Topic summary
HP-25C
Extracted from the Wikipedia article HP-25.
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 memory in a calculator, termed continuous memory by HP.