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What is RPN?
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There are basically three ways to input data for calculation:

Algebraic (or Infix notation):
This is the most widely recognized way to write a mathematical expression. You input the number then the function: 1 + 2 =

Polish Notation (or Prefix Notation):
Invented by the Polish logician Jan Lukasiewicz in the 1920s, it was designed to avoid the use of parentheses in logical expressions. It is the least often used of the three. You input the function first then the number: + 1 enter 2 enter

Reverse Polish Notation (Postfix notation):
Reverse Polish Notation (Postfix notation): Same as Polish Notation only you put the function at the end. Proposed in the 1950s by Australian philosopher Charles L Hamblin, this is the way most people would actually calculate an expression in their head or on paper: 1 enter 2 enter +
Benefits:
  • RPN saves time and keystrokes. You avoid using and keeping track of parentheses while doing calculations. The process is similar to the way you learned math on paper.
  • You can see the intermediary results as you perform your computations rather than just the answer at the end. This is extremely helpful for learning the logic. Math teachers are using this feature to improve student understanding of mathematics.
  • An intermediate result allows the user to check the answer and correct errors more easily. It's easier to follow the stream of calculation. The user defines the priority of operators.
  • RPN is logical because the user first gives the number and then tells what to do with it.

Here's an example:
3 + 5
-------
7 + 6

Algebraic method:
Add 3+5=8. Write down the answer or store it in memory. Add 7+6=13. Now enter the 8 from the first answer and then divide it by entering the second answer to get x=0.62.

RPN method:
Press 3 then the ENTER key. Press 5 then the + key. Press 7, and then ENTER. Press 6 then the + key. Note that the answer to the second sum is displayed. Now here's the magic part. Touch the divide key and the calculator gives the answer, 0.62.

Algebraic:
13 strokes, not counting the effort to write down or memorize the first answer while you calculated the second answer.

RPN:
9 strokes, and no need to write anything down.
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Try RPN with our Computer Based Training!
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Solving problems with RPN

HP and RPN:
In 1968 HP introduced the first calculator to use RPN, the HP 9100A desktop calculator. Hewlett-Packard recognized that using RPN would be the most efficient method for the user as well as the processor. A loyal following of RPN users has developed ever since. After some initial learning, RPN becomes very logical and avoids extra symbols and parentheses which help to reduce keystrokes on complex expressions. As a matter of fact, most winners of time-based math competitions use HP calculators because of the speed of RPN. HP still features RPN as an option on their higher-end models below:

Financial:
Scientific:
Graphing:
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