[Nasm-users] prob with bios int 10h

[zak100 <zul...@ya...>]

Hi,
I have written the following program to be exeuted when my system boots up
using int 10h.
But its not printing any mesg. Can somebody plz. help me with this??

Zulfi.


org 7C00h; starting the program at 7C00H. Address generated at reset

section .text


section .text; why twice????


    call overdata    ; Call? WTF? Don't worry, we pop the. 
                     ; return address off to get initial IP.
                     ; Note that "call" is longer than
;    nop             ; "jmp short", so we don't want the nop. At 7C00H we
have to make a jmp where our actual code starts

    db 'MyOS    '    ; OEM id - space-padded to 8 bytes
    dw 200h          ; bytes/sector
    db 1             ; sectors per cluster
    dw 1             ; sectors before FAT
    db 2             ; number of FATs
    dw 0E0h          ; max rootdir entries
    dw 0B40h         ; total sectors
    db 0Fh           ; media descriptor
    dw 9             ; sectors per FAT
    dw 12h           ; sectors per track
    dw 2             ; number heads
    times 0Ah db 0
    db 29h
    db 0EFh
    db 7

    db 10h
    db 24h
    db 'LINUX BOOT FAT12   ' ; guess where I
                             ; cribbed this from
;----------------------------writing a mesg on screen at startup. We cant
use int 21h


overdata:
    xor di,di
     mov ds,di
     mov ax,0B800h
     mov es,ax
     ; should probably set up a sane stack here, too.
     ;mov ah,03h
     ;xor bh, bh
     ;int 10h
 ;----------------------------
    mov cx, 15
    mov bh,0
    mov bl,0011_1011b
    mov bp, msg
    mov ax,1301h
    mov dl,10
    mov dh,7
   int 10h
    
 
 
 blackhole:
     jmp blackhole
 
 msg db "We be bootin2'!",0
 
     times 510-($-$$) db 0
     db 55h, 0AAh       ;  ??????I know times is like dup.But what is ($-$$)
and 55h and 0AAh
       ; boot sector signature
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