General information about HP calculators.


Classification on input method.

The first series of the HP calculators used explicitly RPN. In 1988 HP introduced its first calculator that could also work with an algebraic input mode. This was the model HP 18C. Nowadays the input mode can be chosen for the high-end calculators. The low-end calculators can only be used in algebraic mode.

The RPN calculators can be recognized by the ENTER key i.s.o. the = key used for algebraic calculators. The RPN models from the Pioneer series have the text "RPN" printed on the housing.

Text on a HP-20S calculator. Additional RPN for the HP-32SII calculator.
HP20S Keys
HP32SII Keys
The HP-20S has an = key. The HP-32SII has a (wide) ENTER key.

For more information about RPN see here.


Classification: Scientific or Business

Already from the beginning HP build scientific and business calculators. For scientific calculators the accent is on transcendental functions, like exp, ln, log, sin, cos, tan, etc. For business calculators the accent is on build in functions to do TVM (Time value of money) calculations.

Scientific Business
The HP 20S scientific calculator. The HP 10B business calculator.
Keys scientific Keys Business
Keys to run transcendental functions. Keys to run TVM calculation.

A pdf document about the possibilities of business calculators can be downloaded here.


Classification on the type of display used: LED or LCD.

This is a technological evolution. The LED display made it possible to build a compact battery supplied pocket calculator. The LCD was introduced later to extend the battery life and to have more flexibility to build a dedicated display that can also show graphs. LED displays are not used anymore for calculators.

Display HP55 Display HP19B
LED display of the HP 55 LCD display of the HP 19B

For more information about HP LED displays, click here.
For more information about HP LCD displays, click here


Classification on programmability

Almost from the beginning HP build programmable calculators. These were often the high-end models of the series. Low power memory made it possible to add a continues memory that will keep the entered programs stored when the calculator is switched off. In all series we find programmable and not programmable models. Some calculators even have a (build in) magnetic card reader to read and store programs.