A daughtercard, also known as a daughterboard, is a circuit board that serves as an extension to another circuit board, such as a motherboard or sound card. In particular, daughterboards often have plugs, sockets, pins, connectors, or other attachments for other boards, which is what differentiates them from standard expansion boards such as for PCI or ISA, which are usually called expansion cards. It can access resources such as memory and the central processing unit on the main board, and let people install expansion cards in their computers so that these expansion cards are in an upright position and save space. Daughterboards are also sometimes used to expand the basic functionality of an electronic device. Rather than redesign the first model completely, a daughterboard may be added to a special port or connector on the motherboard or mainboard.