Hewlett Packard HP 35s Scientific Calculator

The HP 35s replaces the HP 33 s model as the top of the range model in non-graphing scientific calculators from HP. It's case and keyboard are retro-styled in tribute to the HP 35 model from 1972 which was the world's first mass-produced pocket scientific calculator.

  It features a 2 line x 14 character display  with additional annunciators, RPN or algebraic input, 31K of user memory, full programmability with direct and indirect registers, 42 inbuilt physical constants, unit conversions and a simultaneous equation solver in addition to the usual transcendental functions. The calculator works internally to 15 digit precision. Many features are carried over from the HP 33s model (which itself emulates the now defunct HP 32 SII model) with a number of changes to address that model's known usability issues. The main differences are in the keyboard which has a more conventional layout with a more legible colour scheme and a clearer dot matrix display with wider spacing between characters and a larger radix. There is however no direct operation in complex number mode with rectangular<>polar conversions now being a function of the selected display mode. There is also a fraction display mode which allows entry and display of results in either decimal or fraction format and time calculations are also possible.