Posts filed under the 'PCPlus' category


PCPlus 326: Turing and his machines

In August last year, I read Alan Turing: The Enigma by Andrew Hodges, which turned out to be an excellent biography of Alan Turing, especially so since 2012 was the centenary of his birth (I’d bought the Centenary Edition). Hodges is a mathematician and I certainly appreciated the way he described Turing’s inventions and mathematical insights. Despite (or in spite of) that, Hodges detailed Turing’s life and death in great detail, without causing the reader to flag and get bored. The description of...

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PCPlus 324: The history of streaming media

This particular article was prompted by the (June 2012) news that the BBC was going to not only broadcast the 2012 Summer Olympics as normal through its TV channels, but also multicast it via the Internet. (Of course, that was only to UK residents, us US residents had to make do with NBC’s execrable coverage. Unless you knew about and had UK VPN access, cough, cough.) It prompted me to think about how streaming worked over the Internet and to explain it to the layman. I started off however...

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PCPlus 323: Secrets of Steganography

Ah, steganography, that art of hiding some message in plain sight. These days we’re attuned perhaps to just thinking of hiding a digital message by modifying the bits encoding an image, but it does have a long illustrious history before computers ever came along. There’s Herodotus and his idea of inscribing a message on a wax tablet, underneath the wax; microdots used by spies in WWII and later; using code-words in an otherwise normal-looking letter. But in the age of computers steganography...

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PCPlus 322: Finding palindromic substrings

For June 2012, it was back to some computer science. The problem posed was: given a string of characters, find the longest subsequence in that string that is a palindrome. So, taking the example ‘abbaca’ (hey, computer science is full of nonsense strings), it’s fairly obvious there are two palindromic substrings – ignoring those of length 1, which are just silly – ‘abba’ and ‘aca’. The article delves into some algorithms for solving this problem, from the O(n^2) version to a more intricate O(n) one...

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PCPlus 321: Tilt-shift photography

This was one of those articles where I had to start from scratch with my research: I knew pretty much nothing about the subject. Sure, I was familiar enough with those photos of real buildings that looked as if they were made as a model on the kitchen table, but I had no idea how they were produced. I’d assumed that it might be some kind of digital post-processing of a photo, but I didn’t have any idea that you could purchase special tilt-shift lenses for DSLRs. I start off with the universal...

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PCPlus 320: Error detection and correction

OK, I admit it. I’ve been in the programming industry for more years that I care to count, and although I’d vaguely considered error detection in the past, it wasn’t until I did some research for this next article that I finally got to have some understanding of it all. And not only error detection but correction too: now that was pure magic. But, as with all these things, once you get the basic idea about how it works, all the magic gets stripped away. I suppose the first kind...

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PCPlus 319: Recommendation algorithms explained

For the March 2012 issue, I wrote about a new subject for me, and one that I hadn’t really seen much discussion of elsewhere: recommendation algorithms. Whenever you go to Amazon to buy something, there on the front page is a set of items that you might want to purchase. These recommendations aren’t merely what a lot of people are buying (for example, I never get offered a Justin Beiber CD), but they do seem to be specifically geared to your wants and interests. Yes, they can be hilariously wrong...

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PCPlus 318: The physics of Angry Birds

Without a doubt, this was a fun article to write. Not only was there much research done in order to understand the physics of the game (that is, how gravity worked in the game, how collisions were mimicked, and so on), but I also had to play it. A lot. Can you say that you claimed $0.99 on your taxes because buying the game needed to be offset against the income from the article? I thought not. Anyway, on to the gist of the article. I cover three main topics: the parabolic flight of the red bird...

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PCPlus 317: Optimise your web pages

Although this article appeared in January 2012, I wrote it in November the previous year. How do I know? Because I talk about the Kindle Fire I’d just received (I’d pre-ordered it) and about the Amazon Silk browser. In essence I wanted to talk about how Silk optimized (or not – it gets very subjective) the display of web pages. To begin with I had to talk about how browsers find, download, and render a web page in the first place. I discuss a bit of DNS, the name of a root document...

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PCPlus 316: What is crypto-currency?

I’ve just reread this article and, damn, it’s interesting. I recall it being fun to write as well. In essence, I go from the properties of real money – cash is a physical object (coin, banknote), it’s really hard to clone these physical objects, and transactions with cash are anonymous and untraceable – to thinking about a digital representation of cash – it’s not physical but a collection of bits, unless we take care it’s really easy to clone it like any digital file, and how the heck do you “transfer...

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