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The Medley Interlisp Project
@interlisp.org
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Official account of the open source project to preserve, revive, and modernize Medley Interlisp. This extensible graphical operating and programming environment has roots in Xerox's Palo Alto Research Center (PARC).

https://interlisp.org
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interlisp.org
In the 1980s Interlisp-D came with a read-only remote desktop client for monitoring networked Lisp workstations, like in the screenshot. Medley Interlisp still includes the code which doesn't currently work.

files.interlisp.org/medley/lispu...

#interlisp #RemoteDesktop #retrocomputing
Screenshot of the black and white desktop of a 1980s graphical workstation environment. The desktop has a gray background pattern and some windows with a white background and a title bar with white text on a black background. The screen shows a scaled down version of the entire remote screen of an Interlisp-D workstation, and a small section at full size which can be moved around.
November 26, 2025 at 11:24 AM
interlisp.org
Interlisp source files embed control codes to style the code viewed in the Medley environment, which displays the proper fonts and text attributes. To view the formatted code on modern systems run the "lsee" shell script from a terminal.

github.com/Interlisp/me...

#interlisp #lisp #linux
Screenshot of a Linux terminal window that displays a portion of an Interlisp source file. The code is formatted with syntax highlighting and text colored in white, red, green, and yellow.
November 20, 2025 at 9:03 AM
interlisp.org
To scroll a window on Medley Interlisp hover the mouse pointer slightly beyond the left or bottom edge to bring up a scroll bar, then left-click or right-click. Middle-clicking positions the thumb within the bar.

#interlisp #gui #retrocomputing
Screenshot of a portion of the black and white desktop of a 1980s graphical workstation environment. The desktop has a gray background pattern and one window with a white background and a title bar with white text on a black background. The window is a file browser with a main pane listing some files, status and input panes, and a command menu. The file list has a vertical scroll bar at the left edge. Screenshot of a portion of the black and white desktop of a 1980s graphical workstation environment. The desktop has a gray background pattern and one window with a white background and a title bar with white text on a black background. The window is a file browser with a main pane listing some files, status and input panes, and a command menu. The file list has a horizontal scroll bar at the bottom edge.
October 28, 2025 at 11:20 AM
interlisp.org
Some 1980s Xerox Lisp Machines came with an IBM PC/XT card that allowed running MS-DOS from the Interlisp-D environment, like the spreadsheet program window here. Image from a flyer of the Xerox 1186 AI workstation.

groups.google.com/g/lispcore/c...

#interlisp #msdos #LispMachine #retrocomputing
Screenshot of the black and white desktop of a 1980s graphical workstation environment. The desktop has a gray background pattern and several windows with a white background and a title bar with white text on a black background. The windows display Lisp source code, icons, scientific and business charts, a spreadsheet program, a virtual keyboard, and other graphical elements.
October 19, 2025 at 9:30 AM
interlisp.org
To interactively edit a graph on Medley evaluate at an Interlisp REPL:

(SHOWGRAPH NIL NIL NIL NIL NIL T)

Right-click inside the window for a command menu, click STOP to exit. Right-click on the title bar and click Shape to resize the window.

Try here: online.interlisp.org/guest

#interlisp #lisp
Screenshot of a portion of the black and white desktop of a 1980s graphical workstation environment. The desktop has a gray background pattern and one window with a white background and a title bar with white text on a black background. The window is a graph editor with an open command menu providing the options Move Node, Add Node, Delete Node, Add Link, Delete Link, Change label, label smaller, label larger, Directed, Sides, Border, Shade, STOP. The window also shows a graph consisting of 2 nodes connected by a link.
October 16, 2025 at 9:37 AM
interlisp.org
In NoteCards a "tabletop card" is an arrangement of cards (hypertext nodes) on the screen, such as the 3 cards at the center.

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#NoteCards #interlisp #hypertext #retrocomputing
Screenshot of the black and white desktop of a 1980s graphical workstation environment. The desktop has a gray background pattern and several windows with a white background and a title bar with white text on a black background. The windows display graph structures with nodes and links and other tools of a hypertext system.
October 4, 2025 at 9:18 AM
interlisp.org
A NoteCards "browser" is a type of card that shows a hypertext network as a graph structure, i.e. a graph view like in this example. The thumbnail at the top left corner lets you pan and scroll the graph.

#NoteCards #Interlisp #hypertext #retrocomputing
Screenshot of the black and white desktop of a 1980s graphical workstation environment. The desktop has a gray background pattern and several windows with a white background and a title bar with white text on a black background. The windows display a graph structure with nodes and links and other tools of a hypertext system.
September 26, 2025 at 9:09 AM
interlisp.org
CLISP (Conversational LISP) is the Algol-like infix notation of Interlisp. The 1978 Interlisp Reference Manual (page 554) explains the design goals of the notation and how it integrates with the prefix syntax of Lisp.

www.softwarepreservation.org/projects/LIS...

#interlisp #lisp #retrocomputing
A screenshot of a portion of the reference manual of the Interlisp programming language. The portion contains the following paragraph of text (emphasis is in the original): There have been similar efforts in other LISP systems, most notably the MLISP language at Stanford. CLISP differs from these in that it does not attempt to _replace_ the LISP syntax so much as to _augment_ it. In fact, one of the principal criteria in the design of CLISP was that users be able to freely intermix LISP and CLISP without having to identify which is which. Users can write programs, or type in expressions for evaluation, in LISP, CLISP, or a mixture of both. In this way, users do not have to learn a whole new language and syntax in order to be able to use selected facilities of CLISP when and where they find them useful.
September 18, 2025 at 9:15 AM
interlisp.org
What is the origin of "inter" in Interlisp? From Introduction on page 1.1 (page 19 of the PDF) of the 1978 edition of the Interlisp Reference Manual:

"Interlisp has been designed to be a good on-line _inter_active system (from which it derives its name)."

#interlisp #lisp #retrocomputing
A screenshot of a portion of the reference manual of the Interlisp programming language. The portion contains the following paragraph of text: Interlisp has been designed to be a good on-line interactive system (from which it derives its name). Some of the features provided include elaborate debugging facilities with tracing and conditional breakpoints (Section 15), and a sophisticated LISP oriented editor within the system (Section 9). Utilization of a uniform error processing through user accessible routines (Section 16) has allowed the implementation of DWIM, a 00-What-!-Mean. facility, which automatically corrects many types of errors without losing the context of computation (Section 17). The CLISP facility (Section 23) extends the LISP syntax by enabling ALGOL-like infix operators such as +. -, *, /, =, _, AND, OR, etc., as well as IF-THEN-ELSE statements and FOR-WHILE-DO statements. CLISP expressions are automatically converted to equivalent lnterlisp forms when they are first encountered. CLISP also includes a sophisticated pattern match compiler, as well as a record package that facilitiates "data-less" programming.
August 27, 2025 at 9:05 AM
interlisp.org
To edit a font on Medley Interlisp load and run the EDITFONT font editor like in the screenshot:

(FILESLOAD EDITFONT)
(EDITFONT '(TIMESROMAND 36 BOLD))

Left-click on a character to edit its bitmap, middle-click to bring up a menu.

#interlisp #lisp #fonts
Screenshot of the black and white desktop of a 1980s graphical workstation environment. The desktop has a gray background pattern and some windows with a white background and a title bar with white text on a black background. The main windows show the character table of a font editor and the bitmap of a character of the edited font.
August 21, 2025 at 9:13 AM
interlisp.org
The Common Lisp implementation of Medley Interlisp is closer to CLtL1 than ANSI but does support the condition system. The CONDITIONGRAPH tool shows the hierarchy graph of conditions.

#interlisp #CommonLisp #lisp
Screenshot of the black and white desktop of a 1980s graphical workstation environment. The desktop has a gray background pattern and some windows with a white background and a title bar with white text on a black background. The main window shows a graph of the hierarchy of the condition system of a Common Lisp implementation.
July 22, 2025 at 8:57 AM
interlisp.org
The TEdit WYSIWYG editor of Medley Interlisp has a split window mode that shows different parts of a document. To split at the cursor or unsplit, middle-click on the title bar and select Split Window or Unsplit Window.

#interlisp #lisp
Screenshot of a portion of the black and white desktop of a 1980s graphical workstation environment. The desktop has a gray background pattern and one window with a white background and a title bar with white text on a black background. The window, oriented vertically, is a rich text editor with its area split into three horizontal panes that show different parts of a document.
July 10, 2025 at 9:58 AM
interlisp.org
DIRGRAPHER is a Medley Interlisp tool that shows graphical directory trees and provides file management commands. It's part of the LispUsers collection of user contributed software.

#interlisp #lisp #retrocomputing
Screenshot of the black and white desktop of a 1980s graphical workstation environment. The desktop has a gray background pattern and some windows with a white background and a title bar with white text on a black background. The two main, similar windows are divided into panes. One major pane shows a graphical directory tree of a file system. Next to it is a pane with a menu of file management commands.
July 1, 2025 at 9:49 AM
interlisp.org
The Interlisp function COMPARELISTS compares the structures of two lists and prints a terse description of the differences which highlights the items that differ. More details are in the Interlisp Reference Manual.

interlisp.org/documentatio...

#interlisp #lisp
Screenshot of a portion of the black and white desktop of a 1980s graphical workstation environment. The desktop has a gray background pattern and one window with a white background and a title bar with white text on a black background. The window is a Lisp REPL where the following expressions are evaluated, output printed, and values returned: 2/9_ (COMPARELISTS '(A B C D) '(X B E D)) A -> X, C -> E NIL 2/10_ (COMPARELISTS '(A B C D) '(A D)) (A B C --) (A D) NIL 2/11_ (COMPARELISTS '(A B C D E F G H) '(A B C D X)) (A -3- E F --) (A -3- X) NIL 2/12_ (COMPARELISTS '(A B C (D E F (G) H) I) '(A B (G) C (D E F H) I)) (A & & (D -2- (G) &) &) (A & (G) & (D -2- &) &) NIL
June 17, 2025 at 9:00 AM
interlisp.org
☝️ The 6 windows that make up the GUI of DInfo, the documentation browser of Medley Interlisp.

#interlisp #lisp #gui
Screenshot of the black and white desktop of a 1980s graphical workstation environment. The desktop has a gray background pattern and some windows with a white background and a title bar with white text on a black background. The main application on the desktop is a documentation browser made from 5 windows attached together by a side. A sixth window of the documentation browser is detached from the others and shows a graphical table of contents tree. A number in red marks each of the 6 windows.
June 11, 2025 at 10:44 AM
interlisp.org
The GUI of a Medley Interlisp program is often made from windows attached together or standalone, like the 6 windows (can you spot them?) of this documentation browser. To get the same setup select DInfo from the right-click background menu, then click Menu and History.

#interlisp #lisp #gui
Screenshot of the black and white desktop of a 1980s graphical workstation environment. The desktop has a gray background pattern and some windows with a white background and a title bar with white text on a black background. The main application on the desktop is a documentation browser made from 5 windows attached together by a side. A sixth window of the documentation browser is detached from the others and shows a graphical table of contents tree.
June 7, 2025 at 9:38 AM
interlisp.org
In the 1981 paper "The Interlisp Programming Environment" Warren Teitelman and Larry Masinter explained the origins of the complexity of Interlisp tools and why the environment was designed for experts.

citeseerx.ist.psu.edu/document?rep...

#interlisp #lisp #retrocomputing
A screenshot of a portion of a computer science research paper that contains the following text: Interlisp is for experts. The incremental, evolutionary way in which Interlisp developed was not especially conducive to simple interfaces. It was inappropriate to spend a lot of time and effort trying to design the right interface to a new, experimental capability whose utility had not yet been proven. Would the users like automatic error correction? Was the programmer's assistant really a good idea? The inherent complexity of the interactions among some of the more sophisticated tools, such as Masterscope, DWIM, and the programmer's assistant, made it very difficult to provide simple interfaces. In many cases, unification and simplification came only after considerable experience. Further complexity stemmed from the commitment to accommodate a wide variety of programming styles and to enable the tools to be tailored for many applications. Given the choice of sophistication and generality of tools or simplicity of design, we chose the former, under the assumption that the system was primarily for expert programmers. As a result, mastery of all of the tools and facilities of Interlisp has become quite difficult and initial learning time fairly long. We accept this as part of the price for the system's power and productivity.
June 4, 2025 at 9:21 AM
interlisp.org
The Interlisp library function RNUMBER displays a calculator-type dialog for entering a number with the mouse. This example accepts a floating point number (first T) and also keyboard input (second T).

More details in the documentation:

files.interlisp.org/medley/libra...

#interlisp #lisp #gui
Screenshot of a portion of the black and white desktop of a 1980s graphical workstation environment. The desktop has a gray background pattern and a window with a white background and a title bar with white text on a black background. The window is a Lisp REPL where the following expression is evaluated: (RNUMBER "Enter a number" NIL NIL NIL NIL T NIL T) Above the REPL window is a calculator-type dialog window with the number 1234.56 displayed.
May 30, 2025 at 7:30 AM
interlisp.org
You can use the Interlisp function SHOWGRAPH to display a graph of an S-exp laid out by LAYOUTSEXPR, as in this example of the syntax tree of a setence. More details in the documentation of the grapher library module of Medley:

www.bitsavers.org/pdf/xerox/in...

#interlisp #lisp
Screenshot of a portion of the black and white desktop of a 1980s graphical workstation environment. The desktop has a gray background pattern and a window with a white background and a title bar with white text on a black background. The window is a Lisp REPL where the following expression is evaluated: (SHOWGRAPH (LAYOUTSEXPR '(S (NP (DET The) (NOUN program (VP (VERB displays) (NP (DET a) (NOUN tree)))))) '(VERTICAL) NIL '(HELVETICA 12 BRR))) Beneath the REPL window is a graphical window that displays the syntax tree represented by the expression.
May 21, 2025 at 9:24 AM
interlisp.org
To display a simple yes/no dialog call the Interlisp function MENU to create a menu with the question as the title and two centered items for the answers, as in the example. MENU returns the selected item, i.e. symbol Yes here.

#interlisp #lisp
Screenshot of a portion of the black and white desktop of a 1980s graphical workstation environment. The desktop has a gray background pattern and one window with a white background and a title bar with white text on a black background. The window is a Lisp REPL where the following function call is evaluated: 2/4_ (MENU (create MENU TITLE _ "Delete file?" ITEMS _ '(Yes No) CENTERFLG _ T)) Above the window the function call creates a menu with title "Delete file?" and items named Yes and No.
May 13, 2025 at 9:10 AM
interlisp.org
To print the contents of a window on Medley Interlisp select the Hardcopy > To a file item of the right-click menu of the title bar (first screenshot), then type a file name (second screenshot). This saves a PostScript file suitable for viewing or printing.

#interlisp #lisp
Screenshot of the black and white desktop of a 1980s graphical workstation environment. The desktop has a gray background pattern and some windows with a white background and a title bar with white text on a black background. The main window is a rich text editor with some text in the buffer. On the title bar of the window are an open popup menu and a submenu with the highlighted item Hardcopy > To a file. Screenshot of the black and white desktop of a 1980s graphical workstation environment. The desktop has a gray background pattern and some windows with a white background and a title bar with white text on a black background. The main window is a rich text editor with some text in the buffer. Next to the editor window is a text entry field that requests a file name.
May 5, 2025 at 9:38 AM
interlisp.org
RPT and RPTQ (RePeaT) are Interlisp iteration expressions that evaluate a form a specified number of times, without or with quoting. This is an example, more details in the Interlisp Reference Manual:

interlisp.org/documentatio...

#interlisp #lisp
Screenshot of a portion of the black and white desktop of a 1980s graphical workstation environment. The desktop has a gray background pattern and one window with a white background and a title bar with white text on a black background. The window is a Lisp REPL where the following expressions are evaluated: 2/9_ (RPT 20 '(PRIN1 "*")) ******************** "*" 2/10_ (RPTQ 20 (PRIN1 "*")) ******************** "*"
April 29, 2025 at 11:42 AM
interlisp.org
If an error on Medley Interlisp lands you in a debugger window like this, press Ctrl-D to exit and return to the top level; type ^ and ENTER; or select ^ from the middle-click menu shown here.

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#interlisp #lisp
Screenshot of a portion of the black and white desktop of a 1980s graphical workstation environment. The desktop has a gray background pattern and one window with a white background and a title bar with white text on a black background. The window is a debugger with an open popup menu of commands. The debugger window is divided intwo two panes, a larger one at left for command interaction and a smaller one at right with a stacktrace.
April 16, 2025 at 9:17 AM
interlisp.org
The Programmer's Assistant supports undo/redo of Lisp expressions like in this example. The Programmer's Assistant is the Medley Interlisp facility for expression and command replay, undo, and editing.

#interlisp #lisp #retrocomputing
Screenshot of a portion of the black and white desktop of a 1980s graphical workstation environment. The desktop has a gray background pattern and one window with a white background and a title bar with white text on a black background. The window is a Lisp REPL that evaluates the following Interlisp expressions and displays their outputs and values: 4_ (SETQ VARIABLE 10) 10 5_ VARIABLE 10 6_ (SETQ VARIABLE 20) 20 7_ UNDO SETQ undone. 8_ VARIABLE 10 9_ REDO 6 20 10_ VARIABLE 20
March 31, 2025 at 9:18 AM
interlisp.org
Are you looking to contribute to the Medley Interelisp Project but don't know where to start? Let Medley pick a random GitHub issue to work on:

← (FILESLOAD PICK)
←PICK ISSUE

The documentation of the PICK tool:

files.interlisp.org/medley/lispu...

#interlisp #lisp
Screenshot of a Linux desktop whose area, aside from a horizontal taskbar at the bottom, is mostly taken up by the black and white desktop of a 1980s graphical workstation environment. The workstation desktop has a gray background pattern and some windows with a white background and a title bar with white text on a black background. One of the windows shows the details of a GitHub issue. A web browser window showing the same issue on the GitHub website takes up the lower right quarter of the Linux desktop.
March 24, 2025 at 10:21 AM