The following links are in addition to the model specific links included on the HP Plus RPN Calculator Photo Gallery and HP Plus RPN/RPL Graphing Calculator Photo Gallery pages. They are listed for the following topics:

HP Calculator Resources, HP Calculator Emulators/Simulators/Alternate-OS, HP Calculator Videos, HP and HP Related Calculator Books, HP Magazines and Newsletters and Notable HP Calculator related forum and article posts.

HP Calculator Resources:

The Museum of HP Calculators (MoHPC) - I consider this site to be the best resource for information about HP Calculators from the 1960's, 1970's and 1980's on the Internet. It has so many resources that it should be your first site to visit. The Museum's HP Forum section is very active and is a valuable resource for asking and answering questions. There are also software library sections available here and here as well as a HP Memories Forum. I can't praise this site enough!

hpcalc.org  - This site is the premier repository for additional documentation, tools, utilities and applications/programs related to HP graphing calculator models. Thank you Eric!

HP Calculator Literature - The companion site to hpcalc.org contains the largest collection of documentation, including manuals and books, for HP calculators on the Internet. It features filters for Language, Author, Source and Model as well as a text search filter. Thank you again Eric!

hpcalc.org YouTube channel - This YouTube channel from hpcalc.org has many videos of presentations from HHC (HP Handhelds User Community), HPCC (Handheld and Portable Computer Club) and Allschwil conferences.

SwissMicros - SwissMicros manufactures a number of RPN calculators that simulate or emulate several HP calculator models with enhancements.  Models include: DM42 (HP-42S), DM32 (HP-32SII), DM41X (HP-41CX), DM11L (HP-11C), DM12L (HP-12C), DM15L (HP-15C), DM16L (HP-16C) and others. The SwissMicros Forum section is also very active and is a valuable resource for asking and answering questions about their products. 

Free42 -  Free42 is a simulation of the HP-42S written by Thomas Okken and is available on Windows, Mac, Linux, IOS and Android. This software is also used as the base for the DM42 calculator made by SwissMicros (see the RPN Calculator Photo Gallery page for more information on the DM42). The enhancements over the HP-42S (including an unlimited stack size) are explained at the Free42 website under the section: Free42 Extensions to the HP-42S Instruction Set. Also see the related Plus42 below. Thank you Thomas!

Plus42 - An enhanced version of the Free42, the HP-42S simulator, also written by Thomas Okken. Plus42 builds on Free42 and adds: A Larger Display, with 8 rows and 22 columns (131x64 pixels) by default, which the user may resize at will; Algebraic Expressions modeled after those used on the HP-27S and HP-17B/19B; attached Units and unit conversions modeled after those used on the HP-48/49/50 series; Directories for more organized storage of programs and variables; TVM and amortization tables; and two-dimensional Plotting of functions, with ability to zoom and pan, and find integrals and roots from points in the plot. Also see the Plus42 Review - An Enhanced HP-42S Calculator Simulator CC video for a great review of Plus42.

HPDATAbase - This site has a lot of detailed information on all HP calculator models. It also has a Diagram of Hewlett-Packard Calculator Evolution (or HP Calculator family tree) chart as well as other links to information. Jose E Goncalve expanded on this to create his own Family Tree of HP Calculators in PDF form.

MyCalcDB - This site has a lot of information and photos on many manufactures models of handheld electronic calculators from the 1970's and 1980's. Its HP section has information and many photos of HP calculator models. 

R/S Key (rskey.org) - The R/S Key Programmable Calculator site has information on programmable calculators from many manufactures.  Its HP section has information and some photos of HP programmable calculator models.

Handheld and Portable Computer Club (HPCC)  - HPCC is a voluntary, independent body run by and for users of handheld and portable computers and calculators. Also see DATAFILE, the journal of the HPCC.

HP Handhelds User Community (HHC) - HHC hosts a yearly conference centered on HP calculators and related fields. Their intent is to document and record HP Handhelds User Community history.

PAHHC Handheld Electronics Page - Originally Philadelphia Area HP Handheld Club (PAHHC), this page contains a PPC Archive with over 74,000 pages of HP calculator and handheld devices related material available on a USB drive.

Valentin Albillo's HP Collection - A large collection of vintage calculator materials (HP, SHARP, etc.), old HP computers, HP Calculator Pictures,  HP Calculator Programs, HP Calculator Articles, HP Calculator Brochures and many other topics.

Kees van der Sanden's HP calculator Collection - Kees van der Sanden's site contains a great deal of information on various HP LED and LCD models.

Calculator Culture YouTube channel - This YouTube channel by Antony Kuzmicich has many reviews of HP and other manufacturers models of calculators.

HP41.org - The HP41.org site contains emulators (including V41) for various platforms. It contains a large HP-41 Library of documentation, tools, software and Application Pacs and information for the HP-41C/CV/CX calculators.

Eddie's Math and Calculator Blog - A blog is that is all about mathematics and calculators.

Guido's RPN calculators - A site about RPN calculators and particularly HP calculators.

HP Sales Literature - The Moondew site contains some HP Sales Literature and HP Journal PDF files as well a links to other HP related sites.

RPN/RPL Implementations - This document provides a list of implementations of RPN, RPL, and HP calculators for other systems. 

The Hewlett Packard Calculator Page (VCALC.net) - Sells a poster of HP calculator models (preview) and has links to HP calculator history.

HP Calculators by Date of Introduction - A list of all HP calculators, by date, that were introduced from 1968-2000.

The Calculator Store - This site has many resources for HP calculators including an online store that sells the current HP calculator models. This includes the HP-15C Collectors Edition enhanced pack which includes a HP-15C Collectors Edition calculator, HP-16C overlay and USB programming  cable. They also sell parts and a book for repairing HP-41C models.

A Guide to HP Handheld Calculators and Computers - An excellent book covering all HP handheld models. Written by Wlodek Mier-Jedrzejowicz, Ph.D.

Facebook Groups - Facebook has a number of discussion Groups that are electronic calculator related. Some of the Groups that are HP calculator oriented include;  HP Calculator Fan Club (private), Real Engineers Use HP Calculators (public), HP 48 G/GX Calculator Users (private), HP 48 S/SX Calculator Users (public) and HP-41 Scientific Calculator Fan Club (public). Other Groups that sometimes include HP calculators are; Programmable Calculators Hewlett Packard Texas Instruments Casio Sinclair (private), Vintage Calculators (private) and Vintage Calculator Collectors United! (private). The ones marked private require you to join in order to view or participate in discussions.  Not all of these Groups are active on a daily basis.

William Kahan Oral History Aug 2005 - A PDF transcript of a 2005 interview with William Kahan, Ph D. that covers many subjects that he worked on. As a consultant, Professor Kahan assisted Hewlett Packard with the mathematical functioning of its calculators, improving the accuracy, performance and feature-set of many HP models. In this YouTube video clip (from a 2016 interview), Professor Kahan discusses the Solve, Integrate and Matrix Operations work he did for the HP calculator division. Video of the full interview is available as part of Kahan’s ACM profile at: William Kahan, 1989 ACM Turing Award Recipient. There is also Mathematics Written in Sand (1983) in which Professor Kahan details the philosophy behind the HP-15C as well as examples of its more advanced features.

Calculator Forensics - Seeks to answer the questions of who originally designed a particular calculator's chip set, what features of a particular calculator have been borrowed from earlier designs, and how has calculator technology spread among the manufacturers. Results are from the evaluation of this equation in degrees mode: arcsin(arccos(arctan(tan(cos(sin(9)))))). On this site you will find links to tables of the forensic calculation result sorted either by calculator model or by calculation results. 

Thimet HP Calculator Photo Gallery - Has a very nice photo gallery of all handheld HP calculators with related information on each model. Note this site has information for other calculator manufactures as well.

Handheld Calculator History Website - A nice collection of photos for all HP handhelds plus others. An index of all models covered is available here.

The HP-35 - A great site that describes the development of the HP-35 calculator, the world's first shirt-pocket scientific calculator. "On January 4th, 1972, at a press conference at the St. Regis Hotel in New York, Hewlett finally announced the HP-35. If there was any doubt how well Hewlett’s expensive slide rule replacement was going to sell, it quickly evaporated."

Pocket Calculator: The Death of the Slide Rule - This is a another great site that has additional information on the development of the HP-35 calculator. This site also has stories including The HP-35 Story, From "Inside HP", and HP 35 Handheld Calculator, 

HP calculators and space exploration - Thuis site documents the use of HP calculators in relation to space exploration. Known examples are the  HP-35 (Skylab), HP-65 (Apollo-Soyuz Test Project), HP-41C (Space Shuttle), HP-42S (NASA), HP-48 (Space Shuttle) and definitely NOT the HP 35s, . The National Air and Space Museum also has additional information about HP calculators used during missions to space including the HP-35 (Skylab), HP-65 (Apollo-Soyuz Test Project) and HP-41C (Space Shuttle).

Current HP calculator models from Moravia - Moravia Consulting is the official HP licensee for HP Calculators and has taken over HP calculator development (see announcement). This site sells the current HP scientific, graphing and business calculator models including the HP Prime and HP-15C Collectors Edition. They also have the latest software downloads for the HP Prime. This includes the HP Prime Connectivity Kit and emulator software releases for Windows, Mac and Android. The HP Prime emulators for IOS are available on the IOS App Store.

HP Calculator Memory Sizes - This page lists the ROM and RAM memory size for most HP calculators. This site, created by Eric Smith, also has a lot of information about Hewlett-Packard Calculators, information about HP Calculator Chips the Nonpareil high-fidelity simulator for HP calculators and a lot of other internal information about HP calculators. A very interesting site.

Electronic Slide Rule Calculators (1972-1979) - This section of the International Slide Rule Museum (ISRM) is a great reference and timeline for the history of pocket scientific calculator models. It also includes information and advertisements on various scientific calculators, primarily from 1972-1979  but also includes models up to 1991. The main ISRM site has an amazing amount of information on Slide Rules, their history and related math artifacts. 

HP-35: The HP 9100A in Bill Hewlett's Pocket - The contributions made by David S. Cochran during his career at HP. Also see Tom Osborne’s Story in His Own Words.

Programmable Calculators: Attack of the Clones -  This website was created by Pierre Houbert. Its sole purpose is to allow you to have the pleasure of using programmable calculators. It has a large number of links to information and tools for various HP, TI and SwissMicros calculator models. This includes information, photos and/or tools on the following HP and SwissMicros models: HP-10C, HP-11C, HP-15C, WP 34S, HP-42S and HP-41CX. It also has a large number of calculator related links.

HP Collection - This site by Matthias Wehrli has a database of all HP calculators plus a lot of information on HP calculator hardware and software.

DATAMATH Calculator Museum - The definitive site for detailed information on on all Texas Instruments (TI) calculators ever made. Also has information for other calculator manufacturers, including some HP calculators.

Old HP and TI Calculators - This site, created by Gene Wright, is dedicated to the old Hewlett Packard and Texas Instruments calculators of days gone by. I've also posted articles dealing with HP and TI's including some programs you might like, such as Time Value of Money (TVM) and Games.

TI-Planet - This site contains cutting edge news on the latest calculator developments from many manufacturers including HP. TI. Casio, Sharp and more. This site has program download libraries, tools, gallery and a very nice forum and other sections. It also has a great Calculator Comparison Tool. Here is an example of a comparison of the top models from HP, TI and Casio.

RPN Tutorial - A very comprehensive tutorial and reference site for the Reverse Polish Notation (RPN) logic used on many HP calculators. 

Calculator Clique YouTube channel - This YouTube channel many videos of HP and other manufacturers models of calculators. Here is their playlist of HP related videos.

Virtual Museum of Calculators: Showroom - Has information about HP and and other manufacturers models of calculators.

HP Calculator Emulators/Simulators/Alternate-OS:

Note: While I have installed and used many of these emulators, I make no claims about their performance or the security of their websites. Use them at your own risk.

HP Page of Christoph Giesselink - A large collection of emulators for the Pioneer series calculators (HP10B, HP14B, HP17B, HP17BII, HP20S, HP21S, HP22S, HP27S, HP32S, HP32SII and HP42S) Clamshell series (HP-28C, HP-28S), HP-48/49/50, HP-41C/CV/CX and 71 LCD models. Many of these are also available on Android as EMU42 (HP10B, HP14B, HP17B, HP17BII, HP20S, HP21S, HP22S, HP27S, HP32S, HP32SII and HP42S), EMU28 (HP-28C, HP-28S), EMU48 (HP38, HP39, HP48, HP48, HP49, and HP50). The core of EMU48 has also been ported to IOS as iHP48 (HP38, HP39, HP48, HP48, HP49, and HP50). Also see the iHP48 website for information about iHP48 skins.

HP Emulator Archive - Contains Windows emulator/simulators for a number of HP LCD calculators including the HP Prime, HP 39gII, HP 39gs, HP 40gs, HP 50g, HP 10s, HP 35s, HP SmartCalc 300s, HP 300s+, HP-12C, HP-12C Platinum, HP 20b, HP 30b and HP 17bII+. 

HP Calculator Emulators for the PC (hpcalc.org) - Contains PC emulators and supporting files for a number of HP LCD calculators (145 files). 

Educalc.net Emulator for Windows - Contains Windows PC emulators for a number of HP LCD calculators including the HP-12C, HP Prime, HP 300s, HP 300s+, HP 35s, HP 20b, HP 30b, HP 10bII+, HP 40gs, HP 10s and HP 39gs. 

On-line HP LED Calculator Emulators (sydneysmith.com) - Contains HTML5 online emulators for a number of HP LED calculator models (HP-21, HP-25, HP-29, HP-65, HP-67).

HP Classic Calculator Emulator+ - Contains Windows PC emulator software for most HP LED calculator models (HP01, HP19C, HP21, HP22, HP25, HP25C, HP27, HP29C, HP31E, HP32E, HP33E, HP33C, HP34C, HP37E, HP38E, HP38C, HP35 red dot (2.02 bug), HP35, HP45, HP46, HP55,  HP65, HP67, HP70, HP80, HP91, HP92, HP95C, HP97, HP56i HP9100B). Also manufactures replacement CPU boards for a number of HP LED models along with a hardware emulator for various HP LED calculators.

Panamatik HP Calculator repair kits and emulators - Contains Windows PC emulator software for a number of HP LED calculator models. Also manufactures replacement CPU boards and repair kits for a number of HP LED calculators.

HP-15C Simulator - A HP-15C Simulator for Windows, Linux and macOS. Written by Torsten Manz. This site also has HP-15C program examples.

PockEmul - A platform that emulates a number of HP calculators and calculators/pocket computers from other manufactures. Available for Windows, macOS, IOS, Android or Online.

Olivier De Smet HP related projects -  Contains emulator/simulators and links for a number of HP LED/LCD calculators for Android.

The Calculator Drawer - Hosts on-line emulators for a number of HP (and other manufacturers) graphing calculator models including the HP-38G, HP-48GX, HP-48G+ and HP 49g. 

JRPN - Jovial Reverse Polish Notation Calculators - Hosts online simulators for the HP-15C and HP-16C models. Also has installations for Windows (Store), Mac, Android and IOS (private).

WRPN Calculator -  A Windows and online simulator for the HP-16C.

STENDEC Info Calculators and utilities - Has online Emulators of the entire "Voyager" HP calculator series including the HP-10C, HP-11C, HP-12C, HP-12C Platinum, HP-15C and HP-16C models. Also has links to IOS and Android "Touch RPN" app versions (free and paid). The free version of these apps have all Voyager models but shows ads in the corner of the app.

HP-41C Emulator (HP41.org) - The HP41.org site has a number of HP-41C/CV/CX emulators (including V41) for various platforms. It contains a large HP-41 Library of documentation, tools, software and Application Pacs.  Also see the V41 at HPCalc.org site for an additional download site. The latest version is also available on the HP Pages of Christoph Gießelink on his HP41C/CV/CX Emulator page.

Veniamin Ilmer - His site has a number of HP LED calculator online emulators including the HP-35, HP-45, HP-70 and HP-80. 

RPN83P - An RPN calculator app for the TI-83 Plus and TI-84 Plus calculators, inspired mostly by the HP-42S, with significant features from the HP-12C, and HP-16C. The latest version and version history can be found on the RPN83P Releases page. Here is the original announcement on the Museum of HP Calculators forum: RPN83P: RPN calculator for TI-83+ TI-84+ inspired by HP-42S.

HP Classic Calculators Emulator (paxer.net) - Hardware-based HP emulated calculator kits by Alex Garza. Alex designs and sells horizontal-format Voyager-style emulated calculators for the following HP calculators: HP-15C (PX-15C), HP-16C (PX-16C) and HP-41C (PX-41C). These are sold as easy to build kits with all through-hole parts or as fully assembled units. Visit Alex's main page for more information and reviews.

Free 15C RPN Scientific Calculator (Retro 15C) - A simulator for the HP-15C advanced scientific programmable calculator for Windows, Mac, Java and IOS (Retro 15C).

HP Prime software downloads from HP Moravia (including emulators) - Moravia is the official HP licensee for HP Calculators. This site has the latest HP Prime Connectivity Kit and emulator software releases for Windows, Mac and Android. The HP Prime emulators for IOS are available on the IOS App Store.

Nonpareil high-fidelity simulator for HP calculators - Nonpareil is a high-fidelity simulator for HP calculators. It currently supports many HP calculators models introduced between 1972 and 1982. See the main site for more information about HP calculators.

Vicinno - Makes IOS and Mac emulator apps for the HP-12C, HP 10bii+, HP11C and HP15C.

Moravia Consulting / Royal Consumer Products Inc- As the official license holder for HP calculators since 2022, Moravia/Royal sells and maintains the remaining physical HP brand calculators as well as IOS emulator apps for the HP-12C, HP-12C Platinum, HP-15C and HP Prime (Lite and Pro versions). For Android, thay have emulator apps for the HP-12C Platinum, and HP Prime (Lite and Pro versions). For Windows (and MS Store), they have an emulator/simulator for the HP Prime (32-bit and 64-bit versions). They also have a Mac version of the HP Prime. All of this Windows/Mac HP Prime software including Connectivity Kit software, teaching materials and videos are available at Moravia's HP Prime – Portal

newRPL - newRPL is a modern implementation of the RPL language started near the end of 2013 and is still under development. It is available as a replacement operating system on a number of HP calculator models (HP 50g, HP 48GII, HP 40gs, HP 39gs, HP Prime G1-1st gen only) as well as an app for Windows and Android. newRPL target downloads are available here. Key and bezel labels are available here.

DB48X for the DM42 - The DB48X project intends to rebuild and improve the user experience of the HP48 family of calculators, notably their "Reverse Polish Lisp" (RPL) language with its rich set of data types and built-in functions, and Lisp-level programming power. The DB48X project aims to develop an HP48-like calculator environment on the SwissMicros DM42 and DM32. There is also a simulator that is tested on macOS or Linux. Be sure to look at the ReadMe section for more information. This project is in its early development stages but is making rapid progress. The author, Christophe de Dinechin, has a YouTube site which has demos made during its development as well a a playlist of DB48X videos. More information can also be found on this SwissMicros forum post: Announcing DB48X, RPL for DM42, on this Museum of HP Calculators forum post: DB48X: HP48-like RPL implementation for DM42 and at the DB48X-on-DM42 Github repository. The version release notes can be found here. Overlay labels are available here (see photo of this label on a DM42 here). The latest video demo of V0.7.0 introduces many new features such as graphical rendering of equations, date and time operations, and a few other things.

HP Calculator Emulation/Simulation by Platform and Calculator Model: (Note this is a work in progress)

IOS: RPN-35 SD (HP-35), RPN-45 SD (HP-45), RPN-65 SD (HP-65), RPN-65 Pro (HP-65), RPN-70 HD (HP-70), RPN-55 SD (HP-55), GO-21 SciRPN (HP-21), RPN-25 CE (HP-25C), GO-25 SciRPN (HP-25C), Legendary 67 (HP-67), RPN-67 NP (HP-67), RPN-67 SD (HP-67), RPN-67 Pro (HP-67), RPN-97 Pro (HP-97), GO-29 SciRPN (HP-29C), RPN-32 CE (HP-32E), RPN-34 CE (HP-34C), Touch Fin RPN (HP-10C, HP-11C, HP-12C, HP-12C Platinum, HP-15C, HP-16C), 11C Scientific Calculator (HP-11C), RLM-11CX (HP-11C), 15C Pro Scientific Calculator (HP-15C), RLM-15CX (HP-15C), Free 15C RPN (HP-15C), HP 15C Calculator (HP-15C), HP41CV (HP-41CV), i41CX (HP-41CX), i41CX+ (HP-41CX), my41CX (HP-41CX), RPN 28x Calc (HP-28S), Halcyon Calc Lite (HP-28S), Halcyon Calc (HP-28S), Free42 (HP-42S), Plus42 (HP-42S+), iHP48 (HP38, HP39, HP48S/SX, HP48G/GX, HP49, and HP50), i48 (HP48GX), Emu50g (HP 50g), PockEmul (HP-11C, HP-12C, HP-15C, HP-16C, HP41C, HP-48GX), HP Prime (Lite and Pro versions)

Android: go25c (HP-25C), Touch RPN Calculator (HP-10C, HP-11C, HP-12C, HP-12C Platinum, HP-15C, HP-16C),  Free42 (HP-42S), Plus42 (HP-42S+), EMU42 (HP-10B, HP-14B, HP-17B, HP-17BII, HP-20S, HP-21S, HP-22S, HP-27S, HP-32S, HP-32SII and HP-42S), EMU28 (HP-28C, HP-28S), EMU48 (HP-38, HP-39, HP-48SX, HP-48GX, HP-49g, and HP 50), PockEmul (HP-11C, HP-12C, HP-15C, HP-16C, HP-41C, HP-48GX), HP-12C Platinum, and HP Prime (Lite and Pro versions), goXXX series (many HP models), JRPN 15C (HP-15C), JRPN 16C (HP-16C)

Windows: HP Classic Calculator Emulator+ (HP-01, HP-19C, HP-21, HP-22, HP-25, HP-25C, HP-27, HP-29C, HP-31E, HP-32E, HP-33E, HP-33C, HP-34C, HP-37E, HP-38E, HP-38C, HP-35 red dot (2.02 bug), HP-35, HP-45, HP-46, HP-55,  HP-65, HP-67, HP-70, HP-80, HP-91, HP-92, HP-95C, HP-97, HP-56i, HP9100B), Retro 15C (HP-15C), JRPN 15C (HP-15C), JRPN 16C (HP-16C), Free42 (HP-42S), Plus42 (HP-42S+),  HP Emulator Archive (HP Prime, HP 39gII, HP 39gs, HP 40gs, HP 50g, HP 10s, HP 35s, HP SmartCalc 300s, HP 300s+, HP-12C, HP-12C Platinum, HP 20b, HP 30b and HP 17bII+), Educalc.net Emulator for Windows (HP-12C, HP Prime, HP 300s, HP 300s+, HP 35s, HP 20b, HP 30b, HP 10bII+, HP 40gs, HP 10s and HP 39gs), PockEmul (HP-11C, HP-12C, HP-15C, HP-16C, HP-41C, HP-48GX),  HP Prime (32-bit and 64-bit versions), HP Page of Christoph Giesselink (HP10B, HP14B, HP17B, HP17BII, HP20S, HP21S, HP22S, HP27S, HP32S, HP32SII and HP42S; Clamshell series HP-28C, HP-28S; HP-48/49/50; HP-41C/CV/CX and HP-71B). 

Mac:  Free 15C RPN (HP-15C), Free42 (HP-42S), Plus42 (HP-42S+), PockEmul (HP-11C, HP-12C, HP-15C, HP-16C, HP41C, HP-48GX), 

Linux:  JRPN 15C (HP-15C), JRPN 16C (HP-16C), Free42 (HP-42S), Plus42 (HP-42S+), 

Web Browser: HP LED Calculator Emulators (HP-21, HP-25, HP-29, HP-65, HP-67), PockEmul (HP-11C, HP-12C, HP-15C, HP-16C, HP-41C, HP-48GX), The Calculator Drawer (many models), JRPN 15C (HP-15C), JRPN 16C (HP-16C), HP-35 RPN Calculator (HP-35), TI MultiView (TI-30X Pro, TI-36X Pro, TI-30XS, TI-34, TI-Collège MultiView), TI-55,  TI-57, NumWorks, TI-89, Desmos, TI-30Xa, TI-83 Plus, 

HP Calculator Videos:

The Evolution and History of HP Calculator - A video showing the evolution and history of HP calculators over the years (HP-35 to HP Prime).

The Joys of RPN - An introduction to the Reverse Polish Notation (RPN) entry system used with many HP calculators.

HP 35s A Brief Introduction to RPN - A brief introduction to Reverse Polish Notation (RPN).

hpcalc.org YouTube channel - As noted above, this YouTube channel from hpcalc.org has many videos of presentations from HHC (HP Handhelds User Community), HPCC (Handheld and Portable Computer Club) and Allschwil conferences.

The PPC ROM - HHC 2011, HP Handheld Conference, Sept. 24-25, 2011, San Diego, CA: Richard Nelson presents "The PPC ROM". Also see: HP 41 PPC ROM Production Run Total

Why Are Texas Instruments Calculators So Expensive? - While not HP specific, this 2016 video by LGR's Clint Basinger briefly describes how Texas Instruments achieved such a dominance in the graphing calculator educational market in the U.S. This also helps explain why HP is such a small player in this market, aside from a typically higher cost. Also refer to the related LGR video: LGR Tech Tales - The Pocket Calculator Wars. The Datamath page: Texas Instruments - Education Technology Overview also has some insights on this subject.

HHC 2011: The HP 12C: Why Has it Lasted 30 Years? - This presentation by HP's Dennis Harms at HHC 2011 helps explain why the HP-12C financial calculator has been in continuous production since 1981. He also mentions a lot of trivia for the HP 'Voyager' series calculators.

HPCC 2022: Voyager Single Chip Series 10 (SST) - This presentation by Charles McCord explains the project to reduce the circuitry of some of the HP "Voyager" models to a single chip in order to reduce manufacturing costs.

HP and HP Related Calculator Books:

A Guide to HP Handheld Calculators and Computers - By Wlodek Mier-Jedrzejowicz. This is a fantastic reference book and guide for HP calculators. Includes a complete history of HP calculators and information about collecting them. See a review of this book here. Wlodek also wrote a series of articles on HP Calculators which was published in DATAFILE, the journal of the HPCC.

HP Calculator Literature - The companion site to hpcalc.org contains the largest collection of online documentation, including manuals and books, for HP calculators on the Internet. 

All Known HP Calculator Literature - Includes all of the documents in the above link Plus documents that are know to have been produced but may not have been scanned yet (or are missing).

RCL20: People, Dreams and HP Calculators - RCL 20: People, Dreams & HP Calculators, edited by Wlodek Mier-Jedrzejowicz and Frank Wales, celebrates 20 years of HPCC, the Handheld and Portable Computer Club.

RCL40: Recollection, Reinvention and HP Calculators - RCL40 includes stories from some of the people at HP who designed the calculators we cherish, as well as from club members and people around the world. A follow-up to the above RCL20 book.

HP 48 Insights Part I: Principles and Programming (HP 48G/GX Edition) - This book, by William C. Wickes, helps explain the principles behind RPL in the HP-48 series and includes many examples. William C. Wickes was the project manager for the HP-28 and HP-48 calculator projects and is very good at explaining how RPL works and the reasoning behind the evolution of RPN to RPL.

HP 48 Insights Part II: Problem Solving Resources - This book, by William C. Wickes, is the second volume of the two-part Insights series for the HP 48 calculator (see Part I above). The principal subjects this book are numerical equation solving, plotting, symbolic algebra and calculus, the HP 48 time system, statistics and curve fitting, and physical unit management. 

HP 41/HP 48 Transitions - This book, by William C. Wickes, is intended to help you make the transition from the HP 41 to the HP 48, by reviewing their similarities and differences. 

Empire of the Sum: The Rise and Reign of the Pocket Calculator by Keith Houston - The hidden history of the pocket calculator—a device that ushered in modern mathematics, helped build the atomic bomb, and went with us to the moon—and the mathematicians, designers, and inventors who brought it to life. This includes information on the development of the HP-35 calculator. Available on Amazon and many other stores.

HP Magazines and Newsletters:

HP Journal Magazine online issues - The HP Journal was published from 1949 - 1998 and covers many of the HP product technical details and accomplishments from HP during that time. Several issues had articles on specific HP calculator models. Alternate link here. The following Jan 1983 HP Journal issue describes the low-power CMOSC process responsible for the Voyager series incredible battery life (decades!): CMOSC: Low-Power Technology for Personal Computer (Voyagers). Links to specific issues for calculator models shown in the  HP Plus RPN Calculator Photo Gallery and HP Plus RPN/RPL Graphing Calculator Photo Gallery are on those pages. The following are a number of indexes to HP Journal issues that have information on specific calculator models: Hewlett Packard Publications (index), Hewlett-Packard Journal articles regarding calculators, Spreadsheet of HP Journal Topics.

HP-65 Key Note - HP began publishing HP-65 Key Note in the Summer of 1974. HP-65 Key Note published information on the HP-65 programmable calculator including programming tips, programming libraries, Q & A, and other articles of interest to HP-65 users.

HP Key Notes Newsletter - HP's Corvallis Division began publishing Key Notes in January of 1977.  Key Notes had a worldwide circulation and replaced the US newsletter HP-65 Key Note. Key Notes was distributed to purchasers of Corvallis Division products and to others who subscribed separately to the newsletter. Key Notes published information on new HP calculator products, price changes, programming tips, programming libraries and other articles of interest to end users. Here is an alternate site for these. There was another HP European magazine in the same line as HP-65 Key Note called HP-65 Users' News. The first and second issue of this newsletter can be found here and here.

HP Solve Newsletter archive - On-line newsletter published by HP from 2008-2012 that covered HP calculating solutions, HP calculator history and Q&A.  Most of the issues are available in PDF form on The Calculator Store Newsletter page.   The June 2010 issue has a good article on Calculator Restorations by Geoff Quickfall.

HP Personal Calculator Digest - HP Personal Calculator Digest was an HP Magazine and Product Catalog published from 1976 to 1981 (8 magazines total). Aside from being a catalog of HP calculators, these often included customer stories of  HP calculators surviving all type of falls and disasters that befell them. These issues are available in PDF form on the HP Calculator Literature site provided in the link. Just type "HP Digest" in the filter box at the top. They are also available here.

HP Pocket Calculator News'n Notes - This was an internal HP newsletter publication for HP employees. It is mentioned on page 18 of the linked article Remembering The HP-35A by Richard J. Nelson. I am not aware of a PDF source of these internal newsletters.

Hewlett Packard Publications (index) - This page on the vcalc.net site features an index for calculator related editions to a number of the above publications. 

Notable HP Calculator related forum, article and video posts:

Note: Most of these posts and articles are from the Museum of HP Calculator HP Forum and SwissMicros Calculator Forum sites.

HP Memories Forum - This forum is intended to post memories related to HP calculators. Here is one posted by me on 2 July, 2000: It Still Works As Good As The Day I Bought It. I am surprised how little has changed in my calculator preferences since then!

Calculator Benchmark: Loops of addition -  This benchmark goes after ONLY goes after one thing: loops of addition. Presently in order from fastest to slowest.

Calculator Benchmark - Calculator Speed Benchmark using the N-Queens Problem for many calculator models.

Summation based benchmark for calculators - Speed test using summation math.

HP cases for HP calculators - Links to a 25 page PDF document created by Didier Lachieze that shows almost every case supplied with various models of HP calculators over the years.

HP-Prime: Documentation & Tutorials - Partial list of HP Prime documentation, tutorials, how-to guides and some overlooked/undocumented behaviors made available by HP and community contributors.

HP 35s Polar to Rectangular in Program mode - A discussion of simple program routines to convert from Polar to Rectangular. Also see the article R->P & P->R for the 35s.

Which calculators run RPL under the hood? - An interesting discussion of where the RPL language was used in creating certain HP models. It is interesting that the HP-42S was mostly written in assembly and that the HP-10b, HP-14B and HP-32 (at a minimum) were completely written in assembly (no RPL at all).

NEW: HP 15C Collectors Edition - Initial announcement of the HP-15C Collectors Edition on the Museum of HP Calculators forum site (long post). Also see a similar discussion in the SwissMicros forum.

Differences between the HP 15c CE and the original HP-15C - The HP 15C CE Owner's Handbook describes all the major differences between the HP 15c CE and the original HP-15C. However, there are some additional minor differences, which arise from the complexities of making firmware written 40 years ago communicate across hardware from today. 

What group made it? - An interesting discussion on some of the history of HP calculator manufacturing and the groups that designed them. Also see the following related items: HP Corvallis Site History, Goodbye to HP's ACO (Australian Calculator Operation), HP San Diego Site History, HP Calculators Timeline, A Little Bit of HP History, The HP-35 Calculator  

Wlodek Mier Jedrzejowicz Hewlett Packard Articles - This page contains a series of articles by Wlodek Mier-Jedrzejowicz. They were published in DATAFILE, the journal of the HPCC.

My crazy HP 15c repair - Also applies to other single-board Voyager models. With photos.

HP-42S Origins - This thread, while primarily about the DM32, briefly discusses the origins of the HP-42S as a replacement/successor for the HP-41C family. At some point HP decided to change it to a replacement/successor for the HP-15C. There is also some discussions of Plus42 advanced features and RPN vs RPL.

Speed Testing Hewlett Packard Calculators (video) - A video showing a speed comparison of various HP LCD models.

RE: HP15c CE POGO programming cable - This forum post by Bob Prosperi that has links to the entire process of using the USB programming cable with a HP-15C Collector's Edition calculator.

When did HP retire their two-shot molded keys? - This forum post explores the question of when did HP stop using double-shot molded keys on their calculators?

Keyboard Layout HP-41C and early models - Discussion on why did HP move the math operators from the left to the right side and also change the order of multiplication, addition, subtraction, and division? To go along with this question, Jake Schwartz has provided a A Survey Of HP Calculator Numeric Keypads and the keyboard layout of all HP calculators for reference.

List of HP 48SX & 48GX cards - A list of all known HP 48SX and 48GX RAM and ROM cards (over 120). Many of the 48 ROM cards are available here (ROM images which you can load in RAM cards).

Which HP calculator had "The New Accuracy" first? - This post discusses when (and in what model) HP switched to higher accuracy algorithms in its calculators. In the order of introduction date, these models had the "old" accuracy: HP-35, 80, 56, 66, 45, 65, 70, 55, 21, 25. "The new accuracy" (Dennis Harms' phrase) began with the HP-22 in September 1975. 

HP Calculator Adjusted Prices -  A spreadsheet with the  inflation adjusted prices for many HP calculators.

Interview with Dave Cochran about the HP 35 Calculator - This is a 2007 interview with Dave Cochran, who was one of the most instrumental people in getting the HP 35 to market.

HP-42S: New Facts - Interesting internal and often hidden information about the HP-42S. Also see the HP-42S debugger / memory scanner function near the bottom of this HP-42S Database page.

The HP35S - Origins and design goals of the HP 35s calculator (2007 to 2021) posted by Tim Wessman (Message #2).

HP 48/49/50 INOUT Program - Forum post with a HP-48/49/50 Utility program to convert an object to a string (and vice versa) for Import/Export to HP RPL emulators. Place the object to convert on level 1 of the stack and run 'INOUT'. If the object was a string then it'll convert it to an RPL object. If not, then it'll convert it to a string.

HP Prime or HP 50g - Forum post that discusses the merits of the HP 50g vs the HP Prime graphing calculators.

The power of the “red”: -  A Facebook Groups post by Geoff Quickfall that describes the repair process of a later generation HP-12C Voyager model using DeOxit-Red.

What is HP-41 half and full nut - This page describes some the differences between the HP-41 family "Full Nut" and later "Half Nut" versions. With pictures.

Free42/Plus42/DM42 Hat Plot Program - Draws/plots a 'hat' graph on the Free42/Plus42/DM42 platforms. See this post on "Possible to turn off pixel?" for more details.

HP 15C - broken key? - This forum post describes cleaning the contacts under a key that is not responding without disassembling the heat-staked keyboard.  This applies to the Voyager series calculators as well as a number of other models.

HP-42S Calculator: How to open case - This topic on the HP Support site describes how to open the HP-42S and other "Pioneer" models without removing the faceplate. This is typically done to fix keyboard problems by replacing the foam pad that presses the keyboard flex circuit to the main circuit board. From a post by Paul J. Brogger.  Also see the following photo of a temporary keyboard fix using nylon tie-wrap.

HP RPN Evolves -  Discusses the difference between the classical RPN Enter key behavior and Entry RPN or eRPN Enter key behavior used in HP RPL models. By Richard Nelson.

Enter vs Equals - A Practical problem-by-problem discussion of the logic system used in today's pocket-sized scientific calculators, by HP.

HP-48/49/50 'INOUT' Import/Export Program - The HP-48/49/50 'INOUT' RPL utility program is used to convert an object to a string (and vice versa) for Import/Export to other HP RPL emulators. Place the object to convert on level 1 of the stack and run 'INOUT'. If the object was a string then it'll convert it to an RPL object. If not, then it will convert it to a string. This post, Syncing iOS iHP48 and HP50g, shows step-by-step instructions on how to use this program. The source of this program is here and another example of using it is here. 

Left vs. right side arithmetic keys - Discusses the order of the arithmetic keys (-, +, x, ÷  ) on HP calculators and whether they are best located on the right or left side. The discussion of this subject has developed into something of a pseudo-religious debate. Other example forum posts include: Calculator Keyboard standards? and Keyboard Layout HP-41C and early models. Surveys have also been done on this subject, including pictures.

Very early HP25 - Discusses the radix point shape on Woodstock model LED displays (triangle vs square). Slide 11 of of a presentation given by Panamatik at HHC2015 shows photos of the difference. On the "Spice" models, the selection for a dot (U.S.) or a comma (Europe) for the radix separator is established by a jumper on the power supply PCB (see another Spice related radix point post here). The MoHPC summarizes the decimal point (dot) vs comma display solution used by HP in their Collector's Corner section.

Order of Operations and RPN - An exposition on notation in Order of Operations and RPN (Master of Arts in Teaching (MAT) Masters Exam) by Greg Vanderbeek, University of Nebraska - Lincoln, July 2007. Also see the related; Advanced Calculator Logic HP RPN/Algebraic - A Comparative Analysis HP document and HP Museum forum post..

Order of operations - what is 6÷2(1+2) ? - A discussion of how "implicit multiplication" is interpreted on various calculator platforms. The interpretation of 6÷2(1+2) on calculator models that support entering algebraic problems with "implicit multiplication" entry varies with no universal convention in place. Some manufactures have changed their interpretation of implicit multiplication for various calculator models over time (or for different markets) such as TI (TI KB article, example) and Casio (example 1, example 2). Some TI models, like the TI-89, will add an explicit multiplication symbol after an implied entry (example). Some of the more recent Casio models, such as the Classwiz series, will add parenthesis after an implied entry to make it clear how they interpret implied multiplication (example). The Casio fx-9750GIII has the option to interpret Implicit Multiplication either way. Its "Imp Multi" option will determine if the answer to problems such as 6/2(1+2) is either 1 or 9 (example). This contentious question has appeared in many forum posts and YouTube videos. These "discussions" often degenerate into arguments where many on each side of the argument express righteous indignation at those whom disagree with their interpretation on the answer to this math problem. Here are a few examples: What is the correct result?, Algebraic HP calculators, hierarchy of operations, Casio anomaly or gremlin or bug, PEMDAS, 8÷2(1+3), Casio fx-9750GIII Implicit Multiplication Option, What is this "order of operation" cult now with math?, How The Casio Classwiz Deals With A Popular Problem, Wikipedia Order of Operations, The Problem with PEMDAS: Why Calculators Disagree, Why Calculators Lie: Can You Solve This Simple Math Problem?, EEVblog 1479 - Is Your Calculator WRONG?, Casio FX-85 calculator comparisons between versions, 6÷2(1+2) = ? | Correct Answer Inside Finally Solved!!, TI KB: Solution 11773: Implied Multiplication Versus Explicit Multiplication on TI Graphing Calculators, The PEMDAS Paradox, Implied Multiplication 2: Is There a Standard?, The Implications of Being Implicit, Math breaking Facebook: 6 ÷ 2(1+2) = ?, What Is the Answer to That Stupid Math Problem on Facebook?, What is the correct answer?, 6/2(2+1) FaceBook post with 8.3K comments!