HP-65
| Company type | Public |
|---|---|
| Industry | Electronics, Computer hardware |
| Founded | January 1, 1939 in Palo Alto, California, United States |
| Founder | Bill Hewlett, Dave Packard |
| Products | Calculators, Computers, Printers, Software |
| Website | www |
The HP-65 holds the distinction of being the first handheld calculator programmable via magnetic cards, launched by Hewlett-Packard in 1974 with a retail price of $795. It offered nine storage registers alongside capacity for 100 keystroke instructions, complemented by a magnetic card reader and writer for program storage and retrieval. The device operated using reverse Polish notation (RPN) and incorporated a four-level automatic operand stack, consistent with HP’s established calculator architecture.
Bill Hewlett mandated that the calculator be compact enough to fit inside a shirt pocket, which influenced its design featuring a tapered depth. The magnetic program cards were inserted at the thicker end beneath the LED display. Comprehensive manuals accompanied the HP-65, detailing algorithms applicable to fields such as differential equations, stock market forecasting, and statistical analysis.
Features
The HP-65 debuted HP’s signature "tall," trapezoidal keys that would become a hallmark of their calculators. Each key supported up to four functions accessible through prefix keys: a gold key or a blue key. For instance, pressing followed by accessed sine; pressing then calculated <math>1/x</math>. An inverse function was available via the gold prefix key, enabling operations like inverse sine (<math>\sin^{-1}</math>).
Available functions encompassed square root, reciprocal, trigonometric functions (sine, cosine, tangent and their inverses), exponentiation, logarithms, and factorial calculations. Among its pioneering features was base conversion capability, including octal (base 8). Additionally, it facilitated conversions between degrees/minutes/seconds (sexagesimal) and decimal degrees (sexadecimal), as well as transformations between polar and Cartesian coordinates.
Programming
The HP-65's programming memory could hold up to 100 six-bit instructions that included subroutine calls and conditional branching based on comparisons between the x and y registers. Certain multi-keystroke commands were compacted into single memory locations. Programs displayed key codes without line numbering.
Programs were stored on magnetically coated mylar cards (), which were fed through the reader by a motorized worm gear paired with a rubber roller at . The writable area occupied half the card’s width; although reversing the card to write a second program on the other half was feasible, it was generally discouraged due to potential wear. Positioned between the display and keyboard, the card’s printed top row (A–E) aligned with shortcut keys for quick program access.
Write protection for cards was achieved by clipping their top-left corner. HP also marketed collections of prerecorded, write-protected programs on cards tailored for scientific and engineering uses.
A known hardware limitation caused register R9 to be overwritten during certain trigonometric calculations or comparison operations; this behavior was documented and typical among early calculators constrained by limited memory.
Significant applications
During the 1975 Apollo-Soyuz Test Project, the HP-65 earned recognition as the first programmable handheld calculator utilized in outer space. Two units aboard the Apollo spacecraft computed thrust maneuver parameters essential for docking with Soyuz, cross-verifying results with those from the onboard Apollo Guidance Computer. Another onboard program calculated antenna pointing angles required for communication with the ATS-6 satellite.
In that same year at Los Alamos National Laboratory, Mitchell Feigenbaum employed an HP-65 to discover what is now known as the Feigenbaum constant (~4.6692), a fundamental value connected to period-doubling bifurcations within chaos theory.
Steve Wozniak
To help finance the early production of the Apple 1 computers, Steve Wozniak sold his Hewlett-Packard scientific calculator.
See also
External links
- The HP-65 featured at an unofficial Hewlett-Packard museum (MyCalcDB); includes an image of the magnetic card.
- 1975 HP Calculator Holiday Guide
- HP Virtual Museum: HP-65
- HP-65 page hosted by the unofficial Museum of HP Calculators
- An HP-65 calculator used during the ASTP space mission is part of the collection at the National Air and Space Museum.