A medium for holding information (data, voice, video, etc.), such as tape and disk. The medium can be erased and reused over and over again. In the digital world, information is recorded by writing tiny spots (bits) of negative or positive polarity on tapes and disks. A read/write head discharges electrical impulses onto the moving ferromagnetic surface. Reading is accomplished by sensing the polarity of the bit with the read/write head.In the analog world, information is recorded by altering the polarity of the magnetic medium to create analogous waveforms of air vibrations (sound) or intensities of color and brightness (video). See magnetic tape, magnetic disk, magnetic stripe, read/write head and ferromagnetic.