![\"1K](\"http:\/\/mybroadband.co.za\/news\/wp-content\/uploads\/2015\/01\/ZX81-Chess.jpg\")
<\/a>1K ZX Chess<\/p><\/div>\n
487 bytes BootChess<\/h3>\n
Red Sector Inc. and Poudade have significantly reduced the memory requirements of BootChess when compared to\u00a01K ZX Chess \u2013 down from 672 bytes to 487 bytes.<\/p>\n
The full program is provided below.<\/p>\n
\n;----------RED-SECTOR-INC.-proudly-presents-a-33-year-old-record-:----------\r\n; ___ _\r\n; \/ \/ _____ _ _ _____ _ _ ___ _\r\n; .::. \/ \/ \/ \/ \/ \/ \/ \/ \/ \/\r\n; :::: \/ \/ ____ .-\/ _ ___\/-. .-\/ _ ___\/-. \/ \/__\r\n; :: \/ \\ | | . | | | . | \/ \/\r\n; :: __ _ \\ l | | | l | | \/ ___\/\r\n; .::. \/ \/ \/ \/ | l |_| l | |__\/ \/ ____\r\n; .::::. \/ __\/ `--' `--' \/ |\r\n; :::::::: \/ \/ |\r\n; ___ __ Cl! ___ ___ \/ ___ _ _ __|\r\n; ___ _ _ \/ __\/_ __ _ _\/ _\/_ _ \/_ \/ \/ ___ \/__\r\n; \/_\/ \/ \/ \/ \/ \/ \/ _____\/ \/ \/ \/ __\/ _ \/ \/ \/\r\n; .-\/ ___\/ \/ \/______ \/ ___\\ \\___ \/ \/ __\/\r\n; | \/ \/ \/ | __\/ ___ | \\ | ___\\ \\___\r\n; | \/ ____ | \/ | | _\/ | | \\ |\r\n; | \/--\/ | ___\/ | | | | | _\/ |\r\n; | | \/ \/ :: | ____\/ :: | | :: \\_____| | |\r\n; |_____\/ :: | __\/ \/_______| \/_______| |_______\\ | :: \\_____|\r\n; \/_______| \/___ _ \/___ _ _ ___\\ |_______\\\r\n; \/___ _ _ ___\\\r\n; BootChess is the smallest computer implementation of chess on any platform\r\n; Chess in a 512-byte x86 boot sector for Windows \/ Linux \/ OS X \/ DOS \/ BSD\r\n; Coded by Olivier \"Baudsurfer\/RSi\" Poudade with extra help of Peter \"QKumba\"\r\n; Ferrie. Logo by Frederic \"Cleaner\/Break\" Cambus. (c)2015 WTFPL v2 license. \r\n; \"Fasm BootChess.asm\" + \"partcopy BootChess.bin 0 200 -f0\" = PC floppy boot \r\n;-BootChess.asm-------------------;-----------------------------------------\r\nx86 equ 1 ; x86=1 PC\/emu vs. win32b\/(DOS)Box\r\nsaf equ 0 ; saf=0 +queening -exotic failsafe \r\n_b equ byte ; DEFAULTS=PC FLOPPY BOOT+QUEENING\r\n_w equ word ; x86=1 saf=0 512b inc. queening \r\n_d equ dword ; x86=1 saf=1 500b+ excl. queening*\r\n_s equ short ; x86=0 saf=1 506b inc. queening \r\n_n equ near ; x86=0 saf=0 487b excl. queening\r\n_f equ far ; *only working version in Bochs\r\n if x86 ; beg of boot vs .com preprocessing\r\n org 7c00h ; std start of bootsector after post\r\n if saf ; beg clear any start ambiguous segment\r\n jmp _f 0:fix ; 7c0:0000 vs. 0:7c000 cs para fix-up\r\n end if ; end clear any start ambiguous segment \r\nfix:push cs ; if post int 19h isr bootsrap loader \r\n pop ds ; left any bda or shadow segment values \r\n push cs ; then enforce ds=cs=0 \r\n pop es ; then enforce es=ds=cs=0\r\n mov aX,13h ; function set vga mode 320x200x256\r\n else ; else if 16-bit binary assume ah=0\r\n org 100h ; start of com binary program ip\r\n mov aL,13h ; function set vga mode 320x200x256\r\n end if ; end of boot vs .com preprocessing\r\n int 10h ; standard bios video api\r\n brd equ bf1+16 ; chess board at end of sector\r\n mov di,brd ; set physical board index\r\n mov bp,12 ; set 6x8+8 empty sqr mid board lines\r\n call in2 ; pass#1 black \"rnbqkbnr\" low-caps\r\n push word opn ; pass#2 hi-caps whites & fall-through\r\nrle:lodsb ; al='.'\/al=null (fixed length rle)\r\n mov cl,8 ; empty sqr mid board line length\r\n rep stosb ; set one empty sqr mid board line\r\n dec bp ; all empty sqr mid brd lines inited ?\r\n jnz rle ; if not repeat init else bp=0 assumed\r\n mov ah,'A'-'a' ; fall-through pass#2 white hi-caps\r\nin2:mov si,br0 ; si points to endrank \"rnbqkbnr\" str\r\n if x86=0 ; if .com binary environment ch=0\r\n mov cL,8 ; \"rnbqkbnr\" endrank str length\r\n else ; assume nothing although tempting \r\n mov cX,8 ; \"rnbqkbnr\" endrank str length\r\n end if ; end of register ch startup value\r\nin3:lodsb ; read physical board str car\r\n add al,ah ; hi-caps rank 1 \/ low-caps rank 8\r\n stosb ; write physical board str car\r\n loop in3 ; all \"rnbqkbnr\" str car written ?\r\n mov cl,8 ; si-;equiv piece vals di-;0x88 brd\r\n rep movsb ; write logical 0x88 board str vals\r\n retn ; return to callers\r\nge0:mov bx,di ; physical board idx (bx=brd)\r\n mov dh,'1' ; beg white move src rank\r\nge1:mov dl,'h' ; beg white move src file\r\nge2:mov [si],dx ; beg white move src str\r\n mov ch,'1' ; beg white move dst rank\r\nge3:mov cl,'h' ; beg white move dst file\r\nge4:mov [si+2],cx ; beg white move dst str\r\n pusha ; save all values\r\n call idx ; passive chess coords to linear indexes\r\n jbe mis ; white move src color not conforming\r\n push bx ; save white move dst idx\r\n call ver ; white move legal chess ?\r\n pop bx ; restore white move dst idx\r\n jc mis ; white move not legal chess\r\n mov di,num+3 ; compare move destination rank in 7dfeh \r\n inc si ; with move source rank in 7dfch \r\n cmpsb ; is taxi distance to topmost bettered ? \r\n jnc wor ; else not getting closer to black king\r\n cmp _b [di],'?' ; does any fallback move exist yet ?\r\n jz lkj ; no, then last valid move good enough\r\nwor:mov aL,_b[si+bx+brd-num-'a'+6]; yes, previous valid legal exist so \r\n dec aL ; only override if it's a capture \r\n js mis ; no, don't want worse taxi distance \r\n mov bx,fs ; it's a capture with piece value=al\r\n cmp bL,aL ; but hightest capture value yet ?\r\n jnc mis ; no, less important opponent piece \r\nmax:mov fs,bx ; fs=best move yet in taxi half-ply\r\nlkj:dec si ; realign source index \r\n dec si ; to copy dword bst=dword idx \r\n movsd ; after 4096 tries : move=dword bst\r\nmis:popa ; restore all values\r\n cmp cl,'a' ; end white move dst file ?\r\n loopnz ge4 ; dec white move else next dst file\r\n inc ch ; inc white move dst rank\r\n cmp ch,'9' ; end white move dst rank ?\r\n jnz ge3 ; else next move dst rank\r\ncpx:inc bx ; inc physical board index\r\n dec dx ; dec white move src file\r\n cmp dl,'`' ; end white move src file ?\r\n jnz ge2 ; else next move src file\r\n inc dh ; inc white move src rank\r\n cmp dh,ch ; end white move src rank ? ch=9\r\n jnz ge1 ; else next move src rank\r\n push _d [si+4] ; get best white move found\r\n pop _d [si] ; set it as final white move\r\nval:mov cl,'.' ; valid : empty sqr replaces src piece\r\n call act ; active chess coords to linear indexes\r\n xor bp,3 ; player turn and pawn unidir. delta\r\n jz ge0 ; white turn to play (case best=0)\r\nbla:mov al,'?' ; input str clear pattern\r\n mov di,si ; input str clear pattern (di=num)\r\n mov cx,8 ; input str clear pattern\r\n rep stosb ; input str clear pattern (di=brd)\r\n call key ; get user keyboard input\r\n jbe bla ; black move src color not conforming\r\nopn:call ver ; di=brd, black move legal chess ?\r\n jc bla ; white move not legal chess\r\n jmp _s val ; validate black move\r\nver:call idx ; get lin indexes \/w implicit passive\r\n xchg bx,dx ; switch bx=dst idx dx=src idx\r\n mov ah,[si+bx+brd-num-'a'+8] ; get piece logical 0x88 brd val...\r\n mov dh,bl ; dh=src idx dl=dst idx\r\n sub dx,\"aa\" ; get move file zero-based indexes\r\n bsr bx,ax ; scan for 1st bit set (si=idx+10)\r\n movsx bx,[si+bx-10-num+tab] ; bl=moved piece type idx (bh=0)\r\n mov cx,_w [si+bx-num+tab] ; piece type deltas cl=repeats ch=num\r\n sahf ; set piece logical 0x88 brd val \r\n jnp sp1 ; branch if piece not pawn (bit#4!=1)\r\n jc sp2 ; branch if pawn prev moved (bit#0=1)\r\nsp1:jns sp3 ; branch if piece not king (bit#7!=1)\r\nsp2:mov cl,1 ; override repeat if piece pawn or king\r\nsp3:jnp sp4 ; branch if piece not pawn (bit#4!=1)\r\n add bx,bp ; pawn player turn unidirection mutex\r\nsp4:inc bx ; advance piece type struct field ptr\r\n and ah,11111100b ; isolate piece bitmask only \r\nvl1:push cx ; save piece type deltas\r\n mov al,dh ; load start dst idx val\r\n inc bx ; advance piece type struct field ptr\r\nvl2:add al,[si+bx-num+tab] ; add this piece delta to dst idx val\r\n xchg aL,bL ; base reg=dst idx val and preserved\r\n mov ch,[si+bx+brd-num+8] ; read projected dst square val\r\n xchg aL,bL ; base reg=piece type struct field ptr\r\n cmp al,dl ; wanted move found (src+delta(s)=dst) ?\r\n jnz dif ; different than requested move\r\nsam:sahf ; get piece logical 0x88 brd val in flgs\r\n jnp yes ; branch if piece is not pawn (bit#2=0)\r\n test [si+bx-num+tab],1 ; pawn piece delta parity=diag vs. vert\r\n jz ord ; branch if pawn piece moving vert\r\n test ch,ch ; pawn piece vert move=;eating ?\r\n jnz yes ; capturing verify dst sqr not empty\r\n jmp _s bad ; else illegal chess move is a miss\r\nord:test ch,ch ; pawn piece vert move=;no eating ?\r\n jz yes ; no eating=;empty dst sqr else illegal\r\ndif:sahf ; store piece nature in flags register\r\n jnp skp ; not pawn piece so skip direction test\r\n test [si+bx-num+tab],1 ; pawn piece delta parity=diag vs. vert\r\n jnz bad ; diagonal pawn move is illegal\r\nskp:test ch,ch ; else skipping over dst square val ?\r\n jnz bad ; projected dst sqr val is not empty\r\n sahf ; get piece logical 0x88 brd val in flgs\r\n jz x88 ; branch if piece is queen (bit#6=1)\r\n jna bad ; branch if piece is not knight(bit#4=0)\r\nx88:test al,88h ; ch=0 dst out of physical board limits?\r\n loopz vl2 ; else cont if delta repeats remain\r\nbad:pop cx ; restore piece type deltas\r\n dec ch ; all possible delta nums verified ?\r\n jnz vl1 ; if not then cont next delta type\r\nnok:stc ; else return \/w no match flg set\r\n retn ; return to caller\r\nyes:pop cx ; correct entry sp and disregard count\r\n retn ; return to caller(s)\r\nkey:call prt ; refresh screen to account input echo\r\n xor bx,bx ; bx=str idx=odd\/even\/alpha\/num mutex\r\nkbd:cbw ; fun blocking wait for keystroke (ah=0)\r\n int 16h ; std bios keybd api (ah=scan al=ascii)\r\nesc:dec ah ; was esc key pressed to quit ?\r\n jnz car ; else default process key input\r\nxit:if x86 ; if x86 boot context environment\r\n int 19h ; exit through bootstrap to reboot cpu\r\n else ; else if .com 16-bit binary\r\n int 20h ; dos 1+ - terminate program\r\n end if ; end of exit methods (os load or shell)\r\ncar:mov [bx+si],al ; sav ascii val to move string (si=num)\r\nprt:pusha ; save game state snapshot\r\n cwd ; curs location dx=(0,0)=(row,column)\r\n mov ax,1301h ; function ega write str write mode 1\r\n mov bl,7 ; page 0 grey car attrib matching tty\r\n mov cl,8 ; src str lngth (curs updated horiz)\r\n mov bp,bf1 ; es:bp is \"abcdefgh\" ptr\r\nlns:int 10h ; standard bios video api\r\n add bp,16 ; bp=para step siz separating strings\r\n push ax ; save old bios video api func params\r\n mov ax,0e39h ; function teletype outp car=rank '9'\r\n sub al,dh ; decrement right handside rank value\r\n int 10h ; standard bios video api\r\n pop ax ; restore old bios video api fx params\r\n cmp dh,cl ; src str total (curs updated vert)\r\n inc dh ; preemptive off-by-one allows 9 verts\r\n jc lns ; all 9 brd gui row strings printed ?\r\n mov bp,si ; 10th row tail bp=move coords, cl=8\r\n int 10h ; standard bios video api\r\n popa ; restore game state snapshot\r\n inc bx ; test if any more keys ?\r\n cmp bl,4 ; frFR format input string\r\n jc kbd ; else continue input \r\nidx:loop idx ; ch=0 passive call load src\/dst lin idx\r\nact:mov si,num ; reinit si to point to coord input str.\r\n mov bx,[si] ; bx=src coord (pass#1)\r\n cbw ; empty sqr val in logical 0x88 board\r\n call put ; place param passed as fun pass#1\r\n mov dx,[si+2] ; bx=dst idx dx=src idx\r\n xchg bx,dx ; fall-through for second pass\r\n push word mat ; test for checkmate and conforming\r\nput:xchg ax,bx ; bx|dx=[num+di]+16*((8-'0')-[num+di+1])\r\n aad -10h ; shl ah,4\/sub al,ah\/xor ah,ah\r\n add al,80h ; bx|dx=al-640%256-16*ah\r\n xchg ax,bx ; bx|dx=al+128-16*ah\r\n jcxz sim ; active call request or simulation ?\r\n if saf=0 ; standard non-failsafe queening\r\n cmp _b [si+3],'8' ; validated dst rank is top-most ? \r\n jz qq ; if so then promote pawn to queen\r\n cmp _b [si+3],'1' ; validated dst rank is bottom-most ?\r\n jnz prm ; if not no pawn queening promotion\r\nqq: sahf ; store piece nature in flag register\r\n jnp prm ; no pawn queening promotion \r\n xor ah,01000110b ; transform p to promoted queen\r\n inc cx ; queen promotion p2q or P2Q\r\n end if ; end of conditional queening\r\nprm:xchg ah,[si+bx+brd-num-'a'+8] ; update piece logical 0x88 board val\r\n xchg cl,[si+bx+brd-num-'a'] ; update piece physical board ascii val\r\n or ah,1 ; update piece moved once (bit#0)\r\nsim:retn ; return to caller(s)\r\nmat:sahf ; catured piece king and mate ?\r\n js xit ; if piece is king then game is over\r\n call chk ; move src color conforming ?\r\n jnz nok ; move src color not conforming\r\nchk:xchg bx,dx ; src idx <- dst idx\r\n mov al,[si+bx+brd-num-'a'] ; pass#1:src idx pass#2:dst idx di=brd\r\n xor _b [si+len-num],8 ; self-modif 8\/26 val=[1;8]\/[a(A);z(Z)]\r\n mov cl,-'a' ; assert black piece car interval\r\n test bp,bp ; test whose turn it is to play\r\n jnz lim ; assert white piece car interval\r\n mov cl,-'A' ; al=ascii value cl=-(lower boundery)\r\nlim:xadd al,cl ; tmp=al+cl cl=al al=tmp +fall-trough\r\n db 0d4h ; aam <self-modified value>\r\nlen:db 12h ; ah=al\/8 al%=8\r\n mov al,cl ; al=restored ascii value\r\n test ah,ah ; set\/clear zf=0 success zf=1 failure\r\n retn ; return to caller(s) nb: destroys ah\r\ntab db p-tab,r-tab,n-tab,b-tab ; piece type mov offset array\r\n db q-tab,q-tab ; note original 1K ZX Chess q=k trick\r\nbr0 db \"rnbqkbnr\",8,16,32,64,128 ; end rank pattern + beg piece values\r\n db 32,16,8,'p',4,'.',0,'.',0 ; end piece values + beg mid board reps\r\n db '.',0,'.',0,'P',4 ; ... end mid board reps\r\np db 2,3,-10h,-15,-17,10h,15 ; bit#2 pf=04 p[6]=r[0] overlay\r\nr db 17,4,10h,-1h,-10h ; bit#3 ??=08 r[5]=n[0] overlay\r\nn db 1,8,1fh,21h,12h,-0eh,-1fh ; bit#4 af=16 n[9]=b[0] overlay\r\n db -21h,-12h ; ... end of knight moves list\r\nb db 0eh,4,-0fh,11h,-11h ; bit#5 ??=32 b[5]=q[0] overlay\r\nq db 0fh,8,10h,11h,0fh,1h,-10h ; bit#6 zf=64 k=q except k[0]=1\r\n db -11h,-0fh,-1h ; ... end of queen\/king moves list\r\nbf1 db \"abcdefgh\" ; gui file index string\r\nnum db \"e2e4\" ; hardcoded Ruy Lopez opening\r\n if saf and x86 ; x86 failsafe exotic boot environment\r\n times 510-($-$$) db 0 ; nul padding if necessary\r\n org 7df0h ; boot signature vbr\/mbr standard offset\r\n sig db 55h,0aah ; magic number no-endian boot signature\r\n end if ; end of conditional failsafe signature<\/pre>\n<\/blockquote>\n","protected":false},"excerpt":{"rendered":"BootChess has smashed the record for the smallest computer implementation for chess, held since 1983, with a total size of only 487 bytes<\/p>\n","protected":false},"author":2,"featured_media":117675,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[9],"tags":[28549,36,28547,28553,28555,28551],"class_list":["post-117673","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-gaming","tag-1k-zx-chess","tag-active","tag-chess","tag-olivier-poudade","tag-peter-ferrie","tag-your-computer-magazine"],"_links":{"self":[{"href":"https:\/\/mybroadband.co.za\/news\/wp-json\/wp\/v2\/posts\/117673"}],"collection":[{"href":"https:\/\/mybroadband.co.za\/news\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mybroadband.co.za\/news\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mybroadband.co.za\/news\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/mybroadband.co.za\/news\/wp-json\/wp\/v2\/comments?post=117673"}],"version-history":[{"count":2,"href":"https:\/\/mybroadband.co.za\/news\/wp-json\/wp\/v2\/posts\/117673\/revisions"}],"predecessor-version":[{"id":117693,"href":"https:\/\/mybroadband.co.za\/news\/wp-json\/wp\/v2\/posts\/117673\/revisions\/117693"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/mybroadband.co.za\/news\/wp-json\/wp\/v2\/media\/117675"}],"wp:attachment":[{"href":"https:\/\/mybroadband.co.za\/news\/wp-json\/wp\/v2\/media?parent=117673"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mybroadband.co.za\/news\/wp-json\/wp\/v2\/categories?post=117673"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mybroadband.co.za\/news\/wp-json\/wp\/v2\/tags?post=117673"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}