CPM Disk Image Filesystem Layouts
---------------------------------

NB: Logical layout only. Does not describe how layout is written to disk.

AcornCPM
--------
Always 400K
00000000: System, usually starts with "AcornCP"
00001E00: DIRECTORY area - 128 entries, occupies blocks 0,1
00002E00: DATA area - starts at block 2
with logical-to-physical sector deblocking and skewing
blocks are 2048 bytes

SloggerCPM
----------
Always 800K
00000000: System, usually starts with "Slogger"
00003C00: DIRECTORY area - 256 entries, occupies blocks 0,1
00005C00: DATA area - starts at block 2
with logical-to-physical sector deblocking and skewing
blocks are 4096 bytes

D10
---
Always 800K(?)
00000000: DIRECTORY - occupies block 0, 1
          Disk title ususally first entry, user area &20
          Directory allocation addresses: 16bit
00001000: DATA area - block 2 onwards
data area contiguous

D20
---
Always 800K(?)
00000000: DIRECTORY - occupies block 0, 1, 2, 3
          Disk title ususally first entry, user area &20
          Directory allocation addresses: 16bit
00002000: DATA area - block 4 onwards
data area contiguous

D2
--
Always 720K(?)
00000000: DIRECTORY - occupies block 0, 1, 2, 3
          Disk title ususally first entry, user area &20
          Directory allocation addresses: 16bit
00002000: DATA area - block 4 onwards
data area contiguous

PCW
---
Always 720K(?)
00000000: System area
00001200: Directory - occupies block 0, 1, 2, 3
          Disk title ususally first entry, user area &20
          Directory allocation addresses: 16bit
00003200: Data area - block 4
data area contiguous

AmsDOS
------
Always 180K(?)
00000000: System
00002400: Directory - occupies block 0, 1
          Directory alloc units: 8bit
00002C00: Data area - block 2
data area contiguous

Einstein
--------
00000000: System
00002800: Directory - occupies block 0
          Directory alloc units: 16bit
00003000: Data area - block 1
data area contiguous

TorchCPN
--------
Disk size determined by disk allocation map
          No System
00000000: Directory
00001400: Data area
uses allocation map list, not allocation addresses