Radio Shack TRS-80 User Manual page 151

Back
to
the Subject
Look
at line
60
very
carefully.
You
have
seen every
symbol
there before
—
but
is
there
something
different
about
how
they
are arranged?
Hmmmm?
Ah
yes
—
the parentheses.
They
are
the
tip-off.
There has been
(until
now) no
reason
at all
to enclose
something
like
A=l
in parentheses.
When
you come
across a pair
of parentheses enclosing an =
sign, a
),
a
(
(or
a combination of these),
you know
logical
math
is
being
used.
(Whew
—
that's
simple
enough!) Having used the * (which
you
know
means
AND) now
it
will
all
make
sense.
EXERCISE
24-1
:
Using the above
program
as a
model, and
the
"OR
logic" seen
in
Figure
2,
write a
program which
will
report Bessie's status as
determined by
the position of Gates
X,
Y
and
Z.
Teacher's Pet
Here
is
a
simple
program which
uses
>instead of the equals
sign in a logical
test.
The student
passes
if
he
or
she has
a final grade over
60
OR
a
midterm
grade over
70
AND
a
homework
grade over 75, Enter the program,
RUN
it
a few
times,
and
see
how
efficiently the logical
OR
and
logical
AND
tests
work
in
the
same program
line
(40).
10
INPUT
"FINAL GRADE"
;F
20
INPUT
"MIDTERM GRADE
" ;M
30
INPUT
"
HOMEWORK GRADE
" ;H
40 IF
(F>60)
+
((M>70) *
CH>75)) THEN 70
50
PRINT "FAILED"
60
END
70
PRINT
"PASSED"
Does
this give
you some
idea
of the
power
and
convenience of
logical
math? The
actual
grade
numbers
could, of course,
be
set at
any
level.
149