Tandy TRS-80 Owner Manual & Programming Manual page 35

NETHINGATA1
memory
by typing NEW
(ENTER)
.
Then
type
and
RUN
this
input
program:
100
OPEN "I".
#li "CHECKS/DAT"
110
INPUT
#1
.
A*
120
PRINT At
130
CLOSE #1
This
is
actually just the reverse
of
the output
program
. .
Line 100 again
OPENs
communication
to
buffer
#1.
This time
communication
is
OPEN
for
"F
—
input.
The Computer
goes
to
the
disk's
directory
to
find
where
to
start
inputting the
file
named
"CHECKS/DAT"
In
line
110,
the
Computer
INPUTs
the
first
data
item
from
the disk
file
named
"CHECKS/DAT"
and
labels
it
A$. Line 120
PRINTs
A$.
Finally, line
130
CLOSEs
communication
to
buffer
#1. In
doing
this,
the
Computer
inputs
any
data
remaining
in the buffer.
JVoie:
You can compare an input
program
to
the
LOAD
command.
An
input
program
inputs
a
dat<
file:
LOAD
inputs a
program
file.
:
©V
ONE
CHECK
AT
A
TIME
At
this point,
we've used
an
output
program and
an
input
program.
Let's
combine
them
into
one
program. Type:
10
OPEN
"0"
i
*1
i
"CHECKS/DAT"
20 WRITE *1
.
"DR.
HORN"
30 CLOSE #1
100
OPEN
"I"
t
«li
"CHECKS/DAT"
110
INPUT *1
,
A$
120
PRINT A*
130
CLOSE
*1
Now
add
these lines
and
RUN
the
program:
25
WRITE
*1
i
"SAFEWAY"
115
INPUT
«1
t
B$
120
PRINT
A$
t
B*
Lines 10-30 output
two checks
into
your disk
file:
" D R
HORNt"
"SAFEWAY"
Lines 100-130 input them. Try
to
input
more
than
two
checks.
Change
line
115
and
120:
115
PRINT A$
120
GOTO
110
and
RUN
the
program
. .
.
The Computer
prints:
?IE ERROR
IN
110
The Computer
is
notifying
you
that
you
are
asking
it
to
input
more checks than are
in
the
file.
Technically,
the
IE
error
means
you've
attempted
to
Input past the
End
of
the
File.
This
error
makes
things
difficult
when
you want
to
input
all
the data,
but
you
don't
know how
much
is
in
the
file.
We
showed you
this
error so
you would
appreciate
our
new word
—
EOF.
Type:
105
IF
EOF(l)
120 GOTO 105
1
THEN
130
and
RUN
. . .
EOF
checks
to
see
if
you've reached
the
end
of buffer
#1
{the
number
in
parentheses).
If
you
have,
EOF(l)
equals
a
-
1.
If
you
haven't,
EOF
equals
0.
27