HP Calculator History - The HP-95C

by Wlodek Mier-Jedrzejowicz Ph.D.


The HP-95C was developed at the same time as the HP-25C, the HP-67 and the HP-97, but was never sold to the public. This makes it extremely interesting to collectors and historians of HP calculators, so I include it in this set of HP history articles.

I believe that fewer than 20 exist; most readers will never have the chance to see one, so I have put a photograph of it on the cover of this issue of DATAFILE. It was apparently meant to be a printing version of the HP-25C, much as the HP-97 was a printing version of the HP-67.

Unlike the HP-97 it did not have exactly the same functions as its non-printing version - some functions were unusual, and I shall mention them below.

The HP-95C was probably not released because it would have competed with the HP-97 and would have required an extra production line, in addition to those set up for the HP-91 and HP-97. (This is not unusual; HP develop many new products which are then never sold - it is a concern to some HP engineers that many of the most interesting and time-consuming projects they work on cannot be mentioned in their CV.)

The units which were made were "pre-production" models, for testing at HP; one sign of this is that they do not have serial numbers stamped on them. Manuals and solution books for the HP-95C had already been printed before the decision not to manufacture it, so they exist in larger numbers than the calculators, but they too are rare - I do not have either myself (and would be happy to hear from anyone who has any spares or could make photocopies for me!)

If you study the photograph you will see keys marked A B C D below the display. These were used to create labels, to execute and go to programs with these labels, and even to clear programs marked by these labels. No such keys were available on the HP-91 and HP-97, though the top row of HP-67 and HP-97 keys could be used to execute program sections beginning with labels A, B, C, D and E (and a, b, c, d, e). The idea of such keys below the display and used for a special purpose may have developed from the top row of keys used on HP's financial calculators. On the HP-95C, though, these keys were used differently - a Label A, B, C or D started a new program whose steps were labelled A000, A001, A002 and so on, then B000, B001, and so on. (The same scheme is used on the HP-32S and HP32SII but I do not think it has been used on any other HP calculator.)

Numbered labels could be used separately in each program - label 1 in program A would be found by a GTO 1 step in program A, and label 1 in program B would be found by a GTO 1 in program B. This separated programs very neatly but meant that GTO (go to label) and GSB (go to a subroutine at a label) steps would not allow program A (for example) to use some program steps inside program B. To allow this, a separate JUMP instruction was provided on the HP-95C. (You might have noticed this in the photograph, below the GTO key next to the yellow and blue f and g keys in the bottom row.) This let you jump into a specified program to a chosen label in that program; for example the program step JPB1 meant "jump into the program B at label 1 in that program. I do not believe this has been used in any other HP calculator, and I even wonder whether some marketing people at HP considered it too confusing, which might have contributed to the decision not to sell the HP-95C.

One more feature of the HP-95C can be inferred from the "C" in its name - unlike the HP-91, the HP-92 or the HP-97, it had continuous memory. This would have been a very useful feature, but the card reader on the HP-97 probably won out as a preferred alternative. A fascinating calculator, and in a way it is a pity it was never sold to customers.


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.