AmigaDOS_Technical_Reference_Manual.pdf

AmigaDOS

Technical Reference

Manual

AmigaDOSTechnicalReferenceManual

TableofContents

1.1 AmigaDOSFileStructure

1.1.1 RootBlock

1.1.2 UserDirectoryBlocks

1.1.3 FileHeaderBlock

1.1.4 File ListBlock

1.1.5 DataBlock

1.2 DISKED-TheDiskEditor

AmigaDOSTechnical Reference Manual

FilingSystem

1.1AmigaDOSFileStructure

The AmigaDOS file handler uses a disk that is formatted with blocks of equal size. It provides an

indefinitelydeephierarchyofdirectories, whereeachdirectorymaycontainotherdirectoriesandfiles,

orjustfiles. The structure isapuretree - thatis, loopsare notallowed.

There is sufficient redundancy in the mechanism to allowyou to patch together most, ifnot all, ofthe

contents ofadisk after a serious hardware error, forexample. Topatch the contents ofa disk, youuse

the DISKED command. For further details on the syntax ofDISKED, see section 1.2, "DISKED -The

Disk Editor," later in this chapter. Before you can patch together the contents a disk, you must

understandthelayout. The subsectionsbelowdescribethelayoutofdiskpages.

1.1.1 RootBlock

The root ofthe tree is the Root Block, which is at a fixed place on the disk. The root is like any other

directory, except that it has no parent, and its secondary type is different. AmigaDOS stores the name

ofthediskvolume inthenamefieldoftherootblock.

Each filing system block contains a checksum, where the sum (ignoring overflow) ofall the words in

theblockiszero.

Thefigureonthefollowingpagedescribesthelayoutoftherootblock.

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