... thus achieving ...
... the ultimate Write-Only Memory.
169 posts • joined 17 Jun 2009
The proof that the exponent of a Fermat prime is a power of 2 is (almost) a one-liner.
If k has an odd factor m (say k = m*n, where m≥3 is odd) then (by an algebraic factorisation) it is trivial to show that 2^n+1 divides 2^k+1 = 2^(m*n)+1 [e.g. 2^2+1 divides 2^10+1]. So if 2^j+1 is prime, then j has no odd factors ≥3, hence j is a power of 2.
Aside from various Windows machines, I run a 2007 iMac and a 2010 MacBook. The iMac is now on its third hard drive (HD failures in 2010 and 2015, each replaced with a larger disk), and the MacBook on its second (HD failure in 2018, replaced with a larger disk). For all three HD replacements, I was able to switch the disks myself (which would not be the case with a soldered-in HD). Also, Time Machine was my friend on all three occasions.
For me, reliability is much more important than weight or thinness.
Both machines are now up for replacement as they have outlived the upgradeability of their operating systems. I hope their replacements run as well and as long.
Back in the late 1980s, I used to work in Cambridge for a company which no longer exists. We had acquired - I for get how or why - an old UNIX box which took up most of a room and could only be housed on the ground floor because of the limitations on floor loading. We then had word from Head Office in Shepton Mallet that they wanted it moved there; again, I don't know why.
I did suggest dropping it off in Salisbury Plain in case anybody there needed a new henge.
When I was a graduate student in the 1980s, my university department had a display of full-face photographs of its staff members, down to and including the cat which frequently visited the place. This means that anyone who wanted to spoof a face-recognition program (which were of course unknown at the time) could simply take a picture of the photo display and extract any desired picture for use in a fake ID.
Also, there was another staff member - I shall call him Richard S - whose photo was very similar to mine (start with a beard and glasses). Just right to confuse a face-recognition system. In real life no-one could possibly confuse us, as I was 20 years younger and more than a foot (30+ cm) taller than him.
No fire here (sorry), but at my first place of IT employment (mid 80s) they had a machine room with controls for temperature and humidity.
Rumour had it that by proper (by which I mean "highly improper") adjustment of controls (humidity right up, temperature right down...), it was possible to get it to snow in the machine room.
I am from a generation which learned how to use (and memorise) maps. I do not use (or possess) a SatNav. That said ...
I live near Farnborough, and it is now Airshow season. The local council has reconfigured the local roads and put up signs "TURN SATNAV OFF", because the roads don't go where (or in the direction) SatNavs think they do.
In a past life, I was on a project in the Netherlands, and we regularly used to take a taxi from our hotel to the project office. Once the taxi driver took a wrong turn, and his SatNav insisted that he correct the mistake ... by turning right into the local canal.
For the same employer, but a different location, I had occasion to take a taxi from central Paris to a factory in one of the less salubrious arrondissements. The factory address did not appear on the taxi SatNav, so I had to instruct the driver to go to another address nearby in the same street, and then follow my verbal directions to the factory.
Years ago, as a graduate student, I was "volunteered" to man the slide projector at an international conference on the evolution of stars (largely owing to the fact that my PhD supervisor was one of the conference organisers).
Midway through one of the presentations, the slide projector decided to catch fire. I managed to eject all the slides (thereby saving the slide set) just before pulling the plug from the wall.
The session MC did make a comment that I was upstaging the speaker!
I had some fun at the Infosec exhibition at Olympia this week by going round the stalls, picking out those pushing their pet solutions for "Total Security" and/or "Incident Response" and grillling them about how their pet systems would have protected the system in a BA-type scenario (power outage causing failure of a single server, failed backup, and legacy systems of all ages dating back to the Wright brothers), had such a system been installed.
Not one vendor produced even a plausible reply.
I was involved in the 2011 UK census, which also had (in the UK, for the first time) a facility for the public to complete the forms online.
I do not intend to detail our solution, save that one of our assumptions was that everyone and his/her dog (all over the UK) would attempt to use the system as soon as it went live - thus creating a usage profile *from legitimate users* which closely resembles a DDoS. We therefore had a very heavyweight Internet-facing gateway which filtered out the Internet's usual cybercrud, and which had behind it a traffic management system which, if threatened by overload, would show a "graceful delay" screen along the lines of "Sorry, we're busy right now - please try later".
We also had a plan (to be performed in the event of loss of functionality in our control centre) to move operations to a secondary centre in another part of the country. One of our test exercises, before the system went live, was to perform exactly this transfer of operations.
Sadly, after the 2011 UK census went live, the team was scattered. However, those planning similar exercises in future might do well to recruit the *individual* members of that team. We've been there and done that - and our system worked.
Years and years ago (early 1990s), I was on a project which did static analysis on a safety-critical system. By static analysis, I mean automated code verification using a tool which checked for all sorts of consistency issues (but it could not deal with anything which involved concurrency, e.g. shared memory).
It would easily have picked up both the OpenSSL bug and the recent Apple GotoFail.
The technology exists, and has existed for a while now (the tool was written in Algol and was old even when I was using it). But it is slow and expensive to use (the tool's users need to be experts).
You get what you pay for.
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