IBM's first magnetic-tape data storage devices, introduced in 1952, use what is now generally known as 7-track tape. The

magnetic tape Magnetic tape is a medium for magnetic storage made of a thin, magnetizable coating on a long, narrow strip of plastic film. It was developed in Germany in 1928, based on the earlier magnetic wire recording from Denmark. Devices that use mag ...

is 1/2" wide, and there are six data tracks plus one parity track for a total of seven parallel tracks that span the length of the tape. Data is stored as six-bit characters, with each bit of the character and the additional parity bit stored in a different track. These 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. 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. Stock shots of such vacuum-column tape drives in motion were widely used to represent "the computer" in films and television.

Technical details

; Density : Initial recording density was 100 characters per inch. Later models supported 200, 556 and 800 characters per inch. ; Inter-record gap : A gap (initially one inch, later 3/4 inch) between records allowed the mechanism time to start and stop the tape. ; Latency : There was only a 1.5 ms delay for the stopped tape to reach its full reading or writing speed. ; Markers : Aluminum strips were glued several feet from the ends of the tape to serve as logical beginning and end of tape markers. ; Write protection : A removable plastic ring in the back of the tape reel was inserted to indicate that writing should be permitted.

Generations

IBM 726

The IBM 726 dual magnetic tape reader/recorder for the IBM 701 was announced on May 21, 1952.

IBM 727

The IBM 727 Magnetic Tape Unit was announced for the IBM 701 and IBM 702 on September 25, 1953. It became IBM's standard tape drive for their

vacuum tube A vacuum tube, electron tube, valve (British usage), or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric voltage, potential difference has been applied. The type kn ...

era computer systems. It was withdrawn on May 12, 1971.

IBM 728

The

IBM 728 The IBM 728 magnetic tape drive was used on the SAGE AN/FSQ-7 computer. It was physically similar to the IBM 727, but with significantly different specifications. This is one of several IBM 7 track tape drives. Tape Word Bit P ...

magnetic tape drive was used on the SAGE AN/FSQ-7 computer. It was physically similar to the

IBM 727 The IBM 727 Magnetic Tape Unit was announced for the IBM 701 and IBM 702 on September 25, 1953. It became IBM's standard tape drive for their early vacuum-tube era computer systems. Later vacuum-tube machines and first-generation transistor ...

, but with significantly different specifications. * tracks: 6 data, 1 synchronization, * words: 6 chars (32 data bits, 1 parity bit, 3 end-of-file bits), * words/inch: 41.33.

IBM 729

The

IBM 729 The IBM 729 Magnetic Tape Unit was IBM's iconic tape mass storage system from the late 1950s through the mid-1960s. Part of the IBM 7 track family of tape units, it was used on late 700, most 7000 and many 1400 series computers. Like its pred ...

Magnetic Tape Unit was IBM's iconic

tape Tape or Tapes may refer to: Material A long, narrow, thin strip of material (see also Ribbon (disambiguation): Adhesive tapes * Adhesive tape, any of many varieties of backing materials coated with an adhesive *Athletic tape, pressure-sensitiv ...

mass storage system from the late 1950s through the mid-1960s. It was used on late 700, most 7000 and many 1400 series computers. A new dual gap head assembly allowed read-after-write verification.

IBM 7330

The IBM 7330 Magnetic Tape Unit was a low cost slower tape system. It was common on 1400 series computers.

IBM 2400 Series

The 2400 Series Magnetic Tape Units were introduced with the

System/360 The IBM System/360 (S/360) is a family of mainframe computer systems that was announced by IBM on April 7, 1964, and delivered between 1965 and 1978. It was the first family of computers designed to cover both commercial and scientific applic ...

. Most were IBM 9 Track format drives, but they could be ordered with seven-track read/write heads, allowing them to read and write seven-track tapes.

Legacy

As of 2020, IBM still sells magnetic tape cartridge drives using half-inch wide tape in the

Linear Tape-Open Linearity is the property of a mathematical relationship ('' function'') that can be graphically represented as a straight line. Linearity is closely related to '' proportionality''. Examples in physics include rectilinear motion, the linear ...

and 3592 formats.

Sources

IBM 726 Magnetic tape reader/recorder

Bitsavers.org Magnetic Tape Equipment manuals
(PDF files) **A22-6589-1_magTapeReference_Jun62.pdf – Reference manual for 7 track drives
IBM 727 Magnetic tape unit
(photo) Sold with 705 in 1955. {{DEFAULTSORT:Ibm 7 Track Tape 7 Track History of computing hardware Tape format Tape-based computer storage Computer-related introductions in 1952