Tandy TRS-80 Owner Manual & Programming Manual page 59

TRIMMING THE
FAT
OUT OF
DIRECT ACCESS
DIRECT INPUT
PROGRAM
*1 'OFFICE/DAT 10 OPEN "D".
20
R = R
+
1
30 GET
#1
,
R
38
INPUT
Hi
A, B$
50
PRINT "RECORD"
R
":"
A
G0
IF
LOF(l) <>
R
THEN
20
70
CLOSE
»1
Note: You
can't use the
"LINE
INPUT
Program"
to
determine
how many
bytes this
file
consumes.
LINE
INPUT
does
not input the spaces
in
a record which
follow the
;
ENTER) character.
EFFICIENCY,
EFFICIENCY
. .
We
can
get
even more
efficient.
Our
next
direct
access
program consumes
only 16 bytes. Erase
memory,
KILL
the old
"OFFICE/DAT"
file,
and
type
and
RUN
Program
7.
PROGRAM
7
16
bytes
10
OPEN "D"»
*1
.
"OFFICE/DAT"
i
8
20
FIELD
»1
3
AS At
t
5
AS Bt
30 LSET At =
"5"
40 LSET 8$ =
"PEN"
50 PUT »1
. 1
S0
LSET A$
=
"-IS"
70
LSET
B$ = "PAPER"
90 PUT «1
.
2
90
CLOSE
*1
There
are
two
new
words
in this
program which
we'll talk
about
later. Let's see
what
the
program
does
first.
SAVE
it.
Then
erase
memory
and
input
the
file
with
this
program:
FIELDED INPUT
PROGRAM
10
OPEN
"D"
,
•
1 t
'OFFICE/DAT"
.
S
20 FIELD
*i
,
3
AS A*
>
5 AS B*
30
R = R +
1
m
GET
»1
,
R
50 PRINT "RECORD" R ":"
At! Bt
60 IF LOF(l)
<>
R
THEN
30
70 CLOSE
»1
By
using
FIELD
and LSET, your program
will
work
the
same
as
any
direct
access program. The
difference
is
what
FIELD
and
LSET
put
in
each
record:
PEN
record
1
-
1
6
P
A
P E R
record
2
"OFF/CS/OAT
Only
the bare
essentials.
Here's
how
Program
7
works
. .
Line 20
tells
the
Computer
to
divide each record
into
two
fields.
The
first field
is
A$
and
the second
is
B$.
These two
fields will be the
same
size in
every
record,
A$
will
always
be
3
bytes
and B$
will
always
be
5 bytes.
Now
that we've established
this,
we
can put data
in each
field.
Line 30
LSETs
5 in the
A$
field
(SETs
the character 5
to
the Left of A$). Since the
character 5 only consumes
1
byte and
there are
3
bytes
in
the
A$
field,
there are
2
empty
spaces at
the end
of
5.
Notice
we
had
to
convert the
number
5
to
a
string
by putting quotes around
it.
You
cannot
LSET
a
number. You must
convert
it
to
a
string.
Line 40
LSETs
the
word
PEN
in
the
B$
field.
Again,
this leaves 2
empty
spaces at the end
of
A$,
since
PEN
is
3 bytes.
Line 50
PUTs
all
this in record
1.
Then,
the
same
process
is
repeated
for
record
2.
49