Xerox AltoXerox Alto: The first "personal computer" that was developed at Xerox PARC in 1973. The Alto was first conceptualized in 1972 in an all points memo written by Butler Lampson. Technically, the Alto was a small minicomputer, but it was a personal computer in the sense of being easier to use than the mainframess and minicomputers of the era and also was the first computer to use the desktop metaphor and graphical user interface (GUI). The Alto had a two-button mouse (see computer mouse) and an optional chord keyset, a device used with SRI's On-Line System that never became popular. The Xerox Alto, like virtually all PARC products, was a commercial failure.
The Xerox Alto was used to design the next influential Xerox PARC computer, the 8010, which was also known as the Xerox Star workstation. The Star would go on to influence both the Apple Lisa and the Apple Macintosh and help popularize the graphical user interface on later personal computers.
Such is the rarity of these computers today, that they are considered to be highly valuable collector items.
See also: Alan Kay