This book treats the various aspects of noise from magnetic recording media and the impact on system performance. Several authors present discussions of: materials and processes used to fabricate media for computer data storage, theoretical aspects of noise and micromagnetic behavior, experimental methods and characterization, and system analysis. In the past decade thin film recording media have largely displaced particlate media in rigid disk recording systems. During the same period of time the field has evolved from the prevalent belief that thin film media were virtually noiseless to a detailed understanding of the origin and the manifestation of noise in these new media. This understanding has lead to the ability to make the very low noise media needed in present applications. The present state of understanding of both particulate and thin film media is summarized.