💾 Archived View for mirrors.apple2.org.za › archive › apple.cabi.net › Z80.CPM › A2.CPM.files › cpmd… captured on 2023-03-20 at 23:40:14.
⬅️ Previous capture (2023-01-29)
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The following contains information about how the file directory in CP/M is
organized. There are some references to Apple dos and Apple CP/M, but the
information in general applies to all CP/M systems.
The Apple CP/M directory tracks are located on track 3, sectors 0 to 5.
Although sectors 6 to 7 are consider to be part of the directory, they are
unused.
There are 4 sectors per CP/M block. In terms of blocks, the directory is
allocated in blocks 0 and 1. There is no header in the start of each sector,
like Apple dos.
Each file entry has 32 bytes/file and 8 files/sector.
Here is the description of entry:
offset description
+00 user number ($e5 if files is deleted).
1 to 8 filename.
9 to 12 filename extension. (note no '.' is stored).
13 extent number, 16 blocks/extent which equals 1 directory entry.
14 to 15 unsed.
16 number of 128 byte records. (max. $80).
17 to 31 block allocation.
The block allocation is like Apple dos track/sector list.
The initial extent number for each file is 0. If the file is longer than 16
blocks, a new directory entry is made. The new entry's extent number is
incremented by 1.