FireWire/1394

FireWire slots - sometimes called "1394" slots because they're based on a standard number IEEE 1394 - used to look like the wave of the future. With the emergence of USB 2.0, though, few manufacturers do much with FireWire: It runs about the same speed as USB 2.0, it's Plug and Play like USB, but it doesn't appear that FireWire holds many advantages over USB 2.0.

FireWire grew up around the camera/video industry, and that appears to be the extent of its support, although you'll find it in widespread use on Macs. You may find yourself someday with a digital video camera or digital camcorder that demands FireWire. If so, you can buy a FireWire-to-USB 2.0 converter box that should solve the problem.

Serial and parallel external interfaces

These two types of external interfaces are used mainly for printers, scanners, and external dial-up modems. Both of them are much older than the other types of external interfaces described previously, and they're becoming much less common - USB is simpler, faster, cheaper, and better. Parallel interfaces are 25-pin plugs, typically used to attach a printer to a PC. Serial interfaces are 9-pin plugs; you frequently see them used with external dial-up modems.

Almost all Windows computers have a parallel interface (good for one device), and most have one or two serial interfaces (good for one device each).