Tower cases are usually designed to sit
vertically on the floor beneath a desk. Some users in the past
resorted to standing the desktop cases on their sides under the desk
to provide more usable workspace on the desktop. This has prompted
computer makers today to develop cases that would naturally fit under
the desk. In general, tower cases typically have enough bays to hold
floppy drives, CD-ROM drives, tape drives, DVD drives as well as just
about anything else that might be installed. The internal design of a
tower system resembles that of the desktop unit.Tower cases come in
three sizes:
- Mid towers
- Mini towers
- Full-size towers

Mini-towers and mid-towers are shorter and less expensive than
their full-size counterparts. There is one major drawback to
choosing the smaller towers. There is little additional space for
internal add-ons or disk drives, particularly if the mini-tower is
chosen.
Many easy-access schemes have been built in to allow quick or
convenient access to the inside of the system case. Some towers,
for example, use removable trays that allow the motherboard and
I/O cards to be plugged in before being slid into the unit. Other
tower cases use hinged doors on the side of the case, allowing the
system and I/O boards to swing away from the chassis. Either of
these features will facilitate the process of assembling the
computer.
It is important to note that the ventilation
characteristics of some tower units tend to be poor. The cause of
this is that the I/O cards are mounted horizontally. When the heat
generated by the boards rises, it passes the upper boards, which
are then subjected to additional heat. Thus, most tower cases
include a secondary case fan to help increase the airflow and
dissipate any excessive heat.