Magnetic tapes. Reels of magnetic tapes in a library used for storing computer data. The tapes are cheap and can hold several hundred megabytes of data each. Unlike computer disks, they do not allow immediate access to their contents. The reel must be wound along to the particular area of the tape which contains the required data. Each tape is coated with ferric oxide, a rust-like substance that contains tiny particles capable of holding a magnetic field. Data is stored on the tape by altering the particles' magnetic orientation. Orientation in one direction represents a 1", and in the other a "0". The series of "1"s and "0"s forms a binary code that computers can interpret."