The [b]central processing unit[/b], the "brains" of a [[computer]].

In Danbooru, it actually refers to the case that houses the actual CPU chip, the motherboard on which it is mounted, other components soldered to the motherboard in order for the computer to function, its power supply, and various input/output ports into which peripherals (such as a [[computer keyboard]], [[computer mouse]], display [[monitor|]], and/or [[printer]]) are connected . Most of the time, these cases are referred to as part of a desktop personal computer, are rectangular, and are either vertical or horizontal.