Thu 15 Dec 2011 15:14

Dealing with unsolicited salescalls (cold calls).

For many years, I've been plagued by unsolicited salescalls. It's not very hard to find my phone number, and various people (mostly in the IT realm) call me up out of the blue hoping to sell me something. The interruption is unwelcome, even if the product isn't.

For some years now, my policy is to explain to the caller that I don't accept unsolicited salescalls, sincerely apologize, and end the call. Occasionally, I am then asked how I am to be contacted. I explain that I prefer to do the contacting myself: when I have a need, I am not too shy to contact likely vendors and make inquiries about their products.

Occasionally I run into someone who is offended by my unwillingness to take their unsolicited salescall. I do feel more than a little sympathy for the salesperson when this happens: I imagine they may think I objected to something they did, or to their manner. The fact is, I handle all unsolicited salescalls this way. As for whether it is intrinsicly offensive to reject unsolicited salescalls out of hand, I don't think it is. Indeed, it is natural for a salesperson to want their salescall, even if unsolicited, to be better accepted. But it is unreasonable for any salesperson to expect that unsolicited sales inquiries to strangers will always be welcome. But I do apologize, each time, and in general, when I so quickly end telephone conversations with salespersons who call me out of the blue.

Dear reader, if you are a salesperson, and you are tempted to contact me to sell me something, please do not call. Instead, just advertise generally (and if you must, send me some mail in the post). Trust me to find you when the need arises. I frequently do.

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Gigabit ethernet, and Category 5, 5e cabling.
There seems to be lots of folklore that says that Category 5 (Cat5) cabling can't run gigabit ethernet. Contrary to widespread belief, that's mostly false. Here's the situation. Cat5 has the bandwidth to run 1000baseT. But early experience with 1000baseT showed that 1000baseT was pickier about certain cabling issues that weren't specified in the Cat5 standard, such as crosstalk and delay skew, so the Cat5 standard was enhanced for 1000baseT to enforce limits on these. This enhanced standard is called Cat5e. But the fact is that most Cat5 installations already perform to the Cat5e spec.

If someone tells you to rip out a Cat5 installation because it can't support 1000baseT, you're being prompted to do something that is expensive and probably unnecessary. All you generally need is test the existing cables to the Cat5e standard (using a Cat5e cable tester) and replace the ones that fail. Often, most if not all the cables will be fine. Or just use the cables for 1000baseT and replace any that exhibit problems.

Cat6 and Cat6a are a different matter. Cat6 supports a spectral bandwidth of 250MHz, up from Cat5/Cat5e's 100Mhz, while Cat6a supports 500Mhz. Cat6 cabling will run ten gigabit ethernet (10GbaseT) to 37-55m, while Cat6a will run 10GbaseT to 100m. So it's worth choosing Cat6 or Cat6a over Cat5e for new cabling, if the cost increment isn't too high, so that the cabling can support 10GbaseT, even if it's not needed today.

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Einstein's special relativity isn't as complicated as many people seem to think.

I run into people who think that special relativity is some sort of mysterious thing that only Einstein and physicists can understand. But it's not. It's a bit weird, but it's no weirder than the earth being a globe.

Originally people thought that light moved like any other moving object. Einstein thought about this and wondered: what would happen if you followed some light and sped up until you travelled at the same speed as it. Then light would look to you like it was stopped. But stopped light (light "standing still") didn't (and still doesn't) make sense. So Einstein thought: what if light travels at the same speed no matter how fast you're going? What would this mean?

Well, what does it mean to travel "at the same speed"? It means light covers the same amount of distance in a given amount of time. Or, put another way, light takes the same amount of time to cover a given distance. So if the distance is short, light takes less time to go the distance. If the distance is longer, light takes proportionally more time to cover it.

So Einstein thought: OK, if light travels at the same speed for everyone no matter how fast they're going, what would that mean for someone going very fast? Imagine they're going nearly the speed of light, and are being chased by a beam of light. Clearly the light isn't going to get closer to that person as quickly as it would get closer to someone who was standing still. Ordinarily, you would think that light was moving "slower" for the person who is moving away from it. But if light moves at the same speed for everyone, than something else must be going "slower" for that person. The only possibility is time.

Put it this way: light covers a certain distance in a second. To someone watching, the pursuing light isn't making up the distance quite so fast between it and the moving person, because the person is moving away so fast. But for the moving person, light is moving as fast as it always does, it is the second that takes longer.

This sounds a little bit crazy since we aren't used to thinking of time moving faster for some people and slower for others. But it does. The reason we don't notice is that the speed of light is very fast and we can't easily go at speeds close to it.

It's the same sort of thing as the world being round (i.e. a globe). It looks flat to us, but only because it is so big that we can't see enough of it at once to see it curve. Go high enough and we can see the curve of the earth's surface easily enough.

Similarly with special relativity. Time moves slower for those who move fast. It's not obvious to us because we usually don't move very fast, so at the speeds we move, the time differences are too small to notice. But in 1971, Joseph Hafele and Richard Keating took some very accurate (cesium atomic) clocks abord commercial airliners and flew around the world. They compared their clocks to the very accurate clocks in the US naval observatory: the clocks were indeed different, and showed the results that Einstein had predicted.

What this this mean? Well, if you can wrap your head around the concept of the world being a globe, you can wrap your head around the concept of time moving more slowly for those who move fast. And that's it, right?

Well, not really. There's also general relativity (and it affects Hafele and Keating's results too). But that's a bit more complicated, and I'm not going to get into it now.

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Exchanging files in docx format may lead to problems
When Microsoft came out with Office 2007, the default save format for files was switched to a new format based on XML. For Microsoft Word, for example, instead of files being saved in .doc format by default, they were now saved in .docx format. If you use Microsoft Word 2007 or 2010, you'll notice that when you save a Word document, it saves it as document.docx instead of document.doc.

Unfortunately, now there seems to be an incompatibility between how Word 2007 and Word 2010 interpret .docx files. Apparently, possibly depending on how one's printer is configured, when users of Word 2007 and Word 2010 share files in .docx format, some spaces (seemingly random) between words in the file are dropped.

This has been reported on various places on the net including the CBS Interactive Business Network, cNET.com, and Microsoft's own user forums.

For now, I suggest using the older .doc format for users of different versions of Microsoft Word to exchange documents. For publishing documents, instead of using a native Word format, I suggest using a widely-used open document standard like PDF. CutePDF is a useful free Windows printer driver that lets you create PDF files from any Windows application by simply printing to a CutePDF printer.

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What's right about ikiwiki?
Chris Siebenmann pointed me today at ikiwiki. It's a wiki that can also function as a blog. It's potentially interesting, he said. And he was right: to me, it seems definitely interesting. I've only started looking at it, but there's something about it that I like very much, something it does right that most web 2.0 applications seem to do wrong: ikiwiki uses the right sort of tool to store the wiki text. What's the right tool? In my opinion, it's a revision control system (well, to be more exact, a filesystem coupled with a revision control system).

Why is this the right tool? Well, what's wiki data? It's a collection of edited text documents. Databases, such as those used by most wikis and blogs, are designed for large collections of data records, not documents. Yes, they can handle documents, but using them for a collection of documents is like using a tractor-trailer for a trip to the beach. Yes, you can do it, but it's a bit excessive, and you may end up stuck in the sand. On the contrary, it seems to me that a filesystem, not a database, is the appropriate tool for document storage, and a revision control system, not a database, is the tool of choice to keep track of document edits.

Then why do so many wiki and blog implementations use databases such as mysql or postgres as their back-end? I don't know. I suspect it's a lack of imagination: when you're holding a hammer, everything looks like a nail. In fact, "lite" versions of these databases (e.g. sqllite) have been created to take advantage of the fact that the full power of these database systems are not needed by many systems that use them. But "lite" databases for wiki/blog back-ends seem to me to be like cardboard tractor-trailers: still the wrong tool, but with some of the overkill stripped out.

Even more to ikiwiki's credit than the fact that it has what I think is the right sort of backend, it also allows you to use a wide array of different revision control systems (svn, git, cvs, mercurial, etc.), or even no revision control system at all. I like this. Revision control systems seem to be a matter of widely varying preference, and ikiwiki's agnosticism in this regard makes it appealing to a wider array of users.

I've only started looking at ikiwiki, and it may be that in the end, I'll decide I don't like it for some reason or another, but whether I end up liking it or not, or whether we use it or not, I think ikiwiki is right in using a revision control system instead of a database for its backend. I wish it were not so rare in this respect.

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Adding logout to Firefox: making HTTP authentication more useful.

The HTTP protocol (on which the world wide web is based) offers two forms of simple authentication that are built into pretty much every web browser: Basic authentication and Digest Authentication. For both these authentication mechanisms, the web browser obtains authentication information from the user and retains it to submit to the web site on the user's behalf. A set of authentication information retained for a site by a running web browser is called an authenticated session.

Unfortunately, in most web browsers, including Firefox, there is no easy way to delete that information. Hence once you are authenticated to a web site as a particular user, your web browser will continue to authenticate you to that web site as that user until you exit your browser. It's easy to see this in action: simply go to a site that requires basic or digest authentication, authenticate, browse somewhere else, then return to that site. Did it ask you to enter your password again? No, it remembered who you had authenticated as before, and connected you immediately as that user.

This is often what you want, but not always. Sometimes you might want to logout as one user and login as a different user. You can't easily do this in most web browers without exiting and restarting the browser. Or perhaps you may want to allow someone else to use your web browser, and you don't want to give them your access to certain sites. It would be useful to be able to clear your authenticated sessions.

Some web browsers, such as Firefox, permit clearing all internal authentication and identification information: cached data, cookies and authenticated sessions. In more recent versions of Firefox, the feature is called private browsing, and is focused primarily on browsing without leaving privacy information behind. But this is a pretty blunt instrument: all potentially sensitive data is cleared, such as cookies, not just authenticated sessions. What if all you want to do is log out?

My HTTP logout add-on for Firefox is intended to change this. It adds two menu options to Firefox, one on the Tools menu, and the other on the menu you get when you right-click on the background. In each case, the menu option is called HTTP logout all, and if you select it, it will clear all authenticated sessions in your running web browser. You can easily try it: after installing the add-on, go to a site that requires basic or digest authentication, and authenticate. Now choose "HTTP logout all", and reload/refresh that page. It will not recognize you as the person who had logged in before, and will ask you to log in again.

I'm not the only person who wants the ability to log out when using HTTP authentication. Many of us who have implemented web sites using Basic or Digest authentication have often been asked by users "How do I log out"? On this topic, the Apache foundation writes:

        Since browsers first started implementing basic authentication,
        website administrators have wanted to know how to let the user log
        out. Since the browser caches the username and password with the
        authentication realm, as described earlier in this tutorial, this
        is not a function of the server configuration, but is a question
        of getting the browser to forget the credential information, so
        that the next time the resource is requested, the username and
        password must be supplied again. There are numerous situations in
        which this is desirable, such as when using a browser in a public
        location, and not wishing to leave the browser logged in, so that
        the next person can get into your bank account.  

        However, although this is perhaps the most frequently asked question
        about basic authentication, thus far none of the major browser
        manufacturers have seen this as being a desirable feature to put
        into their products.  

        Consequently, the answer to this question is, you can't. Sorry.

        - Apache 1.3 documentation.

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Startssl: a better approach to SSL certificates
Perhaps one of the highest profit-margin businesses on the internet is the provisioning of domain SSL certificates. The reason: prices for domain SSL certificates are often very high: up to hundreds of dollars for a 1yr domain certificate, but the cost of producing them is often very low: generally, all that is needed is a simple automated web site that authenticates via email. Typically no human being needs to be involved. Then why do they cost so much money? Probably because only a few certificate vendors are trusted by default in the major web browsers. Nobody wants to use a certificate that is not trusted by default in all the major web browsers, because that would mean a person using one of those browsers will, by default, see scary messages whenever (s)he tries to access the site.

Traditionally, SSL certificate vendors have competed by advertising, each attempting to convince customers that it is more trustworthy than the other guy and thus worth paying more for. But this is generally irrelevant: if the brower trusts the SSL certificate by default, the site will work out of the box, without any scary messages, and the only people who are going to even notice which vendor is used are those who stop to examine the SSL certificate in detail. Few do.

It would be nice (for SSL certificate customers at least) if SSL certificate vendors would start to compete more by price instead. There has been some of that in recent years, but the price of a one year simple domain SSL certificate is still upwards of U$10, with prices most often several times that amount. This is a lot of money for something that is pretty close to zero-cost to create.

Recently, things have started to change. In 2009, Startcom became trusted as a certificate authority by all the major browsers (IE, Firefox, Safari, Chrome). But Startcom is not a traditional SSL certificate vendor. Instead of charging per certificate, Startcom's Certification Authority gives away certificates for free, and charges instead for various authentication services. Simple authentication (the sort that can be done automatically through sending email to a known address and then asking the person to enter into a webpage the secret code that was sent) is free, because it can be fully automated, and thus done cheaply. Once authenticated, the person can generate an unlimited number of the most common sort of domain SSL certificates (1 yr single domain name). More extensive authentication, the sort that requires the participation of a human being to verify a person's identity documents, costs a modest amount of money (U$40/yr). Once authenticated at this higher level, the authenticated person can generate as many as necessary of the less common sort of domain SSL certificates (e.g. 2yr, or wildcard). More extensive authentication services are available, at additional cost. Thus startcom charges for the sort of services that are more intrinsicly expensive (e.g. services that require the attention of a human being, such as extended authentication), and not for automated services that are entirely performed by computer (such as certificate generation). This seems much fairer to the customer.

Is this the future of SSL certificates? I suspect most of the SSL certificate vendors would prefer it not to be: SSL certificate generation is quite profitable at the moment. But it is better economics: the price being charged more closely approximates the cost to offer the service. So if the market for SSL certificates is to more closely approximate a free market, startcom's approach seems quite promising.

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Assessing H1N1 risk
What sort of risk does H1N1 (Swine Flu) present this flu season? To assess this, it might be helpful to estimate some H1N1 risks and then compare it to risks with which we are more familiar.

So let's look at some numbers. The worldwide case fatality rate of H1N1 (the number of people who have died of H1N1, divided by the number of people who have gotten H1N1) has been estimated to be 0.45%. Unlike seasonal flu, roughly 80% of those who have died of H1N1 are less than 65 years old (typically 90% of seasonal flu fatalities are 65 years old or over). If we assume a 15% probability of getting H1N1 this flu season, the likelihood of someone under the age of 65 dying of H1N1 this season is thus 0.15 x 0.0045 x 0.80, i.e 0.054% or 1 in 1852. This is a little less than the one-year general odds of death due to external causes in the US, approximately 1 in 1681.

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What's Good About Twitter?
Twitter has a mixed reputation. Negative views generally express the notion that Twitter is pretty much useless , or is a massive waste of time. Indeed, there is no shortage of evidence for this view. What is the usefulness of knowing that someone is brushing their teeth, or having cereal for breakfast? Probably not much. The problem is that "What are you doing?", the question that a tweet is allegedly supposed to answer, is often not very interesting. What one is thinking, what one has stumbled across, or what one wants to tell the world, could be much more interesting.

One very useful purpose Twitter serves is to announce new articles, blog entries, events, or news items when they appear. Twitterfeed makes this easy: it will check an Atom or RSS feed periodically, and automatically tweet the titles and URLs of new articles to Twitter, allowing anyone following the tweeter to be made aware of the new material. For example, my department now uses Twitter to disseminate its news and events.

So is Twitter a waste of time? Is Twitter useless? Only if one takes Twitter's "What are you doing?" too literally. Indeed, some seem to feel the need to tell others whenever they're yawning, scratching an itch or drinking coffee. Clearly this is not the most interesting of material. But, on the other hand, if one uses Twitter to follow information sources (people or organizations) with a high information content, and/or to disemminate such information oneself, it can be very useful indeed.

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How well do Java Virtual Machines Scale Up?
Java seems to be a popular language for small to medium-sized applications and its use at that scale is well understood. But what happens when you scale it up to something quite large? It seems that very large Java Virtual Machines (JVMs) are still rather rare. Blackboard is a Java-based learning management system (LMS) now in use at the University of Toronto. The University is rather large, with a great many courses and students, and its Blackboard JVM is correspondingly huge. It turns out that an ordinary off-the-shelf JVM suffered some unusual and unpleasant performance issues (mostly related to garbage collection) when scaled this large. The university and Sun Microsystems eventually resolved the issues quite nicely (using the new and still somewhat experimental Java G1 garbage collector) but it was an eventful journey. John Calvin of the University has put together a rather interesting talk about this, which will be given at the university on June 23rd, and later this summer at BBWorld 2009.

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Understanding Portable Displays
Perhaps the most important thing about a portable computer, be it a notebook, netbook, PDA, smartphone, or internet tablet, is what it provides you versus what it demands from you. One of the most important things a portable machine provides is logical screen area or screen resolution: the amount of data it can show you on the screen at one time. But of the most important things a portable machine requires/demands is weight: what does it take to carry it?

Screen resolution is measured as a grid of pixels (dots) in width x height format, e.g. 1024x768 means a screen that is 1024 dots wide and 768 dots high. Weight is of course not the only thing that determines portability: size is important too, but generally larger machines are heavier and smaller ones are lighter, so weight is a good shorthand for "weight and size".

A quick way to approach the costs and benefits of a portable computer is to compute the ratio of its benefits (e.g. screen resolution) to its portability cost (e.g. weight). So a quick assessment of a portable computer is to compute its pixel to weight ratio: if the weight ratio is high, the portable computer may compare better to one that has a lower pixel to weight ratios. I've written a little tool to compute this information (in units of pixels per milligram, i.e. ppmg), at http://www.cs.toronto.edu/~jdd/screenspec.cgi.

Pixel to weight ratio isn't quite enough, though, because there are limits to human sight: a portable computer is of no use if the pixels are so small that they cannot be easily seen. "Too small" depends on the distance the screen is from one's eyes. I tend to use devices like cellphones and PDAs at a distance of 18 inches from my eyes, and laptops at 24 inches. Generally, distance multiplied by the pixels per inch of the screen is a constant. For example, for me, I'm quite comfortable with 170 ppi at 24 inches, but beyond that, I feel some eyestrain. At 18 inches, that works out to (170 x 24) / 18 = 227 ppi. In my (anecdotal) experience, many people seem comfortable with 125ppi at 24 inches and 167ppi at 18. Of course, there is much more to this than a simple ratio: tolerance for high pixel densities varies depending on what the person is doing, what fonts are being used, and many other things.

Still, a pixel to weight approach lets one compare machines in interesting ways: for example, an Apple Ipod Touch has a 3.5" 480x320 screen and weighs 115g; that's 164 ppi and a pixel to weight ratio of 1.3. This is comparable to a Nokia E90 Communicator, which has a 4" 800x352 screen and a weight of 210g; its ppi is 218 and pixel to weight ratio is 1.34. But now consider a Nokia N810 Internet tablet: its 4.13in 800x480 screen (ppi is 225) and weight of 226g gives a significantly higher pixel to weight ratio of 1.69. But with ppi around 220 vs. the Ipod's 164, either Nokia device may result in eyestrain where the Ipod Touch does not.

Now look at some notebooks. A (large and heavy) Dell Vostro 2510 notebook weighing 5.72lbs with a 15.4" WUXGA (1920x1200) screen offers 147ppi and a pixel to weight ratio of 0.9, which is (perhaps surprisingly) a higher pixel to weight ratio than a (small and light) netbook, the Dell Mini 10 with the new high-resolution 10" 1366x768 screen (ppi of 155); its weight of 2.86lbs results in a lower pixel to weight ratio of 0.8 (at a slightly higher ppi, too). Compare this to a Macbook Air: with a 13.3" 1280x800 screen, it weighs 3 lbs; its pixel to weight ratio is 0.75. Unlike the other too, though, the Macbook air has an easier-to-read ppi of 113.

Of course, this doesn't mean that one should pick portable computers based solely (or even mostly) on pixel to weight ratios, or ppi for that matter. It is merely one possibly useful way to compare portable machines, and should be at most only one criterion among many, when making a decision.

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Why a netbook?
What is a netbook anyway? It's a new type of low-cost ($350-$600) notebook that is particularly small and light: it typically has a 7-10" screen, and a weight not much more than two pounds. Small and light notebooks are not new, but they have for years been quite expensive, marketted to busy executives who want something small and light to use when travelling, and are willing to pay for the privilege. But an inexpensive small and like notebook is new, so new that it has been given its own name: netbook. The rationale behind the name is that this meant to be an "internet" device: its primary role is web browsing, and office productivity applications are secondary. Such a device relies on wireless: wifi for now, but increasingly 3G and other forms of cellular data service.

Why buy one? It's affordable, by notebook standards. It's also very portable: while it's too large for a pocket, it can easily slip into a handbag. And while it may be designed for internet connectivity, it can run modest office productivity applications. But it is limited in various ways: the small screen, while generally bright and visible on most models, does not have a great deal of screen real-estate; typically 1024x600 or less. RAM and hard drive space is generally less than most notebooks or desktops, and RAM in particular is limited to a maximum of 1GB or 1.5GB, depending on the model, enough for Linux or Windows XP, but not generally enough to run Microsoft Vista quickly. It lacks any form of CD/DVD drive. And the internal CPU (generally an Intel Atom or a VIA C3) is slow, and single-core. A low-end laptop can be bought for as little as $500-$600 with a much larger screen, more memory, a built-in DVD-writer and a more powerful CPU. But it will be quite a bit larger and heavier. That in the end is the key question: is the portability of a netbook worth its tradeoffs? Sometimes yes: if one's computing needs are modest but one wants one's computer whereever you go, then portability is paramount. Sometimes no: those with more than modest computing needs will quickly run into the netbooks' limitations. But whether or not a netbook or a notebook is a better fit, it is nice to have the choice, for a reasonable price.

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How to buy a Computer
For years I have been asked for my advice about buying computers. My advice has changed over the years, because computers have changed, but one thing seems to be constant: a great many people seem to be very insecure about buying computers. This leads to a great deal of angst, and sometimes to purchases that are much more expensive than they need to be. But there are a few common-sense principles that are generally constant:

1. Think carefully about how the computer is going to be used.
This is the key principle that overrides all others. A computer is a tool. Tools are useful only when they can be used effectively. Do not choose a computer that does not fit with the way you use computers. For example, if you are a small person and like to work in many different places, a large and heavy laptop, or worse, a desktop, will not be a good choice: it is worth investing in something small, light and easily carried. If you are a gamer, particularly if you plan to invest a great deal of time playing games that require high-performance video, you'd best invest in a desktop with high performance graphics, even if it is expensive. Playing a demanding game on a cheaper machine with poor video performance will be frustrating. But if you merely browse the web and run productivity applications like spreadsheets and word processors, investing in high-performance gaming computing is a waste of your money.

2. If a better option is available for a lot more money, choose it only if you know you need it.
Insecurity about buying computers prompts people to pay a great deal more money for things that they think they might need: particularly a fast CPU (the computer's processing unit) or a high-end computer model instead of a lower-end one. The price difference can be significant: a high-end model can cost 3-4x the price of a lower-end model, and a high-end CPU can more than double the cost again. For example, the base configuration of the lowest-end home desktop with the lowest-end CPU on Dell Canada's web site is currently $329; the highest-end base configuration with the highest-end CPU is $3150. That is an order of magnitude difference in price. Put another way, the high-end configuration is the price of a formal dining-room suite. The low-end configuration is the price of a single chair in that dining-room suite. If you are paying the high-end price, make sure you need what you are paying for.

3. If a better option is available for only a little more money, chose it unless you know you don't need it.
If it only costs $20 to get a little more memory, a bit faster CPU, or a potentially useful device like a webcam, a fax modem, or a media card reader, why not get it, especially if it's much more money and less convenient to get it separately later? An integrated webcam is a $20 option on many laptops; adding later an external webcam of comparable quality that clips onto your laptop may cost you as much as $90. Or, for example, a fax modem may sound like obsolete technology, and it is, but it can be very convenient to send a fax from your computer by simply printing to the "fax" printer and typing a phone number. The one exception here is to watch out for large price increments for tiny increases in hard drive size: the price difference between a 250G and a 320G hard drive should be a on the order of $10, not $60-70. While one may argue that there is perhaps some value in paying a bit extra for the convenience of ensuring that your computer comes with a decently large hard disk, even a small hard disk these days is quite large. Another thing to consider: if the price difference between a notebook and a desktop is fairly small, and there is no compelling reason to choose a desktop over a notebook, just get a notebook.

4. Assess carefully your need for extended warranties.
Extended warranties can be expensive. However, if you are accident-prone (coffee over the keyboard, dropping your laptop), anxious or risk-adverse, an extended warranty may be worthwhile, particularly the sort that covers accidental damage. Note, though, that on average one spends much less over the lifetime of the computer to repair it (often $0) than one would pay for an extended warranty. Such warranties are often bought out of insecurity, and are highly profitable for computer vendors and technology stores. If, however, you do not expect to have free funds to handle an unexpected repair, especially if the computer is particularly expensive, an extended warranty may be worthwhile as a form of insurance.

5. Don't panic. Most of the available options are all reasonable choices.
Most computers are quite acceptable: there are few bad choices. Choosing a computer is most often a matter of choosing the best choice from among good choices. So relax: even if you miss the best choice, you'll probably end up with a perfectly good computer.

6. Don't forget backups.
The most valuable part of your computer is your data. Make sure you have backups of it, so that if something bad happens to your computer, you will not lose your data. You can always replace a computer. Can you replace your data? The easiest way to back up data is to buy an external hard disk and copy your data to it. Buy that external hard disk when you buy your computer. Yes, you can back up to writeable DVDs if you want, or copy to flash memory of some sort, but it can be a lot of work to divide up your data into DVD-sized chunks, and backups that are a lot of work often turn into backups that are not done.

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Why own a Desktop computer?
The thirty-year reign of the desktop computer may be coming to an end. According to various news reports, since about the mid 2000s, notebook (or laptop) computers have been outselling desktops. More surprisingly, perhaps, miniature notebook computers like the Asus EEE PC, with small screens and low-power CPUs that are no more powerful than mainstream CPUs of a half-decade ago are becoming increasingly popular, with a flurry of new low-cost (about $500) models. The reasons are intriguing: few productivity applications such as personal databases, spreadsheets, word processors and presentation tools need more than a small fraction of today's fastest CPUs. Thus the sort of CPU tradeoffs that need to be made to ensure long battery life in a notebook are less and less noticeable in practice. Other tradeoffs are also diminishing in importance: notebook screens can be large and bright, more and more rivalling desktop screens, notebook hard drives can be spacious and increasingly fast, and the rise of USB peripherals has made a portable notebook with a couple of USB ports as easily expandable in practice as any desktop computer. While notebooks are still pricier than desktops, the price difference is steadily diminishing as manufacturing economies of scale begin to weigh in. Even many who are in the habit of using their computer in one spot most of the time are realizing that an external screen, keyboard and mouse can be added to a notebook to make it function as if it were a desktop for general use, but when necessary, the notebook can be used elswhere, providing the convenience of having one's computer along (with all its data and software) when needed, without the fuss of copying data and worrying about different versions of applications. Moreover, notebooks have been improving in those areas where they offer abilities not found in desktops: battery life has steadily increased from the one to two hours common a few years ago to three or four hours. Lightweight notebooks are increasingly available, and not all of them are expensive. Most importantly, various forms of wireless networking are becoming ubiquitous, providing internet connectivity to notebooks without the need for wires. As such, it is no surprise that notebook computers are being widely purchased, and many peoples' first computer is now a notebook, not a desktop.

There are still some good reasons to buy desktops. The lowest-cost computers are still desktops, not notebooks. The very best CPU and graphics hardware is available only for desktops, and many modern games use as much of these resources as they can get. Hence desktops suit hardcore gamers much better than notebooks. Finally, Microsoft Windows Vista generally requires much more CPU and memory than most other operating systems, and the introduction of Vista has put some pressure on computing resources; because of this, some of the less powerful notebooks are now shipping with versions of Linux or with a previous version of Microsoft Windows, such as Windows XP. Nevertheless, it seems clear that given the increasing attractiveness of notebooks in comparison to desktops, a sensible way to approach buying a computer is to simply buy a notebook unless one has some concrete reason to need a desktop.

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Web shell scripting
It is a very handy thing to be able to write a quick script. UNIX and its derivitives have long been superb at making this possible: they possess a great many utilities that are designed to be used both from the command line and within scripts, and they possess shells that have all the control structures one might expect from any programming language. In fact, the traditional UNIX philosophy is to write small programs that do one thing well, and then combine them using scripts into rich and powerful applications. Indeed, the UNIX scripting environment is a rich one. But it is difficult to write shell scripts for the web. The unix scripting environment is designed for files, not web forms, the contents of which are encoded as url-encoded or multipart-encoded data. Hence, while unix shell scripts are sometimes used for web applications (cgi scripts), they are relatively rare, and generally frowned upon. The reason is no surprise: url-encoded and multipart-encoded data is complex to parse, and shell scripts that parse such data using sed, awk, etc. tend to be slow and hard to get right.

But this is easily fixed. If UNIX shell scripts like files, then they should be fed files. Hence I've written a small program (in C and lex), urldecode (ftp:/ftp.cs.toronto.edu/pub/jdd/urldecode) that parses url-encoded and multipart-encoded data, and converts the data into files. No complex file encoding is used. urldecode reads url-encoded or multipart-encoded data, creates a directory, then populates it with files such that each filename is a variable name, and the file contains the variable value. So all a web shell script needs to do to parse url-encoded data is to run urldecode on the data received from a web form, then read the results out of suitably named files. While this is hardly a replacement for PHP or .NET, it does provide a surprisingly simple and straightforward way to script for the web, because it allows all the handy UNIX utilities in the UNIX shell script environment to be leveraged to process web data. That's useful.

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CRT to LCD computer lab replacement: how much of a difference?
We are replacing all the remaining CRTs in our Computer Science teaching labs this summer with LCD panels, a total of 84 units (we replaced about fifty last summer). It's well known that LCD panels generally use less power when displaying than CRTs do, but the question is: roughly how much power/carbon emissions will we be saving through this summer's CRT replacement?

Using a Kill-A-Watt electricity consumption meter, we measured the power consumption of our CRTs (19" Dell P992) and our new LCD panels (19" Samsung 920BM and 22" Samsung 2253BW). When displaying an image, the CRTs draws between 85W and 110W of power, depending on how bright/white the image is. In comparison, the 19" LCD draws 35W of power, and the 22" draws 41W. If we assume an average CRT power draw (when displaying) of 97.5W (the mean), that's a power savings of 62.5W for the 19" LCDs, and 56.5W for the 22". We are replacing 48 CRTs with the 19", and 36 with the 22", for a total power savings of about five kilowatts.

What does this mean over time? If we assume the machines in our labs are displaying for an average of one hour out of eight (our labs are open to students on a seven-day twenty-four hour basis), and if we consider our projected equipment lifetime of four years, this implies about twenty-two thousand kilowatt-hours saved over this period. If we multiply this by a carbon intensity ratio estimate for grid electricity of 0.0453 kgC/kWh, this suggests a savings of about a metric tonne of carbon over the expected lifetime of these LCD panels.

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IT Support and human nature
IT is not about computers, but about people. This may be surprising: after all, when we think about technology, we generally think about equipment, gear, gadgets, code. But this gear doesn't exist for itself alone. Quite frankly, an unused computer is nothing more than a combination of space-heater and white noise generator. The I in IT is information, and that information is generated by, used by, and valued by people. For IT to be effective, it needs to be used effectively. Technology is a tool: powerful and complex, and like all powerful and complex tools, it takes time, effort and a certain amount of talent to learn to use the tool effectively. People are social beings, and so we learn to use tools in a social context: people who "know how" teach and help those who don't. This, broadly speaking, is the logic of IT support, which, ultimately, is a social construct to ensure that those who know how to use IT tools are available to help those who need help to effectively use them.

Human beings live in the tension between the collective and the individual. This is a fancy way of saying that people live by interacting with other people in ways that range from the genuinely interpersonal to impersonal embodiments of complex social constructions. Consider the difference between "I love you" on one extreme and "One Way, Do Not Enter" on the other. Both the collective and the interpersonal elements of human interaction are present in IT support: the nature of the technology imposes the need to interact with complex technical systems, while the nature of the human beings who use the technology requires one-on-one personal interaction. Indeed, IT support fails when it becomes too much like the notion of a "computer centre", too removed from the individual and the person-to-person act of helping and receiving help. But it also fails when it becomes too individualized, because of simple economics: there are many fewer IT experts than there are people in need of their help, and the one-to-one dynamic begins to fail when there are so few on one side of the equation and so many on the other. Effective IT support requires a balance between the two.

One way to maintain this balance, if there is a "critical mass" of IT needs and resources, is to make the commitment to do both at the same time. At the Department of Computer Science at the University of Toronto, we have found an effective way to do this for research computing support. We have a broad and diverse community of researchers, divided up into research groups. They have access to a core IT infrastructure of technical services, equipment and highly skilled staff to run it. But the department also has dedicated IT support staff who partner with specific groups: each group has their own person, their own IT expert, to call upon, and this person knows the people in the group and their research. We call such staff "points of contact", or POCs. Research IT support in the department is not a matter of contacting an anonymous service centre in one's moment of need, in the desperate hope of finding a sympathetic stranger with the requisite skills. Instead, it becomes an interaction between people who know each other, people who have been able to build a trust-relationship over time. Yet the economics of purely individualized support have been overcome: this organization "scales", because POCs do not need to do everything themselves. They and their groups have access to a complete infrastructure that offers common services across the entire department: secure and reliable file storage, web services, email, and more, and the expertise of the skilled technical staff that run it. POCs are freed to focus more fully on the unique, individualized needs of the research groups they serve.

Sounds idyllic, doesn't it? It is, in theory. In practice, there are plenty of challenges. Communication is key: POCs need to communicate well with their groups, and with other POCs and the core infrastructure staff. And the groups themselves need to be responsible for communicating with their POC: in human relationships, even those of IT support, there is both benefit and burden in knowing and understanding the other. A POC who is "shut out" of the research activities of the group is hampered in any effort to provide support that is well-tuned to those activites. That does not mean that poor support will result: even generic IT support, with a human face, can be superior to that offered by an anonymous service centre. But it does mean that the full benefit of having a POC will not be realized. But if a group and a POC fully commit to regular communication, the quality of IT support can be significantly greater than anything from a large service centre, because the POC who is offering that support has the potential to be a creative participant in the group's mission, the very mission that the group's use of IT is intended to serve.

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Blogging: Keeping It Simple
When I decided it was time to start blogging about information technology and information communication issues, I needed to choose some suitable blog software, something that would provide good results but also be easy to use. Open source is preferable. So I decided to do a quick web search and see what I could find. Most blog software seems to be pretty heavyweight: a database on the back-end to hold the blog entries, plus some sort of complex PHP web front end to display them. But this makes no sense to me: why use a database for blog entries? Blog entries are simple bits of text data that are organized in simple ways. There's no need for powerful query languages, transactional locking, and the various good things databases provide. These things are not free: databases have overhead to set up and run - I'm not worried so much about the computational resource overhead, but rather the human overhead: the time and energy required to configure, maintain, and back up databases. Do we really need such a thing for a blog?

Happily, I found blosxom, a piece of open-source blogging software that consists of a simple Perl CGI that uses a simple filesystem backend (a directory hierarchy) to hold all the blog entries. This is a nicely designed piece of software: simple, straightforward, low overhead, and very quick and easy to get going. It's also quite customizable. Clever simplifying details abound: for example, the date of the blog entry is simply the timestamp of the file, you create a new blog entry by simply creating a new file of the right name wherever you wish in the blog directory hierarchy, and writing something into it with your favourite text editor. You can organize your blog entries by topic if you want, and blosxom gets it all right. RSS seems all the rage these days: blosxom does that too: just add /index.rss to the end of the URL. For me, the only annoying bit of this software so far is the spelling of its name: I keep typing "bloxsom" for some reason.

Why is blosxom so good? Because it leverages what is already present on most systems: the filesystem, rather than introduce a complex, powerful and costly tool (a relational database) when it's not really needed. Kudos to Rael Dornfest, who, instead of taking the most popular or obvious approach, took the time to understand the problem being solved and the tools already available to solve it. This is an example of sensible economizing: human time and effort is a valuable commodity, the use of powerful tools (e.g. relational databases) uses up some of that commodity, and so such tools should be avoided unless they are really needed. If you think this sounds a little like "green" or "environmental" thinking, you're quite right: conserving energy to preserve the environment is very similar to conserving human energy to preserve the human environment. Just as the natural environment suffers strains from excessive energy consumption, so the human environment suffers from excessive demands on each person's time and energy. In both realms, economical thinking at design time is a prerequisite to good technology.

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