The Discrete-Time Fourier Transform (DTFT) maps a discrete time sequence into a continuous function of frequency, represented by the complex exponential sequence [e-jωn] where ω is the real frequency variable. The DTFT and z-transform can be applied to arbitrary sequences, unlike the discrete Fourier transform (DFT) which can only be used on finite length sequences. The DTFT is useful for transforming a signal from the time domain to the frequency domain.