HP-41 calculator


There is such a thing as an Ultimate Calculator. It was made by Hewlett Packard and was named HP-41. I call it the UC-41. Along with the appropriate programs, it can do almost anything you want it to. This is of course subjective. Given enough brain washing, this will be true for you too 🙂

HP-41CL – the modern HP-41 calculator

HP-41CL is a brain transplanted HP-41 – a new motherboard in the original HP-41 body. With huge amount of flash memory, it contains all known HP-41 roms. And with 50x turbo speed, you have a massive, superfast swiss army-knife calculator. The HP-41CL board is created by Monte Dalrymple and sold through his company, Systemyde (http://www.systemyde.com/hp41/index.html).

I have created some solutions for the HP-41CL:


The most useful of my FOCAL programs below is now contained in one 4K ROM image – the ISENE.ROM. Here you will find the Ultimate Alarm Clock, the PDA programs NOTES and REM as well as CRYPT to encrypt and decrypt ascii files and other neat stuff for your HP-41. You can find the ISENE ROM on GitHub.

FOCAL programs

My most useful FOCAL programs (many are contained in the ISENE ROM)

  • DATA and STAT – The mother of all statistical analysis. Work with single or double points data sets, save and retrieve from extended memory, analyse and curve fit.
  • EVAL – A tool for making the best choices in life. The evaluation of cases against requirement specifications becomes a breeze.
  • ASTRO – user interface for the ASTRO2010 module (you will find it at hp41.org).
  • UAC – the HP-41 Ultimate Alarm Clock.
  • REM – the HP-41 REMembering (event manager, PDA).
  • NOTES – the HP-41 quick notes taker.
  • CRYPT – Encrypt/Decrypt XM ASCII files.
  • SCOPE – Calculate values for telescope and occulars
  • OUTSOURCING – Gain/loss, break-even and risk analysis if IT outsourcing
  • BOAT – Calculate properties of a sail boat.
  • D-W-D – A date-to-weeknumber-to-date converter.
  • SLA – Calculate guaranteed uptimes and allowed downtimes.
  • SUBN – Subnet mask to # of IP addresses.
  • W Lambert – Calculates the W Lambert function.
  • FILEMAN & FILE – File management system.
  • LIBXM & LIBHPX – Utilities to manage XM and HEPX files.

The FOCAL Factory

There were 26 different User Library Solutions published for the HP-41. These were collections of FOCAL programs for the calculator that could be manually keyed in or loaded via a barcode wand. With the advent of new accessories for the HP-41, these programs can now be easily converted to ROM images. This is the purpose of The FOCAL Factory project. To create brand new FOCAL modules, use Raymond Wiker’s barcode generator. All the User Library Solutions are available at hp41.org and at the HP-41CL wiki.

The NOV CHAP module

The NOV CHAP (on Github) is the main companion module for the physical NoV modules – an excellent memory expansion for the HP-41 by Diego Diaz. It contains special routines to get the most out of these Non-Volatile RAM modules as well as advanced HEPAX functions, advanced Extended Memory functions and some really neat utilities.

Other Tools

A set of useful tools for programming the HP-41:

  • HP-41 Coding Standard – a standard for HP-41 programs.
  • pc41 – facilitating serial/USB connection to an HP-41. With this program you can use your PC as a printer for an HP-41 (with Diego Diaz’ USB41 module) or transfer modules/data to/from an HP-41CL (with the serial interface)
  • lifasread – a Ruby script to read an ascii file stored in a lif-formated file (used by the HP-41 as file format on mass storage mediums. Tested on Linux. Run the script with the -h (or –help) option to see how it is used.
  • lifaswrite – a Ruby script to write a text file to a lif-formated file (the reverse of “lifasread”. Run the script with the -h (or –help) option to see how it is used.
  • HP-41 VIM syntax – gives you syntax highlighting in VIM when writing HP-41 programs (code on Github).
  • HP-41 VIM ftplugin – gives you tools to more easily write HP-41 programs in VIM (code on Github).


This page is an attempt at elevating the HP-41 to the ultimate calculator (the UC-41) by giving you good quality, useful software. Here is a list of further resources:

To let you in on a secret: HP rot13 is UC, and 41 rot13 is of course 41 in base 13 🙂 Hence, UC-41 = HP-41 rot13.

Here’s an article I wrote for HP: From little nerd to calculator enthusiast

And a video from when I gave a talk to HP about their calculators: