EULER is a program for quickly and interactively computing with real and complex numbers and matrices, or with intervals, in the style of MatLab, Octave,... It can draw and animate your functions in two and three dimensions. It features: - real, complex and interval scalars and matrices, - a programming language, with local variables, default values for parameters, variable parameter number, passing of functions, - two and three dimensional graphs, - marker plots, - density and contour plots, - animations, - numerical integration and differentiation, - statistical functions and tests, - differential equations, - interval methods with guaranteed inclusions, - function minimizers (Brent, Nelder-Mean), - Simplex algorithm, - interpolation and approximation, - finding roots of polynomials, - Fast Fourier transform (FFT), - An exact scalar product using a long accumulator, - Postscript graphics export