I began with the HP-35 - the first handheld electronic calculator from HP; before that, HP made only electronic calculators nearly as big as a desktop computer. From the 35 to the HP-91 any HP calculator with a model number of two digits is a handheld calculator.

The HP-91 was still a calculator, and much smaller than the big desktop models, but it can not really be called handheld. It is related to the handhelds, though, and worth studying with them, so instead of talking about "handheld" calculators, I shall use a different adjective: "small" calculators.

A further ambiguity arises when we begin to ask if a particular model is a programmable calculator or a handheld computer - we could call the HP-65 and HP-67 either, and we can certainly call the HP-41 both - but that means we can include them in a history of small calculators. The HP-01 is both a wristwatch and a calculator, so it too can be included. The HP-75C causes more trouble - it is a handheld computer, programmed in Basic, and the designers went to some trouble to distinguish it from a calculator - for instance its display does not show the current angle mode nor the status of any flags. People who want to make a point of studying or collecting only calculators would not include it in their list, but those interested in the development of HP handhelds overall do include it.

In any case, the HP-75C was closely related to HP handheld calculators, and led directly to the HP-71B which was a smaller handheld computer, but with a calculator mode.

On the basis of taking an interest in any handheld related to HP calculators, the HP-75D, HP-71B, all three HP-94 models, and even the HP-95LX and HP-100LX should be included too.

I shall even make a brief mention of the desktop series 80 models, which led to the HP-75C, and of the HP-81 and HP-46 - desktop versions of the HP-80 and the HP-45. In fact, I plan to include in these articles any handheld or easily portable calculator or computer with a model number less than or equal to 100.

The next size up, the HP-110 and HP Portable Plus, do not really fit. I am still not sure about the OmniBooks - they are bigger but are in many ways enlarged versions of the HP95LX. What would happen if HP were to introduce an HP100LX successor called the HP105LX or the HP200WP? I suppose I would include them in this series if they proved to be of interest to enough HPCC members!

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.