Computer tower

In personal computing, a tower unit, or simply a tower, is a form factor of desktop computer case whose height is much greater than its width, thus having the appearance of an upstanding tower block, as opposed to a traditional "pizza box" computer case whose width is greater than its height and appears lying flat.

Compared to a pizza box case, the tower tends to be larger and offers more potential for internal volume for the same desk area occupied, and therefore allows more hardware installation and theoretically better airflow for cooling. Multiple size subclasses of the tower form factor have been established to differentiate their varying heights, including full-tower, mid-tower, midi-tower and mini-tower; these classifications are however nebulously defined and inconsistently applied by different manufacturers.

Although the traditional layout for a tower system is to have the case placed on top of the desk alongside the monitor and other peripherals, a far more common configuration is to place the case on the floor below the desk or in an under-desk compartment, in order to free up desktop space for other items.^[1] Computer systems housed in the horizontal "pizza box" form factor — once popularized by the IBM PC in the 1980s but fallen out of mass use since the late 1990s — have been given the term desktops to contrast them with the often underdesk-situated towers.