Editing Commodore 1581 (section)

=== 1581 Image Layout ===
The 1581 disk has 80 logical tracks, each with 40 logical sectors (the actual physical layout of the diskette is abstracted and managed by a hardware translation layer).  The directory starts on 40/3 (track 40, sector 3).  The disk header is on 40/0, and the BAM (block availability map) resides on 40/1 and 40/2.

Header Contents

 $00–01 T/S reference to first directory sector (40/3)
     02 DOS version ('D')
  04-13 Disk Label, $A0 padded
  16-17 Disk ID
  19-1A DOS type ('3D')

BAM Contents, 40/1

 $00–01 T/S to next BAM sector (40/2)
     02 DOS version ('D')
  04-05 Disk ID
     06 I/O byte
     07 Autoboot flag
  10-FF BAM entries for Tracks 1–40

BAM Contents, 40/2

 $00–01 00/FF
     02 DOS version ('D')
  04-05 Disk ID
     06 I/O byte
     07 Autoboot flag
  10-FF BAM entries for Tracks 41–80