Useful discrete-time signals and systems properties are introduced. This is followed by a brief review of the z-transform. Spectral analysis of seismic data and useful transforms are discussed. Signal analysis in the spectral or other domains is very important and assists in obtaining a better understanding of signals. Particularly when dealing with seismic data, it becomes almost standard to analyze seismic data sets in the 2-D frequency-wavenumber domain. Also, other discrete transforms such as the Radon transform are very useful for processing seismic data sets, which can be used, for example, for seismic wavefield decomposition as well as seismic multiple removal.