System information

The cks parameter determines the number of directory items to check on each directory scan and
is used internally to detect changed disks during system operation, where an intervening cold or
warm start has not occurred. When this situation is detected, CP/M automatically marks the disk
Read-Only so that data is not subsequently destroyed.
As stated in the previous section, the value of cks = dir when the medium is easily changed, as is
the case with a floppy disk subsystem. If the disk is permanently mounted, the value of cks is
typically 0, because the probability of changing disks without a restart is low.
The ofs value determines the number of tracks to skip when this particular drive is addressed,
which can be used to reserve additional operating system space or to simulate several logical
drives on a single large capacity physical drive. Finally, the [0] parameter is included when file
compatibility is required with versions of 1.4 that have been modified for higher density disks.
This parameter ensures that only 16K is allocated for each directory record, as was the case for
previous versions. Normally, this parameter is not included.
For convenience and economy of table space, the special form:
DISKDEF i,j
gives disk i the same characteristics as a previously defined drive j. A standard fourdrive,
single-density system, which is compatible with version 1.4, is defined using the following macro
invocations:
DISKS 4
DISKDEF 0,1,26,6,1024,243,64,2
DISKDEF 1,0
DISKDEF 2,0
DISKDEF 3,0
......
ENDEF
with all disks having the same parameter values of 26 sectors per track, numbered 1 through 26,
with 6 sectors skipped between each access, 1024 bytes per data block, 243 data blocks for a total
of 243K-byte disk capacity, 64 checked directory entries, and two operating system tracks.
6.11 The DISKDEF Macro Library CP/M Operating System Manual
6-36