Files
Landon Curt Noll a1c86c8a7a add original C links to entry navigation bars
The navigation bar for a winning entry now has a "_Original C_" link
(between the ✅ and the Inventory on the right hand side) so that one
may easily view the original C code that was submitted for IOCCC judging.

Ran `make www timestamp` to perform the above.
2025-08-10 12:46:23 -07:00

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<h1>The International Obfuscated C Code Contest</h1>
<h2>1996/dalbec - Best numerical obfuscation</h2>
<h3>Generator of strong probable-primes to a given base</h3>
</div>
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<div class="navbar">
<a class="Left" href="../august/index.html">&larr; 1996/august</a>
<a class="Left" href="../index.html">&uarr; 1996 &uarr;</a>
<a class="Left" href="../eldby/index.html">1996/eldby &rarr;</a>
<a class="Right" href="https://github.com/ioccc-src/winner/blob/master/1996/dalbec/dalbec.c">C code</a>
<a class="Right" href="https://github.com/ioccc-src/winner/blob/master/1996/dalbec/Makefile">Makefile</a>
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<a class="Right" href="https://github.com/ioccc-src/winner/blob/master/1996/dalbec/dalbec.orig.c">Original C</a>
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<h2 id="author">Author:</h2>
<ul>
<li>Name: <a href="../../authors.html#John_Dalbec">John Dalbec</a><br>
Location: <a href="../../location.html#US">US</a> - <em>United States of America</em> (<em>United States</em>)</li>
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<h2 id="to-build">To build:</h2>
<pre><code> make all</code></pre>
<h2 id="to-use">To use:</h2>
<pre><code> ./dalbec</code></pre>
<h2 id="try">Try:</h2>
<pre><code> ./try.sh</code></pre>
<p>Why does the output end with 121?</p>
<h2 id="judges-remarks">Judges’ remarks:</h2>
<p>The output is mis-leading … why does it also print 2047?</p>
<p>For a hint see
<a href="https://web.archive.org/web/20000510191341/https://www.utm.edu/research/primes/prove2.html">https://web.archive.org/web/20000510191341/https://www.utm.edu/research/primes/prove2.html</a>.</p>
<p>… and then try to understand the source! :-)</p>
<p>We (the judges) recommend that you take the time needed to understand
how this program works. The source is small enough to make the effort
reasonable, and complex enough to make it interesting.</p>
<h2 id="authors-remarks">Author’s remarks:</h2>
<p>This program assumes that your terminal wraps lines automatically.
If this is not the case, you may need to change the space in the
“printf” format string to a newline character.</p>
<p>An extra feature of this program is that it allows you (in most
cases) to estimate the stack space available to programs on your
system. Simply allow the program to run to completion. The stack
space is roughly proportional to the last number printed.</p>
<p>(On SunOS/cc, the proportionality constant is about 48 bytes.)</p>
<p>On completion, the program produces a core file that may be used to
refine this estimate. (Or you could try typing <code>limit</code> if you’re
running <code>csh</code>.) In rare cases the stack space may exceed <code>24*INT_MAX</code>
bytes, in which case the program will produce an inaccurate estimate.</p>
<p>This program is obfuscated by:</p>
<ol type="1">
<li><p>The use of easily-confused variable names.</p></li>
<li><p>Using the implicit <code>!=0</code> in conditional expressions.</p></li>
<li><p>Substituting expressions such as <code>!a</code> for <code>0</code> where <code>a!=0</code> and <code>!a</code> for <code>1</code>
where <code>a==0</code>.</p></li>
<li><p>The fact that <code>main()</code> is a single expression and so beautifies poorly.</p></li>
<li><p>The fact that <code>main()</code> is used:</p>
<ul>
<li>to compute powers in modular arithmetic.</li>
<li>to recursively call itself in the main loop.</li>
</ul></li>
</ol>
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<div id="inventory">
<h1 id="inventory-for-1996dalbec">Inventory for 1996/dalbec</h1>
</div>
<h2 id="primary-files">Primary files</h2>
<ul>
<li><a href="https://github.com/ioccc-src/winner/blob/master/1996/dalbec/dalbec.c">dalbec.c</a> - entry source code</li>
<li><a href="https://github.com/ioccc-src/winner/blob/master/1996/dalbec/Makefile">Makefile</a> - entry Makefile</li>
<li><a href="https://github.com/ioccc-src/winner/blob/master/1996/dalbec/dalbec.orig.c">dalbec.orig.c</a> - original source code</li>
<li><a href="https://github.com/ioccc-src/winner/blob/master/1996/dalbec/try.sh">try.sh</a> - script to try entry</li>
</ul>
<h2 id="secondary-files">Secondary files</h2>
<ul>
<li><a href="1996_dalbec.tar.bz2">1996_dalbec.tar.bz2</a> - download entry tarball</li>
<li><a href="https://github.com/ioccc-src/winner/blob/master/1996/dalbec/README.md">README.md</a> - markdown source for this web page</li>
<li><a href="https://github.com/ioccc-src/winner/blob/master/1996/dalbec/.entry.json">.entry.json</a> - entry summary and manifest in JSON</li>
<li><a href="https://github.com/ioccc-src/winner/blob/master/1996/dalbec/.gitignore">.gitignore</a> - list of files that should not be committed under git</li>
<li><a href="https://github.com/ioccc-src/winner/blob/master/1996/dalbec/.path">.path</a> - directory path from top level directory</li>
<li><a href="index.html">index.html</a> - this web page</li>
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<div id="coda"><h3>Coda</h3>
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