/**************************************************************************\
| Toledo Nanochess (c) Copyright 2009 Oscar Toledo G. All rights reserved  |
| 1258 non-blank characters. Evolution from my winning IOCCC 2005 entry.   |
| o Use D2D4 algebraic style for movements.  biyubi@gmail.com  Aug/10/2009 |
| o On promotion add a number for final piece (3=N, 4=B, 5=R, 6=Q)         |
| o Press Enter alone for computer to play.                                |
| o Full legal chess moves.                     http://nanochess.110mb.com |
| o Remove these comments to get 1326 bytes source code (*NIX end-of-line) |
\**************************************************************************/
char*l="ustvrtsuqqqqqqqqyyyyyyyy}{|~z|{}"
"   76Lsabcddcba .pknbrq  PKNBRQ ?A6J57IKJT576,+-48HLSU";
#define F getchar()&z
#define v X(0,0,0,21,
#define Z while(
#define _ ;if(
#define P return--G,y^=8,
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 _ h&&c-L<0)P L;N=L _!h&s>1)i=n,B=O,b=p;}n+=J
||(g=I+p,m=p<O?g-3:g+2,*m<z|I[p+=p-O]|m[p<O?1:-1]);}}}}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);}}

• Rev. Mar/25/2009, 100% slower, twelve character bigger.
• Rev. Mar/07/2009, 66% slower, one character bigger.
• Rev. Feb/13/2009, 43% slower, 3 characters bigger, castling bug in special cases and crashes with Cygwin.

    gcc -O3 -fexpensive-optimizations toledo_nanochess.c -o toledo

• Download toledo_nanochess_pack.zip, 100.3 kb.

• http://www.mediafire.com/?ojn4ejmhx0z

• WinBoard graphical interface, the original program by Tim Mann, minimum needed for playing with WinBoard engines.
• WinBoard Gold graphical interface, an enhanced version by H.G. Muller.
• Arena graphical interface, can use any WinBoard/UCI engine. It has an easy interface to add engines.

/**************************************************************************\
| Toledo Nanochess (c) Copyright 2009 Oscar Toledo G. All rights reserved  |
| 1258 non-blank characters.                 biyubi@gmail.com  Aug/10/2009 |
| o This version includes a minimal Winboard adapter (697 extra bytes)     |
| o Full legal chess moves.                     http://nanochess.110mb.com |
| o Remove these comments to get 2023 bytes source code (*NIX end-of-line) |
\**************************************************************************/
#include <stdio.h>
#include <time.h>
char*l="ustvrtsuqqqqqqqqyyyyyyyy}{|~z|{}"
"   76Lsabcddcba .pknbrqmove %s\n\0?A6J57IKJT576,+-48HLSU";
#define v X(0,0,0,21,
#define Z while(
#define _ ;if(
#define P return--G,y^=8,
B,i,y,u,b,I[411],*G=I,x=10,z=15,M=1e4,f,j,m,n,t,o,L,E,D,O=100;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;D++;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 _ h&&c-L<0
)P L;N=L _!h&s>1)i=n,B=O,b=p;}n+=J||(g=I+p,m=p<O?g-3:g+2,*m<z|I[p+=p-O]|m[p<O?1
:-1]);}}}}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;}
#define D(z)_!strcmp(g,#z))
main(){char*a,g[80];clock_t k;setbuf(stdout,0);Z fgets(g+x,69,stdin)){sscanf(g+
x,"%9s%d%d",g,&n,&D)D(quit)break D(force)f=1 D(post)j=1 D(nopost)j=0 D(level)o=
n,E=n?n:20,O=D*6e3/E D(time)O=n/(E-L%E)D(new){_*l-'u')l-=32;G=I;B=y=u=f=L=0;Z++
B<121)*G++=B/x%x<2|B%x<2?7:B/x&4?0:*l++&31;}D(go)f=0 D(protover)puts(
"feature myname=\"Toledo Nanochess Aug/10/2009\" done=1")_ isalpha(*g)&&isdigit
(g[1])){a=g;B=*a++&z;B+=100-(*a++&z)*x;b=*a++&z;b+=100-(*a++&z)*x;i=(*a-'q'?*a-
'r'?*a-98?*a-'n'?I[B]&z^y:11:12:13:14)^y;v u,1)_!f)strcpy(g,"go");}D(go){k=
clock();D=0;n=O<50?4:5;B=21;do{m=X(0,0,0,B,u,n);t=(clock()-k)*1e2/
CLOCKS_PER_SEC;*g=B%x+96;g[1]=58-B/x;g[2]=b%x+96;g[3]=58-b/x;g[4]=I[B]-i&z?l[i&
7|16]:0;g[5]=0;n++;_ j)printf("%d %d %d %d %s\n",n,m,t,D,g);}Z m>-M&m<M&t*x<O);
_ o)L++;v u,1);printf(l+23,g);}}}

/**************************************************************************\
| Toledo Picochess (c) Copyright 2007 Oscar Toledo G. All rights reserved  |
| 944 non-blank characters. Evolution from my winning IOCCC 2005 entry.    |
| o Use D2D4 algebraic style for movements.  biyubi@gmail.com  Jan/21/2007 |
| o Only promotion to queen, no en passant or castling. nanochess.110mb.com|
| o Press Enter alone for computer to play (num.args+5 == depth of search) |
| o Remove these comments to get 1009-bytes source code (*NIX end-of-line) |
\**************************************************************************/
#define F (getchar()&15)
#define v main(0,0,0,0,
#define Z while(
#define P return y=~y,
#define _ ;if(
char*l="dbcefcbddabcddcba~WAB+  +BAW~              +-48HLSU?A6J57IKJT576,";B,y,
b,I[149];main(w,c,h,e,S,s){int t,o,L,E,d,O=*l,N=-1e9,p,*m=I,q,r,x=10 _*I){y=~y;
Z--O>20){o=I[p=O]_ q=o^y,q>0){q+=(q<2)*y,t=q["51#/+++"],E=q["95+3/33"];do{r=I[p
+=t[l]-64]_!w|p==w&&q>1|t+2<E|!r){d=abs(O-p)_!r&(q>1|d%x<1)|(r^y)<-1){_(r^y)<-6
)P 1e5-443*h;O[I]=0,p[I]=q<2&(89<p|30>p)?5^y:o;L=(q>1?6-q?l[p/x-1]-l[O/x-1]-q+2
:0:(p[I]-o?846:d/8))+l[r+15]*9-288+l[p%x]-h-l[O%x];L-=s>h||s==h&L>49&1<s?main(s
>h?0:p,L,h+1,e,N,s):0 _!(B-O|h|p-b|S|L<-1e4))return 0;O[I]=o,p[I]=r _ S|h&&(L>N
||!h&L==N&&1&rand())){N=L _!h&&s)B=O,b=p _ h&&c-L<S)P N;}}}t+=q<2&t+3>E&((y?O<
80:39<O)||r);}Z!r&q>2&q<6||(p=O,++t<E));}}P N+1e9?N:0;}Z I[B]=-(21>B|98<B|2>(B+
1)%x),++B<120);Z++m<9+I)30[m]=1,90[m]=~(20[m]=*l++&7),80[m]=-2;Z p=19){Z++p<O)
putchar(p%x-9?"KQRBNP .pnbrqk"[7+p[I]]:x)_ x-(B=F)){B+=O-F*x;b=F;b+=O-F*x;Z x-F
);}else v 1,3+w);v 0,1);}}

    gcc -O3 -fexpensive-optimizations toledo_picochess.c -o toledo