Continuous memory

The term continuous memory was used by HP calculators to indicate that the calculator can preserve it's memory contents at all times. Before the HP-25C (first model with this feature) calculators lost all memory contents when turned off. Both HP-25C and HP-29C had the words "Continuous Memory" printed on them in script blue letters. After those models this feature becomes standard in new HP calculators so the use of these words was discontinued, although several later models preserve the C letter in their designations like the HP-10C series.