1. A computer for performing an N-length discrete Fourier transform of N initial data values, where the number N equals the product of a number L of mutually prime factors N.sub.1, N.sub.2,. .. N.sub.i, N.sub.i +1,. .. N.sub.L, comprising: (a) a set of one or more kernels; (b) each kernel being adapted to perform a discrete Fourier transform characterized by a transform length equal to one or more of said prime factors N.sub.i ; (c) wherein for each value of i in the range from 1 to L, said set of kernels includes a kernel adapted to perform a N.sub.i -length transform; (d) wherein each kernel includes: first reorder means for receiving N input data values and reordering them into (N/N.sub.i) groups, with each group consisting of N.sub.i input data values x(n), n=0, 1, 2,. .. N.sub.i -1, computational means for performing a sum and difference conjugate N.sub.i -length discrete Fourier transform upon each of the (N/N.sub.i) groups of N.sub.i reordered input data values x(n), thereby producing (N/N.sub.i) groups of N.sub.i transformed data values X(k), for k=0, 1, 2,. .. N.sub.i -1, and second reorder means for reordering the (N/N.sub.i) groups of N.sub.i transformed data values X(k) into N output data values, wherein N.sub.i equals any of said transform lengths for which that kernel is adapted to perform a discrete Fourier transform; (e) means for connecting said N initial data values to the kernel performing the N.sub.1 -length transform so that said initial data values are received as the N input data values of the N.sub.1 -length transform; and (f) for each value of i in the range from 1 to L-1, means for connecting the N output data values produced by the kernel performing the N.sub.i -length transform to the kernel performing the N.sub.i+1 -length transform so that said output data values are received as the N input data values of the N.sub.i+1 -length transform; (g) whereby the N output data values produced by the kernel performing the N.sub.L -length transform are the N-length discrete Fourier transform of the N initial data values.