Following suggestions and comments by a dozen reviewers, we have revised all sections of the book to some degree, and a number of major new features have been added as follows: • We have moved some items (especially computer codes) from the text to the website so that they are easily accessible without tedious typing. This endeavor includes all of the Matlab, Mathematica, and Maple computer codes as well as the Appendix on Overview of Mathematical Software available on the World Wide Web. • We have added more figures and numerical examples throughout, believing that concrete codes and visual aids are helpful to every reader. • New sections and material have been added to many topics, such as the modified false position method, the conjugate gradient method, Simpson’s method, and some others. • More exercises involving applications are presented throughout. • There are additional citations to recent references and some older references have been replaced. • We have reorganized the appendices, adding some new ones and omitting some older ones.