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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