How position ID is assigned to a photo?

[^SuPeR^]

Hi,
it possibile to know how position is assigned to a photo?
So
displayimage.php?album=lastup&cat=0&pos=0
position is incremental but for this
displayimage.php?pos=-xxx
?
Thanks

[Abbas Ali]

pos=-xxx actually is the picture id stored in database and not position. so pos=-xxx is actually pid=xxx.

[^SuPeR^]

Thanks!
And is the a rule for pid assigned in database...like first photo pid=001, 2nd pid=002 etc. or it's random?

[Abbas Ali]

Yes, first added photo is 1 second is 2....