The reader learns basic skills in using one of the numerical standard tools MATLAB, Scilab, and Octave. An advantage is that Scilab and Octave are available as freeware. The fundamentals of these numerical programs are introduced to the user step by step. The acquired knowledge can be applied to solve a variety of mathematical, physical, and particularly engineering problems. In the first part, working at the command line level with real and complex variables, vectors, and matrices is explained in a simple and illustrative manner, along with the practical handling of polynomials and the most important graphical output options. For programming, script files and functions are used. The numerical problems addressed include solving linear systems of equations and nonlinear equations.