.286
.model small
.code


CocdeSize = Offset @@End - Offset @@Start

@@Start:
	cli
	xor ax,ax
	mov ss,ax        ;ss=ax=0000h
	mov sp,7c00h     ;sp=7c00h
	sti
	push ax
	pop es		 ;es=0000
	push ax
	pop ds		 ;ds=0000

@@Begin:
	int  12h
	dec  ax
	mov  ds:[0413h],ax

	mov  cl, (10-4)
	shl  ax,cl
	mov  es,ax		;ax=9fc0

	xor  di, di		;di=00
	mov  si,sp		;si=7c00
	mov  cx, CocdeSize
	cld
	rep  movsb

	push ax
	mov  di,Offset  @@HighAddr
	push di
	retf

;	di -> ip
;	ax -> cs

@@HighAddr:
	cli
	xchg ds:[13h*4+2],ax
	mov  cs:[OldInt13Seg],ax

	mov  ax,Offset @@NewInt13
	xchg ds:[13h*4],ax
	mov  cs:[OldInt13Off],ax
	sti

	push ds		;es=ds=0000
	pop  es

@@ReadOldHardBoot:
	mov  ax,0201h		;es:bx=0000:7c00
	mov  bx,7c00h
	mov  cx,0006h
	mov  dx,0080h
	int 13h
	jc   short @@Exit1

@@ExecOldBoot:
	cmp  es:[bx.Flags],0aa55h
	jnz  @@Exit2
	
	lea  si,MsgText
	jmp  @@DispMsg

@@Exit1:
	lea  si,MBRERROR
	jmp  @@DispMsg

@@Exit2:
	lea  si,MOS

@@DispMsg:
	mov  al,cs:[si]
	inc  si
	mov  ah,0eh
	int  10h
	or   al,al
	jnz  @@DispMsg

	xor  ax,ax
	int  16h

@@ExitDisp:
	
	;push  es		;es=0000
	;push  bx		;bx=7c00
	;retf
	db 0eah,00h,7ch,00h,00h

@@NewInt13:
	cmp  dX,0080h
	jnz  short  @@JmpOldInt13
	cmp  cx,0001h		;dx=0000
	jnz  short  @@JmpOldInt13
	mov cx, 0006h			;if caozuo MBR-->0006 sector

@@JmpOldInt13:
	db  0eah
	OldInt13Off  dw  ?
	OldInt13Seg  dw  ?

 	MsgText db 'Night is deep,you must go sleep!',0
	MBRERROR db 'can not find MBR!',0
	MOS	 db 'Invalid Operating System!',0
 		
 @@End:
 	org  1feh
 	Flags  dw  0aa55h
End