Editing Group coded recording (section)

{{Short description|Encoding methods for representing data on magnetic media}}
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{{Use dmy dates|date=May 2019|cs1-dates=y}}
{{Use list-defined references|date=December 2021}}

In [[computer science]], '''group coded recording''' or '''group code recording''' ('''GCR''') refers to several distinct but related encoding methods for representing data on [[magnetic media]]. The first, used in {{val|6250|u=[[bits per inch|bpi]]}} [[magnetic tape]] since 1973,<ref name=CW_1973_IBM /><ref name=X3.54 /> is an [[error-correcting code]] combined with a [[run-length limited]] (RLL) encoding scheme, belonging into the group of [[modulation code]]s.<ref name="Patel_1988_MR" /> The others are similar encoding methods used in [[mainframe computer|mainframe]] [[hard disk]]s or [[microcomputer]] [[floppy disk]]s until the late 1980s. GCR is a modified form of a [[NRZI]] code, but necessarily with a higher transition density.<ref name="Patel_1988_MR" />