assembly program

[vijayanand_sodadasi]

Hello!

Can somebody explain me this statement: times 510-($-$$) db 0 . The comment says that it fills the file with 0's. what is ($-$$)?
The program is written for NASM assembler, can you give the "as" (linux assembler) equivalent for it.


A minimal bootstrap
-------------------
This bootstrap just hangs:

; HANG.ASM
; A minimal bootstrap

hang: ; Hang!
jmp hang

times 510-($-$$) db 0 ; Fill the file with 0's
dw 0AA55h ; End the file with AA55

[fireshell]

NASM has been ported to linux, just download it from the repositories. tho i cant help with $-$$ thing

[nythrix]

The code is a boot sector for a floppy disc (or maybe even a normal disc, not sure). The $-$$ is the length of the program.
So the whole 512B sector looks like this:

|<- ($-$$) bytes of code ->|<- 510-($-$$) zero bytes ->|<- two bytes with AA55 ->|

As far as I can tell it doesn't really need to be there. The boot attempt goes on just fine even without the 510-($-$$) and AA55 stuff. I was able to boot without them.