Международный конкурс запутанного кода на C

Computer programming contest

The International Obfuscated C Code Contest (abbreviated IOCCC) is a computer programming contest for the most creatively obfuscated C code. Held semi 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.

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.

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. Blockquote|text=Hacking the contest rules is a tradition. — Landon Curt Noll, 2011 with one entry creating an 11 bit ALU in the C preprocessor), or avoiding commonly used constructs in the C programming language in favor of much more obscure ways of achieving the same thing. Contributions have included source code formatted to resemble images, text, etc., after the manner of ASCII art, preprocessor redefinitions to make code harder to read, and self modifying code. During several of the years, an entry was submitted that required a new definition of some of the rules for the next year. This is regarded as a high honor. An example is the world's shortest self reproducing program. The entry was a program designed to output its own source code, and which had zero bytes of source code. When the program ran, it printed out zero bytes, equivalent to its source code. In the effort to take obfuscation to its extremes, contestants have produced programs which skirt around the edges of C standards, or result in constructs which trigger rarely used code path combinations in compilers. As a result, several of the past entries may not compile directly in a modern compiler, and some may cause crashes.

Within the code size limit of only a few kilobytes, contestants have managed to do complicated things – a 2004 winner turned out an operating system.