HP Calculator History - Calculator Families

by Wlodek Mier-Jedrzejowicz Ph.D.


The first few HP handheld calculators (HP-35, HP-80, HP-45) were all known simply by a model number; they all had the same size and shape. But then HP introduced the smaller handhelds - HP-21, HP-25 and so on. Soon after came the small desktop models with a built-in printer; theHP-91, the HP- 97, and later the HP-92. (They are "small" compared to HP's older desktop calculators.) It became convenient to give each "family" of calculators its own name.

The original family, or series, came to be known as the "Classic" series. The smaller models were called the series 20 or the "Woodstock" series. The small desktop printer models are the series 90 or "Topcat" series. The next series after that were the two handheld printer models, known as the "Sting" series, then came the series 30, or "Spice/Spike" series.

As you can see, some series are known by both a number and a name - one more series like this is the series 10 or "Voyager" series; the HP-10C, HP-11C, HP-12C, HP-15C and HP-16C. Model numbers are not always a good guide to which series a calculator belongs to, though, so in these "history" articles series are usually referred to by their name, not by a number.


I have tried to keep these "history" articles short, but some will be a bit longer - and this is one of them! It concerns those sometimes mysterious letters which we find after the model number of our HP handheld calculators and computers.

The early HP handheld calculators were all known simply by a model number; HP-35, HP-80, HP-45, HP-65, HP-90, HP-25 and so on. At first, the model number was not even put on the calculator - the early HP-35 and HP-80 calculators had only "Hewlett.Packard" on the label, later ones had "Hewlett.Packard 35" and so on.

The first HP calculator with a letter as well as a number was the HP-25C - this was a version of the HP-25 with "Continuous Memory", in other words the contents of memory were not lost when the calculator was turned off. The "C" obviously stood for "Continuous", in fact the HP-25C, its successor the HP-29C, and the HP-19C which was an HP-29C with a built-in printer, all had the words "Continuous Memory" written along the bottom of the keyboard.

The next model with a letter was the HP-97S - this was a special version of the HP-97, with a serial interface added on - you can guess what the S stood for!

The first series of HP calculators which had a letter after the model number were the so-called "Spice/Spike" series, or series 30. The first four did not have continuous memory and all had the letter E after their model numbers, for example HP-31E or HP-38E. The next four did have continuous memory, and had a C after the model numbers, for example the HP-33C and the HP-38C. I assume that the E was there to distinguish the models without continuous memory from those with, but if anyone knows what the E stood for, please let me know!

The next series of models were the HP-41C, the HP41CV, and then the HP-41CX. The "V" was a Roman five, to show that the HP-41CV had five times as many data registers as the HP-41C, and the "X" stood for "EXtended", because the HP-41CX was an HP-41CV with many extensions built in, especially Extended functions and Extended memory. This was the first time a model had two letters after the number. The HP-41CV was followed by the HP-11C and HP-12C, and soon after by the HP-15C, HP-16C and HP-10C.

The HP-10C was the first model which reused a model number - there had already been an HP-10 - a handheld with a printer built in - a simpler version of the HP-19C. People therefore began to put the letter A
after the names of models which had not had a letter, for example the HP-10 began to be called the HP-10A to distinguish it from the HP-10C (and later the HP-10B, the only case so far where the same number has been used for three different models.) Even the HP-35 came to be called the HP-35A.

The next handheld model after the HP-10C was the HP-75C handheld computer, but this was soon followed by the HP-71B computer, and the HP-75D, a version of the HP-75C with a port for a barcode reader. I have read reports that the HP-75C had originally been planned to be called the HP-75D, presumably the D was to make it one better than a C. Then the original HP-75 became the HP-75C, but they already had HP-75D labels, and presumably used them for the later version. Once again, I would welcome details!

The "B" of the HP-71B is to signify that it was a Basic language computer - but then so were the 75C and 75D! The HP-94 handheld computer followed this pattern, with three models called the HP-94D, HP-94E and HP-94F, the D, E and F showing how much memory the three models had (64k, 128k and 256k). The desktop series 80 computers had just a model number - HP-85, HP-81 and HP-83, but then an HP-85F was introduced; an HP-85 with extras, a bit like the HP-94F.

After the HP-94 series, HP went back to just a "C", with the HP-18C and the HP-28C, but these were replaced by the HP-19B and the HP-28S, where the "B" and "S" stood for Business and Scientific. After that, HP stuck to B and S for business models, such as the HP-10B, the HP-14B, the HP-20S, the HP42S and so on. (I have always thought that "Scientific" is a misnomer - these are really "Technical" calculators, since they are used by mathematicians and engineers, not just scientists.) There seem to be two exceptions - the HP-16C Computer Science calculator, where the C could stand for "Computer", and the HP21S Statistics / Maths calculator, where the S could stand for "Statistics". At this point, HP introduced a new twist - the HP-19BII, the HP-17BII, and then the HP-32SII, all three were improved versions of earlier models without a II in the name. (In all three cases the version II could work with both RPN and algebraic notation.)

The HP48SX went back to two letters after the name; they stand for Scientific EXpandable. The cut-down version of the HP48SX, without expansion ports, was therefore called the HP48S. Next in line came the HP95LX; the letters stand for Lotus EXpandable, since the 95LX has Lotus 1-2-3 built in. The later version, with 1 Megabyte of RAM memory, is called the HP95LX1MB - the most complicated name so far. (Those readers who are keen photographers might ponder the fact that camera manufacturers seem to go for the same business of adding ever more letters to new model names - though cameras are not the only other product identified by a number and a letter.)

Finally, as I write this, HP have just introduced the HP100LX - no change there - and the HP48G and HP48GX - these are new versions of the HP48S and HP48SX, redesigned to emphasise that they are Graphical calculators. Now, have you remembered all that? Then you'll be able to explain exactly what the name means if HP introduce an HP42XLII. Answers on a postcard, please!


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.