, ▁the ▁available ▁memory ▁is ▁too ▁small ▁to ▁contain ▁the ▁mach ining ▁program ▁( for ▁example ▁mach ining ▁complex ▁surfaces ), ▁so ▁in ▁this ▁case ▁the ▁program ▁is ▁stored ▁in ▁a ▁separate ▁computer ▁and ▁sent ▁directly ▁to ▁the ▁machine , ▁one ▁block ▁at ▁a ▁time . ▁If ▁the ▁computer ▁is ▁connected ▁to ▁a ▁number ▁of ▁machines ▁it ▁can ▁dist ribute ▁programs ▁to ▁different ▁machines ▁as ▁required . ▁Usually , ▁the ▁manufact urer ▁of ▁the ▁control ▁provides ▁suitable ▁D NC ▁software . ▁However , ▁if ▁this ▁provision ▁is ▁not ▁possible , ▁some ▁software ▁companies ▁provide ▁D NC ▁applications ▁that ▁ful fill ▁the ▁purpose . ▁D NC ▁networking ▁or ▁D NC ▁communication ▁is ▁always ▁required ▁when ▁C AM ▁programs ▁are ▁to ▁run ▁on ▁some ▁C NC ▁machine ▁control . ▁ ▁W ire less ▁D NC ▁is ▁also ▁used ▁in ▁place ▁of ▁hard - w ired ▁versions . ▁ ▁Control s ▁of ▁this ▁type ▁are ▁very ▁widely ▁used ▁in ▁indust ries ▁with ▁significant ▁sheet ▁metal ▁fabric ation , ▁such ▁as ▁the ▁autom ot ive , ▁app liance , ▁and ▁a eros pace ▁indust ries . ▁ ▁History ▁▁ 1 9 5 0 s - 1 9 7 0 s ▁Program s ▁had ▁to ▁be ▁walked ▁to ▁NC ▁controls , ▁generally ▁on ▁paper ▁t ape . ▁NC ▁controls ▁had ▁paper ▁t ape ▁readers ▁precisely ▁for ▁this ▁purpose . ▁Many ▁companies ▁were ▁still ▁p unch ing ▁programs ▁on ▁paper ▁t ape ▁well ▁into ▁the ▁ 1 9 8 0 s , ▁more ▁than ▁twenty - five ▁years ▁after