Radio Shack TRS-80 User Manual page 92

A
Voice
from
the Past
Remember how
in
a very early
chapter
we
checked the contents of each
Numeric Variable
address,
A
through Z,
by using the calculator
mode?
PRINT AjBtCjDjE;
etc.
We
can
do
the
same
thing
with our
two
new
Strings.
Type:
PRINT A$jB$
Why
does
it
display
TRS-80TRS—
80
?
The
first
TRS-80
is
simple
—
it
was
the
last
string
read
by
A$.
Same
thing
with B$.
Even
though
B$
was not used
in
solving
the
last
problem,
it
was
used in
the
earlier
example,
and
if
the
Computer was not turned off since then,
it
was
held in
memory.
This
fact is
more
than a laboratory
curiosity. It
can
get
you
into
"unexplainable"
programming problems
if
you're not aware of
it.
Oh,
by
the
way
. .
.
There
isn't
room
in
LEVEL
I
BASIC
to
do
everything, obviously,
and we
promised
earlier
that
you would
learn
how
to
answer
"YES"
and
"NO"
to the
Computer.
LEVEL
II
allows
you
to
do
it
in
a straight-forward
manner. Here
in
LEVEL
I
we
have
to
be sneakier.
Enter
this
program:
10 Y
=
1
20 N =
30
INPUT
"ARE
YOU OLD ENOUGH
TO
VOTE
(Y/N)"jA
40 IF
A
=
1
THEN
60
50
PRINT "DON'T FRET. THE
TIME WILL PASS FAST
ENOUGH."
59
END
60
PRINT "SWELL. DON'T FORGET TO
REGISTER!"
. . .
and
RUN.
90