The International Obfuscated C Code Contest (abbreviated IOCCC) is a programming contest for the most creatively obfuscated

Obfuscated code

Obfuscated code is source or machine code that has been made difficult to understand for humans. Programmers may deliberately obfuscate code to conceal its purpose or its logic to prevent tampering, deter reverse engineering, or as a puzzle or recreational challenge for someone reading the source...

 C

C (programming language)

C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....

 code. It was held annually between 1984 and 1996, and thereafter in 1998, 2000, 2001, 2004, 2005 and 2006.
The most recent competition started in 2011. The winning code for the 18th and 19th and contests, held in 2005 and 2006, was released in November 2011.

Prior to 2004, entries were submitted by email. In 2004, for the 17th IOCCC, the competition switched to using an online submission process.

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

C preprocessor

The C preprocessor is the preprocessor for the C and C++ computer programming languages. The preprocessor handles directives for source file inclusion , macro definitions , and conditional inclusion ....

" or "Most Erratic Behavior", and then announced on the official IOCCC website. Entries that do not make it are deleted and forgotten; the contest states that being announced on the IOCCC website is the award for winning.

History

The IOCCC was started by Landon Curt Noll

Landon Curt Noll

Landon Curt Noll is an American computer scientist, co-discoverer of the 25th Mersenne prime and discoverer of the 26th, which he found while still enrolled in high school and concurrently at Cal State Hayward....

 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.

Rules

Each year, the rules of the contest are published on the IOCCC website. 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 subtle loopholes that contestants are somewhat encouraged to find and abuse. This is the result of the contest being a "parody of the software development process". Entries that take advantage of some loophole in the rules (whether or not they pass a final round of judging) can cause the rules for the following year's contest to be adjusted accordingly (although often other subtle loopholes are deliberately introduced in the process).

Obfuscations employed

Due to the nature of the contest, entries often employ strange or unusual tricks, such as using the C preprocessor to do things it was not designed to do, or avoiding commonly-used constructs in the C programming language in favor of much more obscure ways of achieving the same thing. For example, some quotes from 2004 winners include:
Some ways in which contributions are notable include:

• The appearance of the source code, formatted to resemble images, text, etc., after the manner of ASCII art
  ASCII art
  ASCII art is a graphic design technique that uses computers for presentation and consists of pictures pieced together from the 95 printable characters defined by the ASCII Standard from 1963 and ASCII compliant character sets with proprietary extended characters...
  
  .
• Preprocessor redefinitions to make code harder to read.
• Self-modifying code
  Self-modifying code
  In computer science, self-modifying code is code that alters its own instructions while it is executing - usually to reduce the instruction path length and improve performance or simply to reduce otherwise repetitively similar code, thus simplifying maintenance...
  
  .
• Worst abuse of the rules. In several years, an entry was submitted that was so patently absurd that it 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 zero bytes in length that if run printed zero bytes to the screen (simply an empty file).

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 even cause crashes.

Examples

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

Below is a 1988 entry which calculates pi

Pi

' is a mathematical constant that is the ratio of any circle's circumference to its diameter. is approximately equal to 3.14. Many formulae in mathematics, science, and engineering involve , which makes it one of the most important mathematical constants...

 by looking at its own area

Area

Area is a quantity that expresses the extent of a two-dimensional surface or shape in the plane. Area can be understood as the amount of material with a given thickness that would be necessary to fashion a model of the shape, or the amount of paint necessary to cover the surface with a single coat...

:

1. define _ -F<00||--F-OO--;

int F=00,OO=00;main{F_OO;printf("%1.3f\n",4.*-F/OO/OO);}F_OO
{
_-_-_-_
_-_-_-_-_-_-_-_-_
_-_-_-_-_-_-_-_-_-_-_-_
_-_-_-_-_-_-_-_-_-_-_-_-_-_
_-_-_-_-_-_-_-_-_-_-_-_-_-_-_
_-_-_-_-_-_-_-_-_-_-_-_-_-_-_
_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_
_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_
_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_
_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_
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}


(Note that the entry was written in K&R C; it doesn't work correctly in ANSI C without some change.)

Another good example is the following cleverly-written flight simulator, the winner of the IOCCC in 1998 as shown below:

1. include
2. include
3. include
4. include

double L ,o ,P
,_=dt,T,Z,D=1,d,
s[999],E,h= 8,I,
J,K,w[999],M,m,O
,n[999],j=33e-3,i=
1E3,r,t, u,v ,W,S=
74.5,l=221,X=7.26,
a,B,A=32.2,c, F,H;
int N,q, C, y,p,U;
Window z; char f[52]
; GC k; main{ Display*e=
XOpenDisplay( 0); z=RootWindow(e,0); for (XSetForeground(e,k=XCreateGC (e,z,0,0),BlackPixel(e,0))
scanf("%lf%lf%lf",y +n,w+y, y+s)+1; y ++); XSelectInput(e,z= XCreateSimpleWindow(e,z,0,0,400,400,
0,0,WhitePixel(e,0) ),KeyPressMask); for(XMapWindow(e,z); ; T=sin(O)){ struct timeval G={ 0,dt*1e6}
K= cos(j); N=1e4; M+= H*_; Z=D*K; F+=_*P; r=E*K; W=cos( O); m=K*W; H=K*T; O+=D*_*F/ K+d/K*E*_; B=
sin(j); a=B*T*D-E*W; XClearWindow(e,z); t=T*E+ D*B*W; j+=d*_*D-_*F*E; P=W*E*B-T*D; for (o+=(I=D*W+E

• T*B,E*d/K *B+v+B/K*F*D)*_; p

] 0|K K)N=1e4; else{ q=W/K *4E2+2e2; C= 2E2+4e2/ K
*D; N-1E4&& XDrawLine(e ,z,k,N ,U,q,C); N=q; U=C; } ++p; } L+=_* (X*t +P*M+m*l); T=X*X+ l*l+M *M;
XDrawString(e,z,k ,20,380,f,17); D=v/l*15; i+=(B *l-M*r -X*Z)*_; for; u *=CS!=N){
XEvent z; XNextEvent(e ,&z);
++*((N=XLookupKeysym
(&z.xkey,0))-IT?
N-LT? UP-N?& E:&
J:& u: &h); --*(
DN -N? N-DT ?N
RT?&u: & W:&h:&J
); } m=15*F/l;
c+=(I=M/ l,l*H
+I*M+a*X)*_; H
=A*r+v*X-F*l+(
E=.1+X*4.9/l,t
=T*m/32-I*T/24
)/S; K=F*M+(
h* 1e4/l-(T+
E*5*T*E)/3e2
)/S-X*d-B*A;
a=2.63 /l*d;
X+=( d*l-T/S
*(.19*E +a
*.64+J/1e3
)-M* v +A*
Z)*_; l +=
K *_; W=d;
sprintf(f,
"%5d %3d"
"%7d",p =l
/1.7,(C=9E3+
O*57.3)%0550,(int)i); d+=T*(.45-14/l*
X-a*130-J* .14)*_/125e2+F*_*v; P=(T*(47
*I-m* 52+E*94 *D-t*.38+u*.21*E) /1e2+W*
179*v)/2312; select(p=0,0,0,0,&G); v-=(
W*F-T*(.63*m-I*.086+m*E*19-D*25-.11*u
)/107e2)*_; D=cos(o); E=sin(o); } }


This program needs following command line on a Linux system to be compiled:

cc banks.c -o banks -DIT=XK_Page_Up -DDT=XK_Page_Down \

	-DUP=XK_Up -DDN=XK_Down -DLT=XK_Left -DRT=XK_Right \

	-DCS=XK_Return -Ddt=0.02 -lm -lX11 -L/usr/X11R6/lib

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