A report on Group coded recording and 9-track tape

IBM 2401 System/360 tape drives that introduced the 9-track format
Full-size reel of 9-track tape
9 Track tape drive used with DEC minicomputers
Inside a 9 Track tape drive. The vacuum columns are the two gray rectangles on the left.
Full size 1/2" tape reel in protective case
Two small 1/2" tapes, front and back
Aluminum foil strips mark the start and end of tape
The write protection ring prevents the tape from being written when removed
A typical library of half-inch magnetic tape
3M 777 High Grade 6250 CPI - Security Computer Tape

Various recording methods have been employed during its lifetime as tape speed and data density increased, including PE (phase encoding), GCR (group-coded recording) and NRZI (non-return-to-zero, inverted, sometimes pronounced "nur-zee").

- 9-track tape

Group coded recording was first used for magnetic tape data storage on 9-track reel-to-reel tape.

- Group coded recording
IBM 2401 System/360 tape drives that introduced the 9-track format

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Overall
10+1/2 in diameter reel of 9-track tape

Magnetic-tape data storage

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System for storing digital information on magnetic tape using digital recording.

System for storing digital information on magnetic tape using digital recording.

10+1/2 in diameter reel of 9-track tape
Quarter-inch cartridges
An IBM 3590 data cartridge can hold up to 10GiB uncompressed.
Linear
Linear serpentine
Helical
IBM 729V

Tape was an important medium for primary data storage in early computers, typically using large open reels of 7-track, later 9-track tape.

Common 7-track densities started at 200 characters per inch (CPI), then 556, and finally 800; 9-track tapes had densities of 800 (using NRZI), then 1600 (using PE), and finally 6250 (using GCR).