The International Obfuscated C Code Contest (abbreviated IOCCC) is a computer programming contest for the most creatively obfuscated C code. Held annually, it is described as "celebrating [C's] syntactical opaqueness". The winning code for the 27th contest, held in 2020, was released in July 2020. Previous contests were held in the years 1984–1996, 1998, 2000, 2001, 2004–2006, 2011–2015 and 2018–2020. Entries are evaluated anonymously by a panel of judges. The judging process is documented in the competition guidelines and consists of elimination rounds. By tradition, no information is given about the total number of entries for each competition. Winning entries are awarded with a category, such as "Worst Abuse of the C preprocessor" or "Most Erratic Behavior", and then announced on the official IOCCC website. The contest states that being announced on the IOCCC website is the reward for winning. History The IOCCC was started by Landon Curt Noll and Larry Bassel in 1984 while employed at National Semiconductor's Genix porting group. The idea for the contest came after they compared notes with each other about some poorly written code that they had to fix, notably the Bourne shell, which used macros to emulate ALGOL 68 syntax, and a buggy version of finger for BSD. The contest itself was the topic of a quiz question in the 1993 Computer Bowl. After a hiatus of five years starting in 2006, the contest returned in 2011. Compared with other programming contests, the IOCCC is described as "not all that serious" by Michael Swaine, editor of Dr. Dobb's Journal. Rules Each year, the rules of the contest are published on the IOCCC website. All material is published under Creative Commons license BY-SA 3.0 Unported. Rules vary from year to year and are posted with a set of guidelines that attempt to convey the spirit of the rules. The rules are often deliberately written with loopholes that contestants are encouraged to find and abuse. Entries that take advantage of loopholes can cause the rules for the following year's contest to be adjusted. Obfuscations employed Entries often employ strange or unusual tricks, such as using the C preprocessor to do things it was not designed to do (in some cases "spectacularly", according to Dr. Dobbs, with one entry creating an 11-bit ALU in the C preprocessor<ref name="cpp_abuse">IOCCC 2004 – Best Abuse of CPP IOCCC. Retrieved 2013-04-08.</ref>), or avoiding commonly used constructs in the C programming