JRPN 15C/16C - User Guide

This is the user guide for JRPN 15C and JRPN 16C calculator simulators. The main page is here, and the privacy policy is here.

Both simulators try to be a faithful implementation of the behavior of the original 1980s calculator. For the most part, the user guide for the original calculators applies. It can readily be found on the internet. Those guides aren't copied here because I'm unsure of copyright, and JRPN is a clean-room implementation.

This guide concentrates on some slight extensions, and various settings that are part of the application. Be aware that the calculation results in floating point modes can be expected to diverge somewhat from the original calculator. JRPN maintains floating-point numbers internally as a binary-coded decimal value with a ten digit mantissa, like the original. However, for many calculations, the value is converted into a standard 64 bit double, then the calculation is performed and the result is converted back. Other operations, like the 15C's integrate and solve functions, almost certainly use a different algorithm than the original. Addition, subtraction, multiplication and division are performed internally in decimal. The trip operations are special-cased at multiples of 90 degrees/100 gradians, to avoid surprising results. Generally speaking, Results are believed to be compatible, and in some cases slightly more accurate.

To illustrate this, consider 9^7.1. With a 12 digit mantissa, that comes to 5958292.46652. The real HP 15C gives 5958292.466, whereas JRPN gives the slightly more accurate result of 5958292.467. Neither is wrong - the real calculator is behaving as advertised, applying the even-odd rule to an 11 digit internal mantissa, rouding the 5 to an even number in the next digit over. JRPN's value is a 64 bit IEEE float, which has a more precise 53 bit binary mantissa that's used when rounding to a 10 digit decimal mantissa. A 53 bit binary mantissa is equivalent to between 15 and 16 decimal digits.

The ON Button

The original calculators let you access special functions by simultaneously pressing the ON butten and some other buttons. In the simulator, press the ON button once to access these functions; pressing it a second time quits the program. The other "hidden" features are swapping commas and decimal points ("Euro mode"), a calculator reset, and a calculator self-test.

Settings

Note that some settings are only available on mobile platforms (Andriod and IOS).

File Menu - Read

File Menu - Save

File Menu - Import/Export Program

These menu options let you import and export a human-readable program listing. It may be possible to use this to send and receive programs to/from other HP 15C/16C simulators. The format is based on the documentation from Torsten's HP 15C Simulator. I added this feature at Torsten's request.

Reset All

Restores the simulator to its default settings.

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Bill Foote