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:

Feature Value
Type: Scientific
Functions: 56
Keys: 42
Precision: 12
Logic: RPN
Display type: LED
Printer: Yes
Length: 202mm
Width: 228mm
Thickness: 64mm
Weight: 1134g
Power Source: 4x1.2V NiCd battery pack
Year introduced: 1976
YearDiscontinued: 1979

See other calculators by Hewlett-Packard