The Main Case
The System Unit The "system unit" is the name given to the main PC box that houses the various elements that go together to make up the PC. For instance within the system unit is the computer system's motherboard, which contains all the main components, such as the CPU. The system unit also houses items such as the hard disk, the memory stick and CD-ROM drives etc. System units come in two basic varieties, the tower version, as illustrated, or a desktop version which is like a tower case on its side and the computer can be placed on top of it.
RAM (Memory)
CPU