HP Calculator History - The HP-55

by Wlodek Mier-Jedrzejowicz Ph.D.


Introduced on January 1 1975, this was the sixth handheld electronic calculator sold by HP, and the fourth scientific model. Its code name was "Merlin" - something to do with wizardry, no doubt.

It was introduced a few days less than a year after the HP-65, as an alternative, and cheaper, programmable calculator. It did not have the card reader of the HP-65, had fewer program steps, and fewer mathematical functions than the HP-65 - no ABS function for example. Instead it had more data registers, a range of conversion functions - to and from metric measure, temperature conversions, and so on - and also statistics functions.

It also had, for the first time in an HP handheld calculator, a real built-in stopwatch - an "official" version of the stopwatch earlier found on some HP-45 models.

The HP-55 is an interesting step in the development of the HP handheld range, especially the stopwatch, but it seems to have generated less excitement among the HP fans than the HP-65. Nevertheless, it is eagerly sought after by collectors.


This article is part of the WMJARTS file. This file contains a series of articles written by Wlodek Mier-Jedrzejowicz and published in DATAFILE, the journal of the HPCC. The article was reproduced with permission of the author.

Copyright Wlodek Mier-Jedrzejowicz Ph.D.