Hewlett Packard HP-45 Electronic Calculator (1973-1976)

Hewlett Packard 45 (HP-45)

🥇First Scientific Calculator with a "Shift" Key 

The Hewlett-Packard HP-45, introduced in May 1973 for a hefty $395 (roughly $2,800 in 2026 dollars), was the high-performance successor to the legendary HP-35 and the world’s first scientific calculator to feature a "Shift" key—the iconic gold Prefix key. This innovation allowed HP to map multiple functions to a single physical button, effectively doubling the machine's capabilities without increasing its pocket-sized footprint. It introduced several features that became industry standards, including fixed-point, scientific, and engineering notation modes, as well as a dedicated register for "Last X" to recover from input errors. Perhaps its most famous "Easter egg" was a hidden stopwatch function; while HP didn't officially support it due to the lack of a crystal oscillator for perfect quartz accuracy, the hardware was already capable of timing, a testament to the over-engineered brilliance of 1970s Hewlett-Packard labs. With its rugged build and tactile "clicky" keys, the HP-45 solidified Reverse Polish Notation (RPN) as the preferred logic for an entire generation of engineers and astronauts.

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