Fast Fourier transform — FFT — is speed-up technique for calculating discrete Fourier transform — DFT, which in turn is discrete version of continious Fourier transform, which indeed is origin for all its versions. So, historically continious form of

语音识别程序，STC12C5620AD单片机，利用DFT算法-Voice recognition program, STC12C5620AD microcontroller using DFT algorithm