This book expands lecture notes by the authors taught in the past few years in USA,Canada and China. The overall emphasis of these notes is to present basic algorithms together with some applications of spectral methods. The aim is to provide a sufficient background on the implementation and analysis of spectral and high-order methods so that the readers can approach the current research literature with the necessary tools and understanding. .It is expected that this book will be a useful supplement for people studying spectral methods on their own. This book is especially suited to students interested in high-order methods for PDEs, but it will appeal to numerical analysis and mathematically oriented students and researchers in engineering, physics, and related areas. ...