Tape Drives Use Magnetic Tapes
Computer tape drives rely on magnetic tapes, the same kind found in audio cassettes, for storing and retrieving data. When the tape is blank, thousands of microscopic magnets are randomly oriented on the tape; the lack of any particular pattern is useless to the computer and does not represent any form of data. As data is written to the tape, a magnetic tape head orients the magnets on the tape into binary data, using the magnetic field North to represent ones and South to represent zeros. As long as the tape remains in a relatively stable environment and is not exposed to magnets, it will retain the data as long as needed.
Software Controls Tape Movement
When a computer tape drive is reading or writing data, it moves far too fast for manual intervention in the magnet orientation process. To instruct the magnetic tape head on orient the magnets, the tape drive interfaces with the computer through a standard serial, parallel or universal serial bus (USB), or even internal disk (IDE) connection. Software on the computer sends instructions to the tape head through the connected port, indicating how the magnets on the tape should be oriented to store data for later retrieval. When the tape is read, the process works the same way; a different magnetic tape head senses the orientation of the magnets and feeds the magnetic information to the computer through the connected port. With the data successfully read, special software interprets the data retrieved from the tape drive, and applies it as necessary.
Computer Tapes Are Reusable
Because the magnetic tape head that orients the magnets on the tape (in other words, writes data to the tape) is separate from the tape head and function that reads back information, it can perform its function regardless of any information that may already be stored on the tape. As the tape passes over the tape head, it simply reorients the magnets into the new data, destroying any old data already stored on the tape media. For this reason, computer tapes may be used over and over until the thin plastic film on which the magnets are situated becomes frail or breaks.
