simple boot sector coding: Filling the 512 Byte with 0

Question

I use the Bochs simulator to run a boot sector, which coded in NASM like this:

  org 07c00h                  ;told the compiler to load the code to 0x7c00h
  mov ax, cs                 
  mov ds, ax
  mov es, ax
  call    DispStr             ;call the string process 
  jmp $                       ;infinite loop
 DispStr:
   mov ax, BootMessage        
   mov bp, ax                 ;ES:BP = string address    
   mov cx, 16                 ;CX = length of the string
   mov ax, 01301h             ;AH = 13, AL = 01H
   mov bx, 000ch              ;(BH = 0) 
   mov dl, 0                  
   int 10h                    ;10h interrupt
   ret
 BootMessage:    db  "Hello, OS world!"  ;message printed
 times    510-($-$$)  db  0              ;fill the left of the 510 byte with 0 
 dw  0xaa55

If times 510-($-$$) db 0 if forbidden, is there any alternative way to fill the left of 510 byte area with 0?

I've tried loop command, but can not work properly.

Answer 1

An alternative way would be to use a preprocessor loop (%rep):

%rep 510-($-$$)
db 0
%endrep

If your TA still isn't satisfied I'll leave it to you to dig through the NASM manual for other possible ways of achieving the same thing.