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-backed CMOS memory) as a standard feature.
The HP-19C included a small thermal printer, one of the very few hand-held scientific calculators to offer such a feature (the HP-97 was a desktop unit, and later models like the HP-41C only supported external printers). Due to the printer's power requirements, the 19C used a battery pack of four AA-sized NiCd cells, adding to the weight of the calculator and printer mechanism.
All other capabilities were the same in both models – RPN expression logic, 98 program memory locations, statistical functions, and 30 registers.
Users could develop software for the HP-29C/19C, such as a prime number generator. The calculators expanded the HP-25's program capabilities by adding subroutines, increment/decrement looping, relative branching and indirect addressing (via register 0 as index).