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APPENDIX
..J
MDOS 3.00
DirTe~ences
3.
The double-sided diskette has no unused sectors as de
the
single-sided diskettes,
since an integral number
or clusters exists.
A
program using the
IaCB
for diskette
IIO
must
have
the
~ull
IOeB
conTiguTed
as
desc~ibed
in all MDOS
manuals.
This includes
the
until-now-unused
entry
IOCSBI.
4.
A
program
using the IOCB Tor diskette
1/0
will have
to be changed iT the sector
bur~er
at the time of the
. OPEN function call is not exactly an integral number
or
sectors.
In previous versions of
MDOSI
the sector
size
did
not
get
check,ad
until
a
subseq,uent
IIO
transfer was made (even though the
entry
parameters
for
the
. OPEN call specified that !OCSBS and IOeSBE
must
be
set
up),
5.
A program using the
IOCB
Tor diskette 110
will
have
to
be
changed if the sector burTer pointers (IOCSBS
and lOeSBE) are altered after the . OPEN runction
has
been
called.
Since, OPEN
sets
rOeSB!
to the same
value as IOCSBEI moving the
sector
bu~fg~
~e~uires
that
all sector
bu.pfe~
pOinters
(IOCSBS,
IOCSBEJ
and
lOeSBI) be changed accordingly.
6.
A program accessing
logical
unit
1
without
first
using
the
system runction . OPEN, .DlRSM, . CHANG,
or
,LOAD,
will have to be changed so that the
~ead
head
is
restored
before
the unit is accessed.
Previous
versions of
MDOS
resto~gd
both logical units 0 and
1
each
time
the
system initialized and each time the
MDOS command interpreter received
control;
however,
in
MDOS
3.0
th is
is
no
longe~
true.
Thus.
the
diskette controller
rir~a~e
entr~
point
RESTOR
must
be
used
to
restore
the
head
on
the
unit to be
accessed
if
not
using
one
or
the
above
system
functions
(Ulh ich
do
the
restore themselves).
The
same is true if the
p~ogram
is to access un{ts 2 or 3
without first using one of these Tunctions.
7.
A
program
that
has
been
designating logical unit
numbers in the diskette
controlle~
variable
CURDRV
<ioeation $0000) as either a zero or a
non-ze~o
value
(to access either unit 0
01"
1),
will
have
to
be
changed
so
that
the
actual
binary number is used
instead.
A
non-ze~o
value no longer guarantees
that
unit 1 \.Uill be accessed (physical
liD).
B.'
If
a
program
has
. ALUSM,
the
entry
changed.
Section
detailed description
c ond i ti ons.
been
using
the
syst~m
function
and
exit
conditions
have
be~n
27.5.5
should be consulted Tor a
of the current
entry
and
exit
• J-O=:>
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