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<h1 id="mostly-oberon">Mostly Oberon</h1>
<p>By R. S. Doiel, 2020-04-11</p>
<p><strong>Mostly Oberon</strong> is a series of blog posts documenting
my exploration of the Oberon Language, Oberon System and the various
rabbit wholes I inevitably fell into.</p>
<h2 id="overview">Overview</h2>
<p>Oberon is a classical computer language and operating system
originated by Professors Niklaus Wirth and Jürg Gutknecht at <a
href="https://en.wikipedia.org/wiki/ETH_Zurich">ETH</a> circa 1987. It
was inspired by their experiences in California at the <a
href="https://en.wikipedia.org/wiki/PARC_(company)">Xerox Palo Alto
Research Center</a>. This series of blog posts are my meandering
exploration of Oberon-07 language based on <a
href="http://www.projectoberon.com/">Project Oberon 2013</a>.</p>
<p>NOTE: Oberon grew from Wirth’s Modula, which grew from Pascal, which
grew from his experiences with Algol.</p>
<h3 id="my-voyage">My Voyage</h3>
<p>I am new to both Oberon and the Oberon System. Oberon language is in
the tradition of ALGOL, Pascal, Modula 1 and 2 as well as incorporating
ideas from the parent of Object Oriented languages Simula. The Oberon
language reminds me of my first programming language <a
href="https://en.wikipedia.org/wiki/Turbo_Pascal">Turbo Pascal</a>.
Oberon’s language shape is more Pascal than C. For that reason I think
it has largely been overlooked.</p>
<p>Oberon-07 is Wirth’s most recent refinement of the Oberon language.
It is a terse and powerful systems language. It strikes a different
computing path then many popular programming languages used in 2020. You
find its influence along with Simula in more recent popular languages
like <a href="https://golang.org">Go</a>.</p>
<p>While Wirth conceived of Oberon in the context of a whole system it’s
use in research and instruction means it is also well suited <a
href="https://en.wikipedia.org/wiki/POSIX">POSIX</a> based systems
(e.g. BSD, Linux, macOS). The difference in programming in Oberon for a
POSIX system versus a native Oberon System is primarily in the modules
you import. These posts will focus on using Oberon language in a POSIX
environment.</p>
<p>NOTE: Oberon was initially a project including the CERES Hardware,
Oberon compiler and Oberon operating system for networked
workstations.</p>
<p>The latest Oberon is Prof. Niklaus Wirth and Paul Reeds’ Project
Oberon 2013. If you want to explore it I suggest using Peter De
Wachter’s <a
href="https://github.com/pdewacht/oberon-risc-emu">emulator</a>. Project
Oberon also his links to the updated books and articles in PDF format
which are easy to read (or print) on most computing devices.</p>
<h2 id="a-starting-point">A starting point</h2>
<p>I am starting my exploration with Karl Landström’s <a
href="https://miasap.se/obnc/">OBNC</a> compiler. I am focusing on
getting comfortable using and writing in the Oberon language.</p>
<p>Here’s an example of a simple “Hello World” program in Oberon written
for a POSIX system. I’ve named the <a href="HelloWorld.Mod">source
code</a> <code>HelloWorld.Mod</code>.</p>
<p>NOTE: In 2020 common POSIX systems include <a
href="https://en.wikipedia.org/wiki/Linux">Linux</a>, <a
href="https://en.wikipedia.org/wiki/Berkeley_Software_Distribution">BSD</a>
and <a href="https://en.wikipedia.org/wiki/MacOS">macOS</a>.</p>
<pre><code>
    MODULE HelloWorld;
      IMPORT Out;
    BEGIN
      Out.String(&quot;Hello World!&quot;); Out.Ln;
    END HelloWorld.
</code></pre>
<p>While this is longer than a Python “hello world” program it is much
shorter than I remember writing in Java and about the same number of
lines as in C. <code>BEGIN</code> and <code>END</code> are similar to
our opening and closing curly braces in C and the module is the basic
unit of source code in Oberon. <code>IMPORT</code> includes the module
<code>Out</code> (modules are similar to a included library in C) for
sending values to the console (stdout in POSIX). One thing to note,
Oberon language(s) are case sensitive. All language terms are
capitalized. This makes it easy to distinguish between source code
written in Oberon versus the Oberon language itself.</p>
<p>The <code>Out</code> module includes methods for displaying various
data types native to Oberon. There is a corresponding <code>In</code>
for receiving input as well as some additional modules provided with our
chosen compiler implementation.</p>
<p>Modules in Oberon can include a module wide initialization block. The
<code>BEGIN</code> through <code>END HelloWorld.</code> are an
initialization block. This is similar to C or Go’s “main” function for
our POSIX environment.</p>
<h3 id="obnc">OBNC</h3>
<p>If you want to run my “Hello World” you need to compile it. I have
found that <a href="https://miasap.se/obnc/">OBNC</a> compiler runs well
on Linux, macOS and <a href="https://www.raspberrypi.org">Raspberry
Pi</a>. Karl has also made a precompiled version that runs on Windows
available too. It is the Oberon compiler I plan to use in this series of
posts.</p>
<p>OBNC compiles Oberon source into C then into machine code for the
computer system you are running on. Because it is compiling to C it can
function as a <a
href="https://en.wikipedia.org/wiki/Cross_compiler">cross compiler</a>.
This opens the door to <a
href="https://en.wikipedia.org/wiki/Bare_machine">bare metal
programming</a>.</p>
<p>If you’re following along please install OBNC on your computer.
Instructions are found at https://maisap.se/obnc. Karl also has
excellent documentation and is responsive to questions about his
implementation. His contact methods are included on his website.</p>
<h3 id="running-obnc">Running OBNC</h3>
<p>OBNC provides a Oberon-07 compiler with some optional modules for
working in a POSIX environment. Compiling our “Hello World” is easy from
your shell or terminal.</p>
<pre><code>
    obnc HelloWorld.Mod
</code></pre>
<p>If all goes well this should produce an executable file named
<code>HelloWorld</code> (or <code>HelloWorld.exe</code> on Windows). You
can now run this program with a command like <code>./HelloWorld</code>
(or <code>HelloWorld</code> on Windows).</p>
<h3 id="learning-more-about-oberon">Learning more about Oberon</h3>
<p>I have faced two challenges in my exploration of Oberon, finding a
compiler I was happy with (thank you Karl for OBNC) and sorting out the
literature around Oberon language implementations and system
versions.</p>
<p>Oberon has a rich history though it was not well known in Southern
California in 2020. Oberon’s history is primarily academic and European.
It was commonly used in college level instruction in Europe from it’s
inception at ETH in the late 80’s through the early 2000s. The Oberon
System is an Open Source system (predating the term by a decade) and was
created in the spirit of other academic systems such as BSD. There are
many books (physical books as opposed to ebooks) dating from that era.
They covered the Oberon language and system of their time. From a
historical computing perspective they remain very interesting. But
running Oberon on modern 2020 hardware is a little more challenging.
Fortunately Prof. Emeritus Wirth and Paul Reed brought things up to date
in 2013. I recommend Reed’s <a
href="http://www.projectoberon.com">www.projectoberon.com</a> as a good
place to start. He includes links to revised versions of the classic
Oberon and Oberon System texts written by Wirth et el. Prof. Wirth’s <a
href="https://inf.ethz.ch/personal/wirth/">website</a> is still
maintained and he features links to most of his major publications. His
is the canonical source of information on Oberon.</p>
<p>NOTE: Prof. Wirth’s personal website at ETH was available as of
2020-04-11.</p>
<p>I have found the ACM <a href="https://dl.acm.org/">Digital
Library</a> and the ETH <a
href="https://www.research-collection.ethz.ch/?locale-attribute=en">Research
Collection</a> very helpful. While much of the material is now historic
it remains useful for both techniques and inspiration. Today’s hardware,
even a Raspberry Pi Zero, is more resource rich than the original
systems Oberon ran on.</p>
<p>The online community for Oberon and Oberon System seems mostly
centered around a <a
href="https://lists.inf.ethz.ch/mailman/listinfo/oberon">mail list</a>
at ETH and net news group <a
href="https://groups.google.com/forum/#!forum/comp.lang.oberon">comp.lang.oberon</a></p>
<h3 id="next">Next</h3>
<ul>
<li>Next <a href="../12/Mostly-Oberon-Modules.html">Modules and
Procedures</a></li>
</ul>
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