Group Code Recording
GCR
(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 magnetic
change.
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.
(2004-06-01)
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