Interlisp logo -- 3/4 circle of overlapping windows with the word Medley in the center and below that the words Interlisp and Common Lisp

What is Medley Interlisp?

Interlisp is a software development environment, originating from Xerox PARC in the 1970s and 1980s. supporting software research in AI, computational linguistics, graphical user interfaces, hypertext, and other research areas. Software development in Interlisp-D is a different experience than is common, even today. The features of structure editing, source code management, code analysis and cross-referencing combined to support rapid incremental development. The 1992 ACM Software System Award was awarded to the Interlisp system for pioneering work in programming environments.

Interlisp evolved from an interactive terminal style programming tool to Interlisp-D – GUI and the entire operating system for the Xerox Lisp machines (called D-machines, named Dorado, Dolphin, Dandelion, Daybreak) with a common byte-code virtual machine. The virtual machine was then ported to C for Sun Unix and many other Unix systems, and the system was extended to support the Common Lisp standard as well.

Development of the system moved from Xerox PARC to a Xerox AI Systems division, to a spin-out company called Envos, to a smaller company called Venue. The system was called Interlisp, Interlisp-D, and various named releases (Koto, Lyric, Medley) until the name “Medley” was used for the whole thing. More background.

Project overview

March 18, 2023 we presented an overview of the project to the BALISP group (Bay Area Lisp).

What are we trying to accomplish?

We aim to revive Medley Interlisp to support not just a demo or test drive but actual use as a development and learning tool. To make the software usable, we need to overcome a number of compatibility problems with current systems and interfaces.

We also want to restore and present earlier versions of Interlisp, for the student of computer history. See Interlisp and Software Preservation Network for more.

What have we done so far?

There has been a lot of cleanup and adaptation to make it usable again in the modern world. Among other developments, you can now run Medley Interlisp on many OS and hardware configurations, or at in the cloud, using a web browser. See our 2021 Annual Report, Project News, and recent release notes . We’ve also been working on integration of the Interlisp style development with git and GitHub, Docker and other modern components.

Who is involved?

We are some of the original developers and users of the system 30 years ago, joined by newcomers interested in software history and preservation, along with members of the Lisp community. We work with organizational partners. And with you! See Get Involved for ways to get involved.


What have we lost? A presentation from the 2020 Remote Chaos Experience conference highlights some of the interesting aspects of Interlisp. The presentation synopsis states it this way:

We have ended up in a world where UNIX and Windows have taken over, and most people have never experienced anything else. Over the years, though, many other system designs have come and gone, and some of those systems have had neat ideas that were nevertheless not enough to achieve commercial success. We will take you on a tour of a variety of those systems, talking about what makes them special.