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Basic Disk Operating System (BDOS) Functions
WRITE PROTECT DISK
ENTRY
RETURN
III
CL:lCH
FUNCTION 28
WRITE PROTECT DISK
The Write Protect Disk function provides temporary write protection for the
currently selected disk. Any attempt to write the disk before the next cold start,
warm start, disk system reset, or drive reset operation produces the following
message: "BDOS Err on d: RIO".
ENTRY
CL: lDH
FUNCTION 29
GET READIONLY
VECTOR
RETURN
•
BX: RIO Vector Value
The Get ReadlOnly Vector function returns a 16-bit vector in register BX which
indicates drives which have the temporary readlonly (RIO) bit set. Like function
24, the least significant bit corresponds to Drive A, while the most significant bit
corresponds to Drive P. The RIO bit is set either by an explicit call to function 28, or
by the automatic software mechanisms within
CP/M-86
which detect changed disk
media.
SET FILE ATTRIBUTES
ENTRY
CL: lEH
DX: FCB
Offset
III
FUNCTION 30
SET FILE
ATTRIBUTES
RETURN
AL: Return Code
The Set File Attributes function programmatically manipulates permanent indica-
tors attached to files. In particular, the RIO, System, and Archive attributes (tl', t2',
and t3') can be set or reset. The DX pair addresses an FCB containing a file name
4-21
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