Tandy TRS-80 Owner Manual & Programming Manual page 45

A MORe
DIRECT
APPROACH
communication
for
output
or input.
The
"D"
suf-
fices
for
both.
Line 20
WRITEs
"J.
DOE"
to buffer #1.
Since
this
program
is
open
for direct access,
"J.
DOE"
will
remain
in buffer
#1
until the
program
sends
it
elsewhere.
Line 30 does
just that.
It
PUTs
the contents of
buffer
#1
into the disk
file
as record
2:
Notice our drawing shows
only
two
records in the
file.
GET
record
4.
Type:
34 GET
»1
.
a
and
RUN
. . .
The Computer
gives
you an
IE (Input
past the
End
of
the
File) error.
This
is
because the
last
record the
program
PUT
in the
file
was
record
number
2.
Hence,
record 2
became
the
end
of the
file.
it
Note: Didn't
get this error?
You must
already have
"NAMES/DAT"
file
on your
disk with three or mo.
records.
:
record
1
"
J
DOE"
record
2
/
W^MES/DAT"
^
To
PUT
more
records
in
the
file,
add
these
lines.
Then
RUN
the
program:
31
WRITE
»1
t
"BILL SMITH"
32 PUT
si
,
a
Now
your
"NAMES/DAT"
file
will
have
these four
records:
At
this point,
"J.
DOE"
is
no
longer
in buffer #1.
It is
in
record 2 of the disk
file.
Line 34
GETs
record 2
and
reads
it
back
into
buffer
#1.
Now
"J.
DOE"
is
in both the disk
file
and
buffer #1.
Line 36
INPUTs
the record
from
buffer
#1
into
main
memory
and
labels
it
A$.
Now
"J.
DOE"
is
in
both the disk
file
and
main
memory.
It is
no
longer
in buffer
#1.
With
"J.
DOE"
in
main memory,
line
38 can
PRINT
it.
record
1
"
J
.
DOE"
.
record 2
record 3
"BILL SMITH"
record 4
Note:
In
the
sequential access
programs
in
Chapters
5
and
6,
you
didn't
need
PUT
and GET. The Com-
puter did
this automatically.
The
OPEN
line specified
whether the buffer
should
output
(PUT)
data
into the
disk
file
or input
(GET)
data from
the disk
file.
JtMdb
X
W/)M£S
r
5/DA7
>*
35