HP-25

The HP -25 was the successor to the highly successful first programmable pocket calculator in the world, the HP -65 from Hewlett -Packard.

He was born in 1975 at a price of U.S. $ 195 to the U.S. market. In Germany in 1976 it cost "only" about 650, - DM He renounced a magnetic card reader, and therefore could be programmed via the keyboard exclusively by typing a key sequence. After switching off the program was lost and had to be re-entered.

Overall, the HP -25 had space for 49 program steps, unlike its predecessors combined key sequences needed just one step. In addition, he owned eight memory registers and special scientific and statistical functions. The included 161 -page, four-color printed Programming Manual, included a variety of mathematical, scientific, navigational or financial engineering program examples, which represented an incredible for that time calculator performance.

Like all HP calculators, he used to enter the Reverse Polish Notation (RPN ) and processed the figures on a four levels deep stack (register numbers: x, y, z and t). Almost all keys were triply occupied and could be accessed via a blue and yellow Präfixtaste. To switch between calculation mode and programming mode used was a sliding switch. As a reminder, he had a 10 - digit red LED display. The HP -25 was the first calculator of the so-called " technical display format " dominated - one exponential in the exponent is always a multiple of 3, which would be matched with the SI prefixes (eg, mega, kilo, milli, micro ).

A year later, in 1976, brought Hewlett- Packard HP -25C the largely identical (Continuous memory) out of retained its been tipptes program even after turning off due to the use of new low-power CMOS technology. But were not nearly as many buyers are addressed, as with the previous model.