CMakeLists.txt - the cmake config file to build this code.  

fourier.cxx - contains a function for the interface to the fourier transform, some
examples of low-pass transforms, and a main() that demonstrates how to
use them.   

fourn.c - A C program that contains code for the low-level operations
of the fft().  Don't edit this.  Link against it, as in the CMakeLists file.