HP 15c Scientific 012-42,5, −−011- 42, 013-43,30,9

Section 10: The Index Register and Loop Control 113

Here is a revision of the original radioisotope decay program. This time, we will limit the program to three executions of the loop rather than setting a specific limit value. This example uses e with a

loop control number in R2 of
3.0	0	0	0	1.
initial loop counter				decrement value

test (goal) value

Make the following changes to the program (assuming it is in memory). A loop counter will be stored in R2 and a line number in the Index register.

Keystrokes	Display
¥	000-
t“013	013-43,30, 9

−−011- 42 31

´e2	012-42, 5, 2
tV	013- 22 25

Program mode.

The second of the two loop test condition lines.

Delete lines 013 and 012.

Add your loop counter function (counter stored in R2).

Go to given line number (015).

Now when the loop counter (stored in R2) has reached zero, it will skip line 013 and go on to 014, the ninstruction, thereby ending the program. If the loop counter has not yet decreased to zero, execution continues with line 013. This branches to line 015 and continues the program and the looping.

To run the program, put t1 (day 1) in R0, N0 (initial isotope batch) in R1 the loop counter in R2, and the line number for branching in the Index register.

Keystrokes	Display
¥		Run mode.
2 O0	2.00000	t1.
100 O1	100.0000	N0.
3.000001 O2	3.0000	Loop counter. (This
		instruction could also be
		programmed.)