Oberon Computing Systems

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                " ... simple as possible, but no simpler."   ... A. Einstein

This book is about the Oberon family of computing systems[1] with a focus on technicalities. For an overview, refer to the Wikipedia article. For authoritative documents see Support and References. For other uses of the name Oberon, refer to the disambiguation page.

Oberon V5 RISC emulator on GNURoot Debian on Android on an Alcatel 9015B tablet with keyboard and mouse connected by Bluetooth.


A novice interested to learn computing from the foundations will appreciate the freedom from overwhelming and unnecessary complexity imposed by other systems. The more advanced user will find an efficient tool with complete sources allowing study in depth. The system engineer might adapt Oberon to specific requirements such as intensive computation, big data computation and automation.

Typical usage progresses through these stages.

  1. Installation
  2. Configuration
  3. Production
  4. Bug repair
  5. Customization and development

The reader should install and use at least one Oberon system. As preparation, an introductory course covering programming basics is advantageous but not essential.

System Characteristics[edit]

Oberon was developed as a stand-alone personal workstation and remains viable in that capacity. The system was designed to attain compactness, comprehensibility, efficiency, reliability, responsiveness,[2] security and simplicity. The extreme compactness is immediately evident to a novice installing Oberon S3 (System 3) on a bare PC. The complete system including applications, documentation, graphical interface, fonts and source texts was installed from ten HD diskettes[3].

This Book[edit]

An Oberon system comprises a collection of modules and this book presents one module per page[4]. An example is Sort.Mod from S3. Additionally there are Tool pages, each of which is a template of executable commands. An example is Sort.Tool. A system building Tool is a template for rebuilding the entire system, including system installer and module packages.


Contributions range from suggestions to authoring of complete pages. Also "View history".

Contributor Affiliation
André Fischer Zürich, Swiss Confederation
Bernhard Treutwein Ludwig-Maximilians-Universität München, Bundesrepublik Deutschland
Felix Friedrich Computer Science Department, ETH (Swiss Federal Institute of Technology) Zürich, Swiss Confederation
Prof. Pablo Cayuela Universidad Tecnológica Nacional, Facultad Regional Córdoba, República Argentina

Historical Perspective[edit]

Following development of the programming languages Euler, Algol W, Pascal, Modula and Modula-2, Niklaus Wirth proceeded to create the Oberon language with original release occurring in 1986. The language design was driven by the wish to design an operating system similar to the OS of the Alto and the insight that Modula-2 did not have the required language construct, which we would now call type inheritance. Wirth chose the other viewpoint and called it type extension. Beside other syntactic differences, which were mainly simplifications, type extension is the major difference between Modula-2 and Oberon . Having met at Xerox PARC, Wirth collaborated with Jürg Gutknecht to build a complete operating system written in the Oberon language. This system was also named Oberon. The distinction between language and system is usually obvious from the context where the term appears.

In subsequent developments, small syntactical changes created various dialects of the language (Oberon-2, Component Pascal, Active Oberon, and Oberon-07), with compatibilities and incompatibilities. Variants of the operating system also evolved, again entailing small incompatibilities. The four most prominent of these OS flavors are

  • ETH Oberon (aka System 3, S3) written mostly in Oberon with some parts in Oberon-2,[5]
  • V4 Oberon (aka Linz-Oberon) basically written in Oberon but with many extensions in Oberon-2
  • AOS (aka Bluebottle and A2) written in Active Oberon, and
  • Oberon V5, described in Wirth's Project Oberon, 2013 Edition and written in Oberon-07.

With reasonable effort, incompatibilities can always be resolved to allow shift of source text from one system to another.

Beside being a stand-alone operating system, Oberon has been implemented as an emulated operating system atop other systems, decades before virtualization became a buzz-word. The most prominent of these emulated Oberon Systems was Oberon V4, which was implemented on top of SunOS 1 & 2, Ultrix, Irix, AIX, MacOS 7,8,9 (both 68K and Power PC), AmigaOS, TOS (Atari), OS/2, Microsoft Windows, HPUX, and (of course) Linux[6]. Oberon V4 was sometimes also called Linz-Oberon, due to the fact that it was maintained by the group around Hanspeter Mössenböck, who joined the faculty at JKU Linz in 1994. But also System 3 was implemented on top of another operating system for MacOS (68K and PowerPC), SunOS (SPARC and x86), and Microsft Windows. A2 is running as an emulated OS on Microsoft Windows, Linux, and Solaris (x86). In 2015 Peter Matthias revitalized System 3 under the name "Oberon Linux Revival" (OLR) as a multi-platform proof of concept running both in framebuffer-mode and in the X-Window System on X86, Mips, and ARM hardware under Linux.[7]

Refer to the articles about the language and about the OS for further details and to find references to the extensive literature.

System Variants[edit]

The Oberon system runs directly on several machine architectures and as a subsystem in several host operating systems. To see pages specific to a variant, click on the hyperlink in the identifier (3rd) column. Order of rows is approximately chronological.

Host Environment[8] Software Identifier[9] Installation
Ceres workstation

preserved Ceres
preserved Ceres
photo of Ceres 3

The Oberon System V1, V2  
Bare X86 PC[10] ETH Oberon
= PC-Native Oberon
= System 3
S3 SourceForge ETHZ, actual diskettes and hypervisor using images.

Hypervisor using diskette images.
Oberon Tutorials at YouTube[11]

X86 PC with MS Windows Spirit of Oberon System3 for Windows S3 Spirit of Oberon System3 for Windows JKU Linz,
J.L. Marais
X86, ARM, ARMv7,
RISC-V or MIPS with Linux
Oberon Linux Revival; sources following S3 closely. OLR P. Matthias
X86 PC with Linux[12] Linz-Oberon V4 JKU Linz and
X86 PC with MS Windows[12] Linz-Oberon V4 JKU Linz and
X86 PC with Windows or with *nix and Wine BlackBox Component Builder, an IDE for Component Pascal BB BB Community download area
.NET and CLI Gardens Point Component Pascal application for .NET and CLI[13] GPCP Current project at github
Original site from Archive.org
JVM Gardens Point Component Pascal application for JVM[13] GPCP Current project at github
Original site from Archive.org
Bare X86 PC Bluebottle
= A2
A2 SourceForge ETHZ[14]
X86 PC with Solaris,
Linux or MacOSX (Darwin).
= UnixA2
A2 Uni-Bremen,
 G. Feldmann
 G. Feldmann
X86 PC with A2 or UnixA2 or WinA2 Oberon subsystem A2O Included in A2, UnixA2 and WinA2
FPGA RISC Oberon V5 V5 N. Wirth

P. Reed

Android, Linux,

Mac OS X, Unix or
MS Windows on a wide variety of machines[15]

Emulator written in C. V5 P. De Wachter
Unix command line Norebo, a software allowing
execution of an Oberon
command without the Oberon
system and interface.[16]
V5 P. De Wachter
Oberon RISC processor or emulation of it[17] Experimental Oberon EO A. Pirklbauer
A. Pirklbauer
Web browser Emulator written in JavaScript. V5 Michael Schierl
Web browser Emulator written in Java. V5 Michael Schierl
Linux or Mac OS Integrated Oberon written
in the Go programming language.
V5 Charles Perkins
or MIPS running Linux
Project Oberon Linux, POL;
installed on Linux.
V5 P. Matthias
JVM Oberonc compiler for Oberon-07.[18]   L. Boasso
or MIPS running Linux
Project Oberon Linux, POL;
installed on Linux.
V5 P. Matthias
Any system capable of running QEMU qemu-risc6 fork of QEMU   Charles Perkins.
Any system capable of running BlackBox Component Builder Emulator of V5 written in Oberon-2. V5 Alexander V. Shiryaev

In A2, identifiers "A2" and "Oberon" in the name or text of a source module denote context [19] where necessary. This is the syntax in ActiveOberon.

Module := "MODULE" Identifier "IN" Identifier ";" ...

Where context is not formally recognized, an identifier in a comment is possible.

Module := "MODULE" Identifier "(* IN " Identifier "*);" ...

An identifier can also be prefixed to the module identifier.

Module := "MODULE" Identifier Identifier ";" ...

As the Oberon filesystem does not support folders, name conflict can be avoided by prefixing a file name.

NameOfModuleFile := Identifier Identifier ".Mod"

The name of a file containing a module source can differ from the name of the module. Within the scope of a module, the name of an imported module can be aliased. Syntax is in the Oberon-2 Report.

Use Cases[edit]

Educational Workstation[edit]

Oberon is used as a workstation OS in the course in System Construction at the ETHZ.

Embedded System[edit]

Currently a strong interest in Oberon development is in embedded systems. Astrobe is the leading commercial effort; providing a MS Windows based integrated development environment for producing Oberon source text and executables.

Personal Workstation[edit]

Of all Oberon systems, PC Native (S3) and A2 have the broadest range of application level development for a personal workstation. Nevertheless their capabilities are limited in comparison to familiar commercial systems and Unix-like systems. By using an Oberon subsystem in one of these familiar systems, benefits are combined. The subsystem can be installed as an application such as UnixA2. Alternatively the subsystem can be a guest of a hypervisor as when S3 is hosted by QEMU. The subsystem can also be emulated; the Oberon RISC emulator being a prime example. Refer to the table of system variants.


The Oberon0 installer for S3 running under QEMU in Debian Linux.

A system is chosen and, using the link in the table of variants, an installation archive is retrieved. Instructions for installing and configuring the system are linked in the last column of the table. For some systems, instructions are also available in a system specific page linked in the third column.


S3 can be installed and run on a bare PC and is similar to the Oberon subsystem of A2. In comparison to V5, S3 has relatively advanced application level capabilities including the Gadgets GUI. Discarded desktop and laptop PCs capable of running S3 are widely available, typically at no cost.

A2 and UnixAOS[edit]

A2 can be installed and run on a bare PC and as an emulated OS on various platforms. Refer to the A2 page. A2 contains an Oberon subsystem very similar to S3. The compactness and speed of user level tasks such as email, makes a striking comparison to analogues in the host system. A2 also works well on many desktop and laptop machines considered obsolete for commercial operating systems.


Archives are available from JKU Linz and from Sourceforge. Specific installation instructions are available for Linux and for MS Windows. The instructions should also help with Amiga, HPUX, Macintosh, MIPS, PowerMac, Sparc and UV4.


For installation on FPGA machines, refer to the documentation of N. Wirth and of Paul Reed. Oberon RISC Emulators work on contemporary MS Windows and Unix-like systems. Refer to instructions of the author of the emulator of interest. Additional notes are available for Android. On some machines the size of block random access memory (BRAM) may constrain development objectives.

Getting Started[edit]

The user interface of the Oberon System is quite surprising on the first sight.[20] It is a so called text based user interface (TUI) and combines the point-and-click convenience of a graphical user interface (GUI) with the linguistic strength of a command line interface (CLI). It is closely tied to the naming conventions of the Oberon language. Any text appearing (almost) anywhere on the screen can be edited and can be used as command input. Commands are activated by a mouse-middle, MM, click[21] on a text fragment of the form Module.Command (optionally followed by parameters, which are terminated by ~). A command is defined by a procedure, which has an empty argument list. Parameters to the command have to be defined before executing the middle click and must be explicitly scanned and retrieved by the procedure. There are no checks nor any questions asked during command execution. This is sometimes called a "non-modal" user interface (UI). Nothing like a command prompt is required. Although radically different from a command line, the TUI is very efficient and powerful.[22] Active elements can be embedded in Oberon texts: a clock showing the current time, push buttons, or graphical elements visualizing data. Most user interface elements are realized with the help of documents. A steep ascent in the early learning curve can be somewhat challenging. No questions are asked: this is a deliberate design decision, which needs getting used to. For example, most familiar editors ask the user when closing a modified text: this is not the case in the Oberon System. The usage of the TUI and programming interface is fully documented in Martin Reiser's book "The Oberon System".[23] A short introduction to the user interface can be found on Niklaus Wirth's home page.[24] The later Versions of System Oberon, Oberon V4 (or V4 in short, sometimes also referred to as Linz-Oberon) and Oberon System 3 (or S3, sometimes also called ETH-Oberon or Spirit of Oberon), enhanced the basic interface with different but incompatible implementations for buttons, drop down menus, and other active elements. V4 used for that purpose a dedicated control character embedded in normal text in contrast to System 3, which extended the kernel by introducing persistent objects. Both extensions include a large set of user interface elements.

Mastering the Oberon user interface, both the purely textual and also the so called Gadgets System (under S3), is absolutely non-trivial. Therefore it is recommended to proceed after a successful installation of Oberon System 3 to André Fischer's Oberon System 3 Tutorial. An expanded version of this tutorial is published as a book,[25] which is now out of print. Although the book has a standard copyright, it is available in electronic form under a single user license in every installed version of System 3 (Windows, Linux or Native, i.e. also with the Gadgets toolkit of OLR[7]). If you try to read it in System 3, you are confronted with the classical chicken and egg problem: You have to master the user interface to have access to the documentation of the user interface. Therefore some detailed instructions for reading "The Oberon Companion" – after a successful installation of the Oberon System can be found by opening the file Book.Tool with the command Desktops.OpenDoc. If this command is not present in any of the windows/viewers, which are opened by default when you start the Oberon System, you can click anywhere with the left-mouse button (ML) in any viewer and type the command Desktops.OpenDoc Book.Tool ~. Then move the mouse over Desktops.OpenDoc and do a middle-mouse button (MM) click. This will open an new viewer with a table of contents of "The Oberon Companion". All lines with blue text are hyperlinks to the chapters of the book, which in turn can be clicked with the MM button so that the chapter will open in a new viewer. The license in Book.Tool gives the user the right to print a single copy for personal use. I had good results in print with a GhostScript based free PDF converter. If you want to print an open document in Oberon, i.e., the contents of a window (or viewer in Oberon terminology), you have to set the star shaped mark by hitting the F1 key (see Tutorial) and then issue the command Desktops.PrintDoc Default * ~ by a MM click on Desktops.PrintDoc. In an Oberon command the * is not a wildcard, but symbolizes the marked viewer.

Reading this Book[edit]

In A2[edit]

At 2018-02-06 the WebBrowser in A2 fails to open a page. Hypothetically, follow the system menu, Apps > WebBrowser and specify a URL. Alternatively, mouse middle, MM, on WebBrowser.Open in an A2 window (not in the Oberon subsystem).

WebBrowser.Open https://en.wikibooks.org/wiki/Oberon ~

In S3 and in the Oberon Subsystem of A2[edit]

MM on Desktops.OpenDoc.[26]



In V5[edit]

Desktops and Webrowser are not implemented.

In Any Desktop, Laptop or Smartphone[edit]

Use any browser.

firefox https://en.wikibooks.org/wiki/Oberon

firefox https://en.wikibooks.org/wiki/Oberon/Oberon.Sort.Mod

To see the list of sources available here for a given system, click on the identifier in the third column of the table. Most of the wiki text extraneous to a module Text is eliminated with a click on the "Mobile view" link at the foot of a page.

Oberon Text[edit]

Confusingly for a novice, three forms of line ending can be found in text files in contemporary computer systems.

  • In Oberon and some other systems, a line of text ends with the carriage return character, denoted CR.
  • In Unix-like and some other systems, a line of text ends with the line feed character denoted LF.
  • In DOS, Microsoft Windows and some other systems, a line of text ends with the two characters, CR and LF.

This multiplicity poses no problem for Oberon; most Oberon systems allow convenient editing with any of these line endings.[28]

An Oberon Text[29] can appear to be no more than a plain text comprising a sequence of ASCII characters. Nevertheless Text in Oberon is a type defined in the Text module. A Text of this type is a sequence of characters including non-printing characters. A character in a Text can have attributes including typeface, size and color. Furthermore a Text can include non-character objects; an image or a hyperlink for example. Consequently two documents, one an Oberon Text and the other an HTML text, can have the same appearance and the same behavior of links.

Editing a Text[edit]

Each Oberon system has an Edit module. If Edit.Open Example.Text appears almost anywhere on the screen, a MM on Edit.Open will open a viewer. If a file named Example.Text exists, it's content will appear in the viewer. If no file with the name exists, the viewer will be empty. The caret can be set by ML and characters can be inserted using a keyboard. In S3, edit is extended by ET and by the Gadgets subsystem. Try commands ET.Open <aFile> and Desktops.OpenDoc <aFile>. S3 also has the Hex module providing a hexadecimal editor. Try Hex.Open <aFile>.

Additional Details[edit]

A dedicated page addresses programmatical access to Text and the type structure on which Text is based.

Dataflow of a Text[edit]

This dataflow example illustrates relationships between Oberon Text, HTML and ASCII text.

markup text
Clipboard or
Save operation
text file

Ideally the three Texts in the upper row are identical; but currently Text color and style are not preserved by Desktops.OpenDoc nor by transport of browser text into Oberon. Variations of Text color and style are harmless to compilation.


In this context, compilation is the process of translating a module of Oberon source text into a text of machine code which can be loaded and executed in an Oberon system; typically the system containing the compiler.[30]

File Naming[edit]

If a module name matches an extant object file, compilation can overwrite it. To avoid that, the name of the newer or test module can be altered. Prefixed with an identifier for example; "MODULE Sort" could become "MODULE V4Sort". Overwriting is also avoided when the new and old object files are in different volumes or directories. Object files of S3 are installed to the SYS volume whereas the new file would typically be written to a USR or HOME volume. Object files of UnixA2 are installed to /usr/aos/obj/ and a new file would typically be written to a working directory such as /home/me/aos/.

Compiling in A2 and Oberon[edit]

Compile A2 and Oberon modules in A2; not in the Oberon subsystem. The compiler in A2 is Flexible Oberon Cross Compiler or Fox. Invoke it with the Compile button in the PET editor or MM on a Compiler command in an A2 window, in accord to Fox.Tool. Builder.Tool from S3 is not relevant to A2.

Compiling in S3[edit]

Compiler commands are defined in Compiler.Mod and summarized there following "END Compiler". If a module is opened with Desktops.OpenDoc as described under Reading, it can be compiled directly from the viewer. Select any characters beginning with M in MODULE and MM on Compiler.Compile @ . Otherwise import to the S3 system and use a command according to Compiler.Tool.

Compiling in V5[edit]

Use an ORP.Compile command in System.Tool.

System Startup and the Core[edit]

Brief remarks here are intended to guide the student toward study of the authoritative documents.


For V2 running on a Ceres machine, system startup and the core are described in sections 14.1 and 14.2 of Project Oberon, 1992(PDF).


In S3, the inner core comprises basic operating system functions including storage management, file system, loader, compiler and etc. The outer core comprises management of display, keyboard and mouse. Compilation and linking can be understood from the system building tool, Native.Tool . Inner and outer cores together are somewhat comparable to the kernel of a Unix-like system.



In V5, Project Oberon, the inner core comprises only the modules Kernel (memory mgmt, disk storage mgmt, traps, timer), FileDir (directory handling), Files (File handling) and Modules (module loading). The authoritative exposition is in sections 14.1 and 14.2 of Project Oberon, 2013 Edition(PDF).

Multi-boot and Boot Manager[edit]

S3, A2 and other systems working directly on bare hardware offer the further possibility of multiple operating systems requiring a boot manager. Boot Manager[31] and the instructional document[32] were written by André Fischer according to Oberon principles. Boot Manager is now maintained in the SVN repository at the ETH.

Contributing a Module or Tool Not in the Book[edit]

  • Initialize a Module or Tool page from a published release. Preferably the latest. Oberon.Sort.Mod, for example, is taken from the Oberon subsystem in UnixA2. Indicate the source in the wiki edit subject line.
  • Use Oberon naming conventions.
  • Avoid page duplication. If two systems share a source module, a page redirect might be preferable to duplicate pages.

Addition of a Text is the first two steps of the dataflow diagram above. The first step is performed by the contributor. The second is performed automatically by the MediaWiki server. Retrieve the MediaWiki module (S3, A2O) to your Oberon system and compile it. Open a viewer with the module to be contributed and * mark the Text. Translate to MediaWiki markup with "MediaWiki.Markup * " and save the <Module>.Mod.mw with Edit.StoreAscii or ET.StoreAscii.

To add the page to the book, a browser capable of HTTPS is necessary; Desktops.OpenDoc in S3 is inadequate. Being logged in to a Wikimedia account is advisable. In the table above, click on an identifier to open the system specific page. There add the name of the intended module and "Publish change". The new entry will be colored red. Click on it to open the page for the new module. Copy and paste the text from <Module>.Mod.mw and "Publish change".

Editing this Book[edit]

All progress is welcome. Correct errors in grammar and in algorithms. Present unrefined ideas in the talk pages.

Editing a Module Source Text[edit]

A source can be edited directly using a browser capable of HTTPS. Alternatively it can be edited on your Oberon system, translated using MediaWiki.Markup and applied to replace the existing version, as when adding a new module. If replacing, take care to avoid over-writing a previous edit. The latest version of the page should be retrieved to a working Oberon system and compared using Diff.Do. Alternatively, a registered user can put a new version in the user sandbox and compare as in the following section. Be aware that the non-zero time interval between retrieval from the book and installation of the new version allows an edit conflict.

  • If an edit conflict is inadvertently created, fix it, please.
  • Avoid breaking compilation.
  • Avoid breaking interfaces. If an interface is changed, adjust all modules which connect to it. An idea clearly expressed in a discussion page is preferable to broken interfaces.
  • Avoid breaking functionality.
  • Avoid introducing a bug. If a bug is introduced, the change might be reverted, however brilliant the intended improvement.
  • Prefer more recent syntax over older syntax. Remove LOOP. Where possible remove RETURN.
  • Optionally, color changed text, green; text disabled by commenting, red.

Formatting a Source Text[edit]

Various formatting conventions and preferences exist. Refer to the Oberon Mailing List, 2017-07-22 through 2017-07-26, and search for "indentation?". No particular format is essential here. Any reasonable format preferred by a contributor is welcome.

Styling a Source Text[edit]

Various stylistic conventions also exist. Refer to the Oberon Mailing List, 2017-07-29 through 2017-07-30, and search for "Italicization". Editors such as PET in A2 and the "pretty printers" mentioned in the list automatically style a source Text to highlight syntax. Therefore direct syntax styling can be unnecessary. Color to distinguish a revision is optional and relatively harmless.

Comparing Versions and Pages[edit]

Oberon has module Diff. For example, two pages can be retrieved to files TextFile1 and TextFile2. Then MM on Diff.Do TextFile1 TextFile2 .

To compare versions of a page within the book, open the history using the button at the top of the page. Choose two versions and "Compare selected versions".

To compare distinct pages, ID numbers are specified in a URL. In the page history of S3.HTML.Mod, when the mouse pointer is hovered over the date in the entry for the original version, ID 3205558 is reported by the browser. The original version of Oberon.HTML.Mod is ID 3205420. The URL


produces a side by side comparison. "Compare" works well where a fraction of lines differ. When most or all lines in the compared pages differ, comparison has little or no value.

Contemporary Hardware[edit]

Model Name Image Processor Boot Memory Memory Approximate
Price, US$
Pepino LX9   Xilinx Spartan-6 FPGA 1 MB SRAM 128 MB SPI 100  
OberonStation   Xilinx XC3S700AN FPGA 1 MB SRAM microSD   Website unreachable September 2018.
RiskFive   Xilinx Artix-7 FPGA 16-32 MB SPI Flash 4 MB ZBT, microSD "expensive" Motherboard plus FPGA module.
Radiona ULX3S Installation data and instructions   Lattice ECP5 LFE5U-85F-6BG381C (85K LUT) FPGA 4–16 MB Quad-SPI Flash 32 MB SDRAM 166 MHz, microSD 60-140 Boards with 12K LUT also available.


Why do some Oberon systems have a flat file system? Isn't a tree structured file system indispensable in highly productive contemporary environments?
The tree structured file system came into prominence during the 1950s and '60s when computer memories were miniscule in comparison to memories now available. The tree structure of those early file systems helped with organization of the operating system. Typical memory access is far faster than file access. With current hardware, a data structure can be composed and used in memory with much faster performance than a data structure in a file system. With some focus on choice of meaningful names for files, most users will find the flat file system entirely adequate. Also, most Oberon subsystems have access to a tree structured file system of the host. Additionally, S3 running on a bare PC supports the FAT16, FAT32 and ISO 9660:1988 file systems, all of which are tree structured. In reality, a flat file system in Oberon is a benefit rather than detriment.
In S3 (or A2O) MM+MR opens a viewer with Edit whereas I prefer ET. How can that be fixed?
In S3 open TextFrames.Mod. MM on Edit.Open.
Edit.Open TextFrames.Mod

In the Oberon sub-system of A2.

Edit.Open Oberon.TextFrames.Mod


OpenCmd = "Edit.Open"


OpenCmd = "ET.Open"

, MM on Edit.Store, recompile the module (TextFrames.Mod or Oberon.TextFrames.Mod) and reboot. TextFrames and all modules which import it could be reloaded but rebooting is simpler.


Also refer to the glossary in the Wikipedia article.
Active Oberon, the dialect appearing in system A2.
BRAM, Block Addressable Random Access Memory, as used in the FPGA machine[33].
Columbus, a software tool in S3 used to inspect and modify gadget attributes and to add a new attribute to a gadget. Usage described in the tutorial
Definition ( or Module Definition), a summary of a module presenting constant declarations, type declarations, variable declarations and procedure headings.
fixup, the conversion from address relative to the base address of the module, to absolute address.
Gadgets, software infrastructure in S3 providing graphical entities and a graphical user interface. Usage described in the tutorial.
Inner core, a significant architectural entity in an Oberon system. Refer to System Startup and the Core for details.
INTEGER, an integer type in every Oberon system.
Interclick, a click of a mouse button while holding another button. MM+MR below is an example. The mouse tutorial has additional details. When editing a Text at least six interclick combinations are meaningful.
Lola-2, a hardware description language developed by Niklaus Wirth.
LONGINT, an integer type in S3. Synonymized to INTEGER in the current V5.
LUT, look up table of FPGA. Referenced when quantifying the size of a FPGA device.
ML, the left button of the mouse or a click of that button, depending on context. Ref. Mouse support. Abstracted meaning: specify a location. Example: locate an insertion point in a Text.
MM, the middle button or the wheel of the mouse, or a click of the button or wheel, depending on context. Abstracted meaning: invoke an action. Example: execute a command.
MR, the right button of the mouse or a click of that button, depending on context. Abstracted meaning: select an extent. Example: select a character sequence in a Text.
MM+MR, a click of the right button while holding the middle button or the wheel of the mouse. MR here is termed an "interclick". In a Text, take the word under the mouse pointer as the name of a file and open the text editor on it.
MR+ML, a click of the right button while holding the left button of the mouse. When editing a Text, select characters and delete them.[34]
ML+MM+MR, nullification of an inadvertent mouse click.
native, modifies the name of an Oberon system to indicate that it is installed on bare hardware; distinguishing from a subsystem such as UnixA2 installed atop a host system.
Oberon.Text, a file in S3 and in A2O specifying system configuration.
OMI/Slim binary, a portable object file format created by Michael Franz. Compare with Apple Fat binary. Slim binaries are mentioned in http://www.ethoberon.ethz.ch/compiler/index.html
Outer core, a significant architectural entity in an Oberon system. Refer to System Startup and the Core for details.
(** any comment *), appears in some module sources. It means that any comment is an exported comment. A tool named Def produces a module interface file with this comment included, thus enhancing internal documentation.
(** portable *), this comment in S3 marked a module where OMI/Slim binary code was portable across platforms. More generally, it means there were no SYSTEM dependencies or machine specificities. This exported comment appears in the documentation created by the above mentioned browser, Def, which was integrated into a tool called Watson in S3.
Registry, the content of Oberon.Text specifying file system aliases, sound adapter parameters, LinkSchemes, MIME types and etc.
SHORTINT, an integer type in S3. Not in V5.
SIZE, a signed integer type pertaining to memory address in A2. The difference of two addresses can be negative. New numeric types appeared in rev.9475.[35]
Watson, a tool capable of extracting a module definition from a definition file, module file, module Text or object file. Usage described in the tutorial



A few potential projects.

  • For any system, compile a fresh release, with bug fixes and improvements, and post on a public server.
  • Make a TUI for A2.
  • With the cryptography modules in S3 and in A2 as a base, build an SSL implementation for S3.
  • Using HTTPS, automate the download and upload processes. Allowing MediaWiki.Get Oberon.Sort.Mod ... ~ and MediaWiki.Put Oberon.Sort.Mod ... ~ for example.
  • Improve support of Unicode.
  • Improve HTMLDocs in S3 and in A2O. Add support for styling and tables, for example.


ETH License[edit]

For compatibility of the ETH License with Wikibooks open the archive of Media_copyright_questions and search for "ETH-Oberon".


ETH Oberon Copyright (c) 1990-2003, Computer Systems Institute, ETH Zurich All rights reserved.

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Project Oberon, Revised Edition 2013[edit]


Book copyright (C)2013 Niklaus Wirth and Juerg Gutknecht; software copyright (C)2013 Niklaus Wirth (NW), Juerg Gutknecht (JG), Paul Reed (PR[/PDR]).

Permission to use, copy, modify, and/or distribute this software and its accompanying documentation (the "Software") for any purpose with or without fee is hereby granted, provided that the above copyright notice and this permission notice appear in all copies.



Approximate chronological order. Also refer to the Oberon Bibliography from ETHZ.


  1. This includes systems with the original text user interface and A2 with more conventional windows. Refer to System Variants
  2. In the preface of The Oberon System (Pub. Addison-Wesley, 1991) Martin Reiser commented "It is the most responsive system by far known to the author. This responsiveness substantially improves user productivity;"
  3. With contemporary facilities, the base system is easily installed using the Oberon0.Dsk image and a hypervisor such as QEMU. The additional packages can be retrieved via a network connection and installed. Refer to the installation instructions for S3.
  4. These systems comprise hundreds of modules. At present fewer than twenty modules are available here. Nevertheless even one insight can advance understanding and one small bug fix can be essential to success in a task.
  5. The page formerly on the ETHZ server remains at archive.org. The page here is intended to have the same content and as similar a visual appearance as reasonably possible.
  6. Sources of Oberon V4 at SourceForge
  7. a b Matthias, Peter. "Oberon Linux Revival". http://oberon.wikidot.com/. 
  8. In some cases the host environment is a bare machine. Otherwise it is a machine running another system.
  9. The compiler in A2 recognizes context identifiers "A2" and "Oberon". Other identifiers here are merely hyperlinks to system specific pages. See also "Identifiers" in the discussion page.
  10. Including the Transmeta Crusoe 5400 and the StrongARM SA 110 and SA 1110.
  11. A PC can boot from an Oberon0 diskette in an internal drive. In that case installation of S3 can proceed directly without involvement of DOS. Oberon Tutorial Part 2 includes a helpful explanation of the user interface.
  12. a b V4 can also execute on obsolete systems 680x0 MacIntosh and PowerMac with MacOS to version 9 inclusive, Amiga, Atari ST, DECstation, HP-UX, IBM RS/6000, SGI IRIS and SPARC with Solaris. Refer to ftp://ftp.ethoberon.ethz.ch/Oberon/OberonV4/ and ftp://ftp.ssw.uni-linz.ac.at/pub/Oberon/. A native version has not been produced.
  13. a b GPCP provides a compiler for Component Pascal; not a full Oberon subsystem.
  14. During the summer of 2019 work is underway at the ETHZ to improve portability and other aspects. Until the work is completed, the user may encounter difficulties with the native variant of A2. The Oberon subsystem remains available in UnixA2 and WinA2. A notice is in the mailing list archive at 2019-07-03. Patience is advised.
  15. The SDL2 library and a C99 capable C compiler are required. GCC or Clang suffice for compiling the emulator.
  16. The Oberon compiler, for example, can be executed at the Unix command line.
  17. EO does not modify the RISC processor; it modifies only the Oberon system which runs on it.
  18. The TypeRules document is noteworthy. Specific aspects of types are discussed in the mailing list beginning at 2019-12-07.
  19. Friedrich, F., Negele, F., "Proposal for Modules Contexts"
  20. Video Tutorial 2, produced by Andres Ramos, illustrates salient features of the interface in a readily digestible manner.
  21. Using the mouse and the keyboard http://www.ethoberon.ethz.ch/ethoberon/tutorial/Mouse.contents.html
  22. Franz, Michael (2000). "Oberon - The Overlooked Jewel". in Böszörmény, Lászlo; Gutknecht, Jürg; Pomberger, Gustav. The School Niklaus Wirth - The Art of Simplicity. Morgan Kaufmann Publishers. pp. 41–53. ISBN 1-55860-723-4. https://pdfs.semanticscholar.org/d48b/ecdaf5c3d962e2778f804e8c64d292de408b.pdf. Retrieved 2017-12-14. 
  23. Reiser, Martin: "The Oberon System - User Guide and Programmer's Manual" - Out-of-print - Addison-Wesley/ACM Press (1991) ISBN 0-201-54422-9
  24. Wirth, Niklaus (2015). "How to use the Oberon System". https://www.inf.ethz.ch/personal/wirth/ProjectOberon/UsingOberon.pdf. 
  25. André Fischer & Hannes Marais: The Oberon Companion. A Guide to Using and Programming Oberon System 3. vdf Hochschulverlag AG (1997). ISBN 978-3728124937, out of print, for a personal copy, see notes in text
  26. With an older HTMLDocs module some characters appear as empty boxes. To correct this, install and compile a revised Oberon.HTMLDocs.Mod.
  27. The loband filter allows Oberon to use HTTP while the Wikimedia server provides HTTPS.
  28. As a point of interest, each case is easily displayed explicitly. In an Oberon system with the hexadecimal editor, Hex, MM on Hex.Open <aFile>. In S3 a file with lines ending CR LF is edited by ET.OpenAscii <aFile>.
  29. With Text being a fundamental type in an Oberon system, "Oberon Text" is considered a proper name. Hence the capitalization "Text".
  30. Cross-compilation produces an executable text for a system other than the system of the compiler.
  31. Relevant file names are spelled without the space character. "BootManager" rather than "Boot Manager".
  32. The page formerly on the OCP server at the ETHZ remains available from the WayBack archive. The page here is intended to have the same content and as similar a visual appearance as reasonably possible.
  33. Explained further in the Oberon mailing list at 2019-02-09.
  34. A Text can include non-character objects. Any object in the selection is also deleted.
  35. Renaming of numeric types in A2