Radio Shack TRS-80 User Manual page 88

THE PROGRAM.
This
may
seem
startling,
but do
the following
and you
will see:
1.
Move
the
DATA
line
from
line
10
to line
25
and
run.
No
change
in
the printout,
right?
2.
Move
the
DATA
line
from
line
25
to
line
10000.
Same
thing
—
no change
in the
printout.
Data
line(s)
can be placed
anywhere
in
the
program.
This fact leads different
programmers
to use different
styles.
Some
place
all
DATA
lines at
the beginning of a
program
so
they can be
read
first in
a
LIST and
found
quickly
so
data
may
be changed.
Others place
all
DATA
lines at a
program's end where they
are
out
of the
way and
there are
more
line
numbers
available
to keep adding
DATA
lines as the
need
arises. Still
others
scatter
the
DATA
lines
throughout
the program next
to
the
READ
lines
which
bring that
data into
use.
The
style
you
use
is
of
little
consequence
—
but consistency
is
comfortable.
The
Plot
Thickens
Since
you now know
all
about
FOR-NEXT
loops,
let
us see
what
happens
when
a
DATA
line is
placed
in
the
middle of
a loop. Erase the old
program
with
NEW
and
type
in this
program
:
10
DATA
1,2,3,4,5
20
FDR
N =
1
TO
5
30
READ
A
40 PRINT
As
50
NEXT
N
. .
.
then
RUN
.
That
DATA
line
started outside the loop.
Now
move
it
to
line
25 and
RUN. What
hap-
pened?
Nothing
different! It
is
important
to
note
this
fact or
we
wouldn't have gone to the trouble
to
do
it.
Note
that as
we
went through
the
N
loop 5 times,
we
read the
letter
A,
and
the
PRINT
statement only printed A, but
A's value
was
different
each time.
Its
value
was
the
same
as
the value
it
last
READ
in
the
DATA
line.
The
reason
—
each
piece of data in a
DATA
line
can only be read once each time the
program
is
run.
The
next time
a
READ
statement
requests a piece
of
data,
it
will
read the next
piece
of data
in
the
DATA
line, or,
if that line
is
all
used up, go on
to
the next
DATA
line
and
start
reading
it,
86