There are lots of external devices that you can connect to your computer. All external devices connect to the computer’s system unit via cables and ports (where a “port” is the slot into which you plug a cable). Unless you’re using a portable computer, you probably have several external devices attached to your computer already, including a mouse, keyboard, monitor, microphone, and speakers, as in Figure 1.

Whatever external devices you have, they’re all connected to the system unit (where the actual “computing” takes place) via cables. Each cable plugs into a specific port on the system unit. The ports are usually on the back of the system unit. But they can be on front or side as well.

Everything has a name, even (believe it or not) those little plugs on the back of your computer. Figure 2 shows examples of some ports. But your computer’s ports won’t necessarily be the same.