Techy odds and ends

In a word - well, 8 words, actually - because I respect the privacy of my friends. When it comes to WhatsApp, my contacts can be broken down into two main groups: those who use WhatsApp already and those who don't. Those who do use WhatsApp have already handed over their contact details voluntarily to Meta, WhatsApp's parent company. Those who don't use WhatsApp have not. Now, WhatsApp is almost unusable without access to the contacts stored in your phone. It can't let you choose the recipient of the message you want to send by tapping on their name from the contacts, you have to find and enter their number manually. Nor can it identify the sender of a message that you received without cross-referencing it with the numbers in your contacts. If given access to your contacts, WhatsApp will upload them to Meta to check whether any of them are already WhatsApp users. Let me repeat that: WhatsApp will upload the details of all of your contacts to Meta. What right ...

When smartphones started being a “thing” I went for SymbianOS with the famous Nokia N95. A few more Symbian devices and one MeeGo device later, I remained loyal to Nokia and used a Lumia 1020 powered by Windows Phone, but we all know what happened to that operating system. I think it was around 2014 that I was in the market for a new phone. At the time there were countless “dumb” phones that only had a fraction of the Lumia 1020’s capability. The only way I was going to get close was with a smartphone and at the time there were two major options: iPhone 5 or 6 on one hand and Android phones running Android Kitkat on the other. I hadn’t paid much attention to iPhones having remembered how slow they were to adopt 3G connectivity, so I went to Android and bought an LG G3. I’ve been using Android phones since then. Only recently - within the last month - have I become curious about how green the grass is on the other side and I bought a refurbished iPhone 15 Pro from Apple 3 weeks ago. ...

I’m revising my position on the eSIM vs. pSIM debate. Until now, I was strongly against eSIM. Nothing is simpler than taking a physical SIM (pSIM) out of one phone and sticking it in another. You can do it whenever you want and you don’t need your network’s blessing. The only down-side is a security risk: if someone steals your phone they can whip the SIM out of it to disconnect it from the mobile network so you can’t trace it. They can’t do that with an eSIM and they need to be able to unlock the phone to take it offline. Either that or break it, which defeats the purpose of stealing it in the first place. Mobile networks are beginning to cotton on to the fact that their customers don’t want to give up this freedom to chop and change phones whenever they want. Customers vote with their wallets when they see something they don’t like, so the networks are making things easier for them. The network that I was using only started supporting eSIM at all in August 2025 and even then, onl...

Why this post? The number of "Will this charger work with my phone?" or "Will I damage my battery using this charger?" posts that you see in public fora such as Reddit is quite disturbing. It shows a global lack of understanding of the basic fundamentals that everyone should know to prolong the life of their devices and of themselves in some cases. I'm hoping to address some of the misconceptions out there in the wild. Charging Protocols Brief history Back in the "old" days there were no charging protocols, or at least there was nothing standard. Each manufacturer would do its own thing with different charging connectors and different chargers providing different voltages. Even different products from the same manufacturer would have different charging requirements leading to people having drawers full of different chargers. Then came USB. The USB 2.0 (introduced in 2000) type A outlet on laptop and desktop computers was a conve...

I don't mean power banks in general, they're useful devices and I use a few myself. What I'm referring to specifically here is the type of power bank that includes a small solar panel on it to "charge" the power bank using nothing but light. These devices are actually quite dangerous, which explains why the only companies manufacturing them are brands, usually Chinese, with a brand name that looks like a Scrabble hand, who use the cheapest components possible. There's a reason why more reputable brands don't make these bombs waiting to explode. The capacity of the batteries is significant. OK, you can't always trust the published specifications of these things from less reputable brands, but even so, you're going to end up with a battery pack with a capacity of several thousand milliampere-hours. Let's assume we're working with a 20,000 mAh pack here. Let's also assume that the capacity that the manufacturer is boasting is actually hone...

Cheap and Cheerful and gets the job done. Edit 07-Aug-2023: 19 months after buying this robot and using it every few days, it is dead. Mechanical failure means that one of the wheels is no longer connected to the motor that drives it, so the robot basically goes round in small circles. If you're looking for a smart appliance with all the bells and whistles then this is not it, but it doesn't pretend to be it anyway. This is an entry-level vacuum cleaner robot that fumbles around more or less randomly, cleaning up whatever is in its path. The reason I bought this is because I wanted to see how well the technology coped with a small home on one floor that really is quite cluttered to be honest. If it doesn't cope well, then no great loss. If it does, then I know I can invest a bit more when this one comes to the end of its life. The robot comes with an infra-red remote control allowing you to access its basic features: auto clean, room clean, edge clean, spot clean an...

First of all, let's get one thing out of the way. It's a major thing that you always need to bear in mind when participating in social media in order to enjoy it safely. Your own safety is not the only thing that depends on this, that of your friends and family does, too. Social media is not a safe haven. There. I said it. Social media is open to anyone, not just the "good guys" like you and your friends. The "bad guys" are also out there and they gradually glean snippets of information from you and others that help them build up a profile allowing them to impersonate you, take over your social media account or even perpetrate identity theft. Any of the above can ruin your reputation and your credit rating and get you into trouble with the law if a crime is committed using your identity. That is, unless you deprive the bad guys of this information... Don't even feed them misinformation either because they can detect patterns in tha...

It's about a week since I bought one of these so I thought I'd jot down some of my first impressions of the timepiece. My overall impression is positive. There are a couple of negative points that I'll deal with but, on the whole, I like this watch. The build strikes me as being sturdy. There is no play in the crown or in the buttons and their operation is met with a reassuring amount of smooth friction. The mechanism for setting the watch is slightly unconventional but it actually makes sense. Most analogue watches with date usually allow you to set the date by pulling the crown out to a first position, and then to set the time by pulling the crown out to a second position. This watch does things slightly differently because it also has to allow you to calibrate the chronograph before you use it for the first time. With the crown in the first position you can zero the chronograph's minutes hand (10 o'clock dial) and you can set the date by rotating the h...

We've all seen those status updates from friends stating that they got 9 out of 10 answers right to a so-called impossible test claiming that " Nobody will get more than 60% of these right!" or something similar, haven't we? Let's look at how these things work, what they do and why they do it. Before going any further, help yourself to a decent dollop of cynicism or you're going to be very disappointed in social media. Remember the golden rule: if it looks too good to be true, then the chances are that it is not true. If there is the remotest possibility that something happening on social media could be something other than what it looks like, then it is not what it looks like and someone is trying to pull a fast one for profit in some way. Are the people setting these quizzes doing it out of the goodness of their hearts for the enrichment of the human race? Of course not. They're doing it to make money . So how do they make their money? What is their...

This is a little foray into number theory and presents one method of calculating the value of \(\pi\). It involves using a program to perform iterative calculations, so in order to minimise the impact of compounded rounding errors, it makes sense to use a computing device that operates with sufficient precision. I chose the SwissMicros DM42 for this because it uses Thomas Okken's Free42 Decimal under the hood, which offers around 34 digits of precision. The DM42 is also extremely fast, particularly so if connected to a USB port while operating because it more than triples the CPU clock compared to battery-powered operation. Back in 1735, the Swiss mathematician, astronomer (and a few other things besides) Leonhard Euler stated, and proved in 1741, that as the number \(n\) tends towards \(\infty\), the probability that two natural numbers \(a\) and \(b\) less than or equal to \(n\) are coprime, i.e. that \(a\) and \(b\) share no common divisor other than \(1\), tends towards ...

Am I a good photographer? Am I heck! But I do want to learn, and think the only way to learn techniques that are equally valid both in digital photography and in traditional 35mm film photography is to use a reflex camera with interchangeable lenses. A compact job won't cut it. A camera phone? Forget it! So, bit of a mid-life crisis :) I splurged out some of my savings on a Canon EOS 800D back that came with an 18-55mm zoom lens. I also bought a couple of different lenses to use with it. The 800D is not a professional camera. It's amateur but high-end amateur. I didn't want to spend huge amounts of money on something that will only be a passing fad, but then again I wanted to put enough into it to give me the best chance of seeing good results and being able to monitor progress. The sensor is not a full-frame sensor, it's an APS-C sensor but the results are still pretty good. The lens that came with the camera in a kit is an "EF-S 18-55m f/4-5.6 IS STM...

A while back, another member of the MoHPC forum mentioned a program he'd written for the HP-41C that allows the user to manage multiple alpha registers. I responded saying that I had written something similar many moons ago that behaved like a LIFO (last-in-first-out) stack rather than an indexed array of datasets and said that I'd look it up. I have no idea whatsoever what I did with my little utility so I decided to rewrite it, purely and simply. So here it is. NB: This program creates and manages a data file in Extended Memory called "ASTACK". If you already have a file of that name, it will be deleted! Note also that running these programs uses Flag 01 and trashes registers R07-R10. Finally, since this uses Extended Memory, you will need to run this on a 41CX or SwissMicros DM41, or on a 41C or 41CV with the "X-Function" module. The size of the data file created in Extended Memory depends on the depth of the alpha stack that you want to crea...

The "N Queens" problem is a puzzle where you take an NxN chequers or chess board (it's usually 8x8 but this works for the general case) on which you have to place N queens in such a way that none of them threaten or are threatened by any of the others. Reminder: in the game of chess, a queen can move as many squares as she likes horizontally, vertically or diagonally but cannot jump over any of the other pieces on the board like a knight. This means that any piece in her direct line of sight on the same line, in the same column or on a diagonal to her is fair game. With this in mind, it is clear that there is only one solution to the problem on a 1x1 board, i.e. a single square (you just plonk a queen on it and you're done), and that there is no way to organise two queens on a 2x2 board or three queens on a 3x3 board without them threatening each other. For a 4x4 or greater board, there is more than one solution. I thought I'd have a go at solving th...

The program downloadable from this page is a numerical solver. It attempts to find the zeroes of a function $f(x)$, i.e. it attempts to find $x$ such that $f(x)=0$ There are several methods for this. One that requires little computing power is Newton's Method, or the Newton-Raphson method, a description of which can be found on Wikipedia . We have no way of knowing the exact value of $f'(x)$ on the HP-41CX used here because that machine has no symbolic math capabilities, so we calculate an approximation of $f'(x)$ by taking a small value $\epsilon$ and calculating: \[ f'(x) \approx \frac {f(x+\epsilon)-f(x)} \epsilon \] This then allows us to calculate the next value of $x$ to use and display so that we see the calculator homing in on the zero that we're looking for: \[ x_{n+1} = x_n - \frac {f(x_n)} {f'(x_n)} \] Once we find a value of $x$ such that $|f(x)| \lt \epsilon$, we stop and that value of $x$ is deemed to be a zero of $f(x)$. The s...