The case that contains the electronic components of the computer is called the computer system unit. It is also referred to as the chassis, case or tower.
The computer system unit protects the processor, memory, cards, ports and connectors, many of which are housed on the motherboard. Most system units are made of steel or aluminum, though some are composed of plastic. Many system units are plain boxes, though some manufacturers insert color or other design features. The front of the system unit contains frequently accessed features, such as the power button, while the back of the system unit provides access to connections to power and peripheral devices.