Network Interface Cards (NICs)

Network interface cards is a computer hardware component that connects a computer to a computer network. To connect to a network, a PC must have a NIC. NICs can be built into the motherboard of the computer; can be connected through a USB, PC Card, CompactFlash or FireWire port; or can be an internal adaptor card that is installed into one of the computer's expansion slots. NICs are available that can connect to either wired or wireless networks.

Every Ethernet network controller has a unique 48-bit serial number called a MAC address, which is stored in read-only memory. Every computer on an Ethernet network must have at least one controller. No two NICs will share the same address. Because NIC vendors purchase blocks of address from  Institute of Electrical and Electronics Engineers (IEEE) and assign a unique address to each NIC at the time of manufacture.

The NIC allows computers to communicate over a computer network. It is both an OSI layer 1 (physical layer) and layer 2 (data link layer) device, as it provides physical access to a networking medium and provides a low-level addressing system through the use of MAC addresses. It allows users to connect to each other either by using cables or wirelessly.