Radio Shack TRS-80 Model 100 Basic Manual page 39

Line 40 contains an example of a valid expression containing arithmetic operators.
Here are some more:
a) A*B/C
b) Q
+
A4 - 6.5
c)
F
*
H8
+
J9
You should note that spaces or blanks are not significant in arithmetical expressions of
this type. For example, the expression in a) could have been written
A*B/C or A*B / C or
A
*
B/C
This allows you to space out the symbols so that they can be easily read.
However, it is important to note the order in which expressions such as c) are
evaluated.
In BASIC, mathematical operations always follow a hierarchical order. Exponentiaton
has the highest priority, multiplication and division are next, and finally. addition and
subtraction have the lowest.
Therefore, expression c) above, is interpreted as "the product of F times H8 is added
to J9." However, if you wanted to add H8 and J9 together before multiplying their
sum times F, you would have to place parentheses around H8
+
J9:
F
*
(H8
+
J9)
In this case the addition is performed first because the operation inside the parentheses
is carried out before the outside multiplication.
Multiplication and division have equal priority and will be performed from left to
right. The same is true of addition and subtraction. If you look at line 40 again
40 S = P
*
(1
+
R
*
T)
it should be clear that the parentheses are needed. However, inside the parentheses,
the expression:
1
+
R
*
T
is calculated correctly because the multiplication has higher priority than addition.
Experiment #2 Compound Interest
If you invest P dollars at an annual interest rate r, compounded k times a year, then
after t years, your investment will have grown to the amount S:
S
=
PO
+
r/k)tk
A program will be written to calculate the value of S, for the following values of the
other variables:
Pis $ 5,000
r is 12% per year
tis 5 years
k is 4 (i.e. interest is compounded 4 times a year.)
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