Radio Shack TRS-80 Model 100 Basic Manual page 40

Enter the command NEW to clear the previous program from memory. Then type the
following program:
10
P
= 5000
20
R
=
.12
30 T
= 5
40
K
=
4
50
S
= P
*
( 1 + R / K)
~ (T
*
K)
80
PRINT "TOTAL IS
$" ;
S
After the program is entered, execute it by entering the RUN command or pressing
~.
The output frum this program will be:
TOTAL IS
$
9030.5561733465
Ok
•
Even though the total is supposed to represent dollars and cents, the computer has
displayed the number with 14 significant digits, including 10 to the right of the
decimal place (because this is the precision of numeric variables in Model 100
BASIC). You will see later how to display numbers in dollars and cents format.
The expression in line 50
P
*
(l
+
R / K)'(T
*
K)
uses addition, multiplication and exponentiation operators. The exponentiation operator
has the highest priority and will be performed before multiplication or division and of
course before addition and subtraction. Because of this priority, it was necessary to
place parentheses around the exponent
T*K
Otherwise, the computer would have calculated
P
*
(l
+
R / K)
A
T
and then multiplied this expression by K.
Experiment #3 Compound Interest with
Keyboard Input
If you wanted to run the compound interest program with different values for the
variables, you would have to retype the appropriate lines in the program. Obviously
that isn't very practical, specially if you just wanted to figure the interest for several
values.
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