definitions of FITS headers DATAMIN and DATAMAX? - by: Doliometer

I don't understand how DATAMIN and DATAMAX in the FITS header are derived from the data. When I look at the data table in FV, all the entries are positive integers, but the header entries for DATAMIN and DATAMAX are by definition double precision decimals. How to get from one to the other?

So far I have found the function getMinMax in indiccd.cpp which is simple enough routine for finding extreme values. So I guess the float values come from the function getFrameBuffer for which I have not yet seen the source but will look for. But until then, I'm wondering what could be the reason to use decimal fractions to represent extreme values of binary integers?

Thanks.