Chain Calculations in RPN Mode
The automatic stack lift and stack drop make it possible to do chain calculations
without the necessity for keying in parentheses or storing intermediate results, as
are required on some other calculators. An intermediate result in the displayed
X-register is automatically copied into the Y-register when a number is keyed in
after a function key is pressed.
then pressed, that function is performed using the number keyed into the displayed
X-register and the intermediate result in the Y-register. The number then in the
Y-register, if remaining as an intermediate result from an earlier calculation, can
then be used with the intermediate result in the X-register for another calculation.
The diagram on page 233 illustrates how the automatic stack lift and stack drop
make chain calculations quick and error-free.
Virtually every chain calculation you are likely to encounter can be done using
only the four stack registers. However, to avoid having to store an intermediate
result in a storage register, you should begin every chain calculation at the
innermost number or pair of parentheses and then work outward — just as you
would if you were doing the calculation manually (that is, using pencil and paper).
For example, consider the calculation of
If this calculation were done from left to right — as were the (simpler) examples
under Chain Calculations on page 23 and page 25 — you would have to enter
five numbers into the calculator before doing the first operation possible (6 + 7).
But since the stack holds only four numbers, this calculation cannot be done
left-to-right. However, it can easily be done if you begin with the calculation in the
innermost pair of parentheses — again, (6 + 7).
Except for \ , O , _ , ^ . For more information, refer to Stack Lift, page 234.
Appendix A: RPN and the Stack
Therefore, when a two-number function key is
3 [4 + 5 (6 + 7)]
Intermediate result of (6+7).
Intermediate result of 5 (6+7).
Intermediate result of [4 + 5(6 +
Final result: 3 [4 + 5 (6 + 7)].