magnetic tape (recording) - Audio recording, Video recording, Data storage

A clear plastic film coated with crystalline magnetic particles embedded in varnish, first demonstrated as an effective sound recording and reproducing medium in the 1930s. It came increasingly into use after World War 2, and has more recently been extended to video recording, and data storage for computers. Professional recording practice of the 1980s employed multiple-track open-reel tape, storing the sounds in digital form, while domestic use came to be dominated by the compact cassette introduced first by Philips in 1964. To the convenience of the latter has been added increasing quality with new coatings (chrome dioxide, metal) and noise reduction systems.

Nearly all recording tape is of this type, whether used for video, audio storage or general purpose digital data storage using a computer.

Magneto-optical and optical tape storage products have been developed using many of the same concepts as magnetic storage, but have achieved little commercial success.

Audio recording

Magnetic tape was first invented for recording sound by Fritz Pfleumer in 1926 in Germany, based on the invention of magnetic wire recording by Valdemar Poulsen in 1898.

Video recording

Video recording demands much higher bandwidth than audio recording and was made practical by the invention of helical scan. Early video recorders were reel-to-reel but modern systems use cartridge tapes and videocassette recorders are quite popular.

Data storage

The use of magnetic tape for data storage has been one of the constants of the computer industry.

Magnetic tape was first used to record computer data in 1951 on the Eckert-Mauchly UNIVAC I.

Early IBM tape drives were mechanically sophisticated floor-standing drives that used vacuum columns to buffer long u-shaped loops of tape. Between active control of powerful reel motors and vacuum control of these u-shaped tape loops, extremely rapid start and stop of the tape at the tape-to-head interface could be achieved. (1.5ms from stopped tape to full speed of up to 112.5 IPS) When active, the two tape reels thus fed tape into or pulled tape out of the vacuum columns, intermittently spinning in rapid, unsynchronized bursts resulting in visually-striking action.

Most modern magnetic tape systems use reels that are much smaller than the old 10.5 inch open reels and are fixed inside a cartridge to protect the tape and facilitate handling. A tape drive (or "transport" or "deck") uses precisely-controlled motors to wind the tape from one reel to the other, passing a read/write head as it does.

Tape has quite a long data latency for random accesses since the deck must wind an average of ⅓ the tape length to move from one arbitrary data block to another. Most tape systems attempt to alleviate the intrinsic long latency, either using indexing, where a separate lookup table is maintained which gives the physical tape location for a given data block number, or by marking blocks with a tape mark that can be detected while winding the tape at high speed.

Tape remains a viable alternative to disk due to its higher bit density and lower cost per bit. The rapid improvement in disk storage density and price, coupled with arguably less-vigorous innovation in tape storage, has reduced the market share of tape storage products.