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The idea to create non-standard autobootable disks was born in a primitive attempt to prevent copy of such disks and to avoid the loading and launch of Amiga DOS, in order to directly access the Amiga graphic, audio and memory chipsets. DiskDoctor in fact changed autostart disks bootblocks into standard AmigaDOS-based ones, renaming a disk with "Lazarus" namedisk, and made the autostart disk unusable.
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Files are composed of a file header block, which contains information about the file (size, last access time, data block pointers, etc.), and the data blocks, which contain the actual data. The file header block contains up to BSIZE/4-56 data block pointers (which amounts to 72 entries with the usual
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The date fields in the root block (and other blocks) are structured in the form of DAYS, MINS and TICKS. The DAYS field contains the number of days since
January 1. 1978. MINS is the number of minutes that have passed since midnight and TICKS are expressed in 1/50s of a second. A day value of zero is
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OFS is very good for repairing the filesystem in the event of a problem, although the so-called DiskDoctor provided by
Commodore quickly earned the name DiskDestroyer, because it could not repair No-DOS type autostart disks provided by third-party software manufacturers as bootable disks for games.
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to calculate which 32-bit word in the disk block to use as a pointer to a hash bucket list, which in turn contains the file, directory, or link record. A bucket list is used to support filesystem objects with names that hash to the same offset. For example:
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Prior to AmigaOS 3.5, AmigaDOS file handles maintained a 32-bit wide offset parameter (unsigned), telling where to start the next read or write operation. The biggest size for any single Amiga file under these operating systems therefore comes to 2 = 4
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512 byte blocks). If a file is larger than that, file extension blocks will be allocated to hold the data block pointers. File extension blocks are organised in a linked list, which starts in the file header block ('extension' field).
182:. There are 80 cylinders on an Amiga floppy disk. Each cylinder has 2 MFM tracks, one on each side of the disk. Double density (DD) disks have 11 sectors per MFM track, high density (HD) disks have 22 sectors.
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The rootblock contains information about the disk: its name, its formatting date, etc. It also contains information on accessing the files/directories/links located at the uppermost (root) directory.
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Filename characters can be lowercase and uppercase, but are not case sensitive when accessed. That is to say, "MyFile" and "myfile" in the same directory refer to the same file.
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The characters '/' and ':' are forbidden in file and volume names, but *!@#$ %|^+&_()=\-{}';",<>.? and letters with diacritical marks like âè are allowed.
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files. However, OFS-formatted disks continue to retain the 32-bit limitations, for that is an intrinsic limitation of the format as recorded on the media.
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The rootblock is located at the physical middle of the media: block number 880 for DD disks, block 1760 for HDs. This helps minimize seek times.
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considered illegal by most programs. Since the DAYS value is stored as a 32-bit number, the Amiga filesystem does not have an inherent
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numCyls = highCyl - lowCyl + 1 highKey = numCyls * numSurfaces * numBlocksPerTrack - 1 rootKey = INT (numReserved + highKey) / 2
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An OFS datablock stores block size BSIZE-24 bytes (i.e. normally 488 bytes at most frequently used BSIZE of 512 bytes).
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The DD disk has 11 * 2 * 80 = 1760 (0 to 1759) blocks, while the HD disk has 22 * 2 * 80 = 3520 blocks.
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Originally known as the Amiga File System, it came from the filesystem of
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HD disks: 512 bytes/sector, 22 sector/track, 2 track/cyl, 80 cyl/disk
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DD disks: 512 bytes/sector, 11 sector/track, 2 track/cyl, 80 cyl/disk
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158:. It received the nickname of "Old" or "Original" File System when
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The exact calculation for where it is stored is as follows:
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216:. After Amiga OS 3.5, file handles may reference 2 = 16
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Why was "Disk doctor" so spectacularly bad at its job?
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To reach a file, directory or link, AmigaDOS uses a
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The geometry of an Amiga floppy disk is as follows:
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203:on a DD disk and 1760 KiB on an HD floppy disk.
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51:introducing citations to additional sources
178:encoding/decoding by default when handling
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170:Characteristics of AmigaDOS Floppy Disks
41:Relevant discussion may be found on the
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207:Characteristics of Files under AmigaDOS
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34:relies largely or entirely on a
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162:was released with AmigaOS 1.3.
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270:have the same hash value.
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308:Professional File System
598:AmigaOS version history
122:was the filesystem for
62:"Amiga Old File System"
16:File system for AmigaOS
303:Amiga Fast File System
128:Amiga Fast File System
318:List of file systems
47:improve this article
771:Disk file systems
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648:Amiga Reflections
313:Smart File System
248:Year 2038 problem
244:Year 2000 problem
199:Amiga stores 880
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323:Rigid Disk Block
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45:. Please help
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619:Amiga Forever
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255:hash function
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64: –
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58:Find sources:
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36:single source
32:This article
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540:File systems
406:technologies
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295:Amiga portal
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180:floppy disks
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140:floppy disks
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103:October 2015
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591:OS versions
174:Amiga uses
126:before the
765:Categories
709:Influenced
423:AmigaGuide
413:AmigaBASIC
73:newspapers
663:Hollywood
603:AmigaOS 4
526:Workbench
472:Kickstart
467:Intuition
462:Installer
43:talk page
752:Category
741:Syllable
698:AmiZilla
635:software
547:CrossDOS
516:ReAction
477:RAM disk
418:AmigaDOS
281:See also
156:AmigaDOS
136:metadata
781:AmigaOS
736:MorphOS
683:WHDLoad
501:Ambient
396:AmigaOS
268:file_5u
264:file_24
260:file_1a
146:History
124:AmigaOS
114:On the
87:scholar
721:AtheOS
688:WinUAE
643:Aminet
633:Other
624:AmiKit
521:Scalos
491:Amiga
447:WarpOS
343:Aminet
152:TRIPOS
118:, the
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776:Amiga
658:Games
653:Demos
428:ARexx
404:Amiga
132:block
116:Amiga
94:JSTOR
80:books
726:BeOS
716:AROS
582:NTFS
531:Zune
493:GUIs
457:Hunk
443:Exec
438:CAMD
266:and
134:for
66:news
693:YAM
678:LHA
673:IFF
668:ADF
577:FAT
572:UDF
567:SFS
562:PFS
557:FFS
552:OFS
506:MUI
482:XAD
339:LHA
337:in
246:or
218:EiB
214:GiB
201:KiB
176:MFM
49:by
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262:,
250:.
445:/
388:e
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101:(
91:·
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