The term continuous memory was coined by

Hewlett-Packard (HP) 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 ...

to describe a unique feature of certain

HP calculators HP calculators are various calculators manufactured by the Hewlett-Packard company over the years. Their desktop models included the HP 9800 series, while their handheld models started with the HP-35. Their focus has been on high-end scientif ...

whereby the calculator could internally sustain most, or in later models - all, of the contents of user memory (via 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). Since its introduction on the

HP-25C The HP-25 was a hand-held programmable scientific/engineering calculator made by Hewlett-Packard between early January 1975 and 1978. The HP-25 was introduced as a cheaper ( US$195 MSRP) alternative to the ground-breaking HP-65. To reduce cost ...

, this feature slowly evolved by model to eventually mean maintaining the contents of nearly all calculator memory, including system and scratch RAM, options, settings, flags, and other calculator state information. Before the introduction of the HP-25C in 1976, all calculator random-access memory (RAM) was volatile, i.e. its contents (esp. user data in storage registers and any user programs) were cleared when the calculator was turned off. Three early models with this improved, continuous memory - the HP-25C,

HP-29C The HP-19C and HP-29C were scientific/engineering pocket calculators made by Hewlett-Packard between 1977 and 1979. They were the most advanced and last models of the "20" family (compare HP-25) and included '' Continuous Memory'' (battery-bac ...

, and

HP-19C The HP-19C and HP-29C were scientific/engineering pocket calculators made by Hewlett-Packard between 1977 and 1979. They were the most advanced and last models of the "20" family (compare HP-25) and included '' Continuous Memory'' (battery-bac ...

- actually had the words "'' Continuous Memory ''" printed in conspicuous, white script on the bottom margin of their faceplates. The "C" in the model designations was to distinguish those models within HP's calculator product line. HP did not print this phrase on subsequent, featured models because the novelty of continuous memory had by then faded and also because it could no longer claim it as a feature unique to HP calculators (Texas Instruments would later call their identical feature " Constant Memory"). At introduction over the next 9 years (approx. 1979–1987), subsequent HP models so featured simply had designations in which the letter "C" followed the model number, e.g. the

HP-34C The HP-34C continuous memory calculator was an advanced scientific programmable calculator of the HP 30 series. It was produced between 1979 (cost US$150) and 1983 (cost US$100). Features Root-finding and integration Significant to the HP- ...

and the Voyager series

HP-10C The Hewlett-Packard Voyager series of calculators were introduced by Hewlett-Packard in 1981. All members of this series are programmable, use Reverse Polish Notation, and feature continuous memory. Nearly identical in appearance, each mode ...

HP-11C The Hewlett-Packard Voyager series of calculators were introduced by Hewlett-Packard in 1981. All members of this series are programmable, use Reverse Polish Notation, and feature continuous memory. Nearly identical in appearance, each model ...

HP-12C The HP-12C is a financial calculator made by Hewlett-Packard (HP) and its successor HP Inc. as part of the HP Voyager series. Functionality The HP-12C is HP's longest and best-selling product, in continual production since its introduction ...

HP-15C The HP-15C is a high-end scientific programmable calculator of Hewlett-Packard's Voyager series produced between 1982 and 1989. Models HP-15C The HP-15C is a high-end scientific pocket calculator with a root-solver and numerical integration. ...

and

HP-16C The HP-16C Computer Scientist is a programmable pocket calculator that was produced by Hewlett-Packard between 1982 and 1989. It was specifically designed for use by computer programmers, to assist in debugging. It is a member of the HP Voyage ...

References

* {{HP calculators continuous memory