rsync : delta download

[Chandu B S]

Hi,
I know that rsync does an delta download.
I need to kow one thing
I have one big file on remote machine say 4 GB named abc.exe
I do an rsync and get it to my local machine, after few days abc.exe
is replaced my a new abc.exe ( say 5 GB) now when i do an rsync
what is the expected behaviour ?

can u explain in 2 or 3 line how delta is determined by rsync ?

-- 
Thanks
Chandu.B.S