This book is a tutorial of mathematical programming software OCTAVE, which is free of any charges to the users. This book is written to be very easy and friendly for beginners to follow with numerous examples and graphic examples. In this first revision, more sections and subsections, exercise problems, and four appendices are added. Full solutions of exercise problems are included at the end of the book along with the programs used to solve them. The programs for solving problems show numerous examples of application of Octave. The programs developed in the book are made available for copying electronically from a companion website This book is also a good tutorial for MATLAB users. The author is also an expert in teaching MATLAB.