HP Calculators by HP - Manual (Page 4)

3. The more math minded (student?) would recognize that the algebraic “problem” could be transposed to
be:
A( A + 3 )
1.3
and press 3, ENTER, 2.918273645, +, LASTX, Ч, 1.3, ч to calculate 13.2854938478.
(five keystrokes)
NOTE: The above “keystroke counts” or the method of counting is not clear. Because numbers may range
from a single digit to 10, 12, or more digits, and these digits would be the same for any machine, they are
not counted as keystrokes. To clarify this issue the following is offered.
Counting Keystrokes
RPN Tip #2 showed three RPN methods to solve a problem. Each successive method improved on the
method before it in terms of the “efficiency” of the solution. This efficiency is the number of calculator
operation keys that have to be pressed to solve the problem. The number of keystrokes is related to three
variables.
1. The RPN machine being used. Some RPN operations are shifted keys. R , for example, is shifted on
the HP35s and several of HP’s legacy RPN calculators. Shifted operations require two keystrokes.
2. The order of the operations and the utilization of the RPN automatic stack operations.
3. The mathematical form that is used to express the problem. If the problem is represented by an
algebraic expression, for example, the calculator solution is having the expression rearranged for a
more efficient calculator keyboard solution. Complete books have been written on the topic of
(optimum) “calculator solutions.”
Keystroke counting is the only objective measure of comparing the problem solving efficiency of one
machine to another or one solution method to another. In order to keep everything on a level playing field
the keystrokes required for entering the data (numbers) are not counted. This is illustrated using solution
number three of RPN Tip #2.
4. The more math minded (student?) would recognize that the algebraic “problem” could be easily
transposed to be:
A( A + 3 )
1.3
And press 3, ENTER, 2.918273645, +, LASTX, Ч, 1.3, ч to calculate
keystroke number
13.2854938478. (Total of five keystrokes).
Click here to learn more about
RPN .
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