A desktop computer is a personal computer designed for regular use at a single location on or near a desk or table due to its size and power requirements. The most common configuration has a case that houses the power supply, motherboard (a printed circuit board with a microprocessor as the central processing unit, memory, bus, and other electronic component's), disk storage (usually one or more hard disk drives, optical disc drives, and in early models floppy disk drives); a keyboard and mouse for input; and computer monitor and printer for output. The case may be oriented horizontally and placed atop a desk or vertically and placed underneath or beside a desk.