The HP-25 was a hand-held programmable

scientific Science is a systematic endeavor that builds and organizes knowledge in the form of testable explanations and predictions about the universe. Science may be as old as the human species, and some of the earliest archeological evidence for ...

/engineering calculator made by

Hewlett-Packard The Hewlett-Packard Company, commonly shortened to Hewlett-Packard ( ) or HP, was an American multinational information technology company headquartered in Palo Alto, California. HP developed and provided a wide variety of hardware components ...

between early January 1975 and 1978. The HP-25 was introduced as a cheaper ( US$195 MSRP) alternative to the ground-breaking

HP-65 The HP-65 is the first magnetic card-programmable handheld calculator. Introduced by Hewlett-Packard in 1974 at an MSRP of $795 (), it featured nine storage registers and room for 100 keystroke instructions. It also included a magnetic card re ...

. To reduce cost, the HP-25 omitted the HP-65's magnetic card reader, so it could only be programmed using the keyboard. After switching off, the program was lost and had to be typed in again. The model HP-25C, introduced in 1976, addressed that shortcoming through the first use of battery-backed

CMOS Complementary metal–oxide–semiconductor (CMOS, pronounced "sea-moss", ) is a type of metal–oxide–semiconductor field-effect transistor (MOSFET) fabrication process that uses complementary and symmetrical pairs of p-type and n-type MOSF ...

memory in a calculator, termed ''

continuous memory The term continuous memory was coined by Hewlett-Packard (HP) to describe a unique feature of certain HP calculators whereby the calculator could internally sustain most, or in later models - all, of the contents of user memory (via battery-backed C ...

'' by HP. Like all early HP calculators, the 25 used the

Reverse Polish Notation Reverse Polish notation (RPN), also known as reverse Łukasiewicz notation, Polish postfix notation or simply postfix notation, is a mathematical notation in which operators ''follow'' their operands, in contrast to Polish notation (PN), in wh ...

(RPN) for entering calculations, working on a four-level

stack Stack may refer to: Places * Stack Island, an island game reserve in Bass Strait, south-eastern Australia, in Tasmania’s Hunter Island Group * Blue Stack Mountains, in Co. Donegal, Ireland People * Stack (surname) (including a list of people ...

(x,y,z,t). Nearly all buttons had two alternative functions, accessed by a blue and yellow prefix key. A small sliding switch was used to change between "run" and "program" mode. The HP-25 used a 10-digit red LED display and was the first calculator to introduce the "engineering" display option, a denormalized mantissa/exponent format where the exponent is always a multiple of 3 to match the common

SI prefixes A metric prefix is a unit prefix that precedes a basic unit of measure to indicate a multiple or submultiple of the unit. All metric prefixes used today are decadic. Each prefix has a unique symbol that is prepended to any unit symbol. The pre ...

, e.g. mega, kilo, milli, micro, nano. The HP-25 had memory space for up to 49 program steps. It was the first HP calculator which used fully merged keycodes (storing prefix key and function key together in one program location) to save memory space. Additionally there were eight storage registers and specialized scientific and statistical functions. The owner's manual came with 161 pages in four colors and contained many mathematical, scientific, navigational and financial programming examples. The HP-25 was about 25% smaller than the HP-65. It used the same trapezoid profiled keys introduced with the HP-65. The HP-25 was regarded as a competitor to the

TI-58 The TI-59 is an early programmable calculator, that was manufactured by Texas Instruments from 1977. It is the successor to the TI SR-52, quadrupling the number of "program steps" of storage, and adding "ROM Program Modules" (an insertable ROM ...

and TI-58C calculators offered by Texas Instruments. Looking strictly at the functionality and capacity, the more equal competitor would be the

TI-57 The TI-57 was a programmable calculator made by Texas Instruments between 1977 and 1982. There were three machines by this name made by TI, the first was the TI-57 with LED display released in September 1977 along the more powerful TI-58 and ...

. It lacked a few of the HP-25's functions, but had some other advantages. One notable deficiency of the HP-25/25C was the lack of a subroutine capability, at a time when the TI-58 and even the earlier SR-56 had subroutines. Although 49

fully merged keycodes Fully () is a municipality in the district of Martigny in the canton of Valais in Switzerland. History Fully is first mentioned in the 11th Century as ''Fuliacum''. Geography Fully has an area, , of . Of this area, 30.5% is used for agricultur ...

were roughly equivalent to the unmerged 100 steps of the SR-56; by the time the TI-58 arrived with 480 steps, subroutines, DSZ loops, etc., the HP-25/25C had serious competition. HP would go on to introduce the HP-29C/19C calculators with 99 merged steps, labels, and subroutines. And TI would introduce a TI-58C with continuous memory. A version adapted to support an additional backward-facing display manufactured by Educational Calculator Devices named EduCALC 25 GD existed as well.

Notes

# US$195 in 1975 ≈ US$770 in 2009 (se
The Inflation Calculator

See also

Notes

References

External links