The technique of storing information as a magnetic pattern on a moving magnetic medium. The medium may be a disk, either flexible (floppy) or rigid, or a tape. There are various techniques for “writing” the patterns, including the use of the magnetic field generated by an electric current in a miniature coil, or the use of a laser beam to heat the material. There are several techniques for “reading” the pattern, such as measuring the voltage induced in the same or different coil by the magnetic fields associated with the pattern, measuring the change in the resistance of a metal stripe due to this field, or measuring the polarization of a laser beam upon reflection from the medium.