Tape Basics
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
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.
Reading the Data
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.
Tags: read head, hard drive, head head, magnetic fields, read head head, tape When
