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By the same
token
,
any extended files stored under
DOS
2.5
(i.e
.,
files occupying sectors numbered 720 and
up)
will be
" invisible"
to
DOS
2.08. You will not be able to work with any
such files under
DOS
2.0S,
nor will
they
show
up
in a disk
directory
called
up
under
DOS
2.0S.
Consider the following
directory listing
,
as viewed under
DOS
2.5
:
:.:DOS
SYS
037
*DUP
SYS
042
FILE!
DAT
204
FILE2
DAT
119
<FILE3
DAT>350
<FI
LE4
DAT>022
':1-
.-
<..60
FPEE
:;ECTORS
If you called up a
directory
of the same diskette under DOS
2.0S
,
you would see a somewhat different listing
:
:.:DOS
:.:DUF'
FILE!
FILE2
0~)0
FREE
S'y'S
~)37
SYS
042
DAT
204
DAT !!9
SECTORS
The extended files
,
marked by DOS
2.5
with brackets
,
are not
recognized by DOS 2.0S. Note also that DOS 2.0S shows no
free sectors left on the
diskette,
because in fact the only free
sectors are numbered 720 and
up.
The
dropping
of
FILE-
3.DAT,
which uses sectors numbered both below and above
720
,
from the
DOS
2.0S directory illustrates yet another point:
if
any sector
of
a file is numbered 720 or
up,
the
entire file is
invisible
to
DOS 2.0S.
On
the
other hand
,
those
files visible
to DOS 2.0S are com-
pletely accessible
to
it-
they may be read
,
locked
,
unlocked
,
and so forth using DOS 2.0S. And after you work with such
files
using DOS
2.0S
,
the diskette will still be wholly compati-
ble with
DOS
2.5,
which will again recognize the
extended
files invisible to
DOS
2.08.
Caution: Never use any
DOS
2.0S
"
disk fix
"
program with a
diskette formatted in enhanced density using
DOS
2.5.
The
program may decide that any
"
invisible" files are bad
,
and
attempt
to
erase
them
.
The
program may also destroy the
113
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