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Xerox PARC in 1973, was the first personal computer and the first computer to use the desktop metaphor and graphical user interface (GUI).
The Alto was first conceptualized in 1972 in an all points memo written by Butler Lampson. It had 128 (expandable to 512) Kbytes of main memory and a hard disk drive with a removable 2.5 Mbyte cartridge, all housed in a cabinet about as big as a small refrigerator. The Alto's CPU was essentially the same as the one used by the Data General Nova. This decision probably further cemented the 8-bit byte as a de-facto standard of computer memory measurement, as the Nova also used 8-bit bytes.
Apart from an Ethernet connection, the Alto's only common output device was a bi-level (black and white) CRT display, mounted in the "wrong" orientation (longest side vertical, portrait orientation). Its input devices were a custom keyboard, a three-button mouse, and an optional 5-key chord keyset. The last two items were borrowed from SRI's On-Line System; while the mouse was an instant success among Alto users, the chord keyset never became popular.
All Alto mice had three buttons. The earliest were mechanical and used two wheels perpendicular to each other. These were soon replaced with ball-type mice. Later, optical mice were introduced, first using white light and then using IR. The buttons on the early mice were narrow bars arranged top to bottom rather than side to side.
A number of other I/O devices were available for the Alto, including a TV camera, the Hy-Type daisywheel printer and a parallel port, although these were quite rare. The Alto could also control external disk drives to act as a file server. This was a common application for the machine.
Early software for the Alto was written in the BCPL programming language, and later in the Mesa programming language, which was not widely used outside PARC but influenced several later languages, such as Modula. The Alto keyboard was lacking the underscore key, which had been appropriated for the left-arrow character used in Mesa for the assignment operator. This feature of the Alto keyboard may have been the source for the CamelCase style for compound identifiers. Another feature of the Alto was that it was microcode-programmable by the user.
The Alto helped popularize the use of raster graphics model for all output, including text and graphics. It also introduced the concept of the bit block transfer operation, or BitBLT, as the fundamental programming interface to the display. In spite of its small memory size, quite a number of innovative programs were written for the Alto, including several WYSIWYG editors (for text documents, bitmaps, printed circuit boards, integrated circuits, etc.), and one of the first network-based multi-person computer games.
Technically, the Alto was a small minicomputer, but it was a personal computer in the sense of being easier to use than the mainframes and minicomputers of the era. It was never a commercial product, although several thousand were built. Universities, including MIT, Stanford, CMU, and the University of Rochester received donations of Altos including IFS file servers and Dover laser printers. These machines were the inspiration for the original Stanford University Network (SUN) workstation, which was eventually marketed by a spinoff company, Sun Microsystems.
The Xerox Alto was used to design the next influential Dolphin, Dorado and Dandelion. A network router called Dicentra was also based on this design. The original architecture for these machines, based on the AMD 2900 bitslice microprocessor technology, was developed by Butler Lampson and was presented as a paper design called Wildflower.
Xerox created a product division (SDD) to comercialize the work of PARC, initially attempting to use the Dolphin as the basis for a workstation product. The Dandelion design became the Xerox 8010, which ran the Xerox Star workstation software. The Star inspired Apple's Lisa and Macintosh personal computers, and helped popularize the graphical user interface on later PCs and workstations.
These Xerox machines, and especially the Alto, are now very rare and highly valuable collector items.
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