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OTHER SYSTEM FUNCTIONS
27.4 -- Diskette File Functions
occurred.
rT
no errors
occurl'~d;
the
DFT has been changed in the following
manneT'o
By
tes
3
and
4
C
onta
in
th e
SDW
or
the
last
allocated
segment.
Bytes
5
and 6 contain the starting,
logical sector
number
of
the
last
allocated
segmeryt.
SUF
contains
the
logical sector number of the
logical
end-or-file,
and
RIB,
if
originally
zero,
contains
the
physical
sector
number
of
the
file's
Retrieval
I
n
for
ma
t
ion
!3
1
0
c k .
The
con ten
t
s
0
of
the sector
bUTre~
are indeterminate.
27.4.5 Deallocate diskette space -- .
DEALe
The
.
DEALe
function
deallocates
segments of diskette
space from
a
file.
The
file's
Ret~ieval
Information
Block
and
the
system's
Cluster
Allocation
Table are updated to
account for
the
deallocated space.
Since space
deallocation
is
performed
automatically
by
the
device independent
lID
¥unctionsl
the
.
DEALe
function
should
only
be
used
by
programs
that
are
doing
physical
sector
1/0
on
MDOS
compatible diskettes.
ENTRY PARAMETERS:
x
=
The address
of
the
OFT.
The
DFT
must· contain
parameters:
the
folloUling
LUN
must contain the logical unit number
on
which
the
rile
resides
(ASCII
number 0-3,
$30-$33).
8qtes
1
and
2
must contain the file's
logical sector
number
beqond
which
space is to be deallocated.
If these
two
b~tes
contain
the
value
$FFFFJ
then
the
entire
space belonging to
RIB
the
file
will
be
deallocated;
however,
in
this
special
easel
the
file's directory entry
must
already
have been flagged as deleted.
must
contain
the
physical
sector
number
of
the
file's
Retrieval
Information Bloc k.
DEN
.
mu s t
c on t a in- -t h e
f i
1 e ' s d ire c tor
y
entry number.
SBS must
contain the starting address
of
a
128
(decimal) byte sector buffer.
,-
-"
I
/
- . /
Paa2
27-28
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