In recent years quaternary codes have attracted the attention of the coding community as several notorious binary nonlinear codes containing more codewords than any known linear codes were found to be binary images under the Gray map of linear codes over 94. This discovery opens the way for a broader study of quaternary codes, which constitute a rapidly growing area of coding theory. This book is based on the author's lectures in Xi'an, China and Lund, Sweden and covers the most recent developments of this theory.Contents: Quaternary Linear Codes and Their Generator MatricesWeight EnumeratorsThe Gray Map94-Linearity and (94-Nonlinearity of Some Binary Linear CodesHensel's Lemma and Hensel LiftGalois RingsCyclic CodesKerdock CodesPreparata CodesGeneralizations of Quaternary Kerdock and Preparata CodesQuaternary Quadratic Residue CodesQuaternary Codes and LatticesSome Invariant TheorySelf-Dual Quaternary Codes and Their Weight EnumeratorsReadership: Applied mathematicians.Key Features:Of interest to both academic circles and policy makersSuitable as a reference book for graduate studentsGeneral readers who are interested in cross-Strait relations will find this book useful