The case (or chassis) of a computer is the metallic box which houses the various internal components. Cases also have other uses, such as blocking noise produced by the computer, and protection from electromagnetic radiation. There are norms for guaranteeing such protection in a manner compliant with existing regulation.
The main considerations when choosing a case are its form factor, its dimensions, how many drive slots it has, its power requirements, the connectors it has on the side, and finally its design and color. Although the cases that housed the first PCs all looked alike, today cases come in all shapes; some are even transparent, so that users can "soup up" their computers, such as by installing neon lights inside (this is called "case modding.")
Most cases come with a power supply. The power supply provides electrical current to all of the computer's components. In the United States and Canada, power supplies deliver 110V current at 60 Hz, while in Europe the standard is 220V at a frequency of 50 Hz, which is why most computer power supplies have a switch so that you can choose the voltage.
It is essential to make sure that the switch is in the correct position for the right voltage, so that there is no risk that the CPU components will deteriorate.
The power supply must have enough power to provide electricity to all of the computer's devices.
Close attention should also be paid to the amount of sound that the power supply makes.
Form factor refers to the format of the motherboard slot, the kinds of connectors used, and how they are laid out. It determines which type of motherboard can be inserted in the case.
The case's size affects how many slots are available for disk drives, as well as how many slots there are for internal hard drives. Cases are generally grouped by size as follows:
- Big tower: This is a large case (60 to 70 cm high), with four to six 5"1/4 slots and two to three slots each 3"1/2 on the side, as well as two to three internal 3"1/2 slots.
- Medium tower: This is a medium-sized case (40 to 50 cm high), with three to four 5"1/4 slots on the side and two internal 3"1/2 slots.
- Mini-tower: This is a small case (35 to 40 cm in height), typically with three 5"1/4 slots and two 3"1/2 slots on the side, as well as two internal 3"1/2 slots
- Barebone or mini-PC: This is the smallest kind of case (10 to 20 cm high). Most barebone PCs are pre-assembled computers built with a small form factor (SFF) motherboard. They generally have one or two 5"1/4 slots and one 3"1/2 slot on the side, as well as one internal 3"1/2 slot.
A case houses all of the computer's internal electronic components. Sometimes, a computer's electronics can reach very high temperatures. For this reason, you must choose a case with good ventilation, meaning that it has as many fans as possible, as well as air vents. It is recommended to choose a case which includes at least an air intake in front, a removable air filter, and an air outlet in the rear.
For obvious reasons involving ease of use, more and more cases are including a panel of connectors on the side. In order to work, these connectors must be hooked up internally to the motherboard.