Scilab is open source equivalent for basic MATLAB package. Its usage in scientific and numerical computation is gaining popularity day by day. The biggest advantage of using Scilab over another free software Octave for the purpose is that XCOS(Scilab) rivals Simulink (MATLAB) capabilities whereas Octave does not have any such graphical programming capabilities. Present book gives introduction to Scilab for a new-user. Starting from very basic, it goes on to explain array based computing, plotting and working with files. The book is useful for students, researchers and students who are looking for a open source software for numerical computation.