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.