boot.asm

一个操作系统启动代码

;*******************************************************************
; Boot
;  (c) Andre v.d. Merwe 4-Feb-1999
;  <[e-mail]> <[e-mail]>
;  See "zen.txt" for copyright information
;
; Zen Source Library. Assembler example 3
; http://users.iafrica.com/d/da/dart/zen/zen.html
;-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
;
; Compiler TASM
;
; This is a "bootable" application. Write it to track 0, sector 1
;  on a removable disk (using bm.com). When loaded it reads a number 
;  of sectors from the disk and executes them. In other words it is 
;  a very simple OS loader.
;*******************************************************************

   TITLE Boot
	JUMPS

	.model Tiny

;---------------------------------------------------------------------------------
.code
.286
org 7c00h   ;7c00h = offset loaded to at bootup
;---------------------------------------------------------------------------------

start:  
	mov	ah,	2	;int 13 - 2
	mov	al,	2	;Load 2 sectors  (2 sectors = size of dump.com in bytes / 512)

	mov	bx,	100h	;Offset to load data to  (Offset 100h is same as dos offset for COM files)
	mov	cx,	2000h	;Segment
	mov	es,	cx

	mov	ch,	1	;track
	mov	cl,	1	;start sector
	mov	dh,	0	;head
	mov	dl,	0	;drive
	int	13h

	jnc	Sector1Loaded


	mov	ah,	03h
	mov	al,	'*'
	int	10h
	mov	ah,	0
	int	16h


Sector1Loaded:



Go_Location:	      ;Far jump to 2000:0100 (where data was loaded to)
   db	0eah

Location_Offset		dw	100h
Location_Segment	   dw	2000h




halt:
	jmp	halt

;---------------------------------------------------------------------------------



;---------------------------------------------------------------------------------
.data
;---------------------------------------------------------------------------------
	db	446 	dup(0)
	db      055h,	0AAh ; boot id
;---------------------------------------------------------------------------------


end     start