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Hewlett-Packard HP 9100A

HP 9100A

Hewlett-Packard HP 9100A

Distinctive features:
Programmable scientific calculator, using RPN (Reverse Polish Notation) with a 3-level stack.
Uses a crt (Cathode Ray Tube) to display the contents of the three registers.

Technical details:
Capabilities - Scientific functions, programmable with 16 storage registers and 196 program steps.

Display - 3 lines showing the contents of the three RPN registers, using cathode ray tube, see below.

Technology - DTL (Diode-Transistor Logic) implemented using discrete transistors.  Ferrite core memory.

Made in the USA. Launched in 1968.

The HP 9100A, with its large number of scientific functions and being programmable, was the most capable electronic desktop calculator of the time.  In the following year the even more capable HP 9100B was launched.

Within a few years, as technology advanced, Hewlett-Packard managed to develop hand-held models with similar functionality.  These were the HP-35 (with scientific functions) launched in 1972, and the HP-65 (with scientific functions and programmable) launched in 1974.

HP 9100A

Front view showing the numbers in the 3 register on the green crt display, and the labels to the right indicating that they are the contents of the 'z temporary', 'y accumulator', and 'x keyboard' registers.

HP 9100A keyboard

Close up of the keyboard showing scientific function keys and keys for programming.

There is an enormous amount of information about the HP-9100A and HP-9100B gathered by David Hicks at the Museum of HP Calculators at

Vintage Calculators

© Text & photographs copyright Nigel Tout   2000-2018  except where noted otherwise.