How Do Tape Drives Work?
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Tape Basics
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A tape drive is a storage medium for digital data. Instead of being stored on a platter, as in a hard drive, the information is stored on a long strip of magnetic tape. Because the tape has to be rolled and unrolled to get to a particular piece of data, tape drives are not used for day-to-day computing. Instead, they are used to back up large chunks of data--often a whole hard drive at once. Tapes are a cheap and reliable way to create emergency or archival backups of information.
Writing the Data
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Tapes drives record data in essentially the same way as other magnetic storage media, such as audio tapes and hard discs. The tape itself is coated with a magnetic material which can store a charge. The data written on the tape is digital information--electronic 1s and 0s called bits. The write head is a small electromagnet suspended above the tape. When it needs to create a bit of data, it makes a magnetic pulse as the tape goes by. It can create magnetic fields facing in opposite directions, representing 1s and 0s. That pulse induces a magnetic field on that section of the tape, which stays there until it is written over.
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Reading the Data
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Tape drives have one or more read head to read back the data. The read head is a very small coil of wire close to the surface of the tape. When the tape is wound past the read head, the head is subject to a series of changing magnetic fields from the bits on the tape. These fields induce a small current in the read head. The head can use that current to detect the bits of information on the tape.
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