102 Section 9: Branching and Looping
If you want to terminate the execution of a loop, you can include an o or m
instruction (described below) or an t instruction within the loop. You can
also terminate execution by pressing any key while the loop is being executed.
Example: The following program automatically amortizes the payments on a
home mortgage without requiring you to press f! for each payment. It will
amortize one month’s payments each time or one year’s payments each time the
loop is executed, depending on whether the number 1 or 12 is in the display
when you start running the program. Before running the program, we’ll
“initialize” it by storing the required data in the financial registers – just as we
would do if we were amortizing a single payment manually. We’ll run the
program for a $50,000 mortgage at 12¾% for 30 years, and we’ll key 1 into the
display just before running it in order to amortize monthly payments. For the
first two “passes” through the loop we’ll execute the program one line at a time,
using Ê, so that we can see the looping occurring; then we’ll use t to
execute the entire loop a third time before terminating execution.
Keystrokes Display
fs
000,
Sets calculator to Program mode.
fCLEARÎ
000,
Clears program memory.
?0
001, 44 0
Stores the number from the
display into register R
0
. This
number will be the number of
payments to be amortized.
:0
002, 45 0
Recalls the number of payments
to be amortized. This program
line is the one to which program
execution will later branch. It is
included because after the first
time the loop is executed, the
number in the “display”
a
is
replaced by the result of !.
f!
003, 42 11
Amortizes payment(s).
gu
004, 43 31
Pauses to display amount of
payment(s) applied to interest.
~
005, 34
Brings amount of payment(s)
applied to principal into
“display.”
a
gu
006, 43 31
Pauses to display amount of
payment(s) applied to principal.
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