▁its ▁elim ination ▁in ▁the ▁computer ▁industry . ▁▁ 1 9 8 0 s ▁The ▁focus ▁in ▁the ▁ 1 9 8 0 s ▁was ▁mainly ▁on ▁reli ably ▁transfer ring ▁NC ▁programs ▁between ▁a ▁host ▁computer ▁and ▁the ▁control . ▁The ▁Host ▁computers ▁would ▁frequently ▁be ▁Sun ▁Mic ros ystem s , ▁H P , ▁Prime , ▁DE C ▁or ▁IBM ▁type ▁computers ▁running ▁a ▁variety ▁of ▁C AD / C AM ▁software . ▁ ▁D NC ▁companies ▁offered ▁machine ▁tool ▁links ▁using ▁rug ged ▁propriet ary ▁terminal s ▁and ▁networks . ▁For ▁example , ▁D Log ▁offered ▁an ▁x 8 6 ▁based ▁terminal , ▁and ▁N CP C ▁had ▁one ▁based ▁on ▁the ▁ 6 8 0 9 . ▁ ▁The ▁host ▁software ▁would ▁be ▁responsible ▁for ▁tracking ▁and ▁author ising ▁NC ▁program ▁modifications . ▁Depending ▁on ▁program ▁size , ▁for ▁the ▁first ▁time ▁operators ▁had ▁the ▁opportunity ▁to ▁modify ▁programs ▁at ▁the ▁D NC ▁terminal . ▁No ▁time ▁was ▁lost ▁due ▁to ▁broken ▁t apes , ▁and ▁if ▁the ▁software ▁was ▁correctly ▁used , ▁an ▁operator ▁running ▁incorrect ▁or ▁out ▁of ▁date ▁programs ▁became ▁a ▁thing ▁of ▁the ▁past . ▁ ▁Old er ▁controls ▁frequently ▁had ▁no ▁port ▁capable ▁of ▁receiving ▁programs ▁such ▁as ▁an ▁R S 2 3 2 ▁or ▁R S 4 2 2 ▁conne ctor . ▁In ▁these ▁cases , ▁a ▁device ▁known ▁as ▁a ▁Be hind ▁The ▁Re ader ▁or ▁B TR ▁card ▁was ▁used . ▁The ▁connection ▁between ▁the ▁control ' s ▁t ape ▁reader