運行於虛擬機
彙編風格：NASM
org 0x7c00
jmp begin_real_mode
boot_msg:db "Load boot..."
pm_msg:db "go to protected mode..."
printmsg:
mov ax,0x1301; Service number
mov dx,0; Sursor position
mov bx,0xA; Green Color
int 0x10
ret
clrscr:
mov ax,0x0600
mov cx,0
mov dx,0x174f
mov bh,0
int 0x10
ret
getkey:
mov ah,0x00
int 0x16
ret
[BITS 16]
begin_real_mode:
mov ax,cs
mov ds,ax
mov ss,ax
mov es,ax
mov sp,0x100
call clrscr
mov bp,boot_msg
mov cx,12D
call printmsg
call getkey
call clrscr
mov bp,pm_msg
mov cx,23D
call printmsg
call getkey
call clrscr
cli
lgdt [ gdtr ]
mov eax,cr0
or al,0x01
mov cr0,eax
jmp codesel:begin_proected_mode
[BITS 32]
begin_proected_mode:
mov ax,datasel
mov ds,ax
mov es,ax
mov ax,videosel
mov gs,ax
mov word [gs:0],0x0A41
mov word [gs:2],0x0A42
mov word [gs:4],0x0A43
mov word [gs:6],0x0A44
jmp $
[BITS 16]
gdtr
dw gdt_end - gdt - 1
dd gdt
gdt
nullselequ $-gdt
dd 0,0
codeselequ $-gdt
dw 0x0ffff; 4G
dw 0x0000
db 0x00
db 0x09a
db 0x0cf
db 0x00
dataselequ$-gdt
dw 0x0ffff; 4G
dw 0x0000
db 0x00
db 0x092
db 0x0cf
db 0x00
videoselequ $-gdt
dw 3999; 80 cols * 25 * rows * 2bytes - 1
dw 0x8000
db 0x0b
db 0x92
db 0x00
db 0x00
gdt_end
times 510-($-$$) db 0
dw 0xAA55