HP-65

HP-65
	HP-65 keyboard and display
Type	Programmable
Introduced	1974
Calculator
Entry mode	RPN key stroke
Display type	Red LED seven-segment display
Display size	15 digits (decimal point uses one digit), (±10±99)
CPU
Processor	proprietary
Programming
Programming language(s)	key codes
Memory register	8 (9) plus 4-level working stack
Program steps	100
Other
Power supply	Internal rechargeable battery or 115/230 V AC, 5 W
Weight	Calculator: 11 oz (310 g),; recharger: 5 oz (140 g)
Dimensions	Length: 6.0 inches (150 mm),; width: 3.2 inches (81 mm),; height: 0.7–1.4 inches (18–36 mm)

The HP-65 is the first magnetic card-programmable handheld calculator. Introduced by Hewlett-Packard in 1974 at an MSRP of $795^[1] (equivalent to $4,912 in 2023)^[2], it featured nine storage registers and room for 100 keystroke instructions. It also included a magnetic card reader/writer to save and load programs. Like all Hewlett-Packard calculators of the era and most since, the HP-65 used Reverse Polish Notation (RPN) and a four-level automatic operand stack.

Bill Hewlett's design requirement was that the calculator should fit in his shirt pocket. That is one reason for the tapered depth of the calculator. The magnetic program cards are fed in at the thick end of the calculator under the LED display. The documentation for the programs in the calculator is very complete, including algorithms for hundreds of applications, including the solutions of differential equations, stock price estimation, statistics, and so forth.

^ "HP Virtual Museum: Hewlett-Packard-65 programmable pocket calculator, 1974". Retrieved 2011-01-29.
^ 1634–1699: McCusker, J. J. (1997). How Much Is That in Real Money? A Historical Price Index for Use as a Deflator of Money Values in the Economy of the United States: Addenda et Corrigenda (PDF). American Antiquarian Society. 1700–1799: McCusker, J. J. (1992). How Much Is That in Real Money? A Historical Price Index for Use as a Deflator of Money Values in the Economy of the United States (PDF). American Antiquarian Society. 1800–present: Federal Reserve Bank of Minneapolis. "Consumer Price Index (estimate) 1800–". Retrieved 2024-02-29.

[1] "HP Virtual Museum: Hewlett-Packard-65 programmable pocket calculator, 1974". Retrieved 2011-01-29.

[inflation-US-2] 1634–1699: McCusker, J. J. (1997). How Much Is That in Real Money? A Historical Price Index for Use as a Deflator of Money Values in the Economy of the United States: Addenda et Corrigenda (PDF). American Antiquarian Society. 1700–1799: McCusker, J. J. (1992). How Much Is That in Real Money? A Historical Price Index for Use as a Deflator of Money Values in the Economy of the United States (PDF). American Antiquarian Society. 1800–present: Federal Reserve Bank of Minneapolis. "Consumer Price Index (estimate) 1800–". Retrieved 2024-02-29.

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