# Transform dimension and lengths

The dimension of the transform is a positive integer value represented in an integer scalar of Integer data type in Fortran and MKL_LONG data type in C. For one-dimensional transform, the transform length is specified by a positive integer value represented in an integer scalar of Integer data type in Fortran and MKL_LONG data type in C. For multi-dimensional (≥ 2) transform, the lengths of each of the dimension is supplied in an integer array (Integer data type in Fortran and MKL_LONG data type in C). `DFTI_DIMENSION` and `DFTI_LENGTHS` are the remaining two of four configuration parameters without default.

As mentioned, these four configuration parameters do not have default value. They are most conveniently set at the descriptor creation function. They can only be set in the descriptor creation function, and not by the function DftiSetValue.

Parent topic: Configuration Settings