Definition: magnetic tape

A sequential storage medium used for data collection, backup and archiving. The first electronic storage medium, magnetic tape is made of flexible plastic with one side coated with a ferromagnetic material. The data are recorded as binary digits (bits) in the form of magnetized spots in one orientation or the other (0 or 1). See binary and bit.

Tapes were originally open reels but were superseded by a variety of cartridges and cassettes. Today, LTO is the only thriving tape technology with future plans for increased capacities. See LTO and open reel.

Tape has always been more economical than disks for archival data; however, disk capacities have increased enormously while the cost per bit has been reduced dramatically. In addition, if tapes are stored for the duration, they must be periodically recopied or the tightly coiled magnetic surfaces may contaminate each other.

Sequential Medium
The major drawback of tape is its sequential format. Locating a specific record requires reading every record in front of it or searching for markers that identify predefined partitions.

Track Formats
Data are recorded in blocks of contiguous bytes, separated by a space called an "interrecord gap" or "interblock gap." Drive speed is measured in inches per second (ips). Over the decades, storage density jumped from 200 bits per square inch to millions and billions of bits. See magnetic tape formats.

Tracks on Magnetic Tape

Except for helical scan, most tracks on tape run parallel to the length of the tape. See helical scan and serpentine recording.