You need an inexpensive device called a router. This is basically a box that goes between your DSL or cable modem and all of your Internet devices (computers, HDTV, and so on). The router shares the Internet signal between the multiple devices.
Here’s how it works:
Every device on the Internet needs a unique IP address. Your ISP provides you with one, allowing one device to access the Internet. A router will access the Internet through that IP address, then provide local IP addresses–not visible on the Internet–for the PCs and other devices connected to it. This allows you to access the Internet from multiple computers through one connection.
That arrangement has another advantage. Because your computer’s local IP address isn’t visible to the Internet, it’s not visible to criminals, either, giving you another layer of defense.
A typical router
One thing about a wireless connection: It has to be secure. See Do I Have a Freeloader on my WiFi? for more on this.
Routers not only share the Internet connection; they also put your computers onto a local network, so you can share files and printers between them.
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Contributing Editor Lincoln Spector writes about technology and cinema. Email your tech questions to him at answer@pcworld.com, or post them to a community of helpful folks on the PCW Answer Line forum. Follow Lincoln on Twitter, or subscribe to the Answer Line newsletter, e-mailed weekly.