An output device allows a computer to communicate with you. A monitor printer and speakers are output devices These devices display information on a screen create printer copies and generate sound.

An expansion card allows you to add new features to a computer. For example, an expansion card can add high- speed ports to your computer so you can connect high-speed devices such as a digital camcorder or an MP3 jukebox.

A desktop case usually sits on a desk, under a monitor. Desktop cases were once very popular but are no longer widely available.

A tower case can sit on a desk next to a monitor or sit on the floor. Placing a tower case on floor provides more desk space, but can be less convenient for inserting and removing items such as CD5 and DVDs. Tower cases come in different sizes.