code_seg segment assume cs:code_seg,ds:code_seg org 100h start: push cs push cs push cs pop ds pop es mov ax,0fffeh cli pop ss mov sp,ax sti jmp load old_21 dd ? x dw 0 y dw 0 x1 dw 0 x2 dw 0 y1 dw 0 y2 dw 0 clr db 0 count dw 0 star_h db 34,37,33,38,32,39,32,39,32,39 db 32,39,32,39,32,39,33,38,34,37 star_t db 0 tree_h db 00,00,00,00,34,37,34,37,33,38 db 33,38,32,39,32,39,31,40,31,40 db 31,40,30,41,30,41,29,42,29,42 db 28,43,28,43,27,44,27,44,26,45 db 26,45,26,45,25,46,25,46,24,47 db 24,47,23,48,23,48,22,49,22,49 db 21,50,21,50,21,50,20,51,20,51 db 19,52,19,52,18,53,18,53,17,54 db 17,54,16,55,16,55,16,55,15,56 db 15,56,14,57,14,57,13,58,13,58 db 12,59,12,59,11,60,11,60,11,60 db 10,61,10,61,09,62,09,62,08,63 db 08,63,07,64,07,64,06,65,06,65 db 06,65,05,66,05,66,04,67,04,67 db 03,68,03,68,02,69,02,69,01,70 db 01,70 tree_t db 0 merry db 33,33,'NFSSZ',0 xmas db 'DISJTUNBT',0 new_21: assume cs:code_seg,ds:nothing,es:nothing cmp ax,4B00h je exec cmp ah,69h je im_here do_jmp: jmp dword ptr cs:[old_21] im_here: cmp bx,666 jne do_jmp mov ax,1993 iret exec: push ax push di mov di,dx zero_loop: inc di cmp byte ptr ds:[di],0 jne zero_loop sub di,6 cmp byte ptr ds:[di],'H' jne do_21_jmp cmp byte ptr ds:[di+1],'I' jne do_21_jmp pop di pop ax push ax push bx push cx push dx push di push si push ds push es call graphics pop es pop ds pop si pop di pop dx pop cx pop bx pop ax jmp dword ptr cs:[old_21] do_21_jmp: pop di pop ax jmp dword ptr cs:[old_21] dot: push bx mov bx,y mov ax,320 mul bx mov bx,ax add bx,x mov ah,clr mov byte ptr es:[bx],ah pop bx ret yline: mov ax,y1 mov y,ax yline_loop: call dot inc y mov ax,y2 cmp y,ax jle yline_loop ret xline: cmp x1,0 je return mov ax,x1 mov x,ax mov dx,y push dx add y,15 xline_loop: call dot inc x mov ax,x2 cmp x,ax jle xline_loop pop dx mov y,dx return: ret drawtree: mov bx,offset tree_h mov y,15 mov dl,clr push dx treeloop: xor ax,ax xor cx,cx inc y mov al,byte ptr cs:[bx] mov cl,byte ptr cs:[bx+1] add bx,2 mov x1,ax mov x2,cx call xline cmp y,60 jg highline inc clr cmp clr,122 jne nofixclr mov clr,117 jmp nofixclr highline: dec clr cmp clr,116 jne nofixclr mov clr,122 nofixclr: cmp bx,offset tree_t jne treeloop pop dx mov clr,dl ret drawtrnk: mov dl,clr push dx add dx,18 mov clr,dl mov y,77+15 mov x1,30 mov x2,40 trnkloop: call xline inc clr cmp clr,239 jne nofxtrkc mov clr,234 nofxtrkc: inc y cmp y,85+15 jne trnkloop pop dx mov clr,dl ret drawstar: xor dx,dx mov dl,clr push dx sub dx,53 mov clr,dl mov y,7 mov bx,offset star_h starloop: xor ax,ax xor cx,cx mov al,byte ptr cs:[bx] mov cl,byte ptr cs:[bx+1] add bx,2 mov x1,ax mov x2,cx inc y call xline inc clr cmp clr,70 jne nostarfx mov clr,64 nostarfx: cmp bx,offset star_t jne starloop pop dx mov clr,dl ret printstr: mov al,cs:[si] dec al mov ah,14 int 10h inc si cmp byte ptr cs:[si],0 jne printstr ret graphics: mov ax,0013H int 10h mov ax,0A000H mov es,ax mov bx,100 mov si,offset merry call printstr mov dx,1000h mov bh,0 mov ah,2 int 10h mov si,offset xmas call printstr mov count,0 clr_117: mov clr,117 go_call: call drawstar call drawtree call drawtrnk in al,60h cmp al,39h je done inc clr inc count cmp count,40 je done cmp clr,122 je clr_117 jmp go_call done: mov ax,0003H int 10h ret loadto db 90h load: mov ah,69h mov bx,666 int 21h cmp ax,1993 je leave_ing mov ah,2Ah int 21h cmp dh,12 jne leave_ing cmp dl,21 jl leave_ing cmp dl,25 jg leave_ing mov ax,3521h int 21h mov di,offset old_21 mov [di],bx mov [di+2],es mov dx,offset new_21 push cs pop ds mov ax,2521h int 21h mov dx,offset loadto int 27h leave_ing: int 20h code_seg ends end start