HP-25
| Industry | Electronics, Computer hardware |
|---|---|
| Founded | January 1, 1939 |
| Products | HP-25 programmable calculator |
The HP-25 was a portable programmable device designed for scientific and engineering use, manufactured by Hewlett-Packard from early 1975 until 1978. Priced at an initial retail cost of US$195, it served as a more affordable alternative to the HP-67, continuing the trend set by the HP-55 as a budget-friendly substitute for the HP-65.
To achieve cost savings, the HP-25 did not include the HP-67’s magnetic card reader, meaning all programming had to be entered exclusively through the keypad; consequently, any stored programs were erased when power was turned off. The subsequent 1976 release of the HP-25C introduced battery-backed CMOS memory, marketed as continuous memory, allowing programs to be retained even after shutdown.
Consistent with early Hewlett-Packard calculators, the HP-25 employed Reverse Polish Notation (RPN) utilizing a four-level stack consisting of registers x, y, z, and t. The majority of keys featured two alternate functions accessible via blue and yellow prefix keys. A sliding selector switch enabled users to switch between "run" and "program" modes. The calculator displayed numbers on a 10-digit red LED screen and was among the first to offer an "engineering" display option, which formatted exponents in multiples of three to correspond with standard SI prefixes such as kilo or micro.
Memory capacity allowed for up to 49 program steps through fully merged keycodes—combining prefix and function keys into single entries—to optimize storage efficiency. It provided eight dedicated storage registers alongside specialized scientific and statistical capabilities. The extensive owner's manual comprised 161 pages filled with examples covering mathematical, scientific, navigational, and financial programming applications.
Measuring roughly 25% smaller than the HP-65, the HP-25 retained the trapezoidal key design introduced with its predecessor. Its main competitors were Texas Instruments’ TI-58 and TI-57 models; although the TI-57 lacked several features found in the HP-25, it offered other benefits.
A notable drawback was the lack of subroutine functionality, which was present in competing models like the TI-58 and earlier SR-56. While its 49 merged program steps were approximately equivalent to the SR-56’s 100 unmerged steps, the TI-58’s substantially larger 480-step memory with support for subroutines and loops posed a significant challenge. In reaction to this competition, Hewlett-Packard launched the HP-29C/19C series incorporating enhancements such as subroutines and labels; meanwhile, Texas Instruments released a TI-58C featuring continuous memory.
An alternate variant equipped with an extra rear-facing display was manufactured by Educational Calculator Devices under the name EduCALC 25 GD.
See also
Notes
- The US$195 price in 1975 is approximately equivalent to US$770 in 2009.
External links
- The Museum of HP Calculators' article on the HP-25
- 1975 HP Calculator Christmas Guide
- HP-25 and HP-25C images on MyCalcDB (database of 1970s–1980s pocket calculators)
- HP-25 hardware details
- HP-25 Brochure from Hewlett-Packard
- Hewlett-Packard Journal, November 1975