▁by ▁the ▁user . ▁ ▁Program ming ▁format ▁ ▁The ▁operation ▁of ▁a ▁C NC ▁machine ▁tool ▁is ▁typically ▁controlled ▁by ▁a ▁" part ▁program " ▁written ▁a ▁language ▁known ▁as ▁G - code . ▁ ▁C anned ▁cycles ▁are ▁similar ▁in ▁concept ▁to ▁functions ▁in ▁a ▁traditional ▁computer ▁language , ▁and ▁can ▁be ▁compared ▁also ▁to ▁G - code ▁mac ros . ▁The ▁format ▁for ▁a ▁can ned ▁cycle ▁consists ▁of ▁a ▁series ▁of ▁parameters ▁specified ▁with ▁a ▁letter ▁and ▁a ▁numerical ▁value . ▁The ▁letter ▁is ▁referred ▁to ▁as ▁an ▁" address ". ▁( This ▁use ▁of ▁the ▁term ▁" address " ▁may ▁be ▁un famil iar ▁to ▁program mers ▁of ▁conventional ▁computers . ▁It ▁ar ises ▁because ▁in ▁early ▁and ▁primitive ▁machine ▁controllers , ▁the ▁binary ▁representation ▁of ▁the ▁letter ▁formed ▁a ▁physical ▁address ▁at ▁which ▁the ▁controller ▁would ▁store ▁the ▁value ▁following .) ▁ ▁N .. ▁G .. ▁G .. ▁X .. ▁Y .. ▁R .. ▁P .. ▁Q .. ▁I .. ▁J .. ▁Z .. ▁F .. ▁H .. ▁S .. ▁L .. ▁A .. ▁B .. ▁C .. ▁D .. ▁ ▁These ▁addresses ▁and ▁values ▁tell ▁the ▁machine ▁where ▁and ▁how ▁to ▁move . ▁The ▁syntax ▁of ▁a ▁can ned ▁cycle ▁may ▁vary ▁depending ▁on ▁the ▁brand ▁of ▁the ▁control . ▁In ▁general , ▁the ▁following ▁" words " ▁will ▁be ▁in ▁a ▁can ned ▁cycle ▁" block ". ▁N = ▁Block ▁number ▁G 9 8 ▁or ▁G 9 9 = ▁Tool ▁ret ract ▁to ▁R -