In 1991 the code blocks in the html files should look better with smaller screens. In one entry, rince, an image was added as the formatting is too complicated to get right. The text was changed from two columns to one column and then a screenshot was taken so that it's a bit easier to see with smaller widths. This looks fairly good on mobile phones too. The only downside, of course, is if the web pages ever change to have a different background or code colour it won't match but it did not look right with mobile phones. This required a manifest update. In 1992 one entry's html file defeated me for now so I had to stop. This can be looked at later. The last entry I am committing changes to is 1991/buzzard.1. It was buzzard.2/buzzard.2.design.md that is a big problem and will have to be done another time.
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<h1>The International Obfuscated C Code Contest</h1>
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<h2>1992/buzzard.1 - Most obfuscated algorithm</h2>
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<a class="Left" href="../ant/index.html">← ant</a>
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<a class="Left" href="../index.html">↑ 1992 ↑</a>
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<a class="Left" href="../buzzard.2/index.html">buzzard.2 →</a>
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<a class="Right" href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1992/buzzard.1/buzzard.1.c">C code</a>
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<a class="Right" href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1992/buzzard.1/Makefile">Makefile</a>
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<a class="Right" href="#inventory">Inventory</a>
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<a class="Right" href="https://validator.w3.org/nu/?doc=https%3A%2F%2Fioccc-src.github.io%2Ftemp-test-ioccc%2F1992%2Fbuzzard.1%2Findex.html">✓</a>
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<h2 id="author">Author:</h2>
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<ul>
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<li>Name: <a href="../../authors.html#Sean_Barrett">Sean Barrett</a><br>
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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>
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<pre><code> make all</code></pre>
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<h2 id="to-use">To use:</h2>
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<pre><code> ./buzzard.1 num num</code></pre>
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<h2 id="try">Try:</h2>
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<pre><code> ./try.sh</code></pre>
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<h2 id="judges-remarks">Judges’ remarks:</h2>
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<p>To see good C Preprocessor buzzard.1, try:</p>
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<pre><code> make babble.cppcb
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cat babble.cppcb</code></pre>
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<p>Notice how many statements it takes to do anything useful?</p>
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<h2 id="authors-remarks">Author’s remarks:</h2>
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<h3 id="what-you-shouldnt-think-about-buzzard.1">What you shouldn’t think about <code>buzzard.1</code>:</h3>
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<p><code>buzzard.1</code> doesn’t just do a mass of <code>#define</code>s as its obfuscation.</p>
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<h3 id="what-you-should-be-glad-about">What you should be glad about:</h3>
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<p>I didn’t just submit the post-C-preprocessed output as an entry.</p>
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<h3 id="cute-trick-warning">Cute trick warning</h3>
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<p><code>buzzard.1</code> contains only a numeric <code>printf(3)</code>, yet sometimes it prints out
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short strings.</p>
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<h3 id="what-it-does">What it does</h3>
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<p><code>buzzard.1</code> is a simple mathematical program. It expects two numeric
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arguments.</p>
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<pre><code> ./buzzard.1 0 <num></code></pre>
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<p>will print out the factorial of <code><num></code>.</p>
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<pre><code> ./buzzard.1 <num1> <num2></code></pre>
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<p>will print out the largest common factor of <code>num1</code> and <code>num2</code>.</p>
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<pre><code> ./buzzard.1 1 <num2></code></pre>
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<p>will print out a factor of <code>num2</code> if it’s composite, or else
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it will print a string informing you that <code>num2</code> is prime.</p>
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<p>If the first argument is less than 0, it prints out an
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error message.</p>
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<h3 id="what-it-is">What it is</h3>
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<p><code>buzzard.1</code> is a translator from a pseudo-assembly language into a subset of C
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suitable for execution on Charles Babbage’s Analytical Engine. Or rather, the
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<code>#define</code>s in <code>buzzard.1</code> are that translator. The rest of <code>buzzard.1</code> is a
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<code>buzzard.1</code> program. If you run the whole mess through CPP and a beautifier, you
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will see that all you have is a loop that runs until a variable is not 0, and a
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sequence of assignment statements. The assignment statements are all of the
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form <code>a op= b</code> or <code>a = b</code>. The Engine actually allowed ‘a = b op c’. Only <code>+</code>,
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<code>-</code>, <code>/</code>, and <code>*</code> are used–no boolean or bitwise operators. The infinite loop
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could have been simulated on the AE by connecting the already-processed card
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stack to the input card stack.</p>
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<h3 id="how-to-try-to-understand-it">How to try to understand it</h3>
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<p><em>Don’t</em> expand the <code>#define</code>s! Rather, decipher what they do.
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Some of them are mere obfuscation fodder, put in to encourage
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you to run it through CPP.</p>
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<h3 id="what-it-doesnt-do-quite-right-as-an-emulator">What it doesn’t do quite right as an emulator</h3>
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<p>Because of the definitional constraints, calls to <code>atoi(argv[#])</code> also appear
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inside the loop. These could be put outside–the initial values of the
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“registers” on the AE–but the macro conventions being used didn’t lend
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themselves to it.</p>
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<h3 id="theoretical-observations">Theoretical observations</h3>
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<p>The simulated comparison operations only work with a certain range of numbers;
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numbers that are too large will cause the output code to fail to simulate the
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input code. This means that this implementation of <code>buzzard.1</code> would not be
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Turing-complete, even if the AE could process indefinitely-sized numbers.
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However, this is actually a constraint that no actual computer can meet, either,
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so we can conclude that if an AE, with card bins connected as suggested above,
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were hooked up to a memory unit of sufficient size, it would be as Turing
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complete as any existing machine (or, for those who interpret that excessively
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critically, i.e. “not at all” for both, we can simply say that the AE could
|
||
simulate any existing machine–although not quickly). This would be a good
|
||
place to site some references on the AE, but I don’t have any.</p>
|
||
<h3 id="definition-of-the-input-language-to-buzzard.1-or-what-exactly-do-all-the-macros-do">Definition of the input language to buzzard.1 (OR What Exactly Do All The Macros Do?)</h3>
|
||
<p>[Don’t read this unless you’re stumped!]</p>
|
||
<pre><code> MACRO FUNCTION MNEMONIC
|
||
|
||
V begin variable
|
||
declarations Variable
|
||
|
||
C begin program Code
|
||
|
||
Q(b,a) let b = a eQuals
|
||
A(c,a,b) let c = a + b Add
|
||
S(c,a,b) let c = a - b Subtract
|
||
|
||
D(c,a,b) let c = a / b,
|
||
where b is a Divide
|
||
constant
|
||
|
||
U(c,a,b) let c = a / b,
|
||
where b is Unknown
|
||
anything
|
||
|
||
M(c,a,b) let c = a * b Multiply
|
||
|
||
O(c,a,b) let c = a Or
|
||
boolean-or
|
||
b (a,b are
|
||
0 or 1)
|
||
|
||
B(b, a) let Boolean
|
||
b = boolean
|
||
value of a
|
||
|
||
P(b, a) let b = 1 if
|
||
a>0, else 0. Positive
|
||
|
||
l emit next
|
||
sequential Label
|
||
label
|
||
|
||
J(x) goto label #x Jump
|
||
|
||
Z(a,d) if a is 0
|
||
goto d (a is Zero
|
||
0 or 1)
|
||
|
||
E(a,d) if a is 1
|
||
goto d Else
|
||
(a is 0 or 1)
|
||
|
||
H halt Halt
|
||
|
||
K(x) let x = number
|
||
of cmdline Kount
|
||
arguments
|
||
|
||
G(x,y) let x = the
|
||
value
|
||
of the yth Get arg
|
||
argument
|
||
|
||
T end of code;
|
||
begin output Terminate
|
||
section
|
||
|
||
X(y) print hex
|
||
value of y heX
|
||
|
||
T end of output Terminate
|
||
section
|
||
and program</code></pre>
|
||
<p>You can figure out the other macros yourself. In the sample program, I’ve
|
||
actually implemented subroutines by saving a return address in a variable and
|
||
then jumping to a routine– specifically, a routine that converts a number into
|
||
BCD, so it can be output by the hexadecimal output statement.</p>
|
||
<h3 id="how-it-works-i.e.-how-to-get-useful-programs-from-a-op-b">How it works, i.e., how to get useful programs from a op= b</h3>
|
||
<p>The essential statement to be able to make interesting
|
||
programs is the conditional (given that we have loops).
|
||
Since all you can do in the given operation output set is
|
||
assignment, we implement “conditional assignment”:</p>
|
||
<pre><code> if (x) y = z;</code></pre>
|
||
<p>To implement this, we constrain <code>x</code> to be either 0 or 1, and
|
||
simply compute:</p>
|
||
<pre><code> y = (z * x) + (y * (1-x));</code></pre>
|
||
<p>This is more obscured by factoring out common terms and restricting
|
||
ourselves to two operand operations:</p>
|
||
<pre><code> temp = z; (temp == z)
|
||
temp -= y; (temp == z-y)
|
||
temp *= x; (temp == (z-y)*x)
|
||
y += temp; (y == (z-y)*x + y)
|
||
( == z*x - y*x + y)
|
||
( == z*x + y*(1-x))</code></pre>
|
||
<p>Next we imagine we have a <a href="https://en.wikipedia.org/wiki/Program_counter">pc</a>.
|
||
“I’m supposed to execute statement pc next”, says our emulator. But suppose
|
||
we’re not currently coming up on statement pc. To handle this, we simply make
|
||
every operation conditional on the pc having the correct value:</p>
|
||
<pre><code> if (pc == some_constant) y = z;</code></pre>
|
||
<p>To combine this with other operations, we simply multiply by our
|
||
(<code>pc == some_constant</code>) flag right after the above <code>temp *= x</code>.</p>
|
||
<p>To evaluate <code>pc == some_constant</code> requires one more trick. We assume that
|
||
numbers can only be in some limited range. Then we use successive additions and
|
||
divisions to reduce that number down to <code>-1</code>, <code>0</code>, or <code>1</code>. You could, for
|
||
instance, do this by using mod by <code>2</code> and div by <code>2</code> to count bits, stopping
|
||
after, say, <code>32</code> iterations. The number you get is between <code>0..32</code>, so another
|
||
<code>6</code> iterations on it reduces it to <code>0..6</code>. Three iterations on this produces
|
||
<code>0..2</code> (<code>3</code> would be <code>7</code>), and then two iterations on this produces 0 or 1.
|
||
Instead I use a shorter two-divide approach that assumes I’m allowed to use
|
||
numbers slightly larger than the numbers I’m operating on.</p>
|
||
<p>A similar approach is used to detect positive numbers.</p>
|
||
<p>Note that the obvious code to compute <code>y/x</code> will not work correctly,
|
||
because every value is computed, even if the pc is not set correctly;
|
||
if <code>x</code> is ever <code>0</code> when the real C code reaches this computation the
|
||
program will die. (This was discovered the hard way.) The solution
|
||
is to stick <code>x</code> in a temporary, and if the current code is not about
|
||
to be executed, set the temporary to <code>1</code>.</p>
|
||
<p>Thanks to Bill Pugh for bringing the loop-ability of the AE to
|
||
my attention.</p>
|
||
<p><code>buzzard.1</code> was originally named <code>cb</code>, for obvious reasons, and is
|
||
dedicated to the memory of Charles Barrett.</p>
|
||
<!--
|
||
|
||
Copyright © 1984-2024 by Landon Curt Noll. All Rights Reserved.
|
||
|
||
You are free to share and adapt this file under the terms of this license:
|
||
|
||
Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)
|
||
|
||
For more information, see:
|
||
|
||
https://creativecommons.org/licenses/by-sa/4.0/
|
||
|
||
-->
|
||
<!-- AFTER: last line of markdown file: 1992/buzzard.1/README.md -->
|
||
|
||
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|
||
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||
|
||
<!-- START: this line starts content generated by: bin/output-index-inventory.sh -->
|
||
|
||
<div id="inventory">
|
||
<h1 id="inventory-for-1992buzzard.1">Inventory for 1992/buzzard.1</h1>
|
||
</div>
|
||
<h2 id="primary-files">Primary files</h2>
|
||
<ul>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1992/buzzard.1/buzzard.1.c">buzzard.1.c</a> - entry source code</li>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1992/buzzard.1/Makefile">Makefile</a> - entry Makefile</li>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1992/buzzard.1/buzzard.1.orig.c">buzzard.1.orig.c</a> - original source code</li>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1992/buzzard.1/try.sh">try.sh</a> - script to try entry</li>
|
||
</ul>
|
||
<h2 id="secondary-files">Secondary files</h2>
|
||
<ul>
|
||
<li><a href="1992_buzzard.1.tar.bz2">1992_buzzard.1.tar.bz2</a> - download entry tarball</li>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1992/buzzard.1/README.md">README.md</a> - markdown source for this web page</li>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1992/buzzard.1/.entry.json">.entry.json</a> - entry summary and manifest in JSON</li>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1992/buzzard.1/.gitignore">.gitignore</a> - list of files that should not be committed under git</li>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1992/buzzard.1/.path">.path</a> - directory path from top level directory</li>
|
||
<li><a href="index.html">index.html</a> - this web page</li>
|
||
</ul>
|
||
<hr style="width:10%;text-align:left;margin-left:0">
|
||
<h4>
|
||
Jump to: <a href="#">top</a>
|
||
</h4>
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</div>
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|
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||
<!-- START: this line starts content from: inc/footer.inventory.html -->
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||
|
||
<!--
|
||
|
||
Copyright © 1984-2024 by Landon Curt Noll. All Rights Reserved.
|
||
|
||
You are free to share and adapt this file under the terms of this license:
|
||
|
||
Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)
|
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|
||
For more information, see:
|
||
|
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https://creativecommons.org/licenses/by-sa/4.0/
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||
|
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-->
|
||
|
||
<div class="footer">
|
||
|
||
<div id="copyright"><h3>Copyright © 1984-2024 by Landon Curt Noll:
|
||
<a href="https://creativecommons.org/faq/#what-does-some-rights-reserved-mean"
|
||
target="_blank"
|
||
rel="license noopener noreferrer">Some Rights Reserved</a></h3>
|
||
<p>
|
||
This work is <b>licensed by Landon Curt Noll</b> under
|
||
<b><a href="https://creativecommons.org/licenses/by-sa/4.0/?ref=chooser-v1"
|
||
target="_blank"
|
||
rel="license noopener noreferrer"
|
||
style="display:inline-block;">CC BY-SA 4.0</a></b>.
|
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<img style="height:22px!important;margin-left:3px;vertical-align:text-bottom;"
|
||
src="../../png/cc.png"
|
||
alt="cc inside circle symbol">
|
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<img style="height:22px!important;margin-left:3px;vertical-align:text-bottom;"
|
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src="../../png/by.png"
|
||
alt="person inside circle symbol">
|
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<img style="height:22px!important;margin-left:3px;vertical-align:text-bottom;"
|
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src="../../png/sa.png"
|
||
alt="arrow looping back on itself inside circle symbol"><br>
|
||
You should <b>carefully review</b> the
|
||
<b><a href="https://creativecommons.org/licenses/by-sa/4.0/legalcode.en"
|
||
target="_blank"
|
||
rel="license noopener noreferrer">CC BY-SA 4.0 LEGAL CODE</a></b>
|
||
before using the licensed material.<br>
|
||
You may wish to review the
|
||
<b><a href="../../license.html"
|
||
target="_blank"
|
||
rel="license noopener noreferrer">highlights of some of the key features and terms</a></b>
|
||
of <b>CC BY-SA 4.0</b>.<br>
|
||
</p>
|
||
</div>
|
||
|
||
<div id="coda"><h3>Coda</h3>
|
||
<p>
|
||
<a href="https://validator.w3.org/nu/?doc=https%3A%2F%2Fioccc-src.github.io%2Ftemp-test-ioccc%2F1992%2Fbuzzard.1%2Findex.html" rel="nofollow">Nu HTML check this web page</a><br>
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<a href="#top">Jump to top</a> <a href="#content">Jump to Content</a> <a href="#inventory">Jump to Inventory</a><br>
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