System information

FUNCTION 28: WRITE PROTECT DISK

Entry Parameters:

The Write Protect Disk function provides temporary write protection for the currently selected

disk. Any attempt to write to the disk before the next cold or warm start operation produces the

message:

BDOS ERR on d:R/O

FUNCTION 29: GET READ-ONLY VECTOR

Entry Parameters:

Returned Value:

Registers HL: R/O Vector Value

Function 29 returns a bit vector in register pair HL, which indicates drives that have the

temporary Read-Only bit set. As in Function 24, the least significant bit corresponds to drive A,

while the most significant bit corresponds to drive P. The R/O bit is set either by an explicit call

to Function 28 or by the automatic software mechanisms within CP/M that detect changed disks.

5.2 Call Conventions CP/M Operating System Manual

5-28