The Calculator Reference

(since April 22, 1997)

Last Update: January 31, 2022

CURTA Logo Hewlett Packard Logo Texas Instruments Logo

Posters for Sale
Other Great Posters
Newspaper Article
Frequently Asked Questions
Calculator Lists
HP-42S for the PC
Calc98 for the PC
Desktop Calculators
Keyboard Trivia
Electronic Displays
Calculator Numbers
Collectors Guides
Other Links

  The Curta Poster
Owners Registry
  Curta Registry
Curt Herzstark
  Curt Herzstark
  Curt Herzstark Interview
Curta Simulators
  Olaf Veenstra's
   Curta Stats
   Curta Variations
   Curta Manual
   Curta Date
   Curta: Dimensions & Timing
   Curta Disassembly
   Curta Patents
   Curta Tools
   Curta Lubrication
   Curta Repair Manuals
   Jack's Curta Repair (US)
   Hans' Curta Repair (Europe)
   Romano's Curta Repair (Italy)
  Curta: The Ayen Collection
Curta Pictures
  Curta: Oldest
  Curta Photos
  Curta: Ray Traced
Curta Demos
   Curta Demos
  Curta: Cut & Special
  Curta Prototypes
Curta Literature
  Curta Ads
  Curta Documents
  Curta E-mails
  Curta Literature
  Curta Backup Article
  Miniature Machine
  Curta: Rally
  Curta Articles
Curta Other
   Curta Pins
   Curta Museums & School
   Curta: Media
        - Books
        - Stamp
        - Audio
        - Video
Curta Links
  Curta Links

HPs Needed
HP Guide
Inside a HP-11
About a HP-95
HP Microcode
Made in USA
The HPs
HP Dates
HP Weights
30 Series Derivations
HP Publications
HP Articles
HP Codenames

TIs Needed
TI History
TI Accuracy
Later TIs
TI Games
TI Articles

Welcome to The Calculator Reference

Here you will find a wealth of data I have collected over the years on general calculators, HPs calculators, TIs calculators, and on my all time favorite mechanical calculator, the CURTA.

I recent years I have become an expert with the amazing Curta calculator. And it's mechanical not electronic! But it represents a final ultimate, state-of-the-art achievement in the mechanical world before the electronic calculator revolution took over and over night obsoleted all mechanical machines. Interestingly the Curta held on for many years because it was so popular among road rallyest and surveyors.

I do collect and study the manufacturing variations of the two models of the Curta calculator. My two exploded view Curta posters are wildly popular around the world and have been featured in museum displays and displayed in the halls and offices of NASA.

My favorite electronic calculators are HPs but I don't plan on this page even starting to compete with "The Museum"! HP introduced the 1st scientific calculator (HP-35) then introduced the first business calculator (HP-80). To this day the all time most popular calculator is the HP-12 Business calculator. I still like to gripe about why HP abandoned the scientific calculator (HP-11, HP-15) in this wonderfully convenient format.

My Calculators of HP poster is another popular poster I created. It even serves as a reference in the support offices of HP.

Finally my newest posters of the History of the Telephone and Modern US Currency are the latest additions to my poster line up. Yes, a slight deviation from calculators but I always remembered touring the phone company as a child and receiving a poster that showed the history of the telephone. My Telephone poster is an updated tribute to this now 45 year old poster.

I also find the art and design that is in the US currency amazing. My Modern US Currency poster arranges all the major version of all the denominations. Showing both the front and back side of each bill so you can study and appreciate the art and changes that have happened to the US currency over the past 100 years or so. I also hope this poster can serve as a teaching aid for school teachers.

Look around, enjoy yourself, and marvel over how calculators (both steel and silicon) have changed our world.

-Rick Furr-


The Calculator Reference is proud to now offer SIX fabulous posters. The wildly popular Curta Calculator poster, the Curta German poster, the Calculators of HP poster (version 2), The Telephone Story, Modern US Currency, and Morse Code. Click on any picture to learn more.... -Rick-


Electronic Components poster


Kilo color1
color2 color3

(Click On A Poster)

Here are links to some of my favorite posters that other people have created. Click on a poster to learn more.


NRV Article
(Click Here)

Here's an article that was in the newspaper about my calculator collection. In the photo the newspaper photographer wanted me to be surrounded by some of my calculators. So we arranged a ping-pong table in the background and a card table in the foreground. Then we placed two wide boards on either side so there was a small hole in the center. Next we placed all the calculators we could fit on the tables and then I squoze into the center for the photo shoot.

It made for a cool shot but sadly the photographer would not give me the original.


Hewlett Packard 35s Hewlett Packard 33c Hewlett Packard 12cp

Learn more about the HP-12C Platinum, HP-32C, and the HP-33CS on the HP Reference page.

Frequently Asked Questions

Here are places that will help you with your most frequently asked questions concerning repairs, spare parts, and manuals.


Calculator Collectors, Data, Classifieds, Mail Distribution Lists, and Forums

The title says it all, this is a collection of Collector Lists, Data Lists, Classified Lists, Mail Distribution Lists, and Forums. 

If you are wanting to buy or sell a calculator then reference the Classified Lists, Mail Distribution Lists, and Forums section.

Free 42

Free 42 (HP-42S for your PC)

Download Free-42 (Free) Free42 is a re-implementation of the HP-42S Scientific Programmable Calculator and HP-82240 Printer.

It is a complete rewrite, not using any HP code. It does not require an HP-42S ROM image.

Even though it contains significant enhancements compared to the original calculator, Free42 remains fully compatible with the HP-42S, both in its user interface and in its ability to run programs written for the HP-42S.

Free42 is an Open Source project. The executables and source code are released under the terms of the GNU General Public License, version 2.


Calc 98

Download Calc98 (Free) Over a million PC users have already downloaded Calc98, our popular free engineering, scientific and financial calculator for Windows. The calculator includes functions for statistics, use of different number bases (binary, octal, hexadecimal and base-n), metric units conversions and physical properties and constants. It has financial functions including investment, loan and mortgage calculations. It also calculates time functions and has a stopwatch feature and RPN (Reverse Polish Notation). It runs on Microsoft Windows (WindowsNT, Windows95/98/ME, Windows2000/XP) and WindowsCE (Pocket PC).


Desktop Calculators

Here is some information on some very interesting and some very common desktops that I own.


Keyboard Trivia

Why is the telephone touch-tone key pad arranged differently from the calculator key pad?

Why is the keypad arrangement different for a telephone and a calculator?

Doing the Numbers - Why Calculator and Phone Number Layouts Differ


Electronic Displays

This is my article on Electronic Displays that appeared in the Winter-Spring 1997 International Calculator Collector.


The Calculating Machines Numbers

If you've ever been to Erez Kaplan's -- Calculating Machines page (now available at the Wayback Machine--thanks Angelica Landicho) then you will have noticed his cool rolling numbers image. Click this title if you would like to see all of the different numbers used in this cool image. Go to his page if you want to see the real thing.


The Collector's Guide to Pocket Calculators

"This is another must have for ANY calculator collector." - Rick Furr.

"The Collector's Guide to Pocket Calculators" by Guy Ball and Bruce Flamm is back from the printer and now being shipped. This 200+ page, softcover book contains a detailed listing of over 1500 known portable/pocket calculators from the early 1970's (the "Golden Age of Pocket Calculators"), as well as historical information from the 1960's and 1970's.

The book features over 470 photographs of various models from over 220 manufacturers around the world (including calculators from lesser-known companies in England, Switzerland, Netherlands, Spain, Germany, Bulgaria, and Russia).

"The Collector's Guide to Pocket Calculators" also includes a comprehensive value guide to help you gauge rarity and desirability of the various models -- especially as they relate to each other.

The book can be purchased for $23.95 plus $4 for USA first class mailing ($6 to Canada and Mexico, $8 for airmail to other countries). California residents please add $1.86 state sales tax.

Mail to:
Wilson/Barnett Publishing

P.O. Box 345
Tustin, CA 92781-0345

For additional information, contact Guy Ball

Other Links



Mechanical Info






For Sale

The Calculator Reference by Rick Furr (rfurr@vcalc.net)
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