Computer tape is similar to the common cassette tape used for recording music. A plastic housing holds two spools, each of which can fit on the spindle of a tape drive. Around one of the spools is wrapped a plastic tape coated with material capable of taking a magnetic charge. This is fed around a set of pulleys, which positions it to pass by a magnetic |read/write head|. The ribbon is then taken up by the second spool. As the drive spins the spools, the tape can travel in both directions past the head. The read/write head has coils which can detect and alter the polarity (and, therefore, the meaning) of the magnetic charges on the tape.
