To write the vectors X, Y and Z to the file DUM.DAT, using free format, so that there will be three columns of numbers in the file, enter: WRITE DUM.DAT X Y Z If you enter: WRITE DUM.DAT X X Y Y Z Z then the following will be written to the file: X(1) X(2) Y(1) Y(2) Z(1) Z(2) X(3) X(4) Y(3) Y(4) Z(3) Z(4) X(5) X(6) Y(5) Y(6) Z(5) Z(6) ... ... ... ... ... ...