If you're using an older computer, it's possible that the computer does not have a built-in network interface. In that case, you must add one before you can connect it to your network. Fortunately, network interface adapters are inexpensive and easy to install.
As a minimum, look for an Ethernet adapter that can handle both 10Base-T and 100Base-T networks. If you plan to connect the computer to a Gigabit Ethernet network, you'll need a faster and more expensive adapter.
Like other computer components, Ethernet adapters are available both as inexpensive no-name products and slightly more costly brand-name versions that come with better documentation and a manufacturer's warranty. As always, you get what you pay for; considering that you can generally find a brand-name adapter for just a few dollars (or euros or pounds) more, it's usually the better choice.
Internal network adapters are printed circuit cards that fit into one of the expansion slots on your computer's motherboard, like the one shown in Figure 7-3. Unless you're working with a very old computer, the adapter should be a PCI card; that's probably the only kind you will find at your local computer or office supply store. The PCI sockets on the motherboard are almost always white.
Photo courtesy of D-Link
If your computer was made before the mid-1990s, you might need an ISA card instead. ISA sockets on motherboards are usually black. ISA Ethernet adapters are still available, but you'll probably have to go to a specialist source. A Web search for ISA Ethernet card will produce pointers to many choices, but be sure to order a "10/100" or "fast Ethernet" card rather than an older design that works at only 10 Mbps.
To install an internal Ethernet adapter, follow these steps:
Turn off the computer and unplug the power cable.
Remove the cover from the computer's case.
Find an empty expansion slot on the motherboard.
Remove the metal bracket attached to the computer's frame directly behind the empty slot. Save the screw; you'll need it to secure the adapter card.
Line up the bottom of the adapter card with the slots in the expansion socket and push it into place.
Use the screw you saved from the old bracket to secure the adapter card.
While the computer case is off, clean out the accumulated dust and make sure none of the connectors attached to the motherboard and the drives have come loose.
Replace the cover and plug in the power cable.
Plug a network cable into the new Ethernet jack in the back of the computer.
Turn on the computer. If the operating system does not automatically detect the new network connection, load the driver software.
A computer that has built-in USB ports but no Ethernet ports can use an external USB network interface as an alternative to an internal expansion card, but the data transfer speed might not be as fast. USB adapters are widely available, but very few computers need them: By the time USB ports became common features on computers, onboard Ethernet ports were also standard equipment.
An old laptop without a built-in Ethernet port must use a network adapter on a plug-in PC card that fits into the PCMCIA socket on the side of the computer. Figure 7-4 shows a network adapter on a PC card.
Note
A new standard for 32-bit PC cards and services called CardBus was adopted in 1995. CardBus PC cards (with a gold grounding strip next to the 68-hole connector) don't fit older 16-bit PC card sockets, but 16-bit cards will fit into 32-bit sockets. If your laptop was made before 1997, look for a 16-bit 10/100 Mbps PC card adapter.
Very old laptops that don't have PC card sockets can connect to an Ethernet network through a serial-to-Ethernet adapter, but it's probably not worth the effort. Any laptop without a PC card socket is at least a dozen years old, and it won't come close to the performance of today's least expensive models. Considering that a serial-to-Ethernet adapter is likely to cost almost as much as a whole new computer, it's time to replace your "Old Faithful" antique instead.
Figure 7-4. This 16-bit PC card network adapter uses a short cable (sometimes called a dongle) to connect the adapter to an Ethernet socket.
Windows XP, Windows Vista, Mac OS X, and most current versions of Linux and Unix can automatically detect new network adapters. In some cases, you might have to restart the computer after installing the network adapter, but in general, the operating system will load the device driver software right away.
Note
In some less user-friendly Unix or Linux distributions, it might be necessary to compile the kernel to support a specific network driver and load the module at runtime, but this is not common.
However, if you're working with an older operating system or a network interface that the operating system can't recognize, you'll have to find and install the correct device driver. A device driver is a small program that converts between the generic output signals supplied by the computer's central processor and the specific instructions that control the features and functions of a device connected to the computer. It also converts incoming commands and data from the peripheral device to a format that the central processor can recognize.
New network adapters usually come with a software disc that contains the device driver and other related programs and documentation. If yours is missing, or if the disc doesn't contain the right driver for your operating system, you can probably find a driver program on the adapter manufacturer's website or through an online source of open source device drivers.
Several websites offer direct links to hundreds of sources for device drivers: