Oberon/A2

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Overview at ETHZ
Documentation at ETHZ

Installing and Running A2

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

The original instructions 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, sys can be changed to bin.

chgrp -R sys ${aosdir}

vs.

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.

cd <myWorkingDirectory>
aos

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

User and Machine Specific Configuration of UnixAOS

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. 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. 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

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.

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.

SVN in a Unix-like System

Install Subversion. In Redhat, for example,

sudo yum install subversion

and in Debian.

sudo apt install subversion

Before attempting to create the local repository, check that UTF-8 character encoding is present in the system. An encoding failure will interrupt checkout with a report similar to this.

svn: E155009: Failed to run the WC DB work queue associated with '/home/me/a2', work item 15168 (file-install 44 UnixAos/DarwinA2 Installer/A2 64.app/Icon{U+ F00D} 1 0 1 1)
svn: E000022: Can't convert string from 'UTF-8' to native encoding:
svn: E000022: /home/me/a2/UnixAos/DarwinA2 Installer/A2 64.app/Icon{U+F00D}

If a locales package is available, it should be installed and configured according to instructions such as for Debian. Encoding "en_US.UTF-8 UTF-8" and several others will be effective.

At an arbitrary location, <somewhere>, in the user directory make a directory for the working copy of the repository. Eg.

mkdir <somewhere>/a2

Clone the repository into the directory. In a graphical environment, a dialogue prompting for the password may appear. In that case, the password option should be omitted from the command.

cd <somewhere>/a2
svn checkout \
        --username infsvn.anonymous \
        --password anonymous \
    https://svn-dept.inf.ethz.ch/svn/lecturers/a2/trunk .

Files will be reported as they are retrieved.

Redirecting to URL 'https://svn.inf.ethz.ch/svn/lecturers/a2/trunk':
A    UnixAos
A    UnixAos/buildtools
A    UnixAos/buildtools/Darwin.AMD64.Tool
A    UnixAos/buildtools/Solaris.I386.Tool
A    UnixAos/buildtools/Solaris.AMD64.Tool
A    UnixAos/buildtools/UnixAosBuild.Tool
A    UnixAos/buildtools/Linux.I386.Tool
A    UnixAos/buildtools/Linux.AMD64.Tool
A    UnixAos/buildtools/Darwin.I386.Tool
A    UnixAos/boot
  ...

If checkout is interrupted, by an encoding error or communication failure, this should recover.

cd <somewhere>/a2
svn cleanup .
svn update .

Check that the local repository is complete.

svn status <somewhere>/a2

Subsequently, the local repository can be updated.

cd <somewhere>/a2
svn update \
        --username infsvn.anonymous \
        --password anonymous .

See what has changed (including every changed file) since this subversion repository was created. This will produce a very large output.

svn -v log <somewhere>/a2

For additional details refer to the svn manual.

Documentation predating the SVN archive is in A2Documentation.pdf available from http://cas.inf.ethz.ch/projects/a2/repository/show/trunk/ocp/Documentation. Also refer to the Wayback Machine.

Git in a Unix-like System

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. These commands are used where apt is available.

apt install git
apt install git-lfs

Choose a name for the repository directory; "myoberon" in this example. The ls command allows avoidance of name conflict.

ls -ld myoberon

If a "myoberon" file or directory exists, rename it or choose another name. Then create the repository.

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

Use git-lfs to track some zip archives.

cd myoberon
git lfs track "Linux*.zip"
git add .gitattributes

Check which large files are tracked.

git lfs track

Retrieve a specific archive file.

git lfs fetch Linux64.zip

Verify existence of the zip archive.

ls -ld Linux64*

Unzip.

unzip Linux64

Execute the start script.

Linux64/a2.sh

A2 should appear.

The content of a2.sh can be displayed by executing "cat a2.sh" or by opening with an editor. The script performs two actions. "cd `dirname $0`" changes to the directory where a2.sh resides; ~/oberon/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.

SVN in MS Windows

While SVN is not distributed with Windows, third party softwares are available. TortoiseSVN is one possibility. Install an SVN client and proceed as for Unix-like system as described above. SVN commands are executed in Powershell or in the cmd console (instead of "mkdir" use "md"; don't include the Backslash indicating continuity of the svn command), both available in Windows 10. The executable script for Windows is named a2.bat rather than a2.sh. If using PowerShell change "oberon" in a2.bat to "./oberon" or ".\oberon".

Git in MS Windows

Git is available directly from the official Web site.

Module Naming

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

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 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	.GofA	.SymA
ARM, 64 bit	.GofAa	.SymAa

Object and Symbol File Names

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

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.

./Win32/a2.bat

For a 64 bit machine running Linux.

./Linux64/a2.sh

A window as at the right should appear.

User Level Applications

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

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 "127.0.0.1" (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.

Email

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

The Oberon subsystem in UnixAos on an XO-1.5.

Opening the Oberon Sub-system

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.

<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

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

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.

Email

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

News Reader

Notes pending.

Text

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 TextDesc	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
	ref	INTEGER
	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
	GName	POINTER

Texts.Piece

Type	Fields of PieceDesc	Types of Fields	Notes
Texts.Piece, a pointer to a Texts.PieceDesc	f	Files.File	Pointer
	off	LONGINT	Integer
	len	LONGINT
	obj	Objects.Object	Pointer
	lib	Objects.Library	Pointer
	ref	INTEGER
	col	SHORTINT
	voff	SHORTINT
	prev	Piece	Pointer
	next	Piece	Pointer

Module Sources, Tools and Configuration Texts

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	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.
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.Configuration.Mod
	Configuration.XML
Oberon.Desktops.Mod
Oberon.Documents.Mod	Oberon.Documents.Mod
Oberon.ET.Mod
Oberon.Files.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.ISO9660Files.Mod
Oberon.ISO9660Volumes.Mod
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.Objects.Mod
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.Streams.Mod
Oberon.Strings.Mod
Oberon.TFTPTool.Mod	Oberon.TFTPTool.Mod
Oberon.TextDocs.Mod
Oberon.TextFrames.Mod	Oberon.TextFrames.Mod	LOOPs removed.
Oberon.Texts.Mod
Oberon.V24.Mod	Oberon.V24.Mod
Release.Oberon.Text	Oberon.Text	Usually Oberon.Text is customized to a user.
TFTP.Mod	TFTP.Mod
Unix.Oberon.NetSystem.Mod	Unix.Oberon.NetSystem.Mod	Handling of "@" characters in parameter of SetUser improved.
	myaos	Start script allowing use of a removable working store on multiple machines. Adaptable to requirements of user. Not in A2 repository.