h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

If your PC is equipped with an Infra-red transceiver, that is also a light-emitting diode. The same type of LED that lives at the 'business end' of all of your TV remote controls.

When connecting LED's, the anode (+) is usually connected to the coloured wire and the cathode (-) to the black wire. Take care to connect them the correct way around, otherwise it won't work, or in exteme cases your light-emitting diode may briefly become a 'smoke-emitting diode', and eventually end up as a 'friode'

For the adventurous, interested in installing odd-colour light-emitting diodes in their PC's, the anode (+) terminal is the one with the longer leg (before you snip the legs to length, make sure you know which is which!)

Electricians know that electricity flows from positive (+) to negative (-), but Physicists know that electrons move from negative (-) to positive (+). The physicists are right, of course, but you try explaining that to an electrician..

Would it scare you to know there's an LED inside my PC (connected to my SCSI card)? Where will it end?

One of the boxes at the office has two seven-segment numeric LED's that display POST codes as the machine boots, and when it does BIOS'y things, which in Win98 seems to be virtually all the time, not so much in Win2k, and no activity at all in Linux (which doesn't muck about running BIOS code where it doesn't have to). There are also three other LED's which show the state of the PWRGOOD, RESET, and +5VStandby power.

Of these, the last is the most useful. Remember that most modern (ATX) PC's are ON all the time, as they are waiting for you to hit the power-switch at the front, or waiting for a power-on signal from the network, keyboard, or mouse (depending on how you have the BIOS set up). Having an LED inside the case to remind you about this is useful, as it prevents you from damaging the board by performing service on it with the power on, which is never a good idea. (Many a DIMM has been stuffed by people who don't remember this).

Having acquired some money recently (rather foolishly, considering one of the jobs I do), I'm looking at upgrading the PC I currently have, because I've exhausted it's CPU capacity. It's a dual 1GHz P3 at the moment, so I'm looking at a Dual Athlon-MP, or possibly a dual Xeon box. (Unlike most users, where disk space and graphics are the priority, my work is almost entirely CPU/memory bound, so I need atleast two CPU's and shedloads of high bandwidth memory). It seems you can now get fans with multicolour highbright LED's built in, and cases with neon lights.

It's also possible to build PC cases entirely out of acryllic. I'm drooling over this thing, athough it seems a rather costly item... http://www.redstore.com/fx/techinfo.php?itm_code=AKACAS004 but nice though.