Before we delve more deeply into the nuts and bolts of PC networking, we need to discuss how data is transmitted on the network. The way data travels on the network media (such as copper wire and glass fiber- optic cable) differs from how data flows between the different components in a computer.
First, let's define the bit. A bit is the smallest unit of data found on a computer; bits are represented by either a one (1) or a zero (0). When you type a letter or create a spreadsheet, you see your data as words in paragraphs or numbers in a column. Your computer sees this information as binary dataones and zeros.
On a computer, data in the form of a bit stream travels in parallel across wires arranged on the motherboard. These parallel wires on the motherboard are referred to as the data bus . When data is required by the computer's processor from the computer's hard drive, the data moves along the bus, which is very much like a multilane superhighway, allowing several bit streams to move simultaneously .
To actually move data from one computer to another on the network, there obviously needs to be some kind of network medium; copper wire is actually the most often used network medium (the topic of network media is discussed in Chapter 4, in the section "Choosing a Network Connectivity Strategy"). Unfortunately, no matter what type of network medium you choose, the data can only travel along it as a single bit stream, which is referred to as a serial transmission .
A device is needed to take the parallel data from the computer, which is like a multilane super highway , and condense it into a serial transmission, which is the equivalent of a one-lane road. This device also provides the connection between the PC and the network media.
The device I'm talking about here is a network interface card , or NIC . The NIC contains a transceiver (a transmitter and receiver) that is able to convert data from parallel to serial, and vice versa. A NIC can come in the form of a separate card that you install in the computer (there are a large number of different NIC manufacturers). The NIC must be compatible with the bus slot that you wish to install it in. Some personal computers, such as the Apple iMac, come with a built-in NIC that's ready to go. Figure 1.3 shows two different kinds of NICs.
Figure 1.3. Network interface cards provide the physical connection between a computer and the network.
So it's the NIC that supplies the physical connection between a computer (client or server) and the network media, and it's the network card that supplies the translation of data from parallel to serial. As you can see, the NIC is a very important component of networking PCs. The network interface card is discussed in Chapter 3, "Networking Hardware," in the section "Working with Network Interface Cards."