|  | 1.1 | The Basics of Computer Hardware
| 1.1.3 | The relationship of NICs to PCs

As shown in the figure, a network interface card (NIC) is a printed circuit board that provides network communication capabilities to and from a personal computer. Also called a LAN adapter, it plugs into a motherboard and provides a port for connecting to the network. This card can be designed as an Ethernet card, a Token Ring card, or a Fiber Distributed Data Interface (FDDI) card.

A network card communicates with the network through a serial connection, and with the computer through a parallel connection. Each card requires an IRQ, an I/O address, and an upper memory address to work with DOS or Windows 95/98. An IRQ, or interrupt request line, is a signal informing a CPU that an event that needs its attention has occurred. An IRQ is sent over a hardware line to the microprocessor. An example of an interrupt being issued would be when a key is pressed on a keyboard; the CPU must move the character from the keyboard to RAM. An I/O address is a location in memory used to enter data or retrieve data from a computer by an auxiliary device. In DOS-based systems, upper memory refers to the memory area between the first 640 kilobytes (K) and 1 megabyte (M) of RAM.

When you select a network card, consider the following three factors:

1. type of network (for example, Ethernet, Token Ring, or FDDI)
2. type of media (for example, twisted-pair, coaxial, or fiber-optic cable)
3. type of system bus (for example, PCI or ISA)