I bought another four-function calculator

Something I find rather amusing is that despite my owning… a lot of classic HP calculators1, this here blog only has posts about one old Sinclair calculator (which is, at least, a postfix machine) and one modern four-function, single-step Casio calculator (that somehow costs $300). And, as of today… yet another modern Casio calculator. I actually do want to write something about the HPs at some point, but… they’re well-known and well-loved. I’m excited about this Casio because it’s a weird throwback (that, like the S100, I had to import), and because it intersects two of my collector focuses: calculators and retro video games.

The mid-1970s brought mass production of several LCD technologies, which meant that pocket LCD calculators (and even early handheld video game consoles were a readily obtainable thing by the early 1980s. Handheld video games were in their infancy, and seeking inspiration from calculators seemed to be a running theme. Mattel’s Auto Race came to fruition out of a desire to reuse readily-available calculator-sized LED technology in the 1970s; Gunpei Yokoi was supposedly inspired to merge games with watches (in, of course, the Game & Watch series) after watching someone fiddle idly with a calculator. Casio took a pretty direct approach with this, releasing a series of calculators with games built in. Later games had screens with both normal calculator readouts and custom-shaped electrodes to present primitive graphics (like the Game & Watch units, or all those old terrible Tiger handhelds), some of which were rather large for renditions of games like Pachinko. The first, however, was essentially a bog-standard calculator as far as hardware was concerned2: regular 8-digit 7-segment display, regular keypad. I suspect this was largely to test the reception of the format before committing to anything larger; aside from the keypad graphics, the addition of the speaker, and the ROM mask… it looks like everything could’ve been lifted off of the production line for any number of their calculators: the LC-310 and LC-827 have identical layouts.

This was the MG-880, and it was clearly enough of a hit to demonstrate the viability of pocket calculators with dedicated game modes. The game itself is simple. Numbers come in from the right side of the screen in a line. The player is also represented by a number, which they increment by pressing the decimal separator/aim key. When the player presses the plus/fire key, the closest matching digit is destroyed. These enemy numbers come in ever-faster waves, and once they collide with you, it’s game over. Liquid Crystal has more information on the MG-880 here.

So that’s all very interesting (if you’re the same type of nerd I am), but I mentioned I was going to be talking about a modern Casio calculator in this post. About three years ago, Casio decided to essentially rerelease (remaster?) the MG-880 in a modern case; this is the SL-880. I haven’t owned an MG-880 before, so I can’t say that the game is perfectly recreated down to timing and randomization and what-have-you, but based on what I’ve read/seen of the original, it’s as faithful a recreation as one needs. In fact, while the calculator has been upgraded to ten digits, the game remains confined to the MG-880’s classic eight. Other upgrades to the calculator side of things include dual-power, backspace, negation, memory clear, tax rate functions (common on modern Japanese calculators) and square root3. You can also turn off the in-game beeping, which was not possible on the MG-880. The SL-880 is missing one thing from its predecessor, however: the melody mode. In addition to game mode, the speaker allowed for a melody mode where different keys simply mapped to different notes. The only disappointing thing about this omission is how charming it is seeing the solfège printed above the keys.

So was the SL-880 worth importing? Honestly, yes. The calculator itself feels impossibly light and a bit cheap, but it is… a calculator that isn’t the S100 in the year 2020. The game holds up better than I expected. It is, of course, still a game where you furiously mash two keys as numbers appear on a screen, but given the limitations? Casio made a pretty decent calculator game in 1980. More important to me, however, is where it sits in video game history. One might say I should just seek out an original MG-880 for that purpose, and… perhaps I will, some day4. But I think there’s something special about Casio deciding to release a throwback edition of such an interesting moment in video game history. And while the MG-880 was a success, it certainly isn’t as much of a pop culture icon as, say, the NES. This relative obscurity is likely why I find this much more charming than rereleases like the NES Classic Edition. It feels like Casio largely made it not to appeal to collectors, but to commemorate their own history.

Experiencing the Casio S100

I have a modest collection of calculators – mostly HP, with a few other curiosities thrown in. Some of these have come with not-insignificant price tags attached, due to rarity, collectibility/desirability, present-day usefulness1, &c. Yet, despite a strong desire for Casio’s 2015 release, ‘The Special One’ (models S100 and S200), I could never justify importing one for the ~$300 asking price.

The S1002 is an incredibly simple calculator; it does basic arithmetic, percents, square root, basic memory functions, and some financial bits like rate exchange, tax calculation, and grand total accumulation. Sliders select decimal point fixing and rounding rules. It is, seemingly, functionally identical to the ~$40 heavy-duty Casio JS-20B. Physically, the two share some properties as well – doubleshot keys with ergonomic curvature, three-key rollover, dual solar/battery power, 12-digit display. So… why $300?

The S100 is a showpiece, plain and simple. A 50th-anniversary tribute to the Casio 001, an early desktop calculator with memory3, and the beginning of Casio’s electronic4 calculator business. On the S100’s website, Casio calls out other notable calculators from their history: the compact 6-digit Mini from 1972, and the 0.8mm thick SL-800 from 1983. The S100 is a celebration of decades worth of innovations. Yet it celebrates not by innovating itself, but by refining. It’s an extravagant, luxury version of a product that Casio has been optimizing for half a century.

To this end, the S100 is made in Casio’s control factory in Yamagata Prefecture, Japan. In keeping with the purpose of this factory, assembly and inspection are largely done by hand. Casio brags about the double-sided anti-reflective coating on an FSTN display. The keys are comparable to well-designed laptop keys, with a ‘V-shaped gear link structure.’ The chassis is machined from a single bit of aluminum. It’s all very excessive for a calculator that doesn’t even have trig functions.

I wouldn’t be writing all of this if I hadn’t actually acquired one, right? Certainly, I still paid too much for something so silly, but I did finally find a good deal on a used S100 in black. So is it, in Casio’s words, ‘breathtaking, unsurpassed elegance?’ I mean… it is quite nice. It’s worth noting that I don’t have any experience with Casio’s similar-yet-priced-for-humans-to-actually-use calculators. But I can say that the display is the finest basic seven-segment LCD that I’ve seen. The keys feel great, and the tactility combined with the overall layout make for the ability to calculate very quickly5. It has a satisfying heft about it, and it’s clear that a lot of attention-to-detail went into it6.

But… let’s say you really were considering plonking down $300 on this thing. Any number of classic HPs can be acquired for less (and they all have better key-feel): a 41C/CX/CV or 42S, a 71B, a 15C, an oddity like the 22S. You could get a Compucorp 324G. Any number of exotic slide rules. My point is, $300 will buy you a lot of cool calculating history… or one incredibly fancy showpiece. I guess I’m glad they made it, and I guess I’m glad I own one. But it’d be hard to recommend one as an acquisition to all but the most intense calculator nerds.

A few of my favorite: Slide rules

I link to photos hosted by the International Slide Rule Museum, a really great resource. Unfortunately, they don’t set IDs on their pages for specific rules, but luckily I only discuss two brands: Pickett and Faber-Castell.

I love slide rules nearly as much as I love HP calculators, and much like HP calculators, I have a humble collection of slide rules that is largely complete. While I keep them around more as beautiful engineering artifacts than anything, I do actually use them as well. These are a few of my favorites, from both a conceptual standpoint and from actual use.

Pickett 115 Basic Math Rule:
This is, by far, the simplest rule that I own. It lacks the K1 scale that even the cheap, student 160-ES/T2 has. Aside from the L scale, it is functionally equivalent to a TI-108. But, to be fair, the TI-108 has two functions that nearly all slide rules lack: addition and subtraction. And, true to the name ‘Basic Math Rule,’ the Pickett 115 has two linear scales, X and Y, for doing addition and subtraction. Additionally, it has one scale-worth of Pickett’s ‘Decimal Keeper’ function, which aids the user in keeping track of how many decimal places their result is. All in all, it’s not a particularly impressive rule, but it is quite unique. Faber-Castell made a version of the Castell-Mentor 52/80 (unfortunately ISRM’s photo is not that version) with linear scales as well, and I probably prefer it in practice to the 115. The 115 just has a wonderful sort of pure simplicity about it that I appreciate, however.
Pickett N200-ES Trig:
This is basically the next step up from the aforementioned 160-ES/T. The 160-ES/T is a simplex with K, A, B, C, CI, D, and L scales. The N200-ES/T is a duplex model that adds trig functions with a single set of S and T scales, and an ST scale. It’s a wee little pocket thing, the same size as the 160-ES/T, and it’s made of aluminum as opposed to plastic. It’s nothing fancy, but it handles a very useful number of functions in a very small package. The N600-ES/T does even more, but it becomes a little cluttery compared to the N200-ES/T’s lower information density. Good for playing with numbers in bed.
Faber-Castell 2/83N Novo-Duplex:
The 2/83N is, in my opinion, the ultimate slide rule. It has 31 scales, conveniently organized, and with explanations on the right-hand side. Its braces have rubberized strips on them, and are thick enough that the rule can be used while sitting on a table. The ends of the slide extend out past the ends of the stator so it’s always easy to manipulate (I don’t have any Keuffel & Esser rules on this list, but they had a clever design that combatted this problem as well, with the braces being more L-shaped than C-shaped). The range of C (and therefore everything else, but this is the easiest way to explain) goes beyond 1-10, starting at around 0.85 and ending around 11.5. The plastic operates incredibly smoothly (granted, I bought mine NOS from Faber’s German store a few years ago, that had to have helped), and the whole thing is just beautiful. Truly the grail slide rule.
Faber-Castell 62/83N Novo-Duplex:
This feels like a complete cop-out, because it is essentially identical to the 2/83N, except smashed into half of the width. You lose the nice braces, you get a slightly less-fancy cursor, and you lose precision when you condense the same scale down to half-width. But you end up with something ridiculously dense in functionality for a small package. Even though it’s essentially the same rule as the 2/83N, I think it deserves its own place on this list.
Pickett 108-ES:
This was the piece I’d been looking for to essentially wrap up my collection. It is a circular, or dial, slide rule, and it is tiny – 8cm in diameter. It’s much harder to come by than the larger circular Picketts, particularly the older 101-C. Circular rules have some distinct advantages – notably their compact size (the 108-ES is the only rule I own that I would truly call pocketable, and it cradles nicely in the palm of my hand), and the infinite nature of a circular slide. The latter advantage means there’s no point in adding folded scales, nor is there ever a need to back up and start from the other end of the slide because your result is off the edge.
The 108-ES, by my understanding, was a fairly late model, manufactured in Japan. It is mostly plastic, and incredibly smooth to operate – moreso than non-circular Picketts that I’ve used. The obverse has L, CI, and C on the slide; D, A, and K on the stator. The reverse has no slide, and has D, TS, three scales of T, and two of S. I can’t help but hear “I’m the operator / with my pocket calculator” in my mind when I play with this thing. It really packs a lot of punch for something so diminutive. The larger 111-ES, of the same sort of manufacture, is also quite impressive with (among other things) the addition of log-log scales.

Sinclair Scientific Programmable

The Sinclair Scientific is one of my favorite calculators, though certainly not for its speed, accuracy, or feature set. In fact, in an era where full-featured scientific calculators can be had for under ten bucks, it’s a downright laughably bad machine. But it’s evidence of the ingenuity of Sinclair in their race to have made tech accessible for those with slimmer wallets. The Scientific may well be a post for another day, but recently I fell into another ridiculously quirky Sinclair calculator, the Scientific Programmable. Its manual describes it as ‘the first mains/battery calculator in the world to offer a self-contained programming facility combined with true scientific functions at a price within the reach of the general public’.

As with the Scientific, that last bit is key – this machine was engineered to meet a price point. HPs of the day were engineered for speed and accuracy, and were beautiful, easily operated machines to boot. Sinclairs were affordable, period. To start investigating this thing’s quirks, let’s address the ‘true scientific functions’ that the calculator includes. Sine, cosine, arctan, log, and antilog. No arcsine, arccos, or tangent – instead the manual tells you how to derive them yourself using the included functions. Precisely what I expect from a Sinclair (though the aforementioned Scientific did include all standard trig functions).

The highlight (if you will) of this calculator is, of course, its ‘self-contained programming facility’, which is really what I’d like to discuss. While the terms are oft indistinguishable nowadays, I would really consider the Scientific Programmable’s functionality more of a macro recording system than anything resembling programming. There are no conditionals, there is no branching, and a program can only contain 24 keystrokes. The keyboard is shifted for program entry, and integers thus require two extra keystrokes as they are delimited. I say integers because that is all one can enter during program entry – if your program requires you to multiply by .125, you would need to calculate that with integer math first.

My go-to demo program is Viète’s formula for pi. It’s simple, requiring very little in the way of scientific functions, stack manipulation, memory registers, or instructions; yet it’s fun and rewarding. Unfortunately, I don’t actually think it’s possible on the Scientific Programmable, primarily due to the lack of a stack and the single memory register. I just need one more place to stick a value, and a stack would be ideal – it would contain the previous result ready to be multiplied by the next iteration.

We could try pi the Leibniz (et al.) way, 1 – 13 + 1517 + 19, and so on. But we still need to store two variables – the result of every go, and the counter. I still don’t think it can be done.

How about we eschew pi and just make 3. Easy enough, just type 3 or, perhaps 69 enter 23 ÷. But what if I want to do it Ramanujan-style with more nested radicals? I… still don’t think I can, because again I essentially need a decrement counter. Bit of the inverse of the problem as above, one place for storage just isn’t enough. Sorry, Ramanujan.

So what can we do? I guess the golden ratio is simple enough: ' 1 ' + √ and then just mash EXEC repeatedly until we have something resembling 1.618. Not terribly satisfying. Also, the calculator lacks the precision to ever actually make it beyond 1.6179.

To be fair, the calculator (well, not mine, but a new one) comes with a program library in addition to the manual. Katie Wasserman’s site has them, fortunately. And while none of the programs are particularly interesting in any sort of technical way, they do give a good overview of how this macro mentality would cut down on repetitive calculations. One thing that I do find technically interesting, from a small systems/low level perspective is Sinclair’s advice on dealing with the limitations. For instance, they mention that pi is 355113 which yields 3.1416, as accurate as is possible. But if one is willing to deal with less accuracy, they suggest 4*(arctan 1) for 3.1408 (~.02%) or 227 for 3.1428 (~.04%). Determine needs and spend memory accordingly.

All in all, I don’t know what I’ll do with the Scientific Programmable beyond occasionally pulling it out to mess with. It’s not really fun to program like an old HP, because it’s just too limited. I guess if I come up with any other simple, iterative formulas that I can plug into it, I may revisit. But, much like the Sinclair Scientific, it will largely stay in my collection as a quirk, a demonstration of what was ‘good enough’ alongside the cutting edge.


This is an old post from an old blog; assets may be missing, links may be broken, and my opinions may differ considerably by this point…

Even though I generally have an HP or two handy, the POSIX command-line RPN calculator, dc, is probably the calculator that I use most often. The manpage is pretty clear on its operation, albeit in a very manpagish way. While the manpage makes for a nice reference, I've not seen a friendly, readable primer available on the program before. This is likely because there aren't really people lining up to use dc, but there are a couple of compelling reasons to get to know it. First, it's a (and in fact, the only calculator, if memory serves) required inclusion in a POSIX-compliant OS. This is important if you're going to be stuck doing calculations on an unknown system. It's also important if you're already comfortable in a postfix environment, as the selection of such calculators can be limiting.