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Interlisp Online

Interlisp Online provides access to a version of Medley running in the cloud. You can login as a guest, but if you want to save state from one session to the next, you should create an acccount. All that is needed is an email address and password. Once an account has been created you can log in and start a Medley Interlisp session.

Sessions are preserved for an indefinite time (we haven’t worked out for how long – after 30 days of inactivity?). But it should be good for experimenting and introducing yourself to the environment. Anything you create in the online environment should be treated as transient. If you’re interested in developing and experimenting with Lisp programs then you will want to investigate other options. But, for a first foray, this is a good starting place. The Interlisp/online repository may have more details.

1 - Using Interlisp Online

A Brief Introduction

Running Interlisp Online

  • Go to Interlisp Online
    You may either login as a Guest or create an account. If you plan to save and later retrieve files, you should Register and create an account. Guest logins are not guaranteed to perserve sessions and stored files.

However, if you just want to get a taste of Interlisp without the extra effort of creating an account, the guest login will suit your needs.

  • Select the Exec you want to run. For this exercise, select Interlisp
  • Leave the Fill browser window option set.

Select Run Medley. Your browser will open a window that represents the Interlisp Desktop and looks much like this:


The Interlisp Desktop at startup contains 4 windows of interest:

  • Prompt Window: The black window at the top of the screen. It is used to display system or application prompts
  • Exec (INTERLISP) window: The main window where you run functions and develop programs.
  • Medley logo window: A window containing the Interlisp Medley logo as a bit map.
  • Status Bar window

Writing Interlisp programs

In the Exec window, type the following:

(PLUS 1 1)

When you complete typing the ending ) the Interlisp interpreter will perform the calculation and return the result.

One thing you probably noticed, the command PLUS is capitalized. It’s not that the developers of Interlisp were always shouting at each other. Rather, when Interlisp was developed computer programming was in its infancy and standards for naming commands were still evolving.

Save your program as a file

Opening a saved program

What next?