This calculator was designed to work equally well using either the
Simple, Precedence, or RPN input methods. The
simple input method is most familiar and allows entering calculations
like
to get the desired result of 5. A more
complex example is 2 + 3 x 5 = 17, which can be entered two ways,
or
. The first sequence
required the use of parentheses to instruct the calculator to
multiply before adding the numbers (since most calculators don't know
this algebraic convention). The second sequence avoided the use of
parentheses by re-ordering the operations to generate the correct
result of 17.
The Precedence input method is an improvement over the simple input
method in that the multiplication and division operations are
automatically performed before the addition and subtraction
operations. For example, the previous calculation can be entered
without the parentheses as
to obtain the result of 17.
The benefits of the RPN, or Reverse Polish Notation, input method over the simple input method become apparent when calculating complex expressions. Fewer mistakes are made since fewer keystrokes are required and the intermediate results are always displayed (providing feedback during the calculation, not just at the end). The order of the calculation is changed to avoid using parentheses, as in the previous example, so that the expression is evaluated from the inside working outward.
The general rule of thumb for RPN calculators is to enter the
values, then the operation. Thus,
becomes
. The
key is used to separate
numbers when entering more than one in succession. In the example, 2
+ 3 x 5 = 17, the RPN method could be evaluated using either
, or
. Looking at these two sequences, we can isolate
which always shows the result of 15. The two
sequences then become
15
and 15
which are more easily recognizable as 17.
Keystroke savings are realized in calculations that cannot be
reordered to a form without parentheses. Let's look at the example 2
x 4 + 3 x 5 = 23. Using the simple input method we could calculate
this expression as
, or without using
parentheses,
. Using
RPN, the sequence becomes
. Saving one keystroke is not that significant,
but this is still a relatively simple calculation. One important
distinction between the two input methods is demonstrated by the sub
expression 2 x 4. Using the simple input method, this sometimes needs
to be enclosed in parentheses (when not located at the beginning of
the expression) and sometimes not. Using RPN, this sub expression is
always entered the same way. This consistency also contributes to
fewer mistakes being made.
One final point is that most of the calculations require the
operand to be entered before the operation is executed. For example,
calculating the square root of 2 is always entered
and the inverse of 10 is
entered
. The RPN input method just extends this
methodology to all of the calculator's functions.
The input method can be chosen in the Preferences dialog. If you'd like to learn more about how an RPN calculator works, check out the RPN Tutorial chapter of this guide. With all of the input methods, all of the calculator functions are available allowing you to work the way you're most comfortable.