The International Obfuscated C Code Contest
Copyright (c) Landon Curt Noll, Simon Cooper, Peter Seebach and Leonid A. Broukhis, 2001-2009. All Rights Reserved. Permission for personal, educational or non-profit use is granted provided this this copyright and notice are included in its entirety and remains unaltered. All other uses must receive prior permission from the contest judges.
Obfuscate: tr.v. -cated, -cating, -cates. 1. a. To render obscure. b. To darken. 2. To confuse: Their emotions obfuscated their judgment. [LLat. obfuscare, to darken : ob(intensive) + Lat. fuscare, to darken < fuscus, dark.] -obfuscation n. obfuscatory adj.
Last updated: Tue Jun 29 13:29:27 PDT 1999
The official IOCCC web site is:
How it was started:
The original inspiration of the International Obfuscated C Code Contest came from the Bourne Shell source and the finger command as distributed in 4.2BSD. If this is what could result from what some people claim is reasonable programming practice, then to what depths might quality sink if people really tried to write poor code?
I put that question to the USENET news groups net.lang.c and net.unix-wizards in the form of a contest. I selected a form similar to the contest (Bulwer-Lytton) that asks people to create the worst opening line to a novel. (that contest in turn was inspired by disgust over a novel that opened with the line "It was a dark and stormy night.") The rules were simple: write, in 512 bytes or less, the worst complete C program.
Thru the contest I have tried to instill two things in people. First is a disgust for poor coding style. Second was the notion of just how much utility is lost when a program is written in an unstructured fashion. Contest winners help do this by what I call satirical programming. To see why, observe one of the definitions of satire:
Keen or energetic activity of the mind used for the purpose of exposing and discrediting vice or folly.
The authors of the winning entries placed a great deal of thought into their programs. These programs in turn exposed and discredited what I considered to be the programmer's equivalent of "vice or folly".
There were two unexpected benefits that came from the contest winners. First was an educational value to the programs. To understand these C programs is to understand subtle points of the C programming language. The second benefit is the entertainment value, which should become evident as you read further!
Suggestions on how to understand the winning entries:
You are strongly urged to try to determine what each program will produce by visual inspection. Often this is an impossible task, but the difficulty that you encounter should give you more appreciation for the entry.
If you have the energy to type in the text, or if you have access to a machine readable version of these programs, you should next consider some preprocessing such as:
sed -e '/^#.*include/d' program.c | cc -E
This strips away comments and expands the program's macros without having things such as <stdio.h> macros clutter up the output. If the entry requires or suggests the use of compile line options (such as -Dindex=strchr) they should be added after the '-E' flag.
The next stage towards understanding is to use a C beautifier or C indenting program on the source. Be warned that a number of these entries are so twisted that such tools may abort or become very confused. You may need to help out by doing some initial formatting with an editor. You might also try renaming variables and labels to give more meaningful names.
Now try linting the program. You may be surprised at how little lint complains about these programs. Pay careful attention to messages about unused variables, wrong types, pointer conversions, etc. But be careful, some lints produce incorrect error messages or even abort! Your lint may detect syntax errors in the source. See the next paragraph for suggestions on how to deal with this.
When you get to the stage where you are ready to compile the program examine the compilation comments above each entry. A simple define or edit may be required due to differing semantics between operating systems. If you are able to successfully compile the program, experiment with it by giving it different arguments or input. You may also use the makefile provided to compile the program. Keep in mind that C compilers often have bugs, or features which result the program failing to compile. You may have to do some syntax changing as we did to get old programs to compile on strict ANSI C compilers.
Last, read the judges' comments/spoilers on the program. Hints
foo.c are given in
foo.hint. Often they will contain suggested
arguments or recommended data to use.
If you do gain some understanding of how a program works, go back to the source and reexamine it using some of the techniques outlined above. See if you can convince yourself of why the program does what it does.
Regarding the source archive:
Each sub-directory contains all the entries for a single year. Often
the file names match one of the last names of the author. Judges'
hints are given in files of the form
You may need to tweak the Makefile to get everything to compile correctly. Read the hint files for suggestions.
The rules for a given year are given in the file named
archive contains a copy of the rules for the upcoming contest.
The following URL is the official archive of the winning entries:
Regarding the distribution of sources:
All contest results are in the public domain. We do ask that you observe the following request:
You may share these files with others, but please do not prevent them of doing the same. If some of these files and/or contest entries are published in printed form, or if you use them in a business or classroom setting, please let us know. We ask that you drop a line to the 'judges' EMail box. See the following page for instructions on how to send us a message,
Some final things to remember:
While the idea for the contests has remained the same through the years, the contest rules and guidelines vary. What was novel one year may be considered common the next. The categories for awards differ because they are determined after the judges examine all of the entries.
The judges' hints assume that the program resides in a file with the same username as the author. Where there is more than one author, the first named author is used.
Some C compilers are unable to compile some of these programs. The
judges tried to select programs that were widely portable and
compilable, but did not always succeed. As of 1990, and entry
may use both
K&R and ANSI C compilers. Makefiles for both
types of C compilers are used. See the contest rules for details.
You are strongly encouraged to read the new contest rules before sending any entries. The rules, and sometimes the contest Email address itself, change from time to time. A valid entry one year may be rejected in a later year due to changes in the rules. See:
for up to date information on how to enter.
Last, PLEASE don't code in the style of these programs It is hoped that you will gain an understanding that poor style destroys an otherwise correct program. Real programmers don't write obfuscated programs, unless they are submitting a contest entry! :-)