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Overview at ETHZ
Documentation at ETHZ

Installing and Running A2

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A2 can be installed and used on a bare PC, including desktop and laptop machines considered obsolete for commercial operating systems. A2 can also work as a subsystem on ARM, MS Windows and Unix-like systems.

Installing and Running UnixAOS

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The original instructions[1] for installing UnixAOS are in http://user.informatik.uni-bremen.de/fld/UnixAos/Readme.txt. Installation files are available from http://user.informatik.uni-bremen.de/fld/UnixAos/.

The display of freshly installed LinuxAos Generic 32-bit, rev.9527.

The shell script installer assumes existence of a sys group in the host. For systems lacking this group, the script is easily adapted. For example, the line,

chgrp -R sys ${aosdir}

can be changed to this.

chgrp -R bin ${aosdir}

The UnixAOS working directory can have an ext2 or FAT filesystem on a removable flash store.

The aos start script, installed by install.UnixAos, by default to /usr/bin/aos, adjusts the operating system environment before starting aos.{solaris,linux,darwin}. As noted in Readme.txt, UnixAos can be started with these two commands.[2]

cd <myWorkingDirectory>

Of course <myWorkingDirectory> must be replaced with a specific directory name.

User and Machine Specific Configuration of UnixAOS

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UnixAos is configured by Configuration.XML. The Oberon subsystem is configured by Oberon.Text; refer to the ETH Oberon page and the original betadocu page.

Firefox and A2 with Weston and XWayland on a Debian 10 system with twin screens.

If the working directory is on a removable store, the myaos script allows the storage device to be used in multiple machines with differing configurations. When the store is not already mounted, e2fsck is applied as a precaution.[3] In case the filesystem has been corrupted, e2fsck will usually complete repairs. A reasonable location for the myaos script is the home directory of the user. For each host, create in the working directory, files Configuration.<host>.XML. To use the Oberon subsystem, create Oberon.<host>.Text. This can be done by copying the installed files and editing the copies. For example, a host named blunder requires Configuration.blunder.XML for A2 and Oberon.blunder.Text for the Oberon subsystem. The XML file contains ASCII text and can be edited with Geany, gedit or mousepad in Linux or with Edit > Text in A2. The installed Oberon.Text contains some binary information.[4] In ETH Oberon it would usually be edited with Edit or ET. Nevertheless plain text will also work. After storing Oberon.Text with ET.StoreChar, it can be edited with Mousepad or Gedit in Linux, with Notepad in MS Windows and with Atom in MacOS. This can resolve the difficulty of a file name, Oberon.<Host>.Text, exceeding the 32 character limit of the Oberon system. myaos copies Configuration.blunder.XML to Configuration.XML and Oberon.blunder.Text to Oberon.Text before starting UnixAos.

The A2 Repositories

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Originally, sources and executables for several platforms were maintained in an Apache Subversion (SVN) repository. The contemporary Git based repository began with files from SVN revision 10270. While the Git archive serves most purposes, the notes for SVN remain available.

The repository based method of installation provides the latest version and allows ongoing updates. In summary, the method is to establish a local working copy of the repository and to update when convenient. The repository is checked out from the ETHZ archive and A2 can be built for various platforms including a bare PC. As of 2022 January the repository contained completely working executables in subdirectories for Windows, Linux (Intel 32 and 64 bit) and ARM. The working copy of the repository will occupy 0.5+ GB depending upon inclusion of executables.

Git in a Unix-like System

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Git operations. For details, follow the links in the text.

The Wikipedia article provides a useful overview. Official documentation is available as a Reference Manual, comprising manual pages, and the Pro Git book. git-lfs is documented separately.

Each Linux has an installation procedure for Git with the various procedures summarized in the official Web site. Release specific information is also available. For Debian Linux, refer to the UsingGit wiki page. If apt is available these commands suffice.

# apt install git
# apt install git-lfs

The name of the repository directory is arbitrary. "A2" serves for this example. The ls command allows avoidance of name conflict.

# ls -ld A2
drwxr-xr-x 12 me mygroup 4096 Dec  5 09:22 A2

Create the repository.

# git clone https://gitlab.inf.ethz.ch/felixf/oberon.git A2

Use git-lfs to track some zip archives.

# cd A2
# git lfs track "Linux*.zip"
# git add .gitattributes

Check which large files are tracked.

# git lfs track
Listing tracked patterns
    ARM/ARM.A2/*.bin (ARM/ARM.A2/.gitattributes)
    Linux32.zip (.gitattributes)
    Linux64.zip (.gitattributes)
    LinuxARM.zip (.gitattributes)
    Win32.zip (.gitattributes)
    Win64.zip (.gitattributes)
    *.bin (.gitattributes)
    Linux*.zip (.gitattributes)
Listing excluded patterns

Retrieve a specific archive file.

# git lfs fetch Linux64.zip
fetch: Fetching reference refs/heads/main

Verify existence of the zip archive.

# ls -ld Linux64*
-rw-r--r-- 1 root root 23712521 Dec  5 09:19 Linux64.zip


# unzip Linux64
 Archive: Linux64.zip
    creating: Linux64/
    creating: Linux64/work/
   inflating: Linux64/oberon.ini
    creating: Linux64/bin/
   inflating: Linux64/Kernel.GofU
   inflating: Linux64/OpenTypeScan.SymU
   inflating: ...

Execute the start script.

# Linux64/a2.sh
LinuxA2 Generic 32 bit, rev.9799 started from the Git repository.

The content of a2.sh can be displayed by "cat a2.sh" or with an editor. The script performs two actions. "cd `dirname $0`" changes to the directory where a2.sh resides; ~/A2/Linux64 for example. Then "./oberon run a2.txt" executes Linux command "oberon" with arguments "run" and "a2.txt". a2.txt contains A2 commands and can be displayed by cat and by an editor. The first command is System.DoFile oberon.ini ~. oberon.ini also contains A2 commands. The last command is "FSTools.Mount WORK RelativeFileSystem .~" which mounts pseudo-volume WORK at the current directory. Using an editor, the current directory symbol, ".", can be replaced with the fully qualified Linux name chosen by the user to be the working directory. WORK and contents are visible via the UnixA2 menu, Files > Files.

Git in MS Windows

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Git is available directly from the official Web site.

Module Naming

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In A2, identifiers "A2" and "Oberon" in a source module denote context. This is the syntax in the Oberon (2019) Language Report, section "5 Modules".

Module := 'MODULE' [TemplateParameters] Identifier 'IN' Identifier ';' ...

Within the scope of a module, the name of an imported module can be aliased with this syntax also in the section referred to above.

Import = Identifier [':=' Identifier] ...

Hence this example.

IMPORT ... Out := OutStub ...

Target Systems and File Name Extensions

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Compilation, loading, linking and associated terminology is discussed in https://people.inf.ethz.ch/felixf/pdfs/2011_UnifiedStaticDynamicLoading.pdf. As in all Oberon systems, the name of a file specifying a module can differ from the name of the module. These file name extensions are conventional in A2.

Target System Generic[5] Object File Name Extension Symbol File Name Extension
Unix, x86, 32 bit .GofU .SymU
Unix, AMD64, 64 bit .GofUu .SymUu
Windows, x86, 32 bit .GofW .SymW
Windows, AMD64, 64 bit .GofWw .SymWw
ARM, 32 bit[6] .GofA .SymA
ARM, 64 bit .GofAa .SymAa

Object and Symbol File Names

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Object and symbol file names contain the context separated from the module name by a Minus-Sign. The Minus-Sign prevents use as a proper name in Oberon. Hence the object and symbol files for the Oberon System module are named Oberon-System.GofU and Oberon-System.Sym.

Startup from the Repository

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With the A2 repository in place according to the preceding section, A2 can run.

Identify supported architectures.

cd <somewhere>/a2/

In MS Windows.

dir /ad *

In Linux.

ls -d *

The output should be similar to this.

AosVM  LanguageReport  Linux32  source  UnixAos  Win64
ARM    license.txt     Linux64  tools   Win32    WinAos

Review the startup process. In MS Windows.

dir /ad Win32/*

In Linux 64.

ls -ld Linux64/*

The oberon file must be executable. If necessary, adjust permission as in these examples.

chmod u+x Win32/oberon
The startup display of LinuxA2, Generic, 32 bit at 2022-10-31.
chmod u+x Linux64/oberon

Execute the appropriate start script. This for a 32 bit machine running MS Windows.


For a 64 bit machine running Linux.


A window as at the right should appear.

User Level Applications

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Various documents and applications are available via the menu at the lower left of the A2 display. Note Demos and Docu > Program Demos.

Secure Shell Console

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In the target system, localhost or an external system, install a SSH server. This is one possibility.

sudo apt install openssh-server

In the A2 menu invoke Tools > Secure Shell. For Host specify "localhost" or "" (without the quote marks) or the name or address of the external machine. Specify your user id. Click on Connect. Provide your password when prompted.


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A mail client using IMAP is at Apps > MailClient. The Oberon subsystem described in the subsequent section has Mail.Panel supporting POP, POP3 and SMTP.

Oberon Subsystem

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The Oberon subsystem in UnixAos on an XO-1.5.

Opening the Oberon Sub-system

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At the lower left of the A2 screen, menu Tools > Oberon and Develop > Oberon FullScreen allow interactive startup of an Oberon subsystem.

The subsystem can also be opened with a command or commands in the Autostart section of Configuration.XML. In UnixAos, revision 4929, these lines in Configuration.XML.

<Section name="Autostart">
	<Setting name="OberonDisplay" value="OberonDisplay.Install Oberon 1100x704 0 74 ~"/>		
	<Setting name="OberonStart" value="Oberon.Call System.Init Oberon"/>

This in more recent revisions[7].

<Section name="Autostart"> 
	<Setting name="Start an Oberon" value="Oberon.Start Oberon 1100x704 0 74 ~"/> 

The dimensions, 1100x704, can be adjusted for satisfactory proportioning of text in a viewer. If the Oberon window is stretched, by grabbing the lower right corner with the mouse, the proportionality of text to viewer is preserved.

Usage Tips, Keyboard and Mouse

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Mouse usage is unusual but efficient. Definitely worth the small effort to learn. A mouse with three buttons or two buttons and a wheel is almost essential. The <Esc> key is used to interrupt a task. For example it can interrupt a long running FTP.GetFiles. <F1> sets the * marker. <F2> clears all marks. If a mouse button is pressed unintentionally, all mouse buttons pressed together before releasing any will have no effect. Comprehensive details of mouse and keyboard input and usage are in Mouse support, Mouse tutorial and Keyboard support pages.

Telnet Console

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Telnet is an insecure protocol but provides a host console within the Oberon sub-system. The instructions for ETH Oberon are applicable in the Oberon subsystem.


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The instructions for ETH Oberon are applicable in the Oberon subsystem.

News Reader

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Notes pending.

TextDesc is an extension of Objects.ObjDesc. The fields added to make TextDesc are distinguished from the fields inherited from ObjDesc by differing background colors.

The Type Text
Type Fields of
Types of Fields Notes
Texts.Text, a pointer to a Texts.TextDesc stamp LONGINT Integer
dlink Objects.Object Pointer
slink Objects.Object Pointer
lib Objects.Library Pointer
handle Objects.Handler Pointer
len LONGINT Length of text.
obs Objects.Library Pointer
trailer Texts.Piece Pointer to Sentinel node in list of pieces.
org LONGINT Offset in [0,len) of first character in last found piece.
pce Texts.Piece Last found piece.
Objects.Library in the table above
Type Fields of LibDesc Types of Fields Notes
Objects.Library, a pointer to a LibDesc next Objects.Library Pointer
ind Objects.Index Pointer
f Files.File Pointer
R Files.Rider Pointer
name Objects.Name  
dict Objects.Dictionary Pointer
maxref INTEGER  
Type Fields of PieceDesc Types of Fields Notes
Texts.Piece, a pointer to a Texts.PieceDesc f Files.File Pointer
off LONGINT Integer
obj Objects.Object Pointer
lib Objects.Library Pointer
prev Piece Pointer
next Piece Pointer

Module Sources, Tools and Configuration Texts

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A tiny sample of the approximately 2000 sources in A2.

A contemporary Firefox browser attempts to infer "Content type" from the name extension. By default Firefox infers wrongly that source file *.Mod contains "Amiga SoundTracker audio" and fails to open it. This difficulty is resolved by adjusting the "Action" Firefox associates with "Content Type". Open hamburger menu > Settings > General > Applications. For "Amiga SoundTracker audio" choose an editor such as /usr/bin/mousepad or /usr/bin/gedit. Most sources in A2 have been converted to plain ASCII text; some remain as Oberon Text. Gedit will open all of these. Mousepad and several other editors will not open Oberon Text. Content type "plain text document" should also be set to the chosen editor. With these adjustments Firefox should open most of the files in the repository.

In some contexts the user may fail to find a configuration of a browser to open files in the repository. In any case a browser should open the Wikibook copy.

ETHZ Repository Wikibook[8] Notes
BIOS.V24.Mod BIOS.V24.Mod  
BootManager.Asm BootManager.Asm BootManager source written in Network Assembler by André Fischer.
BootManager.Mod BootManager.Mod Module containing one command Split.[9]
BootManager.Text BootManager Instructional document written by André Fischer. In the repository and in MediaWiki representation.
BootManager.Tool BootManager.Tool Tool file summarizing the instructional document.
Oberon.Documents.Mod Oberon.Documents.Mod  
Oberon.Gadgets.Mod Oberon.Gadgets.Mod  
Oberon.HTML.Mod Oberon.HTML.Mod Revisions for conformance to HTML5.
  HTML.Tool No "preview" in the ETH Repository.
Oberon.HTMLDocs.Mod Oberon.HTMLDocs.Mod InitEntities() expanded to support more characters.
Oberon.MIME.Mod Oberon.MIME.Mod  
Oberon.Mail.Mod Oberon.Mail.Mod Deviation from SMTP corrected. Wrap() added. Names of types revised. Show() revised. Calculation of cont.len corrected.
Oberon.MultiMail.Mod Oberon.MultiMail.Mod
Oberon.News.Mod Oberon.News.Mod Authentication added to allow access to contemporary servers.
  Oberon.MediaWiki.Mod Not in A2 repository.
Oberon.Out.Mod Oberon.Out.Mod Allow delay of execution of Append, using a flag variable.
Oberon.Out1.Mod Allow delay of execution of Append, using a procedure variable.
Oberon.OutStub.Mod Oberon.OutStub.Mod  
Oberon.QuotedPrintable.Mod Oberon.QuotedPrintable.Mod Variant from LinuxA2 Gen. 32-bit, rev.9527.
  Oberon.RFC3986.Mod Percent encoding and decoding of URL. Not in A2 repository.
Oberon.Sort.Mod Oberon.Sort.Mod Better presentation of output. Revisions incomplete.
Oberon.TFTPTool.Mod Oberon.TFTPTool.Mod
Oberon.TextFrames.Mod Oberon.TextFrames.Mod LOOPs removed.
Oberon.V24.Mod Oberon.V24.Mod  
Release.Oberon.Text Oberon.Text Usually Oberon.Text is customized to a user.
Unix.Machine.Mod Unix.Machine.Mod  
Unix.Oberon.NetSystem.Mod Unix.Oberon.NetSystem.Mod Terminology improved. Local procedures moved out of SetUser. RETURN usage updated. Flag "ok" eliminated. Flag "verbose" added to simplify password debugging. Numerous comments clarified.
  myaos Start script allowing use of a removable working store on multiple machines. Adaptable to requirements of user. Not in A2 repository.


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  1. The Git repository, described subsequently, is a more recent method of installation and release tracking.
  2. The command line prefix in a Unix-like system is user configurable and can be configured to the empty string. For simplicity, the prefix is omitted in most of the commands shown here.
  3. A filesystem can become corrupted if not unmounted before the system is shut down. The directory can also be damaged by natural degradation of the storage media. If the filesystem is intact, the execution time for e2fsck is negligible.
  4. See Oberon/Text.
  5. "Generic" refers to applicability of the loader and linker to all target systems, independent of change in language and runtime system.
  6. Allowing A2 on the Raspberry Pi.
  7. The Oberon subsystem is invoked with MenuPage30.XML. The change from two commands to one is reported by svn diff -r 5253:5254 .../MenuPage30.XML
  8. In some cases the Wikibook copy differs from the latest file in the ETHZ repository. For an exact comparison, use a file comparator; Diff.Do in Oberon, comm in Linux. Some sources have a discussion page. Oberon.Mail.Mod discussion for example.
  9. BootManager.Split BootManager.Bin is executed to divide BootManager.Bin into BootManagerMBR.Bin and BootManagerTail.Bin. For additional details, refer to the instructional document of André Fischer.