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host: Randy Kindig
twitter: @floppydays
on iTunes and Stitcher Radio (
part of the Throwback Network (

May 14, 2016

Hello, all, and welcome to the next installment of the podcast that says “vintage electronics: I WANT IT”.  I’m Randy Kindig and I’m your host.  This episode is the first of a 2-parter on the Hewlett Packard HP-41 line of programmable calculators.  The HP-41 is a seminal example of programmable calculators from the late 70’s and into the 80’s and is still very desirable and sought after today.  I was lucky enough to find 2 gentlemen to co-host who are well-known among the active HP calculator community that exists today: Richard J. Nelson, who has written, edited, and published as much HP-41 material as anyone ever.  And Gene Wright who is on the HP Handheld Conference Committee and he was a TI fan before becoming “hooked” on the HP-41.  In this first part on the HP-41, I interview the co-hosts and then we cover the history of the calculator line in detail.  Next month, with the same co-hosts, we will cover Web sites, emulation, software, and much more.

To start out, as usual, I will cover my new vintage computer acquisitions, a little news, and some feedback.

I hope you enjoy this and please let me know what you think.

Links Mentioned in the Show:

New Acquisitions


Upcoming Shows


Interview and History



Garth Wilson
over a year ago

This discussion could have gone for ten hours and not finished talking about the 41's virtues. :)

I started with the TI-58c also, then the 59 and PC-100C printer and four extra modules. a few years later I got a 41cx for the I/O capability and used it for controlling instrumentation on the workbench (via the HP82169A HPIL-to-IEEE488 interface converter and FSI164A HPIL-to-RS232 interface converter, similar to the HP82164A but with two to eight channels instead of just one) and taking data, something the TI's could never do. I never looked back. I find RPN to be much better for that too. The AOS argument is that AOS lets you enter an equation the same way you see it on paper in front of you. However, in engineering work, you usually don't have an equation in front of you at all. You punch buttons as you think through the process that has to happen. The HP-48, 49, and 50 can't touch the 41 in I/O capability.

One of the major things I've used synthetic programming for was putting characters in strings that were not on the keyboard. I started with the byte grabber, but eventually got the ZENROM module which makes synthetics easy and natural (among other added capabilities).

The 41 could handle lots of programs in main memory at once. Extended memory was primarily for files.

The 41 allowed the user program in assembly language for maximum performance. I thought this (MCode) was what was coming in the story about printing out the calendar where the mini printer was used. I never got the tiny printer until 2015, but instead used the full-width Thinkjet printer and later my Epson dot-matrix impact printers. I also have the 80-column video interface for it.

Barely mentioned were the modern hardware modules that hold many older modules' worth of ROM memory size, like Diego Díaz's NoV64 (see with 48K of flash ROM and 64K of nonvolatile RAM, and the module images written very recently like Ángel Martin's 41z module (see which gives the 41 a true 4-level non-jury-rigged complex-number stack and over a hundred complex-number functions written in assembly (not user language) for maximum performance, or his Sandmath module (see which has gobs and gobs of math extensions. The manuals linked here show the incredible quality of his work. For coconut versions (but not halfnuts) there's also the 41CL transplant board which gives up to 50 times the normal speed, 230+ modules built in, 200+ KB of RAM, and retains port compatibility. The downside is poor battery life and that it needs a time module as that is not built in.

I still use my 41cx every day, for calculations, programs I commonly use, my alarm clock, etc, but rarely anymore for controlling equipment.