International Obfuscated C Code Contest
The International Obfuscated C Code Contest (abbreviated IOCCC) is a computer programming contest for code written in C that is the most creatively obfuscated. Held semi-annually, it is described as "celebrating [C's] syntactical opaqueness".[1] The winning code for the 28th contest, held in 2024/25, was announced by live stream 2 Aug 2025.[2] Previous contests were held in the years 1984–1996, 1998, 2000, 2001, 2004–2006, 2011–2015, 2018–2020, and 2024. Entries are evaluated anonymously by the current sitting judges (currently Leonid A. Broukhis & Landon Curt Noll). The judging process is documented in the competition guidelines[3] 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 (plus bragging rights). HistoryThe 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.[4] The contest itself was the topic of a quiz question in the 1993 Computer Bowl.[5] After a hiatus of five years starting in 2006, the contest returned in 2011.[6] Compared with other programming contests, the IOCCC is described as "not all that serious" by Michael Swaine, editor of Dr. Dobb's Journal.[7] RulesEach 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.[8] Rules vary from year to year and are posted with a set of guidelines that attempt to convey the spirit of the rules.
—Landon Curt Noll, 2011[6]
The rules are often deliberately written with loopholes that contestants are encouraged to find and abuse.[3] Entries that take advantage of loopholes can cause the rules for the following year's contest to be adjusted.[3] Obfuscations employedEntries often employ strange or unusual tricks, such as using the C preprocessor to do things it was not designed to do[a] 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. In several years an entry was submitted that required a new definition of some of the rules for the next year, 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.[11] 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. ExamplesWithin the code size limit of only a few kilobytes, contestants have managed to do complicated things – a 2004 winner turned out an operating system.[12] Toledo NanochessToledo Nanochess is a chess engine created by Mexican software developer Oscar Toledo Gutiérrez, a five-time winner of the IOCCC. In accordance with IOCCC rules, it is 1255 characters long. The author claims that it is the world's smallest chess program written in C. The source code for Toledo Nanochess and other engines is available.[13] Because Toledo Nanochess is based on Toledo's winning entry from the 18th IOCCC (Best Game[14]), it is heavily obfuscated.[15] On February 2, 2014, the author published the book Toledo Nanochess: The commented source code, which contains the fully commented source code.[16] As of February 7, 2010, it appears to be one of only two chess engines written in less than 2 kilobytes of C that are able to play full legal chess moves, along with Micro-Max by Dutch physicist H. G. Muller. In 2014 the 1 kilobyte barrier was broken by Super Micro Chess[17] – a derivative of Micro-Max – totaling 760 characters (spaces and newlines included).[18] There is also a smaller version of Toledo's engine, the Toledo Picochess, consisting of 944 non-blank characters. Source code excerpt B,i,y,u,b,I[411],*G=I,x=10,z=15,M=1e4;X(w,c,h,e,S,s){int t,o,L,E,d,O=e,N=-M*M,K
=78-h<<x,p,*g,n,*m,A,q,r,C,J,a=y?-x:x;y^=8;G++;d=w||s&&s>=h&&v 0,0)>M;do{_ o=I[
p=O]){q=o&z^y _ q<7){A=q--&2?8:4;C=o-9&z?q["& .$ "]:42;do{r=I[p+=C[l]-64]_!w|p
==w){g=q|p+a-S?0:I+S _!r&(q|A<3||g)||(r+1&z^y)>9&&q|A>2){_ m=!(r-2&7))P G[1]=O,
K;J=n=o&z;E=I[p-a]&z;t=q|E-7?n:(n+=2,6^y);Z n<=t){L=r?l[r&7]*9-189-h-q:0 _ s)L
+=(1-q?l[p/x+5]-l[O/x+5]+l[p%x+6]*-~!q-l[O%x+6]+o/16*8:!!m*9)+(q?0:!(I[p-1]^n)+
!(I[p+1]^n)+l[n&7]*9-386+!!g*99+(A<2))+!(E^y^9)_ s>h||1<s&s==h&&L>z|d){p[I]=n,O
[I]=m?*g=*m,*m=0:g?*g=0:0;L-=X(s>h|d?0:p,L-N,h+1,G[1],J=q|A>1?0:p,s)_!(h||s-1|B
-O|i-n|p-b|L<-M))P y^=8,u=J;J=q-1|A<7||m||!s|d|r|o<z||v 0,0)>M;O[I]=o;p[I]=r;m?
*m=*g,*g=0:g?*g=9^y:0;}_ L>N){*G=O _ s>1){_ h&&c-L<0)P L _!h)i=n,B=O,b=p;}N=L;}
n+=J||(g=I+p,m=p<O?g-3:g+2,*m<z|m[O-p]||I[p+=p-O]);}}}}Z!r&q>2||(p=O,q|A>2|o>z&
!r&&++C*--A));}}}Z++O>98?O=20:e-O);P N+M*M&&N>-K+1924|d?N:0;}main(){Z++B<121)*G
++=B/x%x<2|B%x<2?7:B/x&4?0:*l++&31;Z B=19){Z B++<99)putchar(B%x?l[B[I]|16]:x)_
x-(B=F)){i=I[B+=(x-F)*x]&z;b=F;b+=(x-F)*x;Z x-(*G=F))i=*G^8^y;}else v u,5);v u,
1);}}
PiBelow is a 1988 entry which calculates pi by looking at its own area:[19] #define _ -F<00||--F-OO--;
int F=00,OO=00;main(){F_OO();printf("%1.3f\n",4.*-F/OO/OO);}F_OO()
{
_-_-_-_
_-_-_-_-_-_-_-_-_
_-_-_-_-_-_-_-_-_-_-_-_
_-_-_-_-_-_-_-_-_-_-_-_-_-_
_-_-_-_-_-_-_-_-_-_-_-_-_-_-_
_-_-_-_-_-_-_-_-_-_-_-_-_-_-_
_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_
_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_
_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_
_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_
_-_-_-_-_-_-_-_-_-_-_-_-_-_-_
_-_-_-_-_-_-_-_-_-_-_-_-_-_-_
_-_-_-_-_-_-_-_-_-_-_-_-_-_
_-_-_-_-_-_-_-_-_-_-_-_
_-_-_-_-_-_-_-_
_-_-_-_
}
(This entry was written in K&R C; it does not work correctly in ANSI C without some changes.[20]) Flight simulatorAnother example is the following flight simulator, the winner of the 1998 IOCCC,[21] as listed and described in Calculated Bets: Computers, Gambling, and Mathematical Modeling to Win (2001)[22] and shown below: #include <math.h>
#include <sys/time.h>
#include <X11/Xlib.h>
#include <X11/keysym.h>
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<y; ){ T=p[s]+i; E=c-p[w]; D=n[p]-L; K=D*m-B*T-H*E; if(p [n]+w[ p]+p[s
]== 0|K <fabs(W=T*r-I*E +D*P) |fabs(D=t *D+Z *T-a *E)> 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(; XPending(e); 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 the following command line on a Linux system to be compiled:[21] $ 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
In order to run the binary file ( $ cat pittsburgh.sc | ./banks
AkariBelow is a 2011 entry which downsamples PGM, PPM images and ASCII art (of Akari from YuruYuri) by Don, Yang:[23] /*
+
+
+
+
[ >i>n[t
*/ #include<stdio.h>
/*2w0,1m2,]_<n+a m+o>r>i>=>(['0n1'0)1;
*/int/**/main(int/**/n,char**m){FILE*p,*q;int A,k,a,r,i/*
#uinndcelfu_dset<rsitcdti_oa.nhs>i/_*/;char*d="P%" "d\n%d\40%d"/**/
"\n%d\n\00wb+",b[1024],y[]="yuriyurarararayuruyuri*daijiken**akkari~n**"
"/y*u*k/riin<ty(uyr)g,aur,arr[a1r2a82*y2*/u*r{uyu}riOcyurhiyua**rrar+*arayra*="
"yuruyurwiyuriyurara'rariayuruyuriyuriyu>rarararayuruy9uriyu3riyurar_aBrMaPrOaWy^?"
"*]/f]`;hvroai<dp/f*i*s/<ii(f)a{tpguat<cahfaurh(+uf)a;f}vivn+tf/g*`*w/jmaa+i`ni("/**
*/"i+k[>+b+i>++b++>l[rb";int/**/u;for(i=0;i<101;i++)y[i*2]^="~hktrvg~dmG*eoa+%squ#l2"
":(wn\"1l))v?wM353{/Y;lgcGp`vedllwudvOK`cct~[|ju {stkjalor(stwvne\"gt\"yogYURUYURI"[
i]^y[i*2+1]^4;/*!*/p=(n>1&&(m[1][0]-'-'||m[1][1] !='\0'))?fopen(m[1],y+298):stdin;
/*y/riynrt~(^w^)],]c+h+a+r+*+*[n>)+{>f+o<r<(-m] =<2<5<64;}-]-(m+;yry[rm*])/[*
*/q=(n<3||!(m[2][0]-'-'||m[2][1]))?stdout /*]{ }[*/:fopen(m[2],d+14);if(!p||/*
"]<<*-]>y++>u>>+r >+u+++y>--u---r>++i+++" <)< ;[>-m-.>a-.-i.++n.>[(w)*/!q/**/)
return+printf("Can " "not\x20open\40%s\40" "" "for\40%sing\n",m[!p?1:2],!p?/*
o=82]5<<+(+3+1+&.(+ m +-+1.)<)<|<|.6>4>-+(> m- &-1.9-2-)-|-|.28>-w-?-m.:>([28+
*/"read":"writ");for ( a=k=u= 0;y[u]; u=2 +u){y[k++ ]=y[u];}if((a=fread(b,1,1024/*
,mY/R*Y"R*/,p/*U*/)/* R*/ )>/*U{ */ 2&& b/*Y*/[0]/*U*/=='P' &&4==/*"y*r/y)r\}
*/sscanf(b,d,&k,& A,& i, &r)&& ! (k-6&&k -5)&&r==255){u=A;if(n>3){/*
]&<1<6<?<m.-+1>3> +:+ .1>3+++ . -m-) -;.u+=++.1<0< <; f<o<r<(.;<([m(=)/8*/
u++;i++;}fprintf (q, d,k, u >>1,i>>1,r);u = k-5?8:4;k=3;}else
/*]>*/{(u)=/*{ p> >u >t>-]s >++(.yryr*/+( n+14>17)?8/4:8*5/
4;}for(r=i=0 ; ;){u*=6;u+= (n>3?1:0);if (y[u]&01)fputc(/*
<g-e<t.c>h.a r -(-).)8+<1. >;+i.(<)< <)+{+i.f>([180*/1*
(r),q);if(y[u ]&16)k=A;if (y[u]&2)k--;if(i/*
("^w^NAMORI; { I*/==a/*" )*/){/**/i=a=(u)*11
&255;if(1&&0>= (a= fread(b,1,1024,p))&&
")]i>(w)-;} { /i-f-(-m--M1-0.)<{"
[ 8]==59/* */ )break;i=0;}r=b[i++]
;u+=(/**>> *..</<<<)<[[;]**/+8&*
(y+u))?(10- r?4:2):(y[u] &4)?(k?2:4):2;u=y[u/*
49;7i\(w)/;} y}ru\=*ri[ ,mc]o;n}trientuu ren (
*/]-(int)'`';} fclose( p);k= +fclose( q);
/*] <*.na/m*o{ri{ d;^w^;} }^_^}}
" */ return k- -1+ /*\' '-`*/
( -/*}/ */0x01 ); {;{ }}
; /*^w^*/ ;}
If the program is run using its own source as the input, the result is: $ ./akari akari.c
int
*w,m,_namori=('n');
#include<stdio.h>/*;hrd"% dnd4%"*/
/**/int(y),u,r[128*2/*{y}icuhya*rr*rya=
*/];void/**/i(){putchar(u);}int/**/main(/*
"(n"l)?M5{YlcpvdluvKct[j skao(tve"t"oYRYR"
*/int(w),char**n){for(m =256;--m;r[m]/*
"<*]y+u>r>u+y-u-r+i+" ) ;>m.a.i+n>()/q*/
=25<(31&( m -1))||64-( m &192)||2>w?m:(2+
m/*"*,/U// R/)/U * & /Y/0/U/=P &=/"*/)\
&16?m-13 : 13+ m) ;u=+10 ;for(;(m=/*
*>/()/{ p u t-s +(yy*+ n1>7?/:*/
getchar ())+1 ;i() ){if(10/*
"wNMR;{ I/=/" )/{*/==u*1
)i(); if(m-10){
u=/*> *./<)[;*/8*
4;i(); }u=r[ m];}return(
* *n/*{i ;w; }_}
( -*/ *00 ) ; }
$ ./akari akari.c > ./akari.small
$ ./akari ./akari.small
wm_aoi(n)
/*ity,,[2*/{}char*y=
(")M{lpduKtjsa(v""YY"
"*yuruyuri") ;main(/*
/",U/ R)U* Y0U= ="/\
*/){puts (y+ 17/*
"NR{I=" ){/=*
=* */);/*
**/{ ;;}}
$
$ ./akari ./akari.small > ./akari.smaller
$ ./akari ./akari.smaller
main
(){puts("Y"
"U RU YU "\
"RI" )/*
*/ ;}
$
See alsoNotesReferences
External links |
||||||||||||||||||||||||
Portal di Ensiklopedia Dunia
