.MODEL TINY

CODE SEGMENT
ASSUME CS:CODE,DS:CODE
org 100h
MAIN:
        mov ah,0fh
        int 10h
        cbw
        push ax
        mov al,13h
        int 10h

;        std   ; pouziji obracene poradi rady a mohu tak vynechat nastaneni direction flagu
        cwd
        xor bx,bx
        mov cx,0ffffh

        mov si,offset diff2
        mov es,[si]
step:
        add dh,[si]
;        inc si
        add cx,[si+2]
part:
        mov ax,1010h
        int 10h
        inc bx
        test bl,03fh
        jnz step
;       lodsb
        lodsw
        and bh,bh
        jz part

        xor cx,cx
kresli:
        mov dx,320                      ; hlavni posun
        mov di,1                        ; vedlejsi posun
        mov ax,cx                       ; ax=abs(x0-x1)..
        mov bl,199                      ; bx=D

;       push cx                         ; test sudost
;       shr cl,1
;       pop cx
;       jnc sude
        test al,1
        jz  sude

        mov si,256                      ; liche: dolu, hp=320, vp=1,-1, K=abs(x0-x1), D=199
        sub ax,192                      ; abs(x0-x1)=abs(256-(64+barva))=abs(192-barva)
        jnc cara                        ; skok pro x0>x1 - nastaveno
        neg di                          ; jinak je x0<x1 a vedlejsi je -1
        neg ax                          ; ax=abs(x0-x1)
        jc cara                         ; zde je vzdy CF=1 -> pouziji jc misto jmp (je to o Byte kratsi)


sude:                                   ; nahoru, hp=-320,1, vp=1,-320, K=x1,199, D=199,x1
        not al                          ; ax=255-cl=K
        neg dx                          ; dx=-320
        mov si,63681                    ; bod vlevo dole
        cmp al,bl
        jc cara                         ; skok pro (x1-x0)<199 - nastaveno
        xchg dx,di                      ; jinak prohod hp s vp a K s D
        xchg ax,bx
;        xchg ch,cl
cara:
        mov bp,ax                       ; bp=K, ax=prubezne
        mov ch,bl                       ; ch=D+1
        inc ch

cyklus:
        mov es:[si],cl

        add si,dx                       ; bod=bod+hp
        push bx                         ; bx/2
        shr bl,1
        cmp ax,bx                       ; ? ax>D/2
        pop bx
        jl pokrac
        add si,di                       ; bod=bod+vp
        sub ax,bx                       ; prub=prub-D

pokrac:
        add ax,bp
        dec ch
        jnz cyklus

        inc cl
        jnz kresli                      ; barva od 0 do 255, konec pri 256(=0)

;       mov ah,8
;       int 21h
        int 16h    ; ah = 0

        pop ax
        int 10h
        ret

diff2    db 0,0a0h,1,0,-1,-1,1,1,0,0
;diff    db 0,0,1,1,-1,-1,1,0,0,0a0h

CODE ENDS
END MAIN