G02 - G03

Hi:

I am trying to update MasterControlCNC to do G02
and G03 circular interpolation and although I now have working code ( thanks
to Doug Fortune) I don't quite understand which is the most common form of
interp.
My post processor on the software I use the most does
not generate circ. only linear. Am I better off using R registers or IJK
interp? or both? Is IJK now pretty much obsolete?

Art