ContrAlto: A Xerox Alto Emulator

In 1973, engineers and researchers at Xerox Palo Alto Research Center (PARC) created a new kind of computer. It was to act as the foundation of their future research.

They called it, Alto.

With the Alto, these talented researchers invented entirely new ways to use computers: Object-Oriented  programming, the Graphical User Interface, desktop publishing, laser-printing and Ethernet networking to name a few.


ContrAlto is an application for modern PCs that simulates the original Xerox Alto, from the graphical display to the Ethernet interface. It allows you to experience part of the world Xerox PARC created 40 years ago.


Installation and Documentation
The installation package (including documentation) for ContrAlto can be found here. At this time, ContrAlto is a Windows-only application and will run on Windows 7 or later.

Software that can be run on ContrAlto can be found at Bitsavers here.

The complete source code for ContrAlto can be found on the LCM+L's GitHub site here. Bugfixes and other contributions are welcomed!

If you believe you have found a new issue (or have a feature request) please send an e-mail to with a subject line starting with "ContrAlto Bug".

When you send a report, please be as specific and detailed as possible:
- What issue are you seeing?
- What Alto software are you running?
- What operating system are you running ContrAlto on?
- What are the exact steps needed to reproduce the issue?

The more detailed the bug report, the more possible it is to track down the cause.

Thanks and Acknowledgements

ContrAlto would not have been possible without the amazing preservation work of and the Computer History Museum.