International Obfuscated C Code Contest

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.{{cite web |url=https://www.ioccc.org/faq.html |title=The FAQ |publisher=IOCCC |access-date=2023-05-01}} The contest itself was the topic of a quiz question in the 1993 Computer Bowl.[http://nl.newsbank.com/nl-search/we/Archives?p_product=SJ&s_site=mercurynews&p_multi=SJ&p_theme=realcities&p_action=search&p_maxdocs=200&p_topdoc=1&p_text_direct-0=0EB71B1E74EA9019&p_field_direct-0=document_id&p_perpage=10&p_sort=YMD_date:D&s_trackval=GooglePM "Top Execs Fail To Compute Correctly"]. San Jose Mercury News, California. May 15, 1993. p. 1A. Via Newsbank. {{subscription required}} After a hiatus of five years starting in 2006, the contest returned in 2011.{{cite web|url=https://www.pcworld.com/article/478306/obfuscated_code_contest_returns.html |title=Obfuscated Code Contest Returns |magazine=PC World|date=November 15, 2011|last=Jackson|first=Joab|access-date=2023-05-01}}

Compared with other programming contests, the IOCCC is described as "not all that serious" by Michael Swaine, editor of Dr. Dobb's Journal.{{cite journal |url=https://www.drdobbs.com/architecture-and-design/there-must-be-contest/207404123 |title=There Must be Contest |first=Michael |last=Swaine |author-link=Michael Swaine (technical author) |journal=Dr. Dobb's Journal|date=May 1, 2008 |access-date=2023-05-01}}

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.[https://www.ioccc.org/ IOCCC home page, footer], and in each hint.txt file 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}}

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.

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,{{cite web |url=https://www.drdobbs.com/open-source/code-finessing/193104882?pgno=2 |title=Code Finessing |magazine=Dr. Dobb's Journal|author=Spinellis, Diomidis |date=October 5, 2006 |access-date=2023-05-01}} with one entry creating an 11-bit ALU in the C preprocessor[https://www.ioccc.org/2004/vik2.hint IOCCC 2004 – Best Abuse of CPP]'' IOCCC. Retrieved 2023-05-01.), 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.{{cite web|year=1994|title=smr.hint|url=https://www.ioccc.org/1994/smr.hint|access-date=2006-09-16|publisher=IOCCC|format=plain text}}

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.{{cite web| url=https://www.ioccc.org/2004/gavin.hint |title=gavin.hint3 |year=2004 |format=plain text |publisher=IOCCC |access-date=2023-05-01}}

Toledo 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.{{cite web |url=https://nanochess.org/chess3.html |title=Toledo Nanochess and Toledo Picochess}}

Because Toledo Nanochess is based on Toledo's winning entry from the 18th IOCCC (Best Game{{cite web |url=https://www.ioccc.org/winners.html#Oscar_Toledo_G. |title=Winners: The authors of winning IOCCC entries}}), it is heavily obfuscated.{{cite web |url=https://github.com/bormand/nanochess |title=Nanochess partially de-obfuscated version |website=GitHub |access-date=1 May 2023}}

On February 2, 2014, the author published the book Toledo Nanochess: The commented source code, which contains the fully commented source code.{{Cite book|title=Toledo Nanochess: The commented source code|isbn=978-1-304-86437-6|first=Oscar|last=Toledo Gutiérrez|year=2014|publisher=Lulu}}

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{{Cite web|url=https://smmax.sourceforge.net|title=Super Micro Chess Engine - Home Page - Extremely Compact C Source and Executable Program Size|website=smmax.sourceforge.net}} – a derivative of Micro-Max – totaling 760 characters (spaces and newlines included).{{cite web |url=https://sourceforge.net/projects/smmax/files/sm-fide%20760.c/download |title=Super Micro FIDE 760}} 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<=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||1z|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|oM;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=p2||(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);}}

Below is a 1988 entry which calculates pi by looking at its own area:[https://www.ioccc.org/1988/westley.c "westley.c"], 5th International Obfuscated C Code Contest 1988

1. 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.using gcc, compile with the following command line: $ gcc -traditional-cpp -o r r.c or $ gcc -E r.c | sed 's/- -/--/g' > r2.c ; gcc -o r2 r2.c (The source file is r.c){{Original research inline|date=April 2017}})

Another example is the following flight simulator, the winner of the 1998 IOCCC,[https://blog.aerojockey.com/post/iocccsim Carl Banks' Blog: IOCCC Flight Simulator]. blog.aerojockey.com. Retrieved 2023-05-01. as listed and described in Calculated Bets: Computers, Gambling, and Mathematical Modeling to Win (2001){{cite book |title= Calculated Bets: Computers, Gambling, and Mathematical Modeling to Win |url= https://archive.org/details/calculatedbetsco0000skie |url-access= registration |author=Skiena, Steven |pages=[https://archive.org/details/calculatedbetsco0000skie/page/152 152], 153 |publisher=The Mathematical Association of America|year=2001|isbn=978-0521009621}} and 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(; 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); } }

File:1998_IOCCC_Flight_simulator_screenshot.png

This program needs the 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

In order to run the binary file ({{code|banks}}) it has to be supplied with a {{code|.sc}} scenery file via standard input input:

$ cat pittsburgh.sc | ./banks

Below is a 2011 entry which downsamples PGM, PPM images and ASCII art (of Akari from YuruYuri) by Don, Yang:{{Cite web|title=Winners: The authors of winning IOCCC entries |url=https://www.ioccc.org/years.html#2011_akari |access-date=2023-05-01 |website=www.ioccc.org}}

/*

+

+

+

+

[ >i>n[t

*/ #include

/*2w0,1m2,]_r>i>=>(['0n1'0)1;

*/int/**/main(int/**/n,char**m){FILE*p,*q;int A,k,a,r,i/*

#uinndcelfu_dseti/_*/;char*d="P%" "d\n%d\40%d"/**/

"\n%d\n\00wb+",b[1024],y[]="yuriyurarararayuruyuri*daijiken**akkari~n**"

"/y*u*k/riinrarararayuruy9uriyu3riyurar_aBrMaPrOaWy^?"

"*]/f]`;hvroai

*/"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

*/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<63> +:+ .1>3+++ . -m-) -;.u+=++.1<0< <; f

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(/*

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+=(/**>> *..

(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/*;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" )/*

*/ ;}

$

• Obfuscated Perl Contest
• Underhanded C Contest
• Esoteric programming language

• {{official|https://www.ioccc.org/}}

Category:C (programming language) contests

Category:Computer humour

Category:Software obfuscation

Category:Ironic and humorous awards

Category:Recurring events established in 1984