Radio Shack TRS-80 model III Owner's Manual page 149

TRS-80
MODEL
III
DISK
SYSTEM
50 IZ=IZ+1
G0 G0T
f
30
70
CLOSE
'
Conversion factors
have been
read-in
100 CLS: PRINT TAB(5)"*** English
to
Hetric Conuersions ***"
110
FOR ITEM'^B
TO 12-1
120
PRINT TAB(9) 5USING"
(##
)
1 %
«
5ITEMZ*
UNIT$(ITEMI)
130 NEXT
140
PRINT
@
704* "Which
conversion
(0-B)"
i
150
INPUT
CHOICER
1G0
INPUT
i!
Er,ter
English quantity"
5V
170
PRINT"The Metric equivalent
is" 0*FACTR(CH0ICE2)
180 INPUT"Press (ENTER)
to
continue"
5X
190
PRINT
@
704*
CHRtOl)
'clear
to end
of
frame
200 GOTO 140
Line
20 opens
the
file
for sequential input.
Input begins
at the
beginning of
the
file.
Line 30 checks
to see
that the end-of-file record hasn't
been
reached.
If
it
has,
control branches
from
the disk input
loop
to the part of
the
program
that
uses
'
the
newly
acquired
data.
Line 40 reads a value
into the string
array unit$(
),
and
a
number
into
the
single-precision array factr(
).
Note
that this
input
list
parallels the
print#
list
that created the data
file (see the section "Sequential Output:
An
Example").
This parallelism
is
not required, however.
We
could
just as successfully have
used:
40
INPUT*!* UNIT*<n,):
INPUT#1 ,FACTR
(
11
How
to
update a
file
Suppose you want
to
add more
entries into the
English-Metric conversion
file.
You
could simply
re-Open
the
file
with
mode
=
e and print#
the extra data.
Or,
you might want
to
leave
the old
file intact
and
output a
new
file:
1
Open
the
file
for sequential input
(Mode
=
i)
2.
Open
another
new
data
file
for sequential output (Mode
=
o)
3.
Input a
block of
data
and
update
the data as
necessary
4.
Output
the
data
to
the
new
file
5.
Repeat
steps 3 and 4
until
all
data has been
read, updated, and
output
to
the
new
file;
then go
to step 6
6.
Close both
files
148