Oberon

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75% developed  as of Aug 5, 2017

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

This book is about the Oberon operating system for a computer, with a focus on technicalities. For an overview of the system refer to the Wikipedia article. For other uses of the name, refer to the disambiguation page.

Audience[edit]

A novice interested to learn computing from the foundations will appreciate the freedom from overwhelming and unnecessary complexity imposed by other systems. The advanced user will find it an efficient tool with complete sources allowing repair of bugs and enhancement of functionality. The system engineer can adapt it to a computationally intensive task, to high throughput data acquisition and processing or to serve as a real-time control system.

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, security and simplicity. The extreme compactness is immediately evident to a novice installing ETH Oberon on a bare PC. The complete system including applications, documentation, graphical interface, fonts and source texts was installed from ten HD diskettes[1].

This Book[edit]

The operating system comprises a collection of modules and this book presents one module per page[2]. An example is Oberon.Sort.Mod from A2.

Additionally there are Tool pages, each of which is a template of executable commands. An example is S3.Sort.Tool. A system building Tool is a template for rebuilding the entire system, including system installer and module packages.

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 then being viable, Wirth collaborated with Jürg Gutknecht to build a complete operating system written in that 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 have created various dialects of the language with compatibilities and incompatibilities. Variants of the operating system have also evolved, again entailing small incompatibilities. The four most prominent of these OS flavors are

  • ETH Oberon (aka System 3) written mostly in Oberon with some parts in Oberon-2,
  • 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 680x0K and Power PC), AmigaOS, TOS (Atari), OS/2, Microsoft Windows, HPUX, and (of course) Linux. 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 (680x0K and PowerPC), SunOS (x86 and SPARC), and Microsft Windows. AOS is running as an emulated OS on Microsoft Windows, Linux, and Solaris (x86).

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

Contexts[edit]

The Oberon system runs directly on several machine architectures and as a subsystem in several host operating systems. The context identifier in the name or text of a source module is a means of denoting this context [3] where the module should compile and work.

In an ActiveOberon source text, context is denoted according to this syntax.

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

Where the context is not formally recognized, context in a comment is preferable to none.

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

Alternatively the context identifier can be prefixed to the module identifier.

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

As the Oberon filesystem does not support folders, a module file name is usually prefixed with a context.

NameOfModuleFile := Identifier "." Identifier ".Mod"
Contexts
Machine Software Context
Identifier[4]
Installation
archives
Installation
Instructions
X86 PC Bluebottle = AOS = A2 A2 SourceForge  
X86 PC UnixAos installed on Solaris,
Linux or MacOSX (Darwin).
A2    
X86 PC BlackBox Component Builder,
Windows application
BB  
X86 PC Component Pascal,
Windows application
CP  
X86 PC[5] ETH Oberon, PC-Native S3    
X86, ARM, ARMv7,
RISC-V and MIPS
Oberon Linux Revival, OLR;
installed on Linux
S3  
JVM and
CLI
Gardens Point Component Pascal,
JVM and .NET applications
GPCP  
X86 PC Oberon subsystem in
A2 and in UnixAos
Oberon Included in A2 and in
UnixAos
X86 PC[6] Linz-Oberon V4 JKU Linz
SourceForge
Linux
Windows
FPGA Oberon V5 V5  
Emulated FPGA Oberon V5 emulator on
*nix or Windows[7]
V5  
X86 and FPGA Experimental Oberon EO  

Installing[edit]

In the table above, a context is chosen. The installation archives are retrieved, and the software is installed and configured according to the instructions cited.

Getting Started[edit]

The user interface of the Oberon System is quite surprising on the first sight. It is a so called text 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 therefore be used as command input. Commands are activated by a middle-mouse click[8] 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.[9] A steep ascent in the early learning curve makes it a little bit difficult in the beginning. No questions are asked: this is a deliberate design decision, which needs getting used to. Most 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".[10] A short introduction to the user interface can be found on Niklaus Wirth's home page.[11] 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 Fischers Oberon System 3 Tutorial. An expanded version of this tutorial was published as a book,[12] now out of print. The whole book 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[13]). 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 it – after a successful installation: The Oberon Companion 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 in any viewer and type the command Desktops.OpenDoc Book.Tool ~. Then move the mouse over Desktops.OpenDoc and do a middle mouse button 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 middle mouse 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 with a GhostScript based free PDF converter. To print 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 middle mouse button click on Desktops.PrintDoc.

Reading[edit]

This book is read with a Web browser. In an Oberon which has the Desktops module, click with the MiddleMouse button on the command "Desktops.OpenDoc"[14].

Desktops.OpenDoc 
"http://www.loband.org/loband/filter/org/wikibooks/en/ /wiki/Oberon"[15]

Desktops.OpenDoc 
"http://www.loband.org/loband/filter/org/wikibooks/en/ /wiki/Oberon/Oberon.Sort.Mod"

In another system 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 context, click on the context identifier in the third column of the table.

Compiling[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 the context 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 LinuxAos are installed to /usr/aos/obj/ and a new file would typically be written to a working directory such as /home/me/aos/.

   ... in A2 and Oberon Contexts[edit]

Compile A2 and Oberon modules in the A2 context; not in the Oberon subsystem. Use the Compile button in the PET editor or use Builder.Tool.

   ... in the S3 Context[edit]

If a module is opened with Desktops.OpenDoc as described above, it can be compiled directly from the viewer. Select any characters beginning with M in MODULE and MiddleMouse click on Compiler.Compile @ . Otherwise import to the Oberon system and use Compiler.Tool.

   ... in the V5 Context[edit]

Use an ORP.Compile command in System.Tool.

Dataflow[edit]

Oberon
Text
Oberon
MediaWiki.Markup
command
MediaWiki
markup text
MediaWiki
processor
HTML5 text
Oberon
Desktops.OpenDoc
command
Oberon
Text
       

Web
browser
browser
text
Clipboard
or Save
operation
ASCII
text file
Oberon
mouse
copy
Oberon
Text

The displayed Oberon Text, on the right, should be identical to the original Oberon Text, on the left. Text color is not preserved by transport of the browser text into Oberon or by the current Desktops.OpenDoc.

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 UnixAos. Indicate the source in the wiki edit subject line.
  • Use Oberon naming conventions, including context naming.
  • Avoid page duplication. If two contexts share a source module, define a page redirect rather than duplicate an existing page.

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[16] 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; the current Desktops.OpenDoc is inadequate. Being logged in to a Wikimedia account is advisable. In the Contexts table above, click on an identifier to open the context 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.

  • Fix an edit conflict.
  • 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. Contexts can converge.
  • 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]

To compare versions of a module, 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

https://en.wikibooks.org/wiki/?diff=3205420&oldid=3205558&diffonly=1

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.

And, of course, Oberon has the Diff module. Pages can be retrieved to an Oberon system and compared as with Diff.Do TextFile1 TextFile2 .

Support[edit]

Developing[edit]

A few open projects worthy of effort.

  • For any context, compile a fresh release, with bug fixes and improvements, and post on a public server.
  • With the existing cryptography modules as a base, build an SSL implementation. Extend support for HTTP to support for HTTPS.
  • 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 the HTMLDocs module. Add support for styling and tables, for example.

License[edit]

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

ftp://ftp.ethoberon.ethz.ch/ETHOberon/license.txt

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

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

o Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

o Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

o Neither the name of the ETH Zurich nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE ETH OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

References[edit]

  1. 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 the S3 context.
  2. These systems comprise hundreds of modules. At present fewer than ten modules are available here. Nevertheless even one small bug fix can be essential to success in a task.
  3. Friedrich, F., Negele, F., "Proposal for Modules Contexts"
  4. New context identifiers.
  5. Including the Transmeta Crusoe 5400 and the StrongARM SA 110 and SA 1110.
  6. Applications for Amiga, Linux, Unix and MS Windows. A native version has not been produced.
  7. The SDL2 library and a C99 capable C compiler are required. GCC or Clang suffice for compilation.
  8. Using the mouse and the keyboard http://www.ethoberon.ethz.ch/ethoberon/tutorial/Mouse.contents.html
  9. 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. 
  10. Reiser, Martin: "The Oberon System - User Guide and Programmer's Manual" - Out-of-print - Addison-Wesley/ACM Press (1991) ISBN 0-201-54422-9
  11. Wirth, Niklaus (2015). "How to use the Oberon System". https://www.inf.ethz.ch/personal/wirth/ProjectOberon/UsingOberon.pdf. 
  12. 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, but see notes in text
  13. Matthias, Peter. "Oberon Linux Revival". http://oberon.wikidot.com/. 
  14. With an older HTMLDocs module some characters appear as empty boxes. To correct this, install and compile the latest Oberon.HTMLDocs.Mod. Desktops is not yet available in EO or V5 contexts.
  15. The loband filter allows Oberon to use HTTP while the Wikimedia server provides HTTPS.
  16. MediaWiki.Markup has replaced MediaWiki.Compile.