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Hewlett-Packard HP 91 (Topcat FELIX)

The Hewlett-Packard HP 91 is a scientific calculator with 12 digits precision and RPN (reverse polish notation) logic. It has 56 functions, 42 keys, and an LED (light-emitting diode) display, typical of calculators of this era. The power source is 4x1.2V NiCd battery pack.

Facts at a glance:

FeatureValue
TypeScientific
Functions56
Keys42
Precision12
LogicRPN
Display typeLED
PrinterYes
Length202mm
Width228mm
Thickness64mm
Weight1134g
Power Source4x1.2V NiCd battery pack
Year introduced1976
Year discontinued1979

Replacements:

If you have a Hewlett-Packard HP 91 that is no longer working, you can consider replacing the calculator with a modern equivalent. We suggest the following current model as a replacement:

See other calculators by Hewlett-Packard