View difference between Paste ID: yskWCjgx and Zcgx8KP9

 ; designed for NASM generating .com file...
 
 cpu 386
 org 100h
 
 section .text
 Start:
 
 	mov ax,0x13 ;SetVideoMode: 320x200x8
 	int 0x10
 
 	;array assumes ds=ss
 	mov bp, LineArrayStart
 .NextLine:
-    xchg bp,sp    ; array <-> stack
+	xchg bp,sp    ; array <-> stack
 	pop si ;X0
 	pop di ;Y0
 	pop cx ;X1
 	pop dx ;Y1
 	pop ax ;Color
 	xchg bp,sp    ; stack <-> array
 	call DrawLine
 	cmp bp, LineArrayEnd
 	jl .NextLine
 	mov sp, bp ;restore sp
 
 	mov ah,0x7  ;wait for a key
 	int 0x21
 
 	mov ax,0x3  ;SetVideoMode: 80x25 (text)
 	int 0x10
 
 	int 0x20    ;end program
 
 LineArrayStart:
 	;   X0  Y0   X1  Y1  Color
 	dw   1,  0, 318,  0 , 9
 	dw 319,  1, 319,198 ,11
 	dw 318,199,   1,199 ,13
 	dw   0,198,   0,  1 ,15
 	dw   8,  8, 311,191 ,10
 	dw 311,  8,   8,191 ,14
 LineArrayEnd:
 ;=========================================================================
 ;=========================================================================
 ;=========================================================================
 
 ;-----------------------------------------------
 ; Draw Line (si,di) to (cx,dx) with color (al) ;
 ; ----------------------------------------------
 ; unused... AH,BP,SP (selfmod is using CS: to not assume CS=DS)
 DrawLine:
 	push ds                  ;save old DS
 	push 0xA000              ;make new DS to be screen segment
 	pop ds
 
 	;   dx = abs(x1 - x0)
 	;   dy = abs(y1 - y0)
 	;   (x0 < x1) ? sx = 1 : sx = -1
 	;   (y0 < y1) ? sx = 1 : sx = -1
 	;   err = dx - dy
 
 	mov bx, dx               ; bx = Y1*320+X1
 	imul bx, 320             ; (end position)
 	add bx, cx               ;
 	mov [cs:.EndOff-2], bx   ; self-mod ending offset for the line!
 
 	mov bx, 1                ; SX = 1
 	sub cx,si                ; cx = (X1-X0)
 	jnb .ChkH                ; jump if not negative
 	neg bx                   ; SX = -1
 	neg cx                   ; cx = -cx (abs DX)
 .ChkH:
 	mov [cs:.SX-2], bx       ; self-mod setting (in code SX)
 
-	mov bx, -320             ; SY = "-1"  (inverse because -dy , 320 because 'row')
+	mov bx, -320             ; SY = "-1"  (inverse because -DY , 320 because 'row')
 	sub dx,di                ; dx = (Y1-Y0)
 	jb .ChkV                 ; jump if negative
 	neg bx                   ; SY = "1"
 	neg dx                   ; dx = -dx (-abs DY)
 .ChkV:
 	mov [cs:.SY-2], bx       ; self-mod setting (in code SY)
 
 	imul di, 320             ; di = Y0*320+X0
 	add di, si               ; (start position)
 
-	mov si, cx               ; ERR = DX+DY
+	;mov si, cx               ; ERR = DX+DY
-	add si, dx               ; (add because DY was negated)
+	;add si, dx               ; (add because DY was negated)
 	lea bx,[ecx+edx]
 	add bx,bx
 
 ;   loop
 ;     printPixel(x0, y0, colour)
 ;     if (x0 = x1) and (y0 = y1) exit loop
 ;     e2 = 2 * err
 ;     if (e2 > -dy) then
 ;       err = err - dy
 ;       x0 = x0 + sx
 ;     end if
 ;     if (e2 < dx) then
 ;       err = err + dx
 ;       y0 = y0 + sy
 ;     end if
 ;   end loop
 
 .NextPixel:
 	mov [di], al             ; store pixel
 	cmp di, 0x5555           ; check if done drawing the line (SELF-MOD!)
 .EndOff:
-	mov bx, si               ; E2 = ERR*2
+
-	add bx, bx
+
 	;lea bx,[esi+esi]
 	;;mov bx, si               ; E2 = ERR*2
-	jle .SX                  ; (inverse jump)
+	;;add bx, bx
-	add si, dx               ; ERR = ERR - DY (DY negativated)
+
 	cmp bx, dx               ; if (E2 > -DY) then
 	jle .NoAddY              ; (inverse jump)
 	;add si, dx              ; ERR = ERR - DY (DY negativated)
 	add di, 0x5555           ; X0 = X0 + SX (Self-Mod SX (-1 or 1))
-	add si, cx               ; ERR = ERR + DX
+
 	cmp bx, cx               ; if (E2 < DX) then
 	lea bx,[ebx+edx*2]	     ; duplicate code because both DX/DY comparsion must use the same BX
 	jl .DoAdd                ; so i do it before the lea (which does not change registers)
 	jmp .NextPixel           ; and jump to add part in positive case (better!!)
 .NoAddY:
 	cmp bx, cx               ; if (E2 < DX) then
 	jge .NextPixel           ; (inverse jump) (optimized jump)
 	;add si, cx               ; ERR = ERR + DX
 .DoAdd:
 	lea bx,[ebx+ecx*2]
 	add di, 0x5555           ; Y0 = Y0 + SY (Self-Mod SX {-1(-320) or 1(320)}
 .SY:
 	jmp .NextPixel
 .Done:
 	pop ds                   ; restore previous DS
 	ret                      ; and return
 
 ;-----------------------------------------------