This book is a comprehensive text on the theory of the magnetic recording process. It gives the reader a fundamental, in-depth understanding of all the essential features of the writing and retrieval of information for both high density disk recording and tape recording. The material is timely because magnetic recording technology is currently undergoing rapid advancement in systems capacity and data rate. The competing technologies of longitudinal and perpendicular recording are given parallel treatments throughout this book. A simultaneous treatment of time and frequency response is given to facilitate assessment of signal processing schemes. In addition to covering basic issues, the author discusses key systems questions of non-linearities and overwrite. The emerging technology of magnetoresisitive heads is analysed separately and three chapters are devoted to various aspects of medium noise. This unique book will be valuable as a course text for both senior undergraduates and graduate students. It will also be of value to research and development scientists in the magnetic recording industry. The book includes a large number of homework problems.