hi,
here I try to explain why I asked:

For example, a code contains next lines:

	ORG	0x0013	; INT1
	RETI            ; not used

	ORG	0x001B	; TF1
	LJMP	INT_T1	; ISR

As result .hex file will contain something like (CS=check Sum):

:0100130032CS
:03001B0002074DCS

By other words, .hex file does not contain info about bytes which are placed at C:0x0014...0x001A.
When such file is loaded to Flash Tool (at least to Atmel`s FLIP) then these locations will not be changed. FLIP has setup options to set unassigned locations to any value (include 0x00 and 0xFF as well) or even allow to keep them at previous state.
To avoid such "not defined" state, I use something like:

GAP_NOP		MACRO size
	REPT size
	DB	0x00
	ENDM
		ENDM

; ... and then:

	ORG	0x0013	; INT1
	RETI            ; not used
	GAP_NOP	7

	ORG	0x001B	; TF1
	LJMP	INT_T1	; ISR

and so .hex file produces:

:080013003200000000000000CS
:08001B0002074D0000000000CS

It is why I asked to to look inside .hex file!

Regards,
Oleg