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 $395 (around $2,800 today), 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 button. This simple innovation allowed HP to assign multiple functions to a single physical key, effectively doubling the machine's capabilities without increasing its pocket-sized footprint. It introduced several features that became industry standards, including a dedicated register that could undo input errors, as well as specialized scientific and engineering notation modes. Perhaps its most famous quirk was a hidden stopwatch function; while HP didn't officially advertise it due to the lack of an internal crystal for perfect quartz accuracy, the hardware was already fully capable of keeping time, a testament to the over-engineered brilliance of 1970s Hewlett-Packard labs.

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