In 1973, Xerox PARC developed the Alto personal computer. It had a bitmapped screen, and was the first computer to demonstrate the desktop metaphor and graphical user interface (GUI). It was not a commercial product, but several thousand units were built and were heavily used at PARC, as well as other XEROX offices, and at several universities for many years. The Alto greatly influenced the design of personal computers during the late 1970s and early 1980s, notably the Three Rivers PERQ, the Apple Lisa and Macintosh, and the first Sun workstations.