Radio Shack TRS-80 User Manual page 27

Chapter 5
Using
(
)
and
the
Order of Operations
Parentheses
play an important
role in
computer programming,
just as in
ordinary
math.
They
are
used here
in
the
same
general way, but there are important
exceptions.
l.In
BASIC,
parentheses can enclose operations to be performed. Those
operations
which
are
within parentheses
are
performed before those not
in parentheses.
2.
Operations buried deepest within parentheses
(that
is,
parentheses
inside parentheses)
are
performed
first.
3.
When
there
is
a "tie"
as to
which
operations the
Computer
should perform
first
after
it
has
removed
all
parentheses,
it
works
its
way
along the
program
line
from
left to
right
doing the multiplication
and
division.
It
then
starts at
the
left again
and
per-
forms
the addition
and
subtraction.
NOTE:
INT.
RND
and
ABS
functions are
performed
before multiplication
and
division.
(We
haven't talked about
these yet,
but
just to
be complete
. . .
)
4.
A. problem
listed as
(X) (Y)
will
NOT
tell
the
Computer
to multiply.
X
*
Y
is
for
multiplication.
Example:
To
convert temperature
in
Fahrenheit
to Celsius (Centigrade), the following
relationship
is
used:
The
Fahrenheit temperature equals 32 degrees plus
nine-fifths
of the
Celsius
tempera-
ture.
Or,
maybe
you're
more
used
to
the simple formula
—
F° =
I-
X
C
+ 32
Assume we
have a Celsius temperature of
25°. Type
in this
program and
RUN
it.
10
REM
*
CELSIUS
TG
FAHRENHEIT CONVERSION *
20 C = 25
30 f =
(
9/5 )*C + 32
40 PRINT
C;
"DEGREES CELSIUS ="
;
F
;" DEGREES FAHRENHE
I
T
.
"
"FRIENDS."
If
you want
to
be
sure your problems
are calcu-
lated
cotreetJJr, iuse (
)
around
operations
you
: ;*ant:p£rf/0ri»e&:fEif$L
ItecaH th« old
memory
aid,
"l#y Dear Aunt y%-.
.Srtly'*?
In math you
are
supposed to do
Multipli-
cation
and
Division
first
(from
left
to righ
i)
,
then
comeback
for
Addition and
Subtraction
(left to
:-^\:;";r
--'
: .;^.
:SS?M^°
-
"
^
:
'-}\.
25