Tandy TRS-80 Owner Manual & Programming Manual page 53

HOW
MUCH CAN
ONE
DISK
HOLD?
SAVE
the
"INPUT
Program" you
now
have
in
memory.
(You'll
be using
it
later.)
Now
change
it
into
a
"LINE
INPUT
Program."
Delete
line
50
and change
lines
40 and
60.
Type:
40
LINE INPUT
#1
,
L*
50
G0 PRINT "DATA LINE
:" L*
and
RUN
.
.
.
Line 40
INPUTs
an
entire
LINE,
rather
than one
single data item from
the disk
file.
This
LINE
includes everything up
to
the
(ENTER)
character
—
punctuation marks, spaces and
all.
In the
"OFFICE/DAT"
file,
the
first
LINE
contains
5,
"PEN." Line
40
labels this line as
L$
and
line
60
PRINTs
it
on your
screen.
The program
then
INPUTs
and
PRINTs
-
16,
"PAPER"
—
the second
and
final line in the
file.
We
can
easily alter this program
so
that
it
will
count
how many
bytes are
in the
file.
Add
these
lines
and
RUN
it:
25
PRINT "THIS FILE CONTAINS
:"
27 PRINT: PRINT: PRINT:
PRINT
57
m
=
Lt+
"*"
G0 PRINT Mt!
G5
L
=
LEN(Mt)
+ L
90
PRINT
@
394t
L
"BYTES"
Line 57 adds an
asterisk
to
each LINE.
This
aster-
isk
represents the
(ENTER) character.
Line 65 then
counts the
total
number
of
characters
(bytes) in
each
line.
This
is
the
entire
"LINE
INPUT
Program":
PLINE
INPUT
PROGRAM
10
CLS
20
OPEN
"I"* «li "OFFICE/DAT"
25
PRINT "THIS FILE CONTAINS
;
27 PRINT: PRINT: PRINT: PRINT
30
IF
EOFU)
=
-1 THEN 80
40 LINE INPUT
*1
f
L*
57 M*
=
L*
+
"*"
G0 PRINT M$!
G5
L =
LEN(M$)
+
L
70 GOTO 30
B0
CLOSE
*l
90 PRINT
@
394
>
L
"BYTES'
SAVE
it.
It
will
be
useful in
comparing what
Pro-
grams
2, 3,
and
4
put
in
your
disk
file.
PRINT— FOR A CHANGE
So
far,
we've used only
WRITE
to
put data
in
a
disk
file.
If
you've used
other
forms
of
BASIC,
you
might
be accustomed
to
using
PRINT
rather than
WRITE.
The
Color Computer
disk
system
allows you
to
do
this.
However,
PRINT
is
much
more
tricky to
use.
If
you're not used
to
it,
don't
bother learning
all
this.
Skip
to
Program
4.
. .
.
Still
with
us?
KILL
your
old
"OFFICE/DAT"
file
by
typing:
KILL "OFFICE/DAT"
(ENTER)
Now
erase
memory, and
type
and
run Program
2.
Then
RUN
the
INPUT
or the
LINE INPUT
Pro-
gram,
if
you'd
like.
Here's
Program
2:
PROGRAM
2
42 bytes
10
OPEN "0"
,
*1
,
"OFFICE/DAT"
20 PRINT
81
,
5» "PEN"
30 PRINT
*1
,
-1G
»
"PAPER"
40
CLOSE
»1
Lines 20 and
30
PRINT
your
data
to buffer
#1
which, as
you know,
is
one
of the
15 buffers
which
will
send your data
to
the disk
file.
To
see
what
Program
2
PRINTs,
type:
PRINT
5» "PEN"
(ENTER)
PRINT -1G
"PAPER"
[
ENTER)
Notice the
Computer
did not enclose the
strings
—
PEN
and
PAPER
—
in quotes, as
WRITE
did.
This
will
be important
to
know
later.
Now
look at the blank
spaces. We'll start
with
the
first
one
—
the one
before the
5.
This
means
the
43