HP HP-15C

112 Section 10: The Index Register and Loop Control
Keystrokes
Display
l %
2.6458
Indirectly recalls contents of R
.2
.
´ X .2
2.6458
Check: same contents recalled by
directly addressing R
.2
.
Exchanging the X-Register
Keystrokes
Display
´ X V
12.3456
Exchanges contents of R
I
and X-
register.
l V
2.6458
Present contents of R
I
.
´ X%
0.0000
Exchanges contents of R
2
(which is
zero) with X.
l %
2.6458
´ X 2
2.6458
Check: directly address R
2
.
Storage Register Arithmetic
Keystrokes
Display
10 O + V
10.0000
Adds 10 to R
I
.
l V
12.6458
New contents of R
I
(= old + 10).
| $ O ÷
%
3.1416
Divides contents of R
.2
by .
l%
0.8422
New contents of R
.2
.
´ X.2
0.8422
Check: directly address R
.2
.
Example: Loop Control with e
Remember the program in section 8 which used a loop to calculate
radioactive decay? (Refer to page 93.) This program used a test condition (x
y?) to exit the loop when the calculated result passed the given limit (50).
As we've seen in this section, there's another way to control loop execution:
through a stored loop counter that is monitored by the I or e
function.