The first Altos were built as research prototypes. By the fall of 1976 PARC's research was far enough along that a Xerox product group started to design products based on their prototypes. Ultimately, ~1,500 were built and deployed throughout the Xerox Corporation, as well as at universities and other sites. The Alto was never sold as a product but its legacy served as inspiration for the future.
With the permission of the Palo Alto Research Center, the Computer History Museum is pleased to make available, for non-commercial use only, snapshots of Alto source code, executables, documentation, font files, and other files from 1975 to 1987. The files are organized by the original server on which they resided at PARC that correspond to files that were restored from archive tapes. An interesting look at retro-future.