One more letter in the display - Comments on V20N5

Jordi Hidalgo, #1046

What a wonderful issue V20N5 was! Definitely, thatís what the HP-12C deserved - I donít know any other electronic device on the market for as long as 20 years.

As to Juergen Rodenkirchenís question in V20N5p4, I think he will enjoy the database that Craig Finseth maintains (

It has detailed descriptions of all HP calculators. Thatís the first resource to be consulted, every time I can add a new calculator to my collection. It would be great to read a review on Craigís project in a future Datafile, especially a few words about those mysterious HP-12BII, HP-56 and HP-66.

I have another answer, though somewhat delayed. In V19N6p34 José Chinchilla asked who wrote the HP-41C manual. According to an HP Journal article (March 1980, V31N3) the author was Ray Tanner.

More on hex digits

Iíve observed that the undocumented keyboard combination ON+n is equivalent to ON+PMT on the HP-12C. This operation is deserving of thorough study, since I suspect that what I described in my previous article (V20N5p26) is just the tip of the iceberg. Tony Duellís remark about the abnormality of that 0.1 (V20N5p24) made me think of potential dangers when using non-naturalised numbers. For example, this sequence: 3 ON+PMT 1/x seems to hang the machine - ON+n or ON+PMT must be pressed to bring it back to life. Sometimes, misleading results are obtained: 1001 ON+PMT g-LN returns 8.19 after 10 seconds.

How do other Voyagers behave? I have no access to them at the moment; hopefully, someone will explore further. With reference to earlier calcs, hereís an excerpt of an article in the November 1975 issue of the HP Journal, describing the way the HP-21 family displayed messages:

"An accessory ROM composed of sixteen words of seven bits each. The words 0 to 9 are used to generate the digits. One word, 15, is a blank. Three of the remaining words generate the letters E, r, and o [...] to spell ĎErrorí [...] One remaining word generates the letter F. This is used by the HP-25 to spell ĎOFí when a storage register overflows."

Let me cite a few cases where non-naturalised numbers are used.

Our Editor, Bruce Horrocks, kindly communicated to me that I have been declared the winner of Bill Butlerís challenge. Well, except for last-minute surprises... Many thanks for the prize, Bill! It has been a thought-provoking challenge, with interesting results. Itíll be funny to explain why my renewal only cost 7 cents!

All the best wishes you can imagine.
Page last modified : 6th June 2002