Hewlett Packard hp-9100

           <<<    >>>    ^^^

The first desktop calculator from Hewlett Packard. It is still built exclusively with discrete components (single diodes, transistors and resistors etc.).

The HP-9100 uses reversed polish notation (stack), like the Friden 132. An oscilloscope-tube serves as the display. Due to a lost patent dispute the display of the stack had to be modified: the result of a calculation is not shown at the end of the stack but in the second to last line. From a mathematical view the HP-9100 is rather powerful: It can compute higher mathematical functions and is programmable with up to 192 steps. The core memory was designed so that programm and data would be conserved when turning of the device.

Magnetic cards served as external storage devices. The printer was optional and could be replaced with a plotter.

Display

The display shows the three stack layers.
The result was not displayed on the 'top of stack' as one would say nowadays, but instead in the accumulator as known from the mechanical calculators.