call gca
; it's the begin of execution call gca -> push cs
gca:
    pop bx          ; bx=cs=0x0,since bootloader is load at 0x
    mov ax,0x07c0
    mov ds,ax
    mov si,bx
    add si,0x200
    ;
;DAP
    mov byte [si],0x10
    inc si
    mov byte [si],0x0
    inc si
    mov word [si],0x1
    mov word [si],0x300
    mov word [si],bx
    mov word [si],0x1
    mov word [si],0x0
    mov dword [si],0
; What to write is here
    mov word [bx+0x300],'AB'
;
; Write
    mov ah,0x41
    mov bx,0x55aa
    mov dl,0x80
    int 0x13
    jc error
;
    mov ah,0x43
    mov dl,0x80
    mov si,bx
    add si,0x200
    int 0x13
    jc error
;
success:
    mov si,suc_msg
print_succ:
    lodsb
    or al,al
    jz hang
    mov ah,0xe
    int 0x10
    jmp print_succ
;
error:
    mov si,err_msg
print_err:
    lodsb
    or al,al
    jz hang
    mov ah,0xe
    int 0x10
    jmp print_err
hang:
    jmp hang
err_msg db "You have encountered an error!",0x0
suc_msg db "You are success!",0x0
times 510-($-$$) db 0
dw 0xAA55