SPADeS (Signal Processing, Analysis, Design and Simulation) is our flagship software product that combines the functionality of the earlier PC-DSP and PC-SIM applications. It facilitates analysis, design, implementation and simulation of discrete-time signals and systems. It can be considered as a special-purpose calculator with powerful graphing capabilities for performing digital signal processing operations such as waveform synthesis and manipulation, Fourier transforms, convolution, correlation, filter design, analysis and implementation, power spectrum analysis, and visual simulation. It is quite simple and straightforward to use, and yet powerful and extensible enough to be used by practicing engineers as well as students of digital signal processing. Discrete-time and continuous-time waveform synthesis using a variety of methods Frequency-domain transforms (DFT, FFT, DTFT, forward & inverse transforms, window functions) Convolution and correlation functions Solution of difference equations Analysis and design of analog filters, IIR and FIR digital filters Interactive pole-zero analysis of filters Digital filter simulation and code generation Power spectrum estimation using classical and modern techniques Powerful visual simulation capabilities for block-diagram based systems User-defined extensions using JScript and VBScript languages