Reverse Polish Notation (RPN)

The RPN Method

If you're a frequent calculator user, you owe it to yourself to investigate the advantages of RPN.

RPN stands for Reverse Polish Notation, the precursor to which, "Polish Notation", was developed in 1920 by Jan Łukasiewicz as a way to write mathematical expressions without using parentheses and brackets.

Hewlett-Packard®, realizing that Łukasiewicz's method was superior to standard algebraic expressions when using calculators and computers, adapted Polish Notation for its first hand-held scientific calculator, the HP-35, in 1972, thus giving birth to "Reverse Polish Notation", RPN.

Why use RPN?

  • RPN saves time and keystrokes. You never have to account for the parentheses while doing calculations. The process is similar to the way you learned maths on paper.
  • You can see the intermediary results as you perform your computations rather than just the answer at the end. This is an extremely helpful byproduct. Maths teachers are using this feature to improve student understanding of mathematics.
  • An intermediate result allows the user to check the results 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 numbers and then tells the calculator what to do with them.

Full RPN

RPN is also consistent in its usage. Most non-RPN scientific calculators are half RPN and half algebraic. For example, to perform addition, you need to enter 2+4 (algebraic), but to perform a sine calculation, you need first to enter the number and then to press the SIN button, which is an RPN method of entering the equation. Our RPN calculators do not suffer from this idiosyncrasy.

Learning RPN is Easy

Believe it or not, the process of using RPN is similar to the way you learned maths. If you think about it, you have to modify the way you learned maths in order to use an algebraic mode calculator.

Here's an example:


Or (3+5) / (7+6) = x

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. Press 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.

RPN Calculator Operation

RPN keeps a record of calculations by placing them in a stack. In the above example, when you pressed ENTER the second time, the answer to the first sum was pushed up in the stack awaiting the next action. After entering the second sum, pressing the divide key looked at the first sum and divided it by the second and popped the answer out of the stack. In other words, RPN performed the calculation in a logical order.

Learning how to use an RPN calculator usually takes just a few minutes and it can save much time and effort in the long run.

Why buy?

Some great reasons to buy DM calculators

DM calculators ...

  • Compact size - they are small enough to easily fit in any shirt pocket or purse or school backpack
  • Extended battery life - they have low power requirements, a single CR2032 will last for many years
  • Full-sized capabilities - they have all of the mathematical functions and programming power of full-sized HP calculators
  • Connectivity - they have a USB connection to save and load the complete state of the calculator including all programs and registers
  • Firmware update - they can be updated to the latest firmware release through the miniUSB connection
  • Nostalgia - they give you that feeling you had decades ago

Why DM calculators are better than cell phone apps

  • Always ready to use - no need to start an app.
  • Battery level - one single battery lasts for years!
  • No conflict with talking - ever tried to use a calculator while talking on the phone?
  • No cell phone radiation - safe to use for extended periods of time, even by children doing homework.
  • No interruption by notifications, emails, etc. keeps you focused.
  • SwissMicros physical calculator keys provide better positive feedback than a cellphone's haptic feedback.

Documentation, Firmware and Downloads

Open Source

SwissMicros strongly believes in the ability for the user to modify the software as per their needs. Please check our Github repositories for the source code and license information: