Basic Disk Operating System (BDOS) Functions
4-22
with the appropriate attributes set
or
reset.
It
is
the user's responsibility
to
insure
that
the file name
is
not ambiguous. Function 30 searches the default disk drive
directory area for directory entries belonging to the current user
number
that
match
the FCB-specified name
and
type fields. All matching directory entries are
updated
to
contain the selected indicators. Indicators
fl'
though
f4' are
not
presently used,
but
may be useful for applications programs, since they are
not
involved in the
matching process during file open
and
close operations. Indicators f5'
through
f8'
are reserved for future system expansion. The currently assigned attributes are
defined as follows.
t1': The
R/O
attribute
indicates whether
or
not
the file
is
in
read/only
status. The BDOS will
not
issue write
commands
to
files in
R/O
status.
t2': The System
attribute
is
referenced by the
CP/M
DIR
utility.
If
the
attribute
is
set,
DIR
will
not
display the file in a directory display.
The
DIRS
command, however, will display the file.
t3': The Archive
attribute
is reserved
but
not
actually used by
CP
/M-86.
If
it
is
set, it indicates
that
the file has been written
to
back-up storage by
a user-written archive program.
To
implement this facility, the archive
program
sets this attribute when it copies a file to back-up storage.
Any programs updating
or
creating files must reset the attribute.
Further,
the archive
program
backs
up
only those files
that
have the
Archive attribute reset. Thus,
an
automatic
back-up facility restricted
to
modified files can be easily implemented.
Register
AL
returns OFFH (255 decimal)
if
the referenced file could
not
be found,
otherwise zero
is
returned.
GET
DISK
PARAMETER
BLOCK
ADDRESS
ENTRY
CL:
1FH
FUNCTION
31
GET
ADDR
(DISK
PARMS)
RETURN
BX: DPB Offset
ES:
Segment Base
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