A typical personal computer assemblage consists of a central processing unit (CPU), which contains the computer’s arithmetic, logic, and control circuitry on an integrated circuit; two types of computer memory, main memory, such as digital random-access memory (RAM), and auxiliary memory, such as magnetic hard disks and special optical compact discs, or read-only memory (ROM) discs (CD-ROMs and DVD-ROMs); and various peripheral devices, including a display screen, keyboard and mouse, and printer.