Radio Shack TRS-80 User Manual page 225

One
last
word
of advice: If
you
PRINT #
a
list
of, say, 10 values onto
tape,
you should
INPUT #
a
list
of 10
values also.
If
you
don't match up
the
number
of
PRINT
#
items
with the
number
of
INPUT
#
items, you'll
end up
either losing data or going into the
lock-up condition described above.
The
following
program
demonstrates
how
a
data
file
can be used to
create a
list
of data
items, process
and update
it.
Study
it
carefully
and
think
how
similar
programs might
handle
inventories,
or any
sequential
lists.
1
REM
5
C =
7
B =
10 IN
.
*AVG
CLS
TEMP AND HUMIDITY USING
A
DATA FILE*
20
30
40
50
53
55
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
2
10
220
230
240
250
"WHAT
DAY OF
'WHAT WAS THE
THE
MONTH
IS
IT"
;D
TEMPERATURE TODAY
" ;T
,
" WHAT WAS THE
D=l THEN
160
HUMIDITY
"
;H
IN
IN
IF
P.
"LOAD PREVIOUS TEMPERATURES
AND
P.
"FIRST REWIND TAPE
TO
BEGINNING
P,
"THEN PRESS RECORDER'S PLAY KEY
IN.
"PRESS
ENTER WHEN
READY"
;A$
FOR
X=l TO D-
1
INPUT
#
Y.Z
B
=
B+Y
C =
C+Z
NEXT
X
B=(
B
+
T
)/D
C=CC+H)/D
CLS:P.
"THE AVERAGE
HUMIDITIES THIS MONTH."
OF
DATA FILE.
"
TEMPERATURE IS"
;B
"THE AVERAGE HUMIDITY IS";C
sP.
"NOW
THE
TRS-80 WILL WRITE"
"TODAY'S TEMPERATURE
AND
HUMIDITY"
"ONTO
THE TAPE.
"
"SO
PRESS RECORD AND PLAY
KEYS"
"BUT
DO NOT
REWIND."
IN.
"PRESS ENTER WHEN READY"
;A$
PRINT
n
T; "
,
" ;H
P. tP.
"NOW TODAY'S INFO
IS
ADDED TO THE TAPE
P
.:
P.
"PLEASE PRESS STDP KEY ON THE RECORDER
END
P.
P
,
P.
P,
P.
P,
FILE
ii
Line
70 reads
back
all
the previous days'
numbers,
two
at
a time.
When
all
the information
is
read
in,
the average
temperature
and humidity
are
calculated (using the current day's
info
as well).
Line 2
1
then writes the current day's
information
at
the
end of the
list.
223