Twenty Fourth International Obfuscated C Code Contest

Standard IOCCC stuff

View the index.html web page for the given winning entry for information on how compile the entry and how to run the winning program. Look at the winning source and try to figure how it does what it does! You may then wish to look at the Author’s remarks for even more details. This year we included most of the information included by the submitter.

Some ANSI C compilers are not quite as good as they should be. If yours is lacking, you may need to compile using gcc instead of your local compiler.

Historical note:

The IOCCC has a website and now has a number of international mirrors. The primary website can be found at www.ioccc.org.

Historical update:

The IOCCC website once had a number of international mirrors. As of 2020 Dec 29, GitHub serves as the distributed server farm for the IOCCC winner repo that GitHub renders as Official IOCCC web site - www.ioccc.org.

Remarks on some of the winning entries

We believe you will again be impressed with this year’s winning entries.

The fraction of worthy entries was higher than usual.

We call to your attention the hou entry that performs the MD5 cryptographic hash. Normally implemented with a set of integer and boolean operations, this code uses floating point variables inside a single while loop filled with unusual constants, cosine, square root, and exponent function calls. The number of lines of code is also smaller than the original algorithm.

The mills2 source code is a very compressed version of a decompression algorithm. We think those who enjoy compression algorithms will particularly enjoy this entry.

We suggest that you attempt to completely understand the endoh4 1-liner program: another impressive compact piece of C code.

And while you are at it, cat the endoh2 prog.c code. Compile it and look at the source code again.

In a “Back to the Future” moment, endoh3 gave us a twist on one of the all time best IOCCC entries from 1984.

We also suggest that you take a very good look at how the muth code makes full use of the C Pre-Processor.

…We’ll stop spouting spoilers now. Have fun exploring all the entries!

Remarks on some of submissions that did not win

The number of entries that would have made it into the final rounds would have been much higher had some people paid attention to rules 2 and 22 (one third of 666).

Rule 22, now known as Catch 22 states:

Your source code, data files, remarks and program output must NOT identify the authors of your code. The judges STRONGLY prefer to not know who is submitting entries to the IOCCC.

The “Peter Honeyman is exempt” guideline also applies to this rule. Identifying yourself, in an obvious way in your code, data, remarks or program output, unless you are Peter Honeyman or pretending to be Peter Honeyman, will be grounds for disqualification of your entry.

A number of other entries were based on iocccsize.c, making derivative works rather than original works.

Still other entries were too large, violating the first line of rule 2:

The size of your program source must be <= 4096 bytes in length.

While these entries might have passed under the 2053 limit for iocccsize, they were larger than <= 4096 bytes, sometimes by an order or magnitude.

We hope the authors of some of those entries will fix and re-submit them for the next IOCCC.

Final Comments

Please feel free to send us comments and suggestions about the competition, this README or anything else that you would like to see in future contests.

If you use, distribute or publish these entries in some way, please drop us a line. We enjoy seeing who, where and how the contest is used.

If you have problems with any of the entries, AND YOU HAVE A FIX, please send us the fix (patch file or the entire changed file).

For the latest information on how to contact the IOCCC Judges please visit