Note
that
in
this
system
of
incrementing
and testing
we do not send the
program
back to
line 8 as
was the
case
with FOR-NEXT.
What
would happen if we did?
Answer:
We
would keep re-initializing the value
of
N to
equal
1,
and would again form an
endless loop.
The
opposite of
incrementing
is decrementing.
Change the program so line 15
reads
15 N
=
N
-
1
. . . then
make other changes as
needed
to make the program work.
Answer: The changed lines read:
8
N
=
6
15 N
=
N
-
1
20 IF
N> 1 THEN 10
Putting
FOR-NEXT
to
work
It isn't very exciting
just seeing or doing the same thing
over and over,
so
there has
to be a
more noble purpose
for the FOR-NEXT loop. There
are
—
many
of them, and we will be
learning
new uses
for
a long, long time.
Let's suppose we want
to
print
out a
chart
showing
how the time
it takes to fly from Boston
to
San Diego varies with the speed at
which
we
fly.
Remember, the formula is D
=
R*T.
Let's print
out the flight time required
for each
speed
between
200
niph and
1000
mph,
in increments of
200
mph. The
program
might look
like
this:
10 REM
*
TIME
VS
RATE
FLIGHT
CHART
*
20
CLS
irs
!
.i;is«jH|||ii..
.
.
.
.:,
-.
To decrement
is
to make smaller.
49
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