Direct numerical at the same time manage the operations of a group of NC machine tools using a shared computer. Programming, editing part programs and downloading part programs to NC machines are main duties of the computers in a NC system. Cincinnati Milacron and General Electric first used idea of direct numerical control in the mid-60s. By 1970, about half dozens vendors marketed their DNC systems. Because of high cost of mainframe computers and introduction of CNC in 1970s, the DNC system couldn’t become popular in industry.