FILE CONVERSION APPARATUS FOR MACHINING PROGRAM OF NUMERICAL CONTROL SYSTEM AND COMPUTER READABLE RECORDING MEDIUM FOR STORING PROGRAM FOR COMPUTER TO EXECUTE FILE CONVERSION PROCESS

A machining program for a NC machine tool including a NURBS interpolation command is input as a source file, the input machining program is sequentially analyzed in such a way that the portions other than the NURBS interpolation command portion are left as they are, and the NURBS interpolation command portion is converted into a minuscule line segment interpolation command, a spline interpolation command or a NURBS interpolation command of a differently presented specification by the conversion unit. In accordance with the conversion mode selectively set by a conversion mode setting unit, the portions other than the NURBS interpolation command portion are left as they are, while the NURBS interpolation command portion is converted into a minuscule line segment interpolation command, a spline interpolation command or a NURBS interpolation command of a differently presented specification thereby to generate destination file.