The main body of a computer is typically referred to as the system unit. The system unit encapsulates the essential components that allow a computer to function, such as the motherboard, CPU, RAM, and storage drives. This enclosure not only houses the internal components but also serves as a protection mechanism against dust and physical damage.
While the terms "case" and "chassis" can sometimes be used interchangeably with "system unit," they often refer specifically to the physical structure or frame within which the components are mounted, rather than the entire assembly containing all of the operational parts. The monitor, on the other hand, is an external display device and not part of the main body of the computer, which further distinguishes the system unit as the correct designation for the core component housing the critical hardware necessary for computer operation.