A printed circuit board that you can insert into a computer to give it added capabilities. For example, all of the following are expansion boards:
Expansion boards for PCs can be half-size (also half-length) or full-size (also full-length). Most PCs have slots for each type of board. A half-size board is sometimes called an 8-bit board because it can transmit only 8 bits at a time. A full-size board is called a 16-bit board. In addition, some expansion boards are designed to operate with a local bus, such as PCI.
Expansion boards are also called adapters, cards , add-ins , and add-ons.