This book evolved from a set of notes used in introductory numerical methods courses at Stanford University, the University of New Mexico and the University of Waterloo. These universities have two such courses, titled something like "Numerical Computing" and "Numerical Analysis". The numerical computing course is for students of science and engineering who simply want to use numerical methods in their work. It lasts only one term and has minimal mathematical prerequisites. The numerical analysis course covers essentially the same methods, but lasts a full year. The additional time is devoted to deeper mathematical analysis. This book is intended primarily for the numerical computing course, but could also be used to supplement a more theoretical text in the numerical analysis course.