A computer case (also known as a computer chassis, cabinet, box, tower, enclosure, housing, '"system unit'" or simply case) is the enclosure that contains most of the components of a computer (usually excluding the display, keyboard and mouse). A computer case is sometimes incorrectly referred to metonymously as a CPU or hard drive referring to components housed within the case. CPU was a more common term in the earlier days of home computers, when peripherals other than the motherboard were usually housed in their own separate cases.