Here are rules:-
1)Selection of carbon chains:- The longest continuios chain of carbon also called parent chain is selected
2) the brach chain are considered to be subtituents and their poistion indicated by the no. of carbom atoms of which they are attached
3)the carbon atoms of longest chain are numbered in such a way that alkly grup get least no.
4)Same applies to functional grup they to are given smallest no.
5)In case diff substituents are attached to chain they are aranged and named alphabetically
6)the poistion of alkkyl group are indicate by writng the positon and name of alkyl group just before the asame of hydrocarbon