A HP11em emulator screenshot

HP11em is a simple GTK calculator emulator for the HP-11C scientific calculator.

HP-11C History

The HP-11C is a mid-range RPN programmable scientific calculator, produced by Hewlett Packard from 1981 to 1989. It was part of the Voyager series, which included a basic scientific calculator (HP-10C), a business one (HP-12C), an advanced scientific one (HP-15C) and another one for computer programmers (HP-16C), too. The Voyager series calculators were very good, and the arithmetic inside them, had a very high quality, too; in fact, the business model, the HP-12C is still available now. Differently from most of the mid-range modern scientific calculators, the HP-11C and its variants implemented the Reverse Polish Notation (RPN), a mathematical notation in which the operator (e.g. +, -) follows the operands (“8 7 +” is equivalent to “8 + 7”). At first sight, the main difference between RPN calculators and the modern ones is the absence of the “=” key, but has been demonstrated that, with the RPN, you can resolve problems with less keystrokes. Because of its good hardware, the good materials and its quite modest price (from $80 to $150), the Voyager was one of the best-selling HP series.


HP11em is a simple C++ GTK emulator of the HP-11C calculator. HP11em aims at reproducing the same functionalities of the original calculator, but without the use of microcode or original ROMs. Everything is natively written in C++, and, at the moment, it uses standard C++ the math library, so the results may differ from the calculator ones. HP11em is being developed for Linux, but it should work under Cygwin too, although it hasn’t been tested yet. This emulator is still in heavy development, and is only about 50% completed, but it already offers basic functionalities.


  • GTK GUI with SVG skin;
  • Full RPN notation and stack operations;
  • Basic operations (+, -, ×, ÷, square root, power, fractional and integer part extraction);
  • Permutation and combination calculation;
  • Fixed and Scientific notation;
  • Full Storage Register implementation;
  • Keyboard and mouse-clicks input methods;
  • Error handling;
  • Trigonometric functions (sin, cos, tan…);
  • Degrees, Radians, Gradians conversion;

Features in development

  • Engineering notation (at the moment falls back to scientific notation);
  • Polar and rectangular conversion;
  • Programming mode;


At the moment HP11em is still incomplete, and there is no package for any distribution, but you can download the development version from GitHub.


The whole HP11em source code is distributed under the GNU GPLv3, the HP-11c image and the icon are distributed under CC-BY SA 4.0.