Dan Tobias: /* Floppy disk formats using GCR encoding */

2013-09-14T15:11:37Z

‎Floppy disk formats using GCR encoding

Dan Tobias at 20:50, 8 May 2013

2013-05-08T20:50:02Z

Dan Tobias: Created page with "{{FormatInfo |formattype=physical |subcat=Floppy disk }} '''GCR encoding''' (Group code recording) is a name for a group of schemes for encoding data on magnetic media such a..."

2013-05-05T04:44:26Z

Created page with "{{FormatInfo |formattype=physical |subcat=Floppy disk }} '''GCR encoding''' (Group code recording) is a name for a group of schemes for encoding data on magnetic media such a..."

New page

{{FormatInfo
|formattype=physical
|subcat=Floppy disk
}}

'''GCR encoding''' (Group code recording) is a name for a group of schemes for encoding data on magnetic media such as [[magnetic tape]] or [[floppy disk]]s. In GCR encoding, a sequence of data bits is represented by a particular other sequence of bits which "translates" to the data bits in a table of encoded values. The use of different sets of bits instead of the raw bits of the data is necessary due to constraints on consecutive bits with no signal transition, as well as (in some formats) providing error-correction.

== Varieties of GCR encoding ==

* [[9-track reel-to-reel tape]] used an error-correcting GCR encoding
* 5 and 3 encoding: invented by Steve Wozniak and used in Apple DOS 3.1 and 3.2 on [[Apple II 13 sector disk]]s
* 6 and 2 encoding: an update to 5 and 3 used on [[Apple II 16 sector disk]]s and later Apple disk formats
* Commodore's encoding scheme used first on PET disks (Commodore 2040) and continued on later Commodore formats

== Floppy disk formats using GCR encoding ==
* [[Apple II 13 sector disk]] (Apple DOS 3.2)
* [[Apple II 16 sector disk]] (Apple DOS 3.3, ProDOS, Apple III SOS)
* [[Apple double-density 3 1/2" disk]]
* [[Commodore 1541 disk]]
* [[Commodore 1571 disk]]

== Links ==
* [[Wikipedia:Group code recording|Wikipedia article]]

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	== Links ==		== Links ==
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 * [[Commodore 1541 disk]]
 * [[Commodore 1571 disk]]
 == Links ==

GCR encoding - Revision history

Dan Tobias: /* Floppy disk formats using GCR encoding */

Dan Tobias at 20:50, 8 May 2013

Dan Tobias: Created page with "{{FormatInfo |formattype=physical |subcat=Floppy disk }} '''GCR encoding''' (Group code recording) is a name for a group of schemes for encoding data on magnetic media such a..."