Copyright © 2019, Landon Curt Noll, Simon Cooper, and Leonid A. Broukhis. All Rights Reserved. Permission for personal, educational or non-profit use is granted provided this copyright and notice are included in its entirety and remains unaltered. All other uses must receive prior permission from the contest judges.
The primary IOCCC web site can be found at,
Use make to compile entries. It is possible that on non-Un*x / non-Linux systems the makefile needs to be changed. See the Makefile for details.
Look at the source and try to figure out what the programs do, and run them with various inputs. If you want to, look at the hints files for spoilers - this year we included most of the information included by the submitter.
Read over the makefile for compile/build issues. Your system may require certain changes (add or remove a library, add or remove a #define).
Some C compilers are not quite as good as they should be. If yours is lacking, you may need to compile using clang or gcc instead of your local compiler.
This year’s winners are impressive!
The “Most in need of debugging” (endoh) is very inventive in a way it produces its own text!
The “Most likely to be awarded” (ciura) has an amazing vocabulary!
There are again nods to winners of the years:
These nods to not run afoul of the guideline:
We tend to dislike programs that: ... are rather similar to previous winners
because the entry (dogon) appropriately pays homage to past winners without blatantly reusing their code.
…We’ll stop spouting spoilers now. Have fun exploring all the entries!
Some entries tried to get around the size limit by submitting a data file that was really C code and then blindly including code in prog.c.
Quite a few entries suffered from undefined behavior like accessing uninitialized locals and/or reading-writing below the stack. We advise running your entry through valgrind to make sure those mistakes are avoided.
Using extra arguments to main, or arguments of wrong types as a quick and dirty way of declaring variables is now passé. Clang, for example, rejects them outright.
We hope the authors of some of those entries will fix and re-submit them for the next IOCCC.
Some entries seemed to have a good idea, but the implementation of the idea was limited in scope.
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
For news of the next contest watch:
© Copyright 1984-2019,
Leo Broukhis, Simon Cooper, Landon Curt Noll
- All rights reserved