Making the most of your HP calculator 

HP15C 
Introduction Principal Features Emulators Availability Books Datafile Articles Links 
Following the success of the HP11C and the HP12C, HP launched two more Voyager models, the HP15C and the HP16C, ten months later, on the first of July, 1982. The HP15C was an advanced scientific programmable calculator  it took the features of the HP11C and added more. In particular, it provided the Solve and Integrate functions first introduced on the HP34C, but not built into the HP41 models.
The HP15C also had two completely new features for an HP handheld calculator. The first was a full fourlevel stack for RPN calculations on complex numbers. On earlier HP calculators, complex arithmetic was carried out by storing the real and imaginary parts of just two complex numbers on the 4level stack. On the HP15C a second stack which carried the imaginary parts of four complex numbers was added instead. This could be disabled to save memory, which was limited, especially since the other innovation was that matrix arithmetic commands were provided. Memory was also used temporarily for internal calculations by the Store and the Integrate commands  as well as for ordinary storage of programs and date. Indeed the HP15C included some quite clever memory control to deal with all this.
Yet another innovation was the provision of all possible conditional tests, comparing the contents of the X register with either the Y register or the number zero. An Advanced Functions Handbook for HP15C users explained the Solve and Integrate functions, and their possible pitfalls, in far more detail than the Owner's Handbook. This superb manual is out of print, but a scanned copy is available on the MoHPC DVD.
For many years HP were lobbied to bring back the HP15C. Their answer was that the HP32SII provides all the functions of the HP15C, and more, and that reintroducing an old calculator is as expensive as making a new one from scratch. That does not seem to be true of the HP15C, for the HP12C is still made, and uses the same components. Many people would like to replace their broken or lost HP15Cs, for the horizontal shape made it an ideal scientific calculator to use on a table next to one's work just as the HP12C's horizontal shape has made it so popular. The lack of alphabetic characters on the HP15C also means that it is accepted in exams where newer HP calculators are rejected because they could be used to store notes and formulae.
Finally, in September 2011, the calls for the HP15C to be reproduced were answered with the HP15C Limited Edition. Ten thousand units, using a newer CPU emulating the Saturn CPU and running the original ROM code, will be made. The only difference with the original being that some functions will run up to 100 times quicker.
More details of the HP15C can be found in the HP Calculator Museum.

HP15C 
HP15C Limited Edition 
HP make an official HP15C Emulator for iOS and sold through Apple's App Store.
HP15C IntroductionDiscontinuation: 19821989
HP15C Limited Edition IntroductionDiscontinuation: 2011
Due to their continued popularity secondhand HP15C books are often available from Amazon, ebay and other outlets.
HP15C Owner's Handbook by HP
Scan of the official HP User Guide for the HP15C is available on the MoHPC DVD.
HP15C Advanced Functions Handbook by HP
Fabulous manual continuing on from the Owner's Handbook and covering in considerable depth: using Solve effectively, working with Integrate, calculating in complex mode, using Matrix operations and accuracy of numerical calculations. Scan of the official HP Advanced Functions Handbook for the HP15C is available on the MoHPC DVD.
An Easy Course In Programming The HP11C and HP15C by Ted Wadman and Chris Coffin
Covers memory organisation, decisions and branching, indirect addressing, sample program development, trigonometry and vectors, flags, complex mode, Solve and Integrate, Matices and Statistical functions. Scan of this book is available on the MoHPC DVD.
Title  Author  Datafile 

Long Live the HP15C!  Valentin Albillo  V22N3P36 
HP15C Nthdegree Polynomial Fitting  Valentin Albillo  V22N4P9 
HP15C Normal Distribution  David Hodges  V5N8P13 
hp15c.org (Petition to bring back the HP15C)
mark.power@btinternet.com  Page last modified : 7th September 2011 