Commodore 1581 - Partitions and Sub-Directories

PARTITIONS and SUB-DIRECTORIES
The 1581 allows the user to create partition areas on the disk.
Partitions were originally implemented to provide a mechanism for
easily protecting a particular section of the disk. That is useful for
permanently allocating part of the disk for things such as BOOT
sectors, CP/M work area, or reserving space for user defined random
files.
Normally, sectors on the disk can be marked as used by setting
the appropriate bit in the BAM (most easily done with the BLOCK-
ALLOCATE command). That prevents them from being overwritten. A
VALIDATE command, however, will de-allocate this area. To protect
these special blocks from being de-allocated during a VALIDATE, place
them in a user defined partition area. The VALIDATE command in the
1581 automatically skips over file entries that are partition files (file
type = CBM), which guarantees the intended area is, and remains,
allocated.
Partition areas are given names by the user when first created.
They appear in the main directory as file type CBM.
A partition area is created by the following command (file#
should be opened to the command channel):
PRINT#file#,"/0:partition name," + CHR$(starting track) + CHR-
$(starting sector) + CHR$(< # of sectors) + CHR$(> # of sec
tors) + ",C"
Large enough partitions can also be used as sub-directories.
There are, however, certain limitations if a partition area is to be used
as a sub-directory area:
1) The partition area must be at least 120 sectors in size.
2) The starting sector must be 0.
3) The ending sector must be a multiple of 40.
4) The area to be allocated cannot contain track 40 (the original
system track).
Partitions can also be created with a partition. This means that
sub-sub-directories can be created if their partitions meet the above
rules. Graphically, it looks like this:
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