| 1234567891011121314151617181920212223242526272829303132333435363738394041424344454647 |
- [org 0x7c00]
- mov ah, 0x0e
- ; attempt 1
- ; Will fail again regardless of 'org' because we are still addressing the pointer
- ; and not the data it points to
- mov al, "1"
- int 0x10
- mov al, the_secret
- int 0x10
- ; attempt 2
- ; Having solved the memory offset problem with 'org', this is now the correct answer
- mov al, "2"
- int 0x10
- mov al, [the_secret]
- int 0x10
- ; attempt 3
- ; As you expected, we are adding 0x7c00 twice, so this is not going to work
- mov al, "3"
- int 0x10
- mov bx, the_secret
- add bx, 0x7c00
- mov al, [bx]
- int 0x10
- ; attempt 4
- ; This still works because there are no memory references to pointers, so
- ; the 'org' mode never applies. Directly addressing memory by counting bytes
- ; is always going to work, but it's inconvenient
- mov al, "4"
- int 0x10
- mov al, [0x7c2d]
- int 0x10
- jmp $ ; infinite loop
- the_secret:
- ; ASCII code 0x58 ('X') is stored just before the zero-padding.
- ; On this code that is at byte 0x2d (check it out using 'xxd file.bin')
- db "X"
- ; zero padding and magic bios number
- times 510-($-$$) db 0
- dw 0xaa55
|
