HP‑15C

Introduction

Following the success of the HP-11C and the HP-12C, HP launched two more Voyager models, the HP-15C and the HP-16C, ten months later, on the first of July, 1982. The HP-15C was an advanced scientific programmable calculator - it took the features of the HP-11C and added more. In particular, it provided the Solve and Integrate functions first introduced on the HP-34C, but not built into the HP-41 models.

The HP-15C also had two completely new features for an HP handheld calculator. The first was a full four-level 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 4-level stack. On the HP-15C 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 HP-15C 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 HP-15C 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 HP-15C. Their answer was that the HP32SII provides all the functions of the HP-15C, 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 HP-15C, for the HP-12C is still made, and uses the same components. Many people would like to replace their broken or lost HP-15Cs, for the horizontal shape made it an ideal scientific calculator to use on a table next to one's work just as the HP-12C's horizontal shape has made it so popular. The lack of alphabetic characters on the HP-15C 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 HP-15C to be reproduced were answered with the HP-15C 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 HP-15C can be found in the HP Calculator Museum.

Principal Features

Scientific programmable Complex number functions Matrix arithmetic Solve function Integrate function Statistical functions Linear regression Storage arithmetic RPN 4 level stack with parallel 4 level stack for complex numbers 448 bytes continuous memory Default 322 bytes program memory Default 21 addressable memory registers Single line 10 digit, 7 segment LCD display

HP-15C

HP-15C Limited Edition

Emulators

HP make an official HP-15C Emulator for iOS and sold through Apple's App Store.

Availability

HP-15C Introduction-Discontinuation: 1982-1989
HP-15C Limited Edition Introduction-Discontinuation: 2011

Books

Due to their continued popularity secondhand HP-15C books are often available from Amazon, ebay and other outlets.

HP-15C Owner's Handbook by HP

Scan of the official HP User Guide for the HP-15C is available on the MoHPC DVD.

HP-15C 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 HP-15C is available on the MoHPC DVD.

An Easy Course In Programming The HP-11C and HP-15C 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.

Datafile Articles

Links

HP-15C at The Museum of HP Calculators