What Is the Function of a Network Interface Card?

By John Papiewski

A network interface card plugs into a computer's motherboard.
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A network interface card connects your computer to a local data network or the Internet. The card translates computer data into electrical signals it sends through the network; the signals are compatible with the network so computers can reliably exchange information. Because of the popularity of the Internet and networks in general, virtually all desktop and notebook PCs have some form of interface card included. You can add a network card to bare-bones computers which don't have one.


A standard PC network adapter is a plastic circuit board about the size of a playing card. It has several computer chips that process signals from the network and the PC. The card slides into the PC's chassis and mates firmly with a connector on the motherboard. A steel bracket holds the card in place. The bracket may have a network cable jack or an antenna, depending on the type of network to which the computer connects. The bracket also has light-emitting diodes that indicate network status and activity.


A network card functions as a middleman between your computer and the data network. For example, when you log in to a website, the PC passes the site information to the network card, which converts the address into electrical impulses. Network cables carry these impulses to a Web server somewhere on the Internet, which responds by sending a Web page back to you, once again in the form of electronic signals. The card receives these signals and turns them into data that your PC displays.


In addition to the network card's hardware, it needs programming to make it work. When you install the card, Microsoft Windows loads software drivers for your card's make and model. Your browser, email and other programs communicate through Windows to reach the network; Windows, in turn, passes data to the drivers that are programmed specifically for your network interface card. The card cannot function without the right driver software.


Most contemporary network cards work with Wi-Fi wireless networks; these cards have an antenna to send data signals via radio waves. Some networks still use wired Ethernet connections; these cables have a rectangular plug which mates with a jack on the network card's bracket. In many new computers, network adapter cards are actually custom computer chips built into the PC's motherboard. Because of the nearly universal use of the Internet, almost all computers include a network capability. Having the chips on the motherboard frees up a card slot for other devices you may want to add later. Computer retailers sell network accessory cards if you want to install one in a PC. For desktop computers, these are standard PCI cards; notebook computers use smaller PC accessory cards that slide into a slot on the computer's side.