HP-19C/-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-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 (HP-91, HP-92 and HP-97 were desktop units 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).

HP's internal code name for the 29C was Bonnie, the 19C was correspondingly named Clyde.

The HP-19C and HP-29C were introduced at MSRPs of $345 and $195, respectively.

A version adapted to support an additional backward-facing display manufactured by Educational Calculator Devices named EduCALC 29C GD existed as well.

Simulators and emulators
 HP-29C simulator for Windows
 HP-19C and HP-29C emulators for Windows
 HP Calculator emulators  for Linux

References

External links 
The Museum of HP Calculators' article on the HP-19C/29C
Interior picture of 19C
http://www.hpmuseum.org/forum/thread-6398-post-73952.html#pid73952

19C