For readers seeking actual FFT software routines without having to buy those high-priced signal processing software packages, public domain radix-2 FFT routines are readily available. References [4–7] provide standard FFT program listings using the FORTRAN language. Reference [8] presents an efficient FFT program written in FORTRAN for real-only input data sequences. Reference [9] provides a standard FFT program written in HP BASIC™, and reference [10] presents an FFT routine written in Applesoft BASIC™. Readers interested in the Ada language can find FFT-related subroutines in reference [11].