A printed circuit board that plugs into a slot in a computer's motherboard and performs a particular function, such as converting and processing signals for communication with other devices.
A printed circuit board that plugs into a slot on the motherboard and enables a computer to control a peripheral device. Also called an "interface card," "adapter" or "controller," all the printed circuit boards that plug into a computer's bus are technically expansion cards, because they "expand" the computer's capability. PCI and PCI Express are common expansion cards in use today (see PCI and PCI Express).Cards Used to Be the NormIn earlier PCs, controllers for drives, input/output ports, display, network and sound all resided on separate plug-in cards. Subsequently, peripheral control was built into the chipset (see PC chipset); however, users still have options to install their own controllers. For example, in order to enhance video game performance, a faster graphics card can be plugged into an empty PCI or PCI Express slot, and the internal display circuit on the motherboard can be disabled. See motherboard and expansion port. See also bus extender.