Group Code Recording
<storage> (GCR) A recording method used for 6250 BPI magnetic tapes.
GCR typically uses a group of five bits of code to represent four bits of data.
The encoding ensures no more than two or three zeros occur in a row, and no more
than eight or so ones occur in a row, where zeros represent an absense of
GCR is also used on Commodore Business Machines diskette drives; the 4040, 8050,
154x, 157x and 158x series of 5.25" and 3.5" low and high density diskette
drives used with 8-bit home computers circa 1977 to 1992. It was also supported
on Amiga internal and external drives but only used for reading non-Amiga disks.
Compare NRZI, PE.
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