical ones.)


  2. Your mention of games caught my eye because my friends and I have been playing a large selection of board games over the last few years and I have been reading the rules to extract the underlying algorithms, or at least rationales. Comparing game rules to computer programs is an interesting exercise. First of all, modern games vary widely in quality and conciseness (or spaghetti-code-ness, if you like). Secondly, the quality of the printed rules isn’t the same as quality of the conceptual rules (sort of like how the quality of the comments is not necessarily related to the quality of the code.) And the quality of the conceptual rules isn’t the same as the quality of the game (sort of like how the quality of the code gets tested as time goes on).


    • Derek, I like your implicit analogy,

      game : conceptual rules : printed rules ::
      program : algorithm : code comments / documentation.

      I agree that games vary in their “quality and conciseness (or spaghetti-code-ness, if you like)”, but why not call it “elegance”? It seems more elegant. 🙂

      Here’s another analogy, using a couple of games from my post:

      Star Fleet Battles : Nonesuch :: spaghetti code :: brief Donald Knuth program

      Do you agree?


      • I haven’t had a chance to try any Decktet games yet, though I would like to. It would be quite interesting to learn some games you know, and teach you some of the ones I’m learning. And I’m not only learning modern ones; I’ve been teaching people how to play Schnapsen and I’d like to try Piquet sometime. OTOH my friends and I played Money, Seven Wonders, Dominion, Eminent Domain, and Race for the Galaxy last night.

        I had “elegance” and then erased it. First of all, reading boardgamegeek, I see a lot of games in the middle of the road. They aren’t spaghetti code, but they aren’t very original either. They are evolutions of other games/mechanics. Second, I can’t define elegance. I think there is more than one aspect of it. Besides, elegance isn’t really the same as fun or replayability.


    • Derek, you’re certainly welcome to come as my guest to my game night, which meets every Saturday evening in the Seattle area. While play generally focuses on Eurogames (which usually strike me as what you call “middle of the road”), there are often a few people in the corner playing Decktet games, chess variants, and even offbeat traditional games like Schnapsen and Piquet (not that we’ve played those, but you could probably find people willing to try).


  3. Another great blog post. Makes me want to break-out one of my slide rules and re-learn how to use it.


  4. My daughter and I went in 50/50 to buy a slide rule from eBay recently. She’s in middle school and thought a mechanical slide rule was about the coolest thing she’d seen in a while. We both have been learning (re-learning, in my case) how to use it. There’s a great Android slide rule emulator that will give you some of the feel if you can’t have the real thing. It also has fun tutorials.


    • Earl Evans! I’m a big fan of your shows. I’m sure you saw my mention of the Retrobits Podcast. I’m also looking forward to Next Without For — I gather the first episode is any day now, and I check frequently for it.

      If your Android slide rule is the same as my favorite (the bright yellow one with the built-in tutorials), then if I recall correctly, it was based on the rule I make such a fuss about in my post (the Pickett N600-ES), but the developer had to switch to more generic graphics for copyright reasons. The semi-interactive tutorials make this app a great educational tool.

      Thanks for stopping by. I’d love to shake your hand and chat a bit if you’re at one of the Seattle Retro-Computing Society meetings again any time soon.


      • Or probably the N-500-ES (which is much more common and easy to find) but they’re both the same except for physical size anyway.


    • Heh, if the N500-ES and the N600-ES are the same except that the 500 is bigger, is the app a 500 when I run it on my tablet, but a 600 when I run it on my phone? 🙂


  5. 1. Slide Rules: Awesome…Love that yellow! You’ve definitely inspired me, here, and a slide rule is going to be in my immediate (as opposed to merely ‘eventual’) future.

    2. Writing: Umberto Eco, writing in his Postscript to the Name of the Rose, writes about creating his ideal reader through his writing (in his, case, such a reader is someone who can make it through the first 100 pages of the book). Speculative fiction authors have the advantage of being able to cut out the middle-man by directly creating their ideal society. I’m definitely looking forward to the eventual release of your new book. (And speaking of which…is there any chance that the deserving public will eventuall see a hard-copy release of Game Frame?)

    3. Complication vs. Complexity: While I tend to agree with you, I still find that the complicated has a beauty of its own. You’ll pry my Arkham Horror from my cold, glabrous fingers! Even so…chess variants are seriously underrated, and there’s nothing that’s as much fun as sight-hacking your way through the tactical consequences of a new rules twist. Once I have some free time again, it’s on my list to start up a “game systems and abstracts” night for the local board game club in an attempt to seduce at least a few a way from their Euro-fixation.

    4. Model M: Welcome to the fold! clickity-clickity-clickity…


    • Hey, Zenoli! Why, I was just talking about you…

      So, some brief responses to your points above:

      1. Slide rules are pretty great. Apparently I have also inspired my six-year-old nephew — he can’t be pulled away from the online virtual slide rule. As he is a little space fanatic, I suspect the moon is pulling on him here too.

      2. I think James Joyce said something similar about his “ideal reader with an ideal insomnia.” I’m glad my book will have at least one reader. Between you and me and the World Wide Web, I don’t know how many more it will have, but at least this once, I decided to throw commercial considerations aside and do something as much for its own sake as possible.

      As for GameFrame, I set it aside because I couldn’t seem to get anyone else interested in it, but maybe I’ll take it up again after my current book is published. We should definitely get our Archon port to a publishable state, and as I’m currently involved in the publication of the Hostage Chess ebook, I may do something with Hostage Ultima and the Hostage frame sooner rather than later, and this may include a GameFrame capsule description.

      3. I perhaps overstated my Arkham Horror and Elder Sign antipathy. I’ve enjoyed playing both. I just don’t want to run them, but it’s hard to find someone who knows the games well (especially the former) who doesn’t treat all the other players as his puppets. Of course, Thomas Ligotti would say that’s fully appropriate…

      I do have a couple of friends who like CVs and abstracts in my group, but they don’t always attend, and when they do, they often end up getting sucked into other games. But I’ve played Rithmomachia and variants there within the last six months, and that’s hardcore, so I count myself luckier than some.

      4. Multajn dankojn. Klak klak klak…


  6. “No wonder that to many people the feel of the slide rule in the hands spells security.” — Isaac Asimov, 1965.

    Asimov was a notorious dirty old man and I wonder if he wrote this line with his tongue in his cheek as well as his slipstick in his hand.


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