The hp42s from the late eighties is the successor of the hp41c[vx] of the early eighties which is the successor of the hp67 of the late seventies.
The devices are designed to be able to run its predecessor's programs.
The hp42s presents itself in quite an understated manner.
It doesn't have hp67's fourfold key usage
and it doesn't have hp41c's expansion slots
or their card reader.
[Programs need to be retyped after reset, though.]
Most of the functionality is only accessible through [scrollable] menus
which are 'hilighted' by a differently textured black bars,
[Often used functionality can be assigned
CUSTOM menu, though.]
Among the cool simple functionality additions can be found: complex numbers and the automatic lin/log/exp/pow regressions.
More data and pictures can be found at www.hpmuseum.org and www.finseth.com. [My thanks to those for collecting the data!]
program the hp42s.