Apple IIe - Page 215

Cassette
and
Disk Storage with
the
Apple
lie
215
sent
to
a
diskette
file
with
PRINT,
the
DOS WRITE
command
must
be
executed
. WRITE
notifies
DOS
that
the
PRINT statement
is
being
used
to
send data
to
a
diskette
file
rather
than
to
the
display.
Configuration
WRITE
filename
After
the
WRITE
command
has
been
executed
,
subsequent
PRINT
statement
output
will
be
sent
to
the
specified
diskette
file.
If
an
error
is
encountE7red,
the
error
message
will
be
sent
to
the
diskette
file.
Howeve
r~
once
an
error
message
has
been
sent
to
the
diskette
file,
the
WRITE
command
will
be
cancelled
.
As
shown
in
the
following
example
, WRITE
must
be
issued
with
a
PRINT
statement
and
preceded
with
Ctrl-D.
100
D$ = CHR$(4)
200
PRINT
D$; " WRITE TEXTA"
300
PRINT " THIS
DATA
IS
BEING
SENT
TO
THE
DISKETTE
"
When
data
is
printed
to
a
file
, DOS
will
update
an
internal
file
pointer.
This
pointer
denotes
the
position
on
the
diskette
··
surface
where
the
next
data
items
will
be
stored.
The
file
pointer
for
a
sequential
data
file
can
only
be
moved
forward
. The
OPEN
statement
moves
the
file
pointer
to
the
beginn
i
ng
of
the
file
.
When
you
are
writing
to
a
sequential
data
file
with
exis
ting
data,
problems
can
occur
unless
the
file
is
first erased. This is
due
to
the
fact
that
although
PRINT
statements
will
overwrite
the
existing
file
contents
,
the
previous
data may
extend
be
y
ond
t
he
end
of
the
new
data.
This
potential
problem
can
be
avoided
by
using
the
DELETE
command
prior
to
the
OPEN
command
as
s
hown
in
the
followin
g
example
: